Huawei Sig Guide

HUAWEI BSC6000 Base Station Subsystem

V900R003

BSS Signaling Analysis Guide

Issue 01

Date 2007-11-26

Part Number 00379162

Huawei Technologies Proprietary

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Contents

About This Document.....................................................................................................................1

1 BSS Signaling Fundamental....................................................................................................1-11.1 A Interface.......................................................................................................................................................1-2

1.1.1 A Interface Protocol Model....................................................................................................................1-21.1.2 Physical Layer on the A Interface..........................................................................................................1-31.1.3 MTP Layer on the A Interface...............................................................................................................1-31.1.4 SCCP Layer on the A Interface..............................................................................................................1-61.1.5 BSSAP Layer on the A Interface...........................................................................................................1-6

1.2 Abis Interface................................................................................................................................................1-111.2.1 Abis Interface Protocol Model.............................................................................................................1-111.2.2 Abis Interface Structure.......................................................................................................................1-121.2.3 Physical Layer on the Abis Interface ..................................................................................................1-141.2.4 LAPD Layer on the Abis Interface.......................................................................................................1-141.2.5 L3 Traffic Management Messages on the Abis Interface....................................................................1-151.2.6 L3 OM Messages on the Abis Interface...............................................................................................1-18

1.3 Um Interface..................................................................................................................................................1-201.3.1 Physical Layer on the Um Interface.....................................................................................................1-201.3.2 LAPD Layer on the Um Interface........................................................................................................1-211.3.3 L3 Entity on the Um Interface..............................................................................................................1-22

2 BSS Signaling Tracing..............................................................................................................2-12.1 Tracing the Messages on the Um Interface.....................................................................................................2-22.2 Tracing Messages on the Abis Interface.........................................................................................................2-3

2.2.1 Tracing the RSL Messages on the Abis Interface..................................................................................2-32.2.2 Tracing the OML Messages on the Abis Interface.................................................................................2-72.2.3 Tracing the ESL Messages on the Abis Interface..................................................................................2-92.2.4 Tracing the LAPD Messages on the Abis Interface.............................................................................2-12

2.3 Tracing the Messages on the A Interface......................................................................................................2-152.3.1 Tracing the BSSAP Messages on the A Interface................................................................................2-152.3.2 Tracing the MTP2 Messages on the Interface......................................................................................2-192.3.3 Tracing the MTP3 Messages on the A Interface..................................................................................2-222.3.4 Tracing the SCCP Messages on the A Interface..................................................................................2-25

2.4 Tracing Messages on the Pb Interface...........................................................................................................2-28

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2.4.1 Tracing the Application Messages on the Pb Interface........................................................................2-282.4.2 Tracing the LAPD Messages on the Pb Interface................................................................................2-30

2.5 Tracing the Messages on the BSC-CBC Interface........................................................................................2-322.6 Tracing User Messages.................................................................................................................................2-33

3 BSS System Information...........................................................................................................3-13.1 BSS System Information Type........................................................................................................................3-2

3.1.1 System Information Type 1 ...................................................................................................................3-23.1.2 System Information Types 2, 2bis, 2ter, and 2quater.............................................................................3-63.1.3 System Information Type 3 ...................................................................................................................3-83.1.4 System Information Type 4 .................................................................................................................3-113.1.5 System Information Types 5, 5bis, and 5ter.........................................................................................3-123.1.6 System Information Type 6 .................................................................................................................3-133.1.7 System Information Type 7 .................................................................................................................3-143.1.8 System Information Type 8 .................................................................................................................3-143.1.9 System Information Type 13 ...............................................................................................................3-14

3.2 Internal BSC Signaling Procedure of the System Information.....................................................................3-15

4 Immediate Assignment.............................................................................................................4-14.1 Immediate Assignment Procedure..................................................................................................................4-24.2 Internal BSC Signaling Procedure of Immediate Assignment........................................................................4-44.3 Abnormal Immediate Assignment Cases........................................................................................................4-4

4.3.1 Failure in Receiving an Establish Indication Message After Channel Activation.................................4-44.3.2 BSC Sending an Immediate Assignment Reject Message.....................................................................4-5

5 Classmark Update......................................................................................................................5-15.1 Classmark Update Procedure..........................................................................................................................5-2

6 Location Update..........................................................................................................................6-16.1 Location Update Procedure.............................................................................................................................6-2

6.1.1 Periodic Update Procedure.....................................................................................................................6-26.1.2 IMSI Attach Procedure...........................................................................................................................6-36.1.3 Generic Location Update Procedure......................................................................................................6-3

6.2 Internal BSC Signaling Procedures of Location Update.................................................................................6-56.3 Abnormal Location Update Cases...................................................................................................................6-5

6.3.1 Location Update Not Started or Aborted on the MS Side......................................................................6-56.3.2 Location Update Failure on the Network Side.......................................................................................6-6

7 Authentication............................................................................................................................7-17.1 Authentication Principles................................................................................................................................7-27.2 Authentication Procedure................................................................................................................................7-27.3 Authentication Failure.....................................................................................................................................7-37.4 Internal BSC Signaling Procedure of Authentication.....................................................................................7-47.5 Abnormal Authentication Cases......................................................................................................................7-4

7.5.1 RR Connection Failure...........................................................................................................................7-5

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7.5.2 Timer T3260 Expiry...............................................................................................................................7-57.5.3 SIM Unregistered...................................................................................................................................7-5

8 Ciphering.....................................................................................................................................8-18.1 Ciphering Procedure........................................................................................................................................8-28.2 Ciphering Mode Change.................................................................................................................................8-38.3 Internal BSC Signaling Procedure of Ciphering.............................................................................................8-38.4 Abnormal Ciphering Cases.............................................................................................................................8-4

8.4.1 BSS Sending a Cipher Mode Reject Message.......................................................................................8-48.4.2 MS Doing No Processing.......................................................................................................................8-4

9 TMSI Reallocation.....................................................................................................................9-19.1 TMSI Reallocation Procedure.........................................................................................................................9-29.2 Internal BSC Signaling Procedure of TMSI Reallocation..............................................................................9-29.3 Abnormal TMSI Reallocation Cases...............................................................................................................9-3

9.3.1 TMSI Reallocation Caused by RR Connection Failure on the Network Side.......................................9-39.3.2 TMSI Reallocation Caused by T3250 Expiry........................................................................................9-3

10 Speech Channel Assignment...............................................................................................10-110.1 Speech Channel Assignment Procedure......................................................................................................10-210.2 Channel Mode Modification Procedure......................................................................................................10-310.3 Internal BSC Signaling Procedure of Speech Channel Assignment...........................................................10-410.4 Abnormal Speech Channel Assignment Cases...........................................................................................10-5

10.4.1 BSC Sending an Assignment Failure Message..................................................................................10-510.4.2 BSC Receiving a Connection Failure Indication Message................................................................10-610.4.3 BSC Receiving an Error Indication Message.....................................................................................10-7

11 Mobile Originating Call Establishment............................................................................11-111.1 Mobile Originating Call Establishment Procedure.....................................................................................11-2

11.1.1 Early Assignment Procedure..............................................................................................................11-211.1.2 Late Assignment Procedure...............................................................................................................11-411.1.3 Very Early Assignment Procedure.....................................................................................................11-6

11.2 Internal BSC Signaling Procedure of Mobile Originating Call Establishment...........................................11-711.3 Abnormal Mobile Originating Call Establishment Cases...........................................................................11-7

11.3.1 Calling MS Cannot Be Heard.............................................................................................................11-811.3.2 MSC Releasing the Call after Sending a CM Service Reject Message..............................................11-811.3.3 Abnormal Procedure Caused by MS in Busy State............................................................................11-911.3.4 MSC Sending a Disconnect Message Instead of an Assignment Request Message..........................11-911.3.5 Abnormal Procedures Caused by MS Hangup...................................................................................11-911.3.6 Abnormal Procedures Caused by MSC Sending a Clear Command Message or a Disconnect Message.....................................................................................................................................................................11-1011.3.7 LAPD Reporting an Error Indication Message During Call Establishment....................................11-10

12 Mobile Terminating Call Establishment...........................................................................12-112.1 Mobile Terminating Call Establishment Procedure....................................................................................12-212.2 Internal BSC Signaling Procedure of Mobile Terminating Call Establishment.........................................12-3


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12.3 Abnormal Mobile Terminating Call Establishment Cases..........................................................................12-312.3.1 No Paging Message on the A Interface..............................................................................................12-312.3.2 No Paging Message on the Abis Interface.........................................................................................12-412.3.3 No Paging Response on the Abis Interface........................................................................................12-512.3.4 No Paging Response on the A Interface.............................................................................................12-6

13 BSC Release.............................................................................................................................13-113.1 Normal Release Procedure..........................................................................................................................13-213.2 Local Release Procedure.............................................................................................................................13-4

14 Handover..................................................................................................................................14-114.1 Handover Procedure....................................................................................................................................14-2

14.1.1 Intra-BSC Handover Procedure.........................................................................................................14-214.1.2 Inter-BSC Handover Procedure.........................................................................................................14-414.1.3 Inter-MSC Handover Procedure.........................................................................................................14-614.1.4 Inter-System Handover Procedure.....................................................................................................14-7

14.2 Internal BSC Signaling Procedure of Handover.........................................................................................14-914.2.1 Internal BSC Signaling Procedure of the Intra-BSC Handover.........................................................14-914.2.2 Internal BSC Signaling Procedure of the Inter-BSC Handover.........................................................14-914.2.3 Internal BSC Signaling Procedure of the Inter-MSC Handover......................................................14-1014.2.4 Internal BSC Signaling Procedure of the Inter-System Handover...................................................14-10

14.3 Abnormal Handover Cases........................................................................................................................14-1014.3.1 No Available Channels in the Target Cell.......................................................................................14-1114.3.2 Old BSS Not Receiving a Specified Message upon T8 Expiry.......................................................14-1114.3.3 Inter-Cell Handover Failure (MS Returning to the Old Channel)....................................................14-1214.3.4 BSC Receiving a Connection Failure Indication Message..............................................................14-1214.3.5 Forced Handover Failure..................................................................................................................14-1314.3.6 Handover Failure Caused by CIC Malfunction................................................................................14-1314.3.7 Handover Failure Caused by MS Access Failure.............................................................................14-13

15 Call Re-Establishment...........................................................................................................15-115.1 Call Re-Establishment Procedure................................................................................................................15-215.2 Internal BSC Signaling Procedure of Call Re-Establishment.....................................................................15-415.3 Abnormal Call Re-Establishment Cases.....................................................................................................15-4

15.3.1 Network Sending a CM Service Reject Message...............................................................................15-415.3.2 Call Re-Establishment Not Allowed or Re-Establishment Failure....................................................15-515.3.3 RR Connection Failure.......................................................................................................................15-5

16 Directed Retry.........................................................................................................................16-116.1 Directed Retry Procedure............................................................................................................................16-2

16.1.1 Intra-BSC Directed Retry Procedure..................................................................................................16-216.1.2 Inter-BSC directed retry procedure....................................................................................................16-416.1.3 Inter-MSC directed retry procedure...................................................................................................16-6

16.2 Internal BSC Signaling Procedure of Directed Retry.................................................................................16-716.2.1 Internal BSC Signaling Procedure of the Intra-BSC Directed Retry.................................................16-8

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iv Huawei Technologies Proprietary Issue 01 (2007-11-26)

16.2.2 Internal BSC Signaling Procedure of the Inter-BSC Directed Retry.................................................16-816.2.3 Internal BSC Signaling Procedure of the Inter-MSC Directed Retry................................................16-9

16.3 Abnormal Directed Retry Cases..................................................................................................................16-916.3.1 No Available Channels in the Target Cell.........................................................................................16-916.3.2 Channel Activation Failure..............................................................................................................16-10

17 BSC Re-Assignment...............................................................................................................17-117.1 BSC Re-Assignment Procedure..................................................................................................................17-217.2 Internal BSC Signaling Procedure of BSC Re-Assignment........................................................................17-317.3 Abnormal BSC Re-Assignment Cases........................................................................................................17-3

17.3.1 BSC Failure in Initiating a Re-Assignment Procedure......................................................................17-3

18 Queuing and Preemption.....................................................................................................18-118.1 Queuing Procedure......................................................................................................................................18-218.2 Preemption Procedure.................................................................................................................................18-318.3 Internal BSC Signaling Procedure of Queuing and Preemption.................................................................18-418.4 Abnormal Queuing and Preemption Cases.................................................................................................18-4

18.4.1 BSC Sending the MSC a Clear Request Message..............................................................................18-4

19 Short Message Service...........................................................................................................19-119.1 Short Message Transfer Procedure.............................................................................................................19-2

19.1.1 Short Message Sending Procedure Initiated by an Idle MS...............................................................19-219.1.2 Short Message Receiving Procedure Initiated by an Idle MS............................................................19-319.1.3 Short Message Sending Procedure Initiated by a Busy MS...............................................................19-519.1.4 Short message receiving procedure initiated by a busy MS...............................................................19-5

19.2 Internal BSC Signaling Procedure of Short Message Transfer...................................................................19-619.3 Abnormal Short Message Transfer Cases...................................................................................................19-7

19.3.1 Short Message Sending Failure due to Authentication and Ciphering Disabled...............................19-7

20 Short Message Service Cell Broadcast...............................................................................20-120.1 SMSCB Procedure......................................................................................................................................20-2

20.1.1 CBC-BSC SMSCB Procedure...........................................................................................................20-220.1.2 BSC-BTS SMSCB Procedure............................................................................................................20-5

20.2 Internal BSC Signaling Procedure of the SMSCB......................................................................................20-620.3 Abnormal SMSCB Cases............................................................................................................................20-6

20.3.1 MS Failure in Receiving Cell Broadcast Messages...........................................................................20-720.3.2 CBCH Not Configured in a Cell........................................................................................................20-7


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Figures

Figure 1-1 A interface signaling protocol model.................................................................................................1-3Figure 1-2 L3 signaling message processing procedure.......................................................................................1-5Figure 1-3 Abis interface protocol model..........................................................................................................1-12Figure 1-4 Abis interface structure.....................................................................................................................1-13Figure 1-5 Logical links on the Abis interface...................................................................................................1-14Figure 1-6 Management objects.........................................................................................................................1-18Figure 1-7 Interfaces of L1 on the Um interface................................................................................................1-21Figure 1-8 L3 signaling message processing procedure.....................................................................................1-24Figure 1-9 Services provided by the RR sublayer..............................................................................................1-25Figure 1-10 Services provided by the MM sublayer..........................................................................................1-25Figure 2-1 Tracing messages on the Um interface (set TRX as the filter condition)...........................................2-2Figure 2-2 Results of tracing messages on the Um interface...............................................................................2-3Figure 2-3 Trace & Monitor tab page...................................................................................................................2-5Figure 2-4 Trace the RSL Message at Abis Interface dialog box........................................................................2-6Figure 2-5 Tracing the RSL messages on the Abis interface ..............................................................................2-7Figure 2-6 Trace & Monitor tab page...................................................................................................................2-8Figure 2-7 Trace the OML Message at Abis Interface dialog box.......................................................................2-8Figure 2-8 Tracing the OML messages on the Abis interface .............................................................................2-9Figure 2-9 Trace & Monitor tab page.................................................................................................................2-10Figure 2-10 Trace the ESL Message at Abis Interface dialog box.....................................................................2-11Figure 2-11 Tracing the ESL messages on the Abis interface ..........................................................................2-11Figure 2-12 Trace & Monitor tab page...............................................................................................................2-13Figure 2-13 Trace the LAPD Message at Abis Interface dialog box.................................................................2-14Figure 2-14 Tracing the LAPD messages on the Abis interface .......................................................................2-15Figure 2-15 Trace & Monitor tab page...............................................................................................................2-16Figure 2-16 Trace the BSSAP Message at A Interface dialog box....................................................................2-17Figure 2-17 Tracing the BSSAP messages at A interface .................................................................................2-18Figure 2-18 Trace the BSSAP Message at A Interface (1)................................................................................2-18Figure 2-19 Trace & Monitor tab page...............................................................................................................2-20Figure 2-20 Trace the MTP2 Message at A Interface dialog box......................................................................2-21Figure 2-21 Tracing the MTP2 messages on the A interface ............................................................................2-22Figure 2-22 Trace & Monitor tab page...............................................................................................................2-23Figure 2-23 Tracing the MTP3 Messages at A Interface...................................................................................2-24

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Figure 2-24 Tracing the MTP3 messages at A interface ...................................................................................2-25Figure 2-25 Trace & Monitor tab page...............................................................................................................2-26Figure 2-26 Tracing the SCCP Messages on the A Interface.............................................................................2-27Figure 2-27 Tracing the SCCP messages on the A interface.............................................................................2-28Figure 2-28 Trace & Monitor tab page...............................................................................................................2-29Figure 2-29 Trace the Application Message at Pb Interface dialog box............................................................2-30Figure 2-30 Trace & Monitor tab page...............................................................................................................2-31Figure 2-31 Trace the LAPD Message at Pb Interface dialog box.....................................................................2-32Figure 2-32 Trace the Message at BSC-CBC Interface dialog box...................................................................2-33Figure 2-33 Trace User Message dialog box......................................................................................................2-34Figure 2-34 Result of tracing user messages......................................................................................................2-35Figure 3-1 Set Cell Attributes dialog box..........................................................................................................3-17Figure 4-1 Immediate assignment procedure.......................................................................................................4-2Figure 5-1 Classmark update procedure...............................................................................................................5-2Figure 7-1 Authentication procedure....................................................................................................................7-3Figure 7-2 Unsuccessful authentication procedure..............................................................................................7-4Figure 8-1 Ciphering procedure...........................................................................................................................8-2Figure 9-1 TMSI reallocation procedure..............................................................................................................9-2Figure 10-1 Speech channel assignment procedure...........................................................................................10-2Figure 10-2 Channel mode modification procedure...........................................................................................10-4Figure 11-1 Early assignment procedure............................................................................................................11-3Figure 11-2 Late assignment procedure.............................................................................................................11-5Figure 11-3 Very early assignment procedure...................................................................................................11-6Figure 12-1 Mobile terminating call establishment procedure...........................................................................12-2Figure 13-1 Normal release procedure...............................................................................................................13-3Figure 13-2 Local release procedure..................................................................................................................13-5Figure 14-1 Intra-BSC handover procedure.......................................................................................................14-3Figure 14-2 Inter-BSC handover procedure.......................................................................................................14-5Figure 14-3 Inter-MSC handover procedure......................................................................................................14-7Figure 14-4 GSM-to-UMTS handover procedure .............................................................................................14-8Figure 14-5 UMTS-to-GSM handover procedure..............................................................................................14-8Figure 15-1 Call re-establishment procedure.....................................................................................................15-2Figure 16-1 Intra-BSC directed retry procedure................................................................................................16-3Figure 16-2 Inter-BSC directed retry procedure................................................................................................16-5Figure 16-3 Inter-MSC directed retry procedure................................................................................................16-7Figure 17-1 BSC re-assignment procedure........................................................................................................17-2Figure 18-1 Queuing procedure.........................................................................................................................18-2Figure 18-2 Preemption procedure.....................................................................................................................18-3Figure 19-1 Short message sending procedure initiated by an idle MS.............................................................19-2Figure 19-2 Short message receiving procedure initiated by an idle MS...........................................................19-4Figure 19-3 Short message sending procedure initiated by a busy MS.............................................................19-5Figure 19-4 Short message receiving procedure initiated by a busy MS...........................................................19-6

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viii Huawei Technologies Proprietary Issue 01 (2007-11-26)

Figure 20-1 Procedure for Sending or Replacing a Message.............................................................................20-2Figure 20-2 Procedure for deleting an existing message....................................................................................20-3Figure 20-3 Procedure for querying the CBCH status.......................................................................................20-3Figure 20-4 Procedure for querying the message status.....................................................................................20-4Figure 20-5 Procedure for resetting a cell..........................................................................................................20-4Figure 20-6 Procedure for setting the DRX.......................................................................................................20-5Figure 20-7 BSC Sending an SMS Broadcast Command Message...................................................................20-5Figure 20-8 BTS Sending the BSC a CBCH Loading Indication Message.......................................................20-6Figure 20-9 SMSCB procedure..........................................................................................................................20-6

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide Figures

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Tables

Table 1-1 BSSAP protocol functionality..............................................................................................................1-8Table 1-2 Administrative State...........................................................................................................................1-18Table 1-3 Operational State................................................................................................................................1-19Table 1-4 Available State...................................................................................................................................1-19Table 3-1 Cell channel description.......................................................................................................................3-3Table 3-2 Format of cell channel description.......................................................................................................3-3Table 3-3 Relation between "S" and "T"..............................................................................................................3-5Table 3-4 Multiband reporting............................................................................................................................. 3-7Table 3-5 Meaning of the CCCH-CONF............................................................................................................. 3-9Table 3-6 Parameters affecting cell priority in cell selection.............................................................................3-11Table 3-7 RACH control parameters in System Information Type 1 and the corresponding parameters on theBSC6000 Local Maintenance Terminal..........................................................................................................3-16Table 3-8 Control channel parameters in System Information Type 3 and the corresponding parameters on theBSC6000 Local Maintenance Terminal..........................................................................................................3-18Table 3-9 Cell option parameters in System Information Type 3 and the corresponding parameters on the BSC6000Local Maintenance Terminal...........................................................................................................................3-18Table 3-10 Cell selection parameters in System Information Type 3 and the corresponding parameters on theBSC6000 Local Maintenance Terminal..........................................................................................................3-19Table 3-11 Rest Oct parameters in System Information Type 4 and the corresponding parameters on the BSC6000Local Maintenance Terminal...........................................................................................................................3-20

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About This Document

PurposeThis document describes the GBSS signaling fundamental, signaling trace, and systeminformation, as well as the procedures such as location update, authentication, encryption, andcall procedure.

VersionsThe following table lists the product versions related to this document.

ProductNames

Models Versions

BSC BSC6000 V900R001

PCU PCU6000 V300R008

BTS BTS3012 V300R004&V300R005&V300R006

BTS3012AE V300R005&V300R006

BTS3006C V300R005&V300R006

BTS3002E V300R005

Intended AudienceThis document is intended for:

l Network planning engineers

l Field engineers

l System engineers

l Shift operators

l Network operators

l Network management engineers

Change HistoryRefer to Changes in BSS Signaling Analysis Guide.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide About This Document

Issue 01 (2007-11-26) Huawei Technologies Proprietary 1

Organization

1 BSS Signaling Fundamental

The external BSS interfaces, which are the Um interface between the BSS and the MS, and theA interface between the BSS and the MSC, are standard interfaces. The Abis interface betweenthe BSC and the BTS is an internal interface.

2 BSS Signaling Tracing

This describes the BSS signaling tracing, which consists of the signaling tracing on the Uminterface, Abis interface, A interface, Pb interface, and BSC-CBC interface, and single usersignaling tracing.

3 BSS System Information

System information (SI) refers to the major radio network parameters on the Um interface suchas the network identification parameters, cell selection parameters, system control parameters,and network functional parameters.

4 Immediate Assignment

This topic describes immediate assignment including its internal BSC signaling procedure andabnormal cases.

5 Classmark Update

The MS classmark specifies the service capability, supported frequency bands, power capability,and ciphering capability of an MS in the GSM network. It is categorized into classmark 1,classmark 2, and classmark 3.

6 Location Update

In the GSM system, MS location information is stored in the HLR, the VLR, and the MS. Whenthe location information changes, relevant information in the HLR, the VLR, and the MS mustbe changed accordingly, which can be realized through the location update procedure.

7 Authentication

The purpose of authentication is to permit the network to check whether the identity providedby the MS is acceptable or not and to prevent the private information of the legal subscribersfrom being stolen.

8 Ciphering

Ciphering is used to secure the information exchange between an MS and a BTS. The informationconsists of the signaling information and the subscriber information. The subscriber informationconsists of the subscriber data and the subscriber voice.

9 TMSI Reallocation

The TMSI reallocation takes place in ciphering mode. It is generally related to another procedure,such as location update or call establishment.

10 Speech Channel Assignment

The speech channel assignment is the procedure for assigning TCHs to the MS according to theservice requests.

11 Mobile Originating Call Establishment

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Mobile originating call refers to an MS calling another MS or a fixed phone.

12 Mobile Terminating Call Establishment

Mobile terminating call refers to an MS called by another MS or a fixed phone.

13 BSC Release

BSC release consists of the normal release and the local release.

14 Handover

Handover is one of the basic functions of the GSM. It enables calls to be set up in better cellsand reduces call drops. Handover also lowers cross interference. The handover procedureconsists of handover triggering, handover preparation, handover decision, and handoverexecution.

15 Call Re-Establishment

The call re-establishment procedure allows an MS to resume a connection after a radio linkfailure. It may take place in a new cell or a new location area.

16 Directed Retry

Directed retry is a special type of handover. It refers to the process of assigning an MS to a TCHin a cell other than the serving cell when no radio resources are available. It is triggered by theassignment procedure and employs internal or external handover procedures.

17 BSC Re-Assignment

BSC re-assignment refers to a TCH assignment procedure initiated by the BSC after the BSCreceives an Assignment Failure message from the MS on the SDCCH. BSC re-assignment raisesthe rate of assignments on the Um interface.

18 Queuing and Preemption

This topic describes queuing and pre-emption.

19 Short Message Service

For an idle MS, short messages are transferred on the SDCCH. For a busy MS, however, shortmessages are transferred on the SACCH. The point-to-point short message procedure comprisestwo fundamental procedures: mobile originating short message transfer procedure and mobileterminating short message transfer procedure.

20 Short Message Service Cell Broadcast

The short message service cell broadcast (SMSCB) is similar to the paging station broadcastservice. The operators broadcast messages to the subscribers in the specified areas. Thesubscribers that subscribe to the service receive the messages broadcast by the operators.

Conventions

1. Symbol Conventions

The following symbols may be found in this document. They are defined as follows



Symbol Description

DANGERIndicates a hazard with a high level of risk that, if not avoided,will result in death or serious injury.

WARNINGIndicates a hazard with a medium or low level of risk which, ifnot avoided, could result in minor or moderate injury.

CAUTIONIndicates a potentially hazardous situation that, if not avoided,could cause equipment damage, data loss, and performancedegradation, or unexpected results.

TIP Indicates a tip that may help you solve a problem or save yourtime.

NOTE Provides additional information to emphasize or supplementimportant points of the main text.

2. General Conventions

Convention Description

Times New Roman Normal paragraphs are in Times New Roman.

Boldface Names of files,directories,folders,and users are in boldface. Forexample,log in as user root .

Italic Book titles are in italics.

Courier New Terminal display is in Courier New.

3. Command Conventions


Boldface The keywords of a command line are in boldface.

Italic Command arguments are in italic.

[ ] Items (keywords or arguments) in square brackets [ ] are optional.

{x | y | ...} Alternative items are grouped in braces and separated by verticalbars.One is selected.

[ x | y | ... ] Optional alternative items are grouped in square brackets andseparated by vertical bars.One or none is selected.

{ x | y | ... } * Alternative items are grouped in braces and separated by verticalbars.A minimum of one or a maximum of all can be selected.

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4 Huawei Technologies Proprietary Issue 01 (2007-11-26)


[ x | y | ... ] * Alternative items are grouped in braces and separated by verticalbars.A minimum of zero or a maximum of all can be selected.

4. GUI Conventions


Boldface Buttons,menus,parameters,tabs,window,and dialog titles are inboldface. For example,click OK.

> Multi-level menus are in boldface and separated by the ">" signs.For example,choose File > Create > Folder .

5. Keyboard Operation


Key Press the key.For example,press Enter and press Tab.

Key1+Key2 Press the keys concurrently.For example,pressing Ctrl+Alt+Ameans the three keys should be pressed concurrently.

Key1,Key2 Press the keys in turn.For example,pressing Alt,A means the twokeys should be pressed in turn.

6. Mouse Operation

Action Description

Click Select and release the primary mouse button without moving thepointer.

Double-click Press the primary mouse button twice continuously and quicklywithout moving the pointer.

Drag Press and hold the primary mouse button and move the pointerto a certain position.



1 BSS Signaling Fundamental

About This Chapter

The external BSS interfaces, which are the Um interface between the BSS and the MS, and theA interface between the BSS and the MSC, are standard interfaces. The Abis interface betweenthe BSC and the BTS is an internal interface.

1.1 A InterfaceThis topic describes the A interface protocol model that consists of the physical layer, MTPlayer, SCCP layer, and BSSAP layer.

1.2 Abis InterfaceThe Abis interface lies between the BTS and the BSC. It complies with GSM Rec.08.5X series.The Abis interface is an internal interface of the BSS. The interworking between the BSC andBTS equipment from different manufactures is not available. The terrestrial traffic channels onthe Abis interface map the radio traffic channels on the Um interface.

1.3 Um InterfaceThe Um interface lies between an MS and the BTS. It is used for the interworking between theMS and the fixed part of the GSM system. The links on the Um interface are radio links. TheUm interface transmits the information about radio resource management, mobilitymanagement, and connection management.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 1 BSS Signaling Fundamental

Issue 01 (2007-11-26) Huawei Technologies Proprietary 1-1

1.1 A InterfaceThis topic describes the A interface protocol model that consists of the physical layer, MTPlayer, SCCP layer, and BSSAP layer.

1.1.1 A Interface Protocol ModelThe A interface is defined as a standard communication interface between the NSS and the BSS.

1.1.2 Physical Layer on the A InterfaceThe physical layer on the A interface is a 2 Mbit/s 75-ohm coaxial cable or 120-ohm twistedpair.

1.1.3 MTP Layer on the A InterfaceThe MTP layer on the A interface provides reliable signaling message transfer in the signalingnetwork. In case of system failure and signaling network failure, it takes measures to avoid orreduce the message loss, repetition, and out of sequence.

1.1.4 SCCP Layer on the A InterfaceThe network layer services provided by the SCCP are classified into connectionless service andconnection-oriented service.

1.1.5 BSSAP Layer on the A InterfaceThe BSSAP protocol, which serves as the A interface specification, describes two types ofmessages, BSSMAP messages and DTAP messages.

1.1.1 A Interface Protocol ModelThe A interface is defined as a standard communication interface between the NSS and the BSS.

It is between the BSC and the MSC. The physical links on the A interface are standard 2.048Mbit/s Pulse Code Modulation (PCM) digital links. The A interface transmits the informationabout MS management, mobility management, connection management, and service flowcontrol.

The A interface connects the BSC and the MSC from different manufactures. The GSM systemuses the SS7 on the A interface.

Physically, the A interface is the trunk circuit interface between the BSC and the MSC. Figure1-1 shows the A interface signaling protocol model.

1 BSS Signaling FundamentalHUAWEI BSC6000 Base Station Subsystem


1-2 Huawei Technologies Proprietary Issue 01 (2007-11-26)

Figure 1-1 A interface signaling protocol model

DTAP BSSMAP

Distribution function

BSSAP

SCCP

MTP

DTAP BSSMAP

Distribution function

BSSAP

SCCP

MTP

Physical layer

A

BSS MSC

DTAP: Direct Transfer ApplicationPart

MTP: Message Transfer Part SCCP: Signaling ConnectionControl Part

BSSAP: Base Station SubsystemApplication Part

BSSMAP: Base Station SubsystemManagement Application Part

1.1.2 Physical Layer on the A InterfaceThe physical layer on the A interface is a 2 Mbit/s 75-ohm coaxial cable or 120-ohm twistedpair.

The features of the physical layer on the A interface are as follows:l The 2 Mbit/s transmission rate complies with the G.703.

l The frame structure, synchronization, and timing comply with the G.705.

l The fault management complies with the G.732.

l CRC4 complies with the G.704.

1.1.3 MTP Layer on the A InterfaceThe MTP layer on the A interface provides reliable signaling message transfer in the signalingnetwork. In case of system failure and signaling network failure, it takes measures to avoid orreduce the message loss, repetition, and out of sequence.

The MTP protocols are defined in ITU-T Q.701–Q.710 recommendations. The MTP layercomprises three sublayers, the signaling data link sublayer, signaling link sublayer, and signalingnetwork sublayer.

Signaling Data Link SublayerThe signaling data link function layer (L1) defines the physical, electrical, and functional featuresof signal data. It specifies the way to connect with data links. A signaling data link transmitssignaling in both directions. It comprises two data paths of 64 kbit/s and of opposite directions.Generally, a signaling data link occupies timeslot 16 of a trunk. The specific timeslot is



determined through the negotiation between the BSC and the MSC. The timeslot can be used toestablish a semi-permanent connection.

A signaling data link serves as an information bearer of SS7. One of the important features ofthe signaling data link is that the information transferred on the link is transparent, that is, thedata transferred on the link cannot be changed. Therefore, equipment such as echo canceler,digital attenuator, and A/u rate converter, cannot be connected to this link.

Signaling Link Function LayerSignaling link function layer (L2) specifies the functions and procedures for sending signalingto data links. Together with L1, it provides reliable signaling message transfer between twodirectly connected signaling points.

Due to long-distance transmissions, a certain rate of bit errors may be caused on the data linkbetween adjacent signaling points. However, no error is allowed in CCS7 signaling messagecodes. L2 guarantees error-free transmission of message codes when there are bit errors on L1.L2 performs signaling unit delimitation, signaling unit alignment, error detection, errorcorrection, initial alignment, processor fault detection, flow control, and signaling link error ratemonitoring.

Signaling Network Function LayerBy controlling the route and performance of the signaling network, signaling network functionlayer (L3) guarantees reliable transmission of signaling information to the user part, no matterwhether the signaling network is functional or not. The signaling network is functionallyclassified into the signaling message processing part and the signaling network managementpart.l Signaling message processing part

The signaling message processing part sends signaling messages from the user part of asignaling point to the target signaling links or user parts. The user part in the BSS refers tothe SCCP only. The signaling message processing part comprises three smaller parts:message routing (MRT), message discrimination (MDC), and message distribution (MDT),as shown in Figure 1-2.




Figure 1-2 L3 signaling message processing procedure

MTP user part

Messagedistribution

Messagediscrimination Message routing

Messages to the localsignaling point

Messages to the othersignaling points

MTP2 signaling link

– Message Routing (MRT)The MRT selects message routes. By using the information contained in the route mark,destination signaling point code (DPC), and signaling link selection code (SLS), theMRT selects a signaling link that transfers the signaling messages to a destinationsignaling point.

– Message Discrimination (MDC)The MDC receives the messages from L2 to ascertain whether the destination of themessages is the local signaling point. If the destination is the local signaling point, theMDC sends the messages to the MDT. If the destination is not the local signaling point,the MDC sends the messages to the MRT.

– Message Distribution (MDT)The MDT allocates the messages from the MDC to the user part, the signaling networkmanagement part, and the test & maintenance part.

l Signaling network management partThe signaling network management part reconstructs the signaling network, and keeps andrecovers the normal transmission of signaling units when the signaling network fails. Itconsists of three smaller parts: signaling traffic management (STM), signaling linkmanagement (SLM), and signaling route management (SRM).– Signaling Traffic Management (STM)

The STM part transmits the signaling data from one link or route to another or to multipleavailable links or routes when the signaling network fails. It also temporarily reducessignaling traffic in case of congestion at a signaling point.

– Signaling Link Management (SLM)The SLM part recovers, enables, or disconnects the signaling links in the signalingnetwork. It ensures the provisioning of certain pre-determined link groups. Theconnections between signaling data links and signaling terminals are normallyestablished through man-machine commands. The operations in the signaling system



cannot automatically change the previous connection relations. The SLM compriseslink test, link prohibition and unprohibion, link switchover and switchback, as well aslink activation and deactivation.

– Signaling Route Management (SRM)The SRM ensures reliable exchange of signaling route availability information betweensignaling points so that signaling routes can be blocked or unblocked. It comprisesprohibited transfer, allowed transfer, controlled transfer, and restricted transfer, as wellas signaling route group test and signaling route group congestion test.

1.1.4 SCCP Layer on the A InterfaceThe network layer services provided by the SCCP are classified into connectionless service andconnection-oriented service.

The SCCP, with the help of MTP L3, provides complete network layer functions and reliableservices for information exchange in any form.

The network layer services provided by the SCCP are classified into connectionless service andconnection-oriented service. The connectionless service indicates that an MS does not establisha signaling or connection in advance, but uses the routing function of the SCCP and of the MTPto directly transmit data in the signaling network. The connectionless service is applicable to thetransmission of a small quantity of data. The connection-oriented service indicates that an MSestablishes a signaling connection in advance and directly transfers data on the signalingconnection, instead of using the route selection function of the SCCP. The connection-orientedservice is applicable to the transmission of a large quantity of data, and effectively shortens thedelay of batch data transmission.

The SCCP also performs routing and network management functions. It performs addressingbased on the address information such as the DPC, subsystem number (SSN), and global title(GT). The DPC is the destination singling point code used by the MTP. The SSN is the subsystemnumber. The DPC and the SSN are used to identify different SCCP users, such as the ISUP users,MAP users, TCAP users, and BSSAP users in the same node. They help to compensate theinsufficiency of MTP users and to enlarge the addressing scope. The BSS does not use the GTaddressing mode, which is not described here.

The SCCP performs signaling point state and subsystem state management, active/standbysubsystem switchover, status information broadcast, and subsystem state test. The SCCPmanagement (SCMG) maintains the network functions by reselecting a route or adjusting thetraffic volume in case of network failure or congestion.

The SCCP protocols are defined in ITU-T Q.711–Q.716 recommendations.

1.1.5 BSSAP Layer on the A InterfaceThe BSSAP protocol, which serves as the A interface specification, describes two types ofmessages, BSSMAP messages and DTAP messages.

Overview of the BSSAP ProtocolThe BSSAP protocol, which serves as the A interface specification, describes two types ofmessages, BSSMAP messages and DTAP messages. For DTAP messages, the A interface ismerely equivalent to a transport channel. On the BSS side, DTAP messages are directlytransmitted to radio channels. On the NSS side, DTAP messages are transmitted to the specificfunctional processing units.




The BSSAP protocol is defined in GSM Rec. 08.08 and 04.08.

Typical Messages

The BSSAP protocol, which serves as the A interface specification, describes two types ofmessages, BSSMAP messages and DTAP messages.l DTAP messages

Based on the functional units that process DTAP messages on the NSS side, the DTAPmessages are classified into Mobile Management (MM) messages and Call Control (CC)messages.– The MM messages include messages related to authentication, Configuration

Management (CM) service request, identification request, IMSI detach, location update,MM state, and TMSI reallocation.

– The CC messages include messages related to alerting, call proceeding, connection,establishment, modification, release, disconnection, notification, state query, andDTMF startup.

l BSSMAP messagesThe BSSMAP messages are classified into connectionless messages and connection-oriented messages.– Connectionless messages

The connectionless messages include block, unblock, handover, resource, reset, andpaging messages.The block and unblock messages consist of block, block acknowledge, unblock, andunblock acknowledge messages.The group block and unblock messages consist of group block, block acknowledge,unblock, and unblock acknowledge messages. The handover messages includehandover candidate request messages and handover candidate response messages.The resource messages include resource request messages and resource indicationmessages. The reset messages include reset and reset acknowledge messages.

– Connection-oriented messagesThe connection-oriented messages include messages related to assignment, handover,clear, and ciphering.The Assignment messages include the assignment request message, assignmentcomplete message, and assignment failure message.The handover messages include the Handover Request, Handover RequestAckowledge, Handover Command, Handover Complete, and Handover Failuremessages.The clear messages include the Clear Request and Clear Complete messages.The ciphering messages include the Cipher Mode Command and the Cipher ModeComplete messages.

BSSAP Protocol Functionality

The BSSAP protocol functions in connection-oriented mode or connectionless mode. When anMS needs to exchange service-related messages with the NSS on radio channels and there is noMS-related SCCP connection between the BSS and the NSS, a new connection must beestablished.



l When an MS sends an Access Request message on the RACH, the BSS assigns a dedicatedchannel (SDCCH or TCH) to the MS. After an L2 connection is established on the assignedSDCCH or FACCH, the BSS starts a connection establishment.

l When the MSC decides to perform an external handover (the target BSS might be theserving BSS), it must reserve a new DCCH or TCH from the target BSS. Then the MSCstarts a connection establishment.

Using the connection and connectionless messages, the BSSAP protocol implements thefunctionalality described in Table 1-1.

Table 1-1 BSSAP protocol functionality

Number Function Description

1 Assignment Assignment ensures that dedicated radioresources are properly allocated or re-allocated to an MS. The BSS automaticallyprocesses the initial random access andimmediate assignment of an MS to a DCCH,without the control of the MSC.

2 Block / Unblock Circuit During an assignment procedure, the MSCneeds to select available terrestrial circuits.If the BSS considers that some terrestrialcircuits become unavailable or available, itnotifies the MSC by initiating a Block/Unblock procedure.

3 Resource Indication Resource indication serves to notify theMSC of the following:l Number of radio resources that can be

used as TCHs in the BSSl Number of available and allocated radio

resourcesl The MSC does not easily obtain the

previous information directly from theMSC-controlled services. The MSC musttake the information into considerationwhen the it decides to perform an externalhandover.

4 Reset The purpose of reset is to initialize the BSSor the MSC. For example, if the BSS isfaulty and loses all the reference messagesabout processing, it sends a Reset messageto the MSC. Upon receiving the Resetmessage, the MSC releases the affectedcalls, deletes the affected referencemessages, and sets all the circuits related tothe BSS to idle.If the MSC or BSS is only partially faulty,the affected parts can be cleared through theClear procedure.





5 Handover Required The BSS may send the MSC a HandoverRequired message, requesting the MSC tohand over an MS that are allocated dedicatedresources. The handover reasons as are asfollows:The BSS detects a radio cause for ahandover.The MSC starts a handover candidateenquiry procedure, and the MS is waiting fora handover.Due to congestion, the serving cell must bechanged during call establishment, forexample, during directed retry.The Handover Required message is resent ata certain interval till one of the followingsituations occurs:l A Handover Command message is

received from the MSC.l A Reset message is received.

l All the communications with MSs aredisrupted and the processing is stopped.

l The processing is complete, for example,the call is cleared.

6 Handover ResourceAllocation

Through handover resource allocation, theMSC requests resources from the target BSSbased on the handover request, and the targetBSS reserves resources and waits for an MSto access the reserved resources (channel).

7 Handover Procedure Handover procedure is a procedure in whichthe MSC instructs an MS to access the radioresources in a target cell. When handover isperformed, the original dedicated radioresources and terrestrial resources aremaintained until the MSC sends a ClearCommand message or until the resources arereset.




8 Radio and TerresterialResource Release

When a processing is complete, the MSCsends the BSS a Clear Command message,requesting the BSS to release radioresources. Upon receiving the ClearCommand message, the BSS starts a clearprocedure on the Um interface, sets theconfigured terrestrial circuits to idle, andresponds the MSC with a Clear Completemessage. Upon receiving the ClearComplete message, the MSC releases theterrestrial resources.If the BSS needs to release resources, itsends the MSC a Clear Request message.Then the MSC initiates a release procedureto release the specific terrestrial and radioresources.

9 Paging The paging to an MS is transmitted throughthe SCCP connectionless service over theBSSMAP. When the BSS receives a PagingResponse message on the Um interface, itestablishes an SCCP connection to the MSC.The paging response message, which iscarried in the Complete L3 Information, istransmitted to the MSC through this SCCPconnection.

10 Flow Control Flow control ensures stable working state ofan entity by preventing the entity fromreceiving too much traffic. Flow control onthe A interface is performed through trafficcontrol at the traffic source. It comprises fivelevels. It is performed based on subscriberclasses.

11 Classmark Update Classmark update serves to notify areceiving entity of the classmark messagesfrom an MS. Generally, the BSS notifies theMSC upon receiving the classmarkmessages from an MS. When a handover iscomplete, the MSC sends the new BSS theclassmark messages from the relevant MSon the A interface.

12 Cipher Mode Control The cipher mode control procedure allowsthe MSC to send the Cipher Mode Controlmessage to the BSS and to start thesubscriber equipment and the signalingcipher equipment using a correct cipheringkey (Kc).





13 Queue Indication The queue indication procedure serves tonotify the MSC that the BSS will delay theallocation of some radio resources. Theprocedure takes effect only when thequeuing function is used for traffic channelassignment and traffic channel handover inthe BSS.

14 Load Indication Load indication serves to notify all neighborBSSs of the traffic state of a cell so that thehandover services in an MSC can becontrolled as a whole. In a certain period, theneighbor BSSs take the traffic states ofneighbor cells into account during ahandover.

1.2 Abis InterfaceThe Abis interface lies between the BTS and the BSC. It complies with GSM Rec.08.5X series.The Abis interface is an internal interface of the BSS. The interworking between the BSC andBTS equipment from different manufactures is not available. The terrestrial traffic channels onthe Abis interface map the radio traffic channels on the Um interface.

1.2.1 Abis Interface Protocol ModelThis topic describes the Abis interface protocol model.

1.2.2 Abis Interface StructureThe Abis interface supports three types of internal BTS configurations.

1.2.3 Physical Layer on the Abis InterfaceThe physical layer on the Abis interface are 2 Mbit/s PCM links. It provides thirty-two 64 kbit/s channels.

1.2.4 LAPD Layer on the Abis InterfaceThis topic describes the functions of the LAPD layer on the Abis interface.

1.2.5 L3 Traffic Management Messages on the Abis InterfaceL3 traffic management messages on the Abis interface enables the MS to exchange informationwith the BSS or NSS on the Um interface and to perform some radio resource managementfunctions under the control of the BSC.

1.2.6 L3 OM Messages on the Abis InterfaceThis topic describes the L3 OM messages on the Abis interface.

1.2.1 Abis Interface Protocol ModelThis topic describes the Abis interface protocol model.

Figure 1-3 shows the Abis interface protocol model.



Figure 1-3 Abis interface protocol model

BTSM SCCP

MTP

BTSM

RR BSSAP

Abis interface

BTS BSC

Sign.Layer 1 Layer 1 Layer1

RRLAPDLAPDm LAPD

BTSM: BTS Management BSSAP: Base Station Subsystem Application Part

SCCP: Signaling Connection Control Part LAPD: Link Access Procedure on the D Channel

LAPD: Link Access Procedure on the Dm Channel RR: Radio Resource Management

MTP: Message Transfer Part

The following describes the Abis interface protocol model:l Layer 1 on the Abis interface is a bottom-layer driver based on the hardware. It transfers

data to the physical link.l The layer 2 protocol on the Abis interface is based on the LAPD. The LAPD addresses a

Transceiver (TRX) or Base Control Function (BCF) through the Terminal EquipmentIdentifier (TEI). The LAPD uses different logical links for message transmissions. Radiosignaling links (RSL) transmit service management messages. Operation and maintenancelinks (OML) transmit network management messages. Layer 2 management links (L2ML)transmit L2 management messages.

l RR messages are mapped onto the BSSAP by the BSC. Most RR messages are transparentlytransmitted by the BTS, except for some messages that must be interpreted and executed.For example, ciphering, random access, paging, and assignment messages are processedby the BTS Management (BTSM) entities in the BSC and in the BTS.

l Neither the BSC nor the BTS interprets Connection Management (CM) messages andMobility Management (MM) messages. These messages are transmitted on the A interfaceby the Direct Transfer Application Part (DTAP). On the Abis interface, DTAP messagesare transmitted as transparent messages.

1.2.2 Abis Interface StructureThe Abis interface supports three types of internal BTS configurations.

Figure 1-4 shows the Abis interface structure. The three types BTS configurations on the Abisinterface are as follows:l A single TRX

l Multiple TRXs connected with the BSC through one physical link

l Multiple TRXs connected with the BSC through different physical links




Figure 1-4 Abis interface structure

Abis

BTS3

BTS2

BTS1

A

Abis

MSC BSC

TRX

BCF

TRX

BCF

Abis

BSS

TRX

TRX

TRX

TRX

TRX

TRX

BCF

l Transceiver (TRX) is a functional entity defined in the Public Land Mobile Network(PLMN). It supports eight physical channels of one TDMA frame.

l The Base Control Function (BCF) is a functional entity that performs common controlfunctions including BTS initialization, software loading, channel configuration, andoperation and maintenance.

The following two types of channels are on the Abis interface:l Traffic channels of 8 kbit/s, 16 kbit/s, and 64 kbit/s, which carry speech or data from radio

channelsl Signaling channels of 16 kbit/s, 32 kbit/s, and 64 kbit/s, which carry signaling between the

BSC and an MS, and between the BSC and the BTS

A TEI is assigned to obtain the unique address of a TRX. Each BCF has a unique TEI. Threedifferent logical links are defined with a TEI, as shown in Figure 1-5.l RSL: used to support traffic management procedures, one for each TRX

l OML: used to support network management procedures, one for each BCF

l L2ML: used to transmit L2 management messages



Figure 1-5 Logical links on the Abis interface

BSC BTS

LAYER 2

TEI

MANAGEMENT

RSL SAP1=0

OML SAP1=62

L2ML SAP1=63TEI1

TRX

BCF

RSL SAP1=0

OML SAP1=62

L2ML SAP1=63

RSL SAP1=0

OML SAP1=62

L2ML SAP1=63

TRX

BCF

TEI2

TRX

BCF

TEI3

OML SAP1=62L2ML SAP1=63 BCF TEI4

BCF

1.2.3 Physical Layer on the Abis InterfaceThe physical layer on the Abis interface are 2 Mbit/s PCM links. It provides thirty-two 64 kbit/s channels.

The electrical parameters of the physical layer conform to the ITU-T G.703 recommendations.

The BSS is the connection point between radio channels and terrestrial channels. The codingschemes and rates of the two types of channels are different. The coding rate of the radio channelsin the BSS is 16 kbit/s, and the rate of the channels on the Abis interface is 64 kbit/s. To savethe transmission cost, different multiplexing modes, for example, 10:1, 12:1, and 15:1, are usedon the Abis interface.

1.2.4 LAPD Layer on the Abis InterfaceThis topic describes the functions of the LAPD layer on the Abis interface.

Overview

The data link layer (L2) on the Abis interface uses the LAPD protocol. It receives data from thephysical layer (L1) and provides connection-oriented or connectionless services for L3. TheService Access Point (SAP) of L2 is the connection point for providing services for L3. It isidentified by an SAPI. A data link connection endpoint is identified by a data link connectionendpoint identifier or a data link connection identifier (DLCI) from the perspective of L2 or L2,respectively.




For the information exchange between two or more L3 entities, data links must be establishedbetween L3 entities.

The co-operation between L2 entities is controlled by the protocol of the peer layer. The messageunits at L2 are transmitted between L2 entities through L1. Inter-layer service requests areprocessed through service primitives.

Functions

The LAPD reliably transfers end-to-end information between L3 entities through the D channel.Specifically, the LAPD supports:l Multiple terminal devices between MSs and physical interfaces

l Multiple L3 entities

The functions of the LAPD layer on the Abis interface are as follows:l Providing one or multiple data links on the D channel

l Delimiting, locating, and transparently transmitting frames so that a string of bitstransmitted in the form of frames on the D channel can be identified

l Controlling and keeping the sequence of frames

l Checking for transmission errors, format errors, and operation errors on data linkconnections

l Making recoveries based on the detected transmission errors, format errors, and operationerrors

l Notifying the management layer entities of unrecoverable errors

l Performing flow control

The LAPD layer on the Abis interface provides the means for information transfer betweenmultiple combinations of data link connection points. The information may be transferredthrough point-to-point data link connections or broadcast data link connections.

1.2.5 L3 Traffic Management Messages on the Abis InterfaceL3 traffic management messages on the Abis interface enables the MS to exchange informationwith the BSS or NSS on the Um interface and to perform some radio resource managementfunctions under the control of the BSC.

In terms of processing, traffic management messages are classified into transparent and non-transparent messages. l The transparent messages refer to the messages directly forwarded without interpretation

or processing by the BTS.l The non-transparent messages refer to the messages that are transmitted between the BSC

and the BTS and that must be processed and structured by the BTS.In terms of functions, traffic management messages are classified into the following:l Radio link layer management messages that are used to manage the data link layer on radio

channelsl Dedicated channel management messages that used to manage dedicated channels such as

the SDCCH and TCHl Common control channel management messages that are used to manage common control

channels



l TRX management messages that are used to manage TRXs

NOTE

The transparency and group of traffic management messages are determined by the message discriminatorat the header of the messages.

l Radio link management procedures

Radio link management procedures consist of the following:

– Link establishment indication procedure: used by the BTS to indicate to the BSC thatan MS-originated multi-frame-mode link establishment is successful. Upon receivingthe indication from the BTS, the BSC establishes an SCCP link to the MSC.

– Link establishment request procedure: used by the BSC to request the establishment ofa multi-frame link on a radio channel.

– Link release indication procedure: used by the BTS to indicate to the BSC that an MS-initiated radio link release is complete.

– Link release request procedure: used by the BSC to request the release of a radio link.

– Transmission of transparent L3 messages on the Um interface in acknowledged mode:used by the BSC to request the transmission of transparent L3 messages to an MS onthe Um interface in acknowledged mode

– Reception of transparent L3 messages on the Um interface in acknowledged mode: usedby the BTS to notify the BSC that transparent L3 messages are received on the Uminterface in acknowledged mode

– Transmission of transparent RIL3 messages on the Um interface in unacknowledgedmode: used by the BSC to request the transmission of transparent L3 messages to anMS on the Um interface in unacknowledged mode

– Reception of transparent RIL3 messages on the Um interface in unacknowledged mode:used by the BTS to notify the BSC that transparent L3 messages are received on theUm interface in unacknowledged mode

– Link error indication procedure: used by the BTS to notify the BSC in case of errors atthe radio link layer

l Dedicated channel management procedures

The dedicated channel management procedures consist of the following:

– Channel activation procedure: used by the BSC to request the BTS to activate adedicated channel for an MS. Then the BSC assigns the activated channel to the MSthrough an Immediate Assignment, Assignment Command, Additional Assignment, orHandover Command message.

– Channel mode modification procedure: used by the BSC to request the BTS to changethe mode of an activated channel.

– Handover detection procedure: used between the target BTS and the target BSC to detectthe access of an MS being handed over.

– Ciphering mode command procedure: used to start the ciphering procedure defined inGSM Rec. 04.08.

– Measurement report procedure: consists of the mandatory basic measurement reportprocedure and optional measurement report preprocessing procedure. The BTS reportsall the parameters related to handover decisions to the BSC through this procedure.

– SACCH deactivation procedure: used by the BSC to deactivate the SACCH related toa TRX according to the Channel Release procedure defined in GSM Rec. 04.08.




– Radio channel release procedure: used by the BSC to release a radio channel that is nolonger needed.

– MS power control procedure: used by the BSS to control the transmit power of an MSfor which a channel is already activated. The power control decision must be performedin the BSC. It can also be performed in the BTS.

– BTS transmit power control procedure: used by the BSS to control the transmit powerof a TRX with an activated channel. The BTS transmit power control decision must beperformed in the BSC. It can also be performed in the BTS.

– Connection failure procedure: used by the BTS to notify the BSC that an activateddedicated channel is unavailable.

– Physical context request procedure: used by the BSC to obtain the information aboutthe physical context of a radio channel prior to a channel change. It is an optionalprocedure.

– SACCH information modification procedure: used by the BSC to request the BTS tochange the filling system information on a specific SACCH.

l Common channel management proceduresThe common channel management procedures consist of the following:– MS-initiated channel request procedure: triggered when a TRX detects a Channel

Request message from an MS– Paging procedure: used to page an MS on a specific paging sub-channel This procedure

is used in an MS terminating call establishment procedure. It is initiated by the MSCthrough the BSC. Based on the IMSI of the called MS, the BSC determines the paginggroup to be used. Then it sends to the BTS the paging group number together with theidentity of the MS.

– Immediate assignment procedure: used by the BSC to immediately assign a dedicatedchannel to an MS when the MS accesses the BTS.

– Delete indication procedure: used by the BTS to notify the BSC that an ImmediateAssign Command message is deleted due to AGCH overload.

– CCCH load indication procedure: used by the BTS to notify the BSC of the load on aspecified CCCH if the load exceeds the preset threshold on the OMC. The indicationperiod is also set on the OMC.

– Broadcast information modification procedure: used by the BSC to notify the BTS ofthe new system information to be broadcast on the BCCH.

– Short message service cell broadcast procedure: used by the BSC to request shortmessage service cell broadcast messages from the BTS.

l TRX management proceduresThe TRX management procedures consist of the following:– SACCH filling information modify procedure: used by the BSC to notify the BTS of

the new system information to be used as filling information on all downlink SACCHs– Radio resource indication procedure: used by the BTS to notify the BSC of the

interference levels on the idle channels of a TRX– Flow control procedure: used by the Frame Unit Controller (FUC) in a TRX to notify

the BSC of the TRX overload due to CCCH overload, AGCH overload, or TRXprocessor overload

– Error reporting procedure: used by the BTS to notify the BSC of the detected downlinkmessage errors, which cannot be reported through any other procedure



1.2.6 L3 OM Messages on the Abis InterfaceThis topic describes the L3 OM messages on the Abis interface.

OM Information ModelThe OM information model consists of the following:

l Management objects

The management objects are site, cell, carrier (TRX), and channel. Figure 1-6 shows themanagement objects.

Figure 1-6 Management objects

SITE

CELL 0 CELL 1 CELL n

TRX0 TRX1 TRXm

BTS TRX

Channel 0

Channel 1

Chanel7

…

…

…

l Addressing of management objects

Network management messages are addressed through the classes and instances of themanagement objects. Each object instance in the BTS has a complete L2 connectiondescription. The first established connection is assigned a semi-permanent or permanentdefault TEI. The subsequent connections are assigned the TEIs provided during theestablishment of TEI procedures. Object instances can also use L3 addresses. The mixeduse of L2 addressing and L3 addressing enables one site to have one or multiple physicallinks.

l Management object state

A management object can be in three states, the administrative state, operational state, andavailability state. For details, see Table 1-2, Table 1-3, and Table 1-4. The available statefurther describes the operational state, and only the BSC controls the administrative state.

Table 1-2 Administrative State

Status Description

Locked The BSC has disconnected all the calls passing thismanagement object, and no new services can beconnected to this object.




Status Description

Shut Down No new services can be connected to this managementobject, and ongoing calls are maintained.

Unlocked New services can be connected to this managementobject.

Table 1-3 Operational State

Status Description

Disabled Resources are totally inoperable and can no longerprovide services for MSs.

Enabled Resources are partially or fully operable.

Table 1-4 Available State

Status Description

In Test The resource is undergoing a test procedure. Theoperational state is disabled.

Failed The resource has an internal fault that prevents it fromoperating. The operational state is disabled.

Power Off The resource requires power and is not powered on. Theoperational state is disabled.

Off Line The resource requires automatic or manual operations tomake it available for use. The operational state isdisabled.

Dependency The resource cannot operate because some otherresources on which it depends are unavailable. Theoperational state is disabled.

Degraded The service is degraded due to some reasons such asspeed or capacity. The operational state is enabled.

Not Installed The hardware or software of the management object isnot installed. The operational state is disabled.

Basic ProceduresAll procedures are based on formatted OM messages. Most formatted OM messages initiatedby the BSC or the BTS require the peer L3 to respond with formatted OM messages. This pairof formatted OM messages or a formatted OM message that does not require a response is calleda basic procedure.



All formatted OM messages are sent on L2 in the form of I frames. A group of messages, alsocalled structured procedures, are based on the combination of some basic procedures.

For a specific object instance, if a certain basic procedure is not complete, the system does notstart the subsequent basic procedures. When there is no response to a formatted OM messagefrom the peer L3 upon L3 timer expiry, the basic procedure is considered as not "completed."When there is no response (ACK or NACK) in the previous basic procedure upon L3 timeout,no subsequent basic procedure is sent to this object instance. The default value for L3 timeoutis 10 seconds. If part of an original message is not understood or supported, the entire messageis discarded. An ACK message from an object instance indicates an affirm response. It is usedto notify the sender that the command is executed or will be executed. An NACK message froman object instance indicates a disaffirm response. It is used to notify the sender of the unsuccessfulexecution of the command and of the failure cause.

The basic procedures are classified into the following:

l Software loading management procedure

l Abis interface management procedure

l Transmission management procedure

l Abis interface management procedure

l Test management procedure

l State management and event report procedure

l Equipment state management procedure

l Other procedures

1.3 Um InterfaceThe Um interface lies between an MS and the BTS. It is used for the interworking between theMS and the fixed part of the GSM system. The links on the Um interface are radio links. TheUm interface transmits the information about radio resource management, mobilitymanagement, and connection management.

1.3.1 Physical Layer on the Um InterfaceThe physical layer (L1) is the bottom layer on the Um interface. It defines the radio accesscapabilities of the GSM and provides basic radio channels for information transfer at higherlayers.

1.3.2 LAPD Layer on the Um InterfaceThe data link layer (L2) is the middle layer on the Um interface. It uses the LAPDm protocol.It defines various data transmission structures for controlling data transmission.

1.3.3 L3 Entity on the Um InterfaceThe L3 entity consists of many functional program blocks. These program blocks transfermessage units between all L3 entities and between L3 and its adjacent layers.

1.3.1 Physical Layer on the Um InterfaceThe physical layer (L1) is the bottom layer on the Um interface. It defines the radio accesscapabilities of the GSM and provides basic radio channels for information transfer at higherlayers.




L1 is the bottom layer on the Um interface. It provides physical links for transmitting bit streams.It also provides higher layers with various logical channels, including traffic channels andsignaling channels. Each logical channel has its own logical access point.

Figure 1-7 shows the interfaces between L1 and the data link layer, the radio resourcemanagement sublayer (RR) of L3, and other functional units.

Figure 1-7 Interfaces of L1 on the Um interface

Radio resourcemanagement (3)

Data link layer

MPH primitive PH primitive

Physical layer

TCH

Other functional units

L1 provides the following services:l Access capability

L1 provides a series of limited logical channels for transmission service. Logical channelsare multiplexed on physical channels. Each TRX has eight physical channels. Through dataconfiguration, logical channels are mapped to physical channels.

l Bit error detectionL1 provides error protection transmission, including error detection and correction.

l CypheringBased on a selected ciphering algorithm, the BSS ciphers the bit sequence.

1.3.2 LAPD Layer on the Um InterfaceThe data link layer (L2) is the middle layer on the Um interface. It uses the LAPDm protocol.It defines various data transmission structures for controlling data transmission.

L2 provides reliable dedicated data links between an MS and the BTS. It uses the LAPDmprotocol that evolves from the LAPD protocol. The SAP of L2 is the connection point forproviding services for L3. An SAP is identified by an SAPI. Each SAP is associated with oneor multiple DLCEPs. Currently, two SAPI values, 0 (main signaling) and 3 (short messages),are defined in the LAPDm protocol.

FunctionsLAPDm transfers information between L3 entities through the Dm channel on the Um interface.LAPDm supports multiple L3 entities, L1 entities, and signaling on BCCH, PCH, AGCH, andDCCH.

NOTE

The Dm channel is a generic term for all the signaling channels on the Um interface in the GSM system.For example, the Dm channel can be PCH or BCCH.

LAPDm performs the following functions:l Providing one or more data link connections (DLCs) on the Dm channel. Each DLC is

identified by a data link connection identifier (DLCI).



l Allowing frame type identification

l Allowing L3 message units to be transparently transmitted between L3 entities

l Performing sequence control to maintain the order of the frames transmitted through a DLC

l Detecting format errors and operation errors on data links

l Performing flow control

l Establishing a contention resolution on a data link after an access request is detected on theRACH

Operation TypeL2 transmits L3 information in unacknowledged and acknowledged modes. One Dm channelcan be in both modes at the same time.

l Unacknowledged mode

In unacknowledged mode, L3 information is transferred in Unnumbered Information (UI)frames. L2 does not acknowledge the UI frames or perform flow control or error correction.The unacknowledged mode is applicable to different types of control channels except theRACH.

l Acknowledged mode

In acknowledged mode, L3 information is transferred in numbered Information (I) frames.L2 acknowledges the I frames. It performs error correction by resending unacknowledgedframes. When L2 fails to correct errors, it informs the specific L3 entity of the correctionfailure. Flow control procedures are also defined. The acknowledged mode is applicableto the DCCH.

Information Transfer ModeInformation is transferred in different modes on different channels.

l Information transfer on the BCCH: The BCCH transfers the broadcast messages from theBTS to the MS. Only the acknowledged mode can be used on the BCCH.

l Information transfer on the PCH+AGCH: These channels transfer messages from the BTSto the MS. Only the unacknowledged mode is applicable to the PCH+AGCH.

l Information transfer on the DCCH: Either the acknowledged or the unacknowledged modecan be used. The transfer mode is determined by L3.

Data Link ReleaseL2 release is initiated by L3. The data links in frame mode are released in the following modes:

l Normal release

The BTS and the MS exchange DISC frames and UA frames or DM frames.

l Local release

No frames are exchanged. Generally used in abnormal cases.

1.3.3 L3 Entity on the Um InterfaceThe L3 entity consists of many functional program blocks. These program blocks transfermessage units between all L3 entities and between L3 and its adjacent layers.




OverviewThe L3 entity consists of many functional program blocks. These program blocks transfermessage units between all L3 entities and between L3 and its adjacent layers.

L3 performs the following functions:l Establishing, operating, and releasing dedicated radio channels (RR)

l Performing location update, authentication, and TMSI reallocation (MM)

l Establishing, maintaining, and terminating circuit-switched calls (CC)

l Supporting supplementary services (SS)

l Supporting short messages service (SMS)

L3 uses L3 signaling protocols between the MS and the network. Here the functions of differententities in the BSS are not taken into consideration. L3 and its supported lower layers, therefore,provide the Mobile Network Signaling (MNS) service to the upper layers.

The service interfaces between L3 and higher layers and the interactions between the adjacentsublayers in L3 are described in primitives and parameters. The three sublayers in L3 performinformation exchange between peer entities.

Structure and FunctionsL3 consists of three sublayers. The CM sub-layer (the highest sub-layer) consists of threefunctional entities: Call Control (CC), Short Message Service (SMS), and SupplementaryService (SS). In total, L3 on the Um interface has five functional entities. The five functionalentities perform the following functions:l Radio Resource Management (RR)

Establishing, maintaining, and releasing physical channels and logical channels, as well asperforming cross-cell connection upon the request from the CM sublayer

l Mobility Management (MM)Performing MS-specific functions and notifying the network when an MS is activated anddeactivated, or when the location area of an MS changes. It is also responsible for thesecurity of activated radio channels.

l Call Control (CC)Performing all necessary functions to establish or release CS connections

l Supplementary Service (SS)Performing all necessary functions to support GSM supplementary services

l Short Messages Service (SMS)Performing all necessary functions to support point-to-point GSM short message services

In addition to the previous functions, L3 performs functions related to the transmission ofmessages, for example, multiplexing and splitting. These functions are defined in the RadioResource Management and Mobility Management. They route messages according to theprotocol discriminator (PD) and transaction identifier (TI), which are part of the message header.

The routing function of the MM enables the MM to route the messages of the CM entities andthe messages of the MM entity to the RR service access point (RR-SAP), and multiplexes themessages in case of concurrent transactions. The routing function of the RR distributes the to-be-sent messages according to their PD and the actual channel configuration.

The messages provided at different service access points of layer 2 are split by the RR routingfunction according to the PD. If a message belongs to the RR sublayer, this message is transmitted



to the RR entity based on the TI. The other messages are sent to the MM sublayer through theRR-SAP. If a message belongs to the MM sublayer, the message is transmitted to the MM entitybased on the TI. The other messages are sent to the CM sublayer through the MM-SAPs, andthen to the CM entities.

Figure 1-8 shows the L3 signaling protocol model on the Um interface.

Figure 1-8 L3 signaling message processing procedure

CC

MNCC-SAP

SS

MNSS-SAP

SMS

MNSMS-SAP

Mobilenetworkservices

MMREG -SAPMMCC-SAP

MMSS-SAP

MMSMS-SAP

MM CC SS SMSMM

RR-SAP

RR

RRPD

RR

SAPI 0 SAPI 3

RA

CC

H

SD

CC

HS

AC

CH

FAC

CH

BC

CH

SD

CC

HS

AC

CH

AG

CH

+PC

H

Laye

r 3si

gnal

ing

The RR sublayer at the bottom receives the services from L2 through various service accesspoints (that is, various types of channels) of L2, and provides services to the MM sublayerthrough RR-SAP. The MM sublayer provides services to different entities through differentSAPs: to the CC through MMCC-SAP, to the SS through MMSS-SAP, to the SMS throughMMSMS-SAP, and to the high layer through MMREG-SAP. The three independent entities(CC, SS, and SMS) of the CM sublayer provide services to higher layers through MNCC-SAP,MNSS-SAP, and MNSMS-SAP respectively.

Service FeatureL3 on the MS side provides the following services:

l Registration services, that is, IMSI attach and detach




l Call control services, including normal establishment of MS originating calls, emergencyestablishment of MS originating calls, call hold, call termination, and support for call-related supplementary services

l Support for call independent supplementary services

l Support for short messages service

L3 on the network side provides the following services:

l Call control services, including call establishment, call hold, call termination, and supportfor call-related supplementary services

l Support for call independent supplementary services

l Support for short messages service

L3 provides the following services between the MS and the network:

l For the services provided by the RR, see Figure 1-9. These services are provided to theMM through RR-SAP. They are used to set up control channel connections and trafficchannel connection, indicate ciphering mode, release control channel connections, andtransmit control data.

l For the services provided by the MM, see Figure 1-10. These services are used to managethe three entities (CC, SS, and SMS) of the CM sublayer.

Figure 1-9 Services provided by the RR sublayer

MS side Network sideMobile

managementsublayer

Radio resourcemanagement sublayer

RR-primitive

Protocol of the peer layer ofthe RR sublayer

SAPRR

Figure 1-10 Services provided by the MM sublayer

CC SMSSS

MS side

Mobilemanagement

sublayer

CC SMSSS

Network side

Mobilemanagement

sublayer

Protocol of the peer layerof the MM sublayer



2 BSS Signaling Tracing

About This Chapter

This describes the BSS signaling tracing, which consists of the signaling tracing on the Uminterface, Abis interface, A interface, Pb interface, and BSC-CBC interface, and single usersignaling tracing.

2.1 Tracing the Messages on the Um InterfaceThis describes how to trace all the layer 3 signaling messages on the Um interface through theLMT.

2.2 Tracing Messages on the Abis InterfaceThis topic describes how to trace the RSL, OML, ESL, LAPD messages on the Abis interface.

2.3 Tracing the Messages on the A InterfaceThis topic describes how to trace the BSSAP, MTP2, MTP3, and SCCP messages on the Ainterface.

2.4 Tracing Messages on the Pb InterfaceThis topic describes how to trace the application messages and LAPD messages on the Pbinterface.

2.5 Tracing the Messages on the BSC-CBC InterfaceThis describes how to trace signaling messages of the interfaces between the BSC and CBCthrough the LMT.

2.6 Tracing User MessagesThis describes how to trace signaling messages on the interfaces of the specified user throughthe LMT.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 2 BSS Signaling Tracing


2.1 Tracing the Messages on the Um InterfaceThis describes how to trace all the layer 3 signaling messages on the Um interface through theLMT.

Prerequisitel The LMT runs normally.

l The communication between the BSC and the BTS is normal.

ContextTracing the messages on the Um interface includes the following:l Tracing layer 3 messages on the Um interface

l Supporting filtering messages based on TRXs or a maximum of 16 cells

l The data of the BSSAP messages on the A interface can be browsed.

Procedure

Step 1 On the Trace & Monitor tab page, choose Trace > Trace the Message at Um Interface. Adialog box is displayed, as shown in Figure 2-1.

Figure 2-1 Tracing messages on the Um interface (set TRX as the filter condition)

Step 2 Set Filter Condition and Color.

NOTE

When the Filter Condition is set to TRX or Cell, the execution interfaces are different. In this topic, theinstance when the Filter Condition is set to TRX is illustrated.

Max Number: 16 indicates that the maximum number of cells that can be selected is 16.

2 BSS Signaling TracingHUAWEI BSC6000 Base Station Subsystem



Step 3 Set the Tracing Mode to start the tracing.

l If the Tracing Mode is set to Report, and click OK, the messages on the Um interface aretraced in the Report mode. The tracing result is shown in Figure 2-2.

l If the Tracing Mode is set to Save on Server, and click OK, the messages on the Uminterface are traced in the Save on Server mode. The LMT no longer displays the tracingmessages.

Figure 2-2 Results of tracing messages on the Um interface

----End

2.2 Tracing Messages on the Abis InterfaceThis topic describes how to trace the RSL, OML, ESL, LAPD messages on the Abis interface.

2.2.1 Tracing the RSL Messages on the Abis InterfaceThis describes how to trace all the signaling messages on the Abis interface through the LMT.

2.2.2 Tracing the OML Messages on the Abis InterfaceThis describes how to trace all the OML messages at Abis interface through the LMT.

2.2.3 Tracing the ESL Messages on the Abis InterfaceThis describes how to trace all the ESL messages at Abis interface through the LMT.

2.2.4 Tracing the LAPD Messages on the Abis InterfaceThis describes how to trace the LAPD messages on the Abis interface through the LMT.

2.2.1 Tracing the RSL Messages on the Abis InterfaceThis describes how to trace all the signaling messages on the Abis interface through the LMT.





ContextTracing the RSL messages on the Abis interface includes the following:l Tracing the RSL messages on the Abis interface based on TRXs or cells. Tracing messages

based on TRXs or cells (a maximum of 16 cells).l Tracing the RSL messages based on message types, such as measurement report, channel

request, paging, RLM, and TRXM.l The data of the BSSAP messages on the A interface can be browsed.

CAUTIONAfter the BTS connected to the Abis interface is moved manually, close the message traceof this type and restart the message trace function.

Procedure

Step 1 Click the Trace & Monitor tab. A dialog box is displayed, as shown in Figure 2-3.




Figure 2-3 Trace & Monitor tab page

Step 2 Choose Trace > Trace the Message at Abis Interface > RSL Message. A dialog box isdisplayed, as shown in Figure 2-4.



Figure 2-4 Trace the RSL Message at Abis Interface dialog box

Step 3 Set Message Type, Filtering Condition, Color, and Tracing Mode.

Step 4 Click OK.l In Figure 2-4, if the Tracing Mode is set to Save on Server, click OK, the RSL messages

on the Abis interface are traced in the Save on Server mode. The LMT no longer receivesthe tracing messages.

l In Figure 2-4, if the Tracing Mode is set to Report, click OK, the RSL messages are tracedin the Report mode. The tracing result is shown in Figure 2-5.




Figure 2-5 Tracing the RSL messages on the Abis interface

----End

2.2.2 Tracing the OML Messages on the Abis InterfaceThis describes how to trace all the OML messages at Abis interface through the LMT.



ContextTracing the OML messages on the Abis interface includes the following:l Tracing the OML messages at Abis interface based on sites (a maximum of 16 sites)

l Tracing the OML messages at Abis interface based on message types, such as publicmessages and OM messages.


Procedure





Step 2 Choose Trace > Trace the Message at Abis Interface > OML Message. A dialog box isdisplayed, as shown in Figure 2-7.

Figure 2-7 Trace the OML Message at Abis Interface dialog box




Step 3 Set Message Type, Color, and Tracing Mode. Select cells from the Candidate Cells box andadd them to the Selected Cells box.

Step 4 Click OK.l In Figure 2-7, if the Tracing Mode is set to Save on Server, click OK, the OML messages


l In Figure 2-7, if the Tracing Mode is set to Report, click OK, the OML messages are tracedin the Report mode. The tracing result is shown in Figure 2-8.

Figure 2-8 Tracing the OML messages on the Abis interface

----End

2.2.3 Tracing the ESL Messages on the Abis InterfaceThis describes how to trace all the ESL messages at Abis interface through the LMT.



ContextTracing the ESL messages on the Abis interface includes the following:l Tracing the ESL messages on the Abis interface based on sites (a maximum of 16 sites)

l Tracing the ESL messages on the Abis interface based on message types, such as publicmessages and OM messages.



Procedure



Step 2 Choose Trace > Trace the Message at Abis Interface > ESL Message. A dialog box isdisplayed, as shown in Figure 2-10.




Figure 2-10 Trace the ESL Message at Abis Interface dialog box

Step 3 Set Message Type, Color, and Tracing Mode. Select cells from the Candidate Cells box andadd them to the Selected Cells box.

Step 4 Click OK.l In Figure 2-10, if the Tracing Mode is set to Save on Server, click OK, the OML messages


l In Figure 2-10, if the Tracing Mode is set to Report, click OK, the ESL messages are tracedin the Report mode. The tracing result is shown in Figure 2-11.

Figure 2-11 Tracing the ESL messages on the Abis interface

----End



2.2.4 Tracing the LAPD Messages on the Abis InterfaceThis describes how to trace the LAPD messages on the Abis interface through the LMT.



ContextTracing the LAPD messages on the Abis interface includes the following:l Tracing the LAPD messages on the Abis interface; supporting tracing TRXs and BTSs

l Tracing link messages based on the link number of the TRX

l Tracing link messages based on the link number of the BTS


Procedure






Step 2 Choose Trace > Trace the Message at Abis Interface > LAPD Message. A dialog box isdisplayed, as shown in Figure 2-13.



Figure 2-13 Trace the LAPD Message at Abis Interface dialog box

Step 3 Set the parameters in the Link Type, Location, Color, and Tracing Mode areas.

Step 4 Click OK.l In Figure 2-13, if the Tracing Mode is set to Save on Server, click OK, the LAPD messages


l In Figure 2-13, if the Tracing Mode is set to Report, click OK, the LAPD messages aretraced in the Report mode. The tracing result is shown in Figure 2-14.




Figure 2-14 Tracing the LAPD messages on the Abis interface

----End

2.3 Tracing the Messages on the A InterfaceThis topic describes how to trace the BSSAP, MTP2, MTP3, and SCCP messages on the Ainterface.

2.3.1 Tracing the BSSAP Messages on the A InterfaceThis describes how to trace all the layer signaling messages on the A interface, such asconnection-oriented messages and non-connection-oriented messages.

2.3.2 Tracing the MTP2 Messages on the InterfaceThis describes how to trace all the layer 2 messages on the A interface, except the FISU message.

2.3.3 Tracing the MTP3 Messages on the A InterfaceThis describes how to trace all the layer 3 messages at A interface.

2.3.4 Tracing the SCCP Messages on the A InterfaceThis describes how to trace the SCCP messages on the A interface based on the DPC, the SCCPuser message, and the MTP3 primal message.

2.3.1 Tracing the BSSAP Messages on the A InterfaceThis describes how to trace all the layer signaling messages on the A interface, such asconnection-oriented messages and non-connection-oriented messages.




l The communication between the BSC and the MSC is normal.

ContextTracing the BSSAP messages on the A interface includes the following:l Tracing the BSSAP messages traces all the layer 3 signaling messages on the A interface,

such as connection-oriented messages and non-connection-oriented messages.l For connection-oriented messages, the BSSAP messages on the A interface are traced based

on cells. The maximum number of cells for this purpose is 16.l For non-connection-oriented messages, the BSSAP messages on the A interface are traced

based on the message type, including DTAP, BSSMAP, and Paging messages.l The data of the BSSAP messages on the A interface can be browsed.

Procedure






Step 2 Choose Trace > Trace the Message at A Interface > BSSAP Message. A dialog box isdisplayed, as shown in Figure 2-16.

Figure 2-16 Trace the BSSAP Message at A Interface dialog box

Step 3 Set Message Type, Color, Tracing Mode, and Site. Select cells from the Candidate Cells boxand add them to the Selected Cells box.

Step 4 Click OK.l In Figure 2-16, if the Tracing Mode is set to Save on Server, click OK, the BSSAP

messages are traced in the Save on Server mode. The LMT no longer receives the tracingmessages.

l In Figure 2-16, if the Tracing Mode is set to Report, click OK, the BSSAP messages aretraced in the Report mode. The tracing result is shown in Figure 2-17.



Figure 2-17 Tracing the BSSAP messages at A interface

----End

PostrequisiteIn Figure 2-17, right-click the message to be analyzed. A shortcut menu is displayed, as shownin Figure 2-18.

Figure 2-18 Trace the BSSAP Message at A Interface (1)




NOTE

As shown in Figure 2-17, the shortcut menu provides the following options:

l To clear the displayed messages at A interface, choose Clear Message.

l To stop scrolling the displayed messages at A interface, choose Stop Scroll.

l To stop the current tracing task, choose Stop Trace.

l To restart the tracing, choose Restart Trace.

l To view the established tracing task, choose View Task.

l To search for the specified character string, choose Search.

l To save the selected messages at A interface, choose Save Selection.

l To save all the traced messages at A interface, choose Save All.

2.3.2 Tracing the MTP2 Messages on the InterfaceThis describes how to trace all the layer 2 messages on the A interface, except the FISU message.



ContextTracing the MTP2 messages on the A interface includes the following:l Tracing the layer 2 messages on the A interface, not including the FISU message

l Tracing the MTP2 messages based on the specified subrack, slot, and link number.

l Filtering MTP2 messages based on message types, such as the LSSU message and MSUmessage.


Procedure





Step 2 Choose Trace > Trace the Message at A Interface > MTP2 Message. A dialog box isdisplayed, as shown in Figure 2-20.




Figure 2-20 Trace the MTP2 Message at A Interface dialog box

Step 3 Set Message Type, Location, Tracing Mode, and Color.

Step 4 Click OK.l In Figure 2-20, if the Tracing Mode is set to Save on Server, click OK, the MTP2 messages

are traced in the Save on Server mode. The LMT no longer receives the tracing messages.l In Figure 2-20, if the Tracing Mode is set to Report, click OK, the MTP2 messages are

traced in the Report mode. The tracing result is shown in Figure 2-21.



Figure 2-21 Tracing the MTP2 messages on the A interface

----End

2.3.3 Tracing the MTP3 Messages on the A InterfaceThis describes how to trace all the layer 3 messages at A interface.


l The communication between the LMT and the BSC is normal.

l The MTP3 links are configured.

ContextTracing the MTP3 messages on the A interface includes the following:l Tracing the MP3 messages based on the link number, link set, and DSP.

l Tracing the MP3 messages based on the message types, such as the SNM, SLT, MT, andL2_CHANGE.

Procedure






Step 2 Choose Trace > Trace the Message at A Interface > MTP3 Message. A dialog box isdisplayed, as shown in Figure 2-23.



Figure 2-23 Tracing the MTP3 Messages at A Interface

Step 3 Set Message Type, Tracing Type, Location, Message Filter, Tracing Mode, and Color.

Step 4 Click OK.l In Figure 2-23, if the Tracing Mode is set to Save on Server, click OK, the MTP3 messages

are traced in the Save on Server mode. The LMT no longer receives the tracing messages.l In Figure 2-23, if the Tracing Mode is set to Report, click OK, the MTP3 messages are





Figure 2-24 Tracing the MTP3 messages at A interface

----End

2.3.4 Tracing the SCCP Messages on the A InterfaceThis describes how to trace the SCCP messages on the A interface based on the DPC, the SCCPuser message, and the MTP3 primal message.


l The communication between the LMT and the BSC is normal.

l The SCCP link is configured.

Procedure





Step 2 Choose Trace > Trace the Message at A Interface > SCCP Message. A dialog box isdisplayed, as shown in Figure 2-26.




Figure 2-26 Tracing the SCCP Messages on the A Interface

Step 3 Set the parameters in the Tracing Type, Location, Tracing Mode, and Color areas.

Step 4 Click OK.l In Figure 2-26, if the Tracing Mode is set to Save on Server, click OK, the SCCP messages

are traced in the Save on Server mode. The LMT no longer receives the tracing messages.l In Figure 2-26, if the Tracing Mode is set to Report, click OK, the SCCP messages are




Figure 2-27 Tracing the SCCP messages on the A interface

----End

2.4 Tracing Messages on the Pb InterfaceThis topic describes how to trace the application messages and LAPD messages on the Pbinterface.

2.4.1 Tracing the Application Messages on the Pb InterfaceThis describes how to trace the application messages on the the Pb interface through the LMT.

2.4.2 Tracing the LAPD Messages on the Pb InterfaceThis describes how to trace the layer 2 messages on the Pb interface through the LMT. You cantrace the LAPD messages on the Pb interface based on the specified link.

2.4.1 Tracing the Application Messages on the Pb InterfaceThis describes how to trace the application messages on the the Pb interface through the LMT.



ContextTracing the application messages on the Pb interface includes the following:




l Tracing application messages on the Pb interface

l Tracing application messages on the Pb interface for the specified PCU.

l Tracing application messages on the Pb interface based on cells (a maximum of 16 cells).

l Tracing PAGING messages, CONFUSION messages, PCIC messages, and other messages


Procedure



Step 2 Choose Trace > Trace the Message at Pb Interface > Application Message. A dialog box isdisplayed, as shown in Figure 2-29.



Figure 2-29 Trace the Application Message at Pb Interface dialog box

Step 3 Set Message Type, Location, Color, and Tracing Mode. Select cells from the Candidate Cellsbox and add them to the Selected Cells box.

Step 4 Click OK.l In Figure 2-29, if the Tracing Mode is set to Report, click OK, the application messages

are traced in the Report mode.l In Figure 2-29, if the Tracing Mode is set to Save on Server, click OK, the application

messages on the Pb interface are traced in the Save on Server mode. The LMT no longerreceives the tracing messages.

----End

2.4.2 Tracing the LAPD Messages on the Pb InterfaceThis describes how to trace the layer 2 messages on the Pb interface through the LMT. You cantrace the LAPD messages on the Pb interface based on the specified link.



ContextTracing the LAPD messages on the Pb interface includes the following:l Tracing layer 2 messages on the Pb interface


Procedure






Step 2 Choose Trace > Trace the Message at Pb Interface > LAPD Message. A dialog box isdisplayed, as shown in Figure 2-31.



Figure 2-31 Trace the LAPD Message at Pb Interface dialog box

Step 3 Set the parameters in the Message Type, Color, and Tracing Mode areas.

Step 4 Click OK.l In Figure 2-31, if the Tracing Mode is set to Report, click OK, the application messages

are traced in the Report mode.l In Figure 2-31, if the Tracing Mode is set to Save on Server, click OK, the LAPD messages

on the Pb interface are traced in the Save on Server mode. The LMT no longer receives thetracing messages.

----End

2.5 Tracing the Messages on the BSC-CBC InterfaceThis describes how to trace signaling messages of the interfaces between the BSC and CBCthrough the LMT.






ContextTracing the messages on the BSC-CBC interface includes the following:

l Tracing signaling messages of the interfaces between the BSC and CBC through the LMT.


Procedure

Step 1 On the Trace & Monitor tab page, choose Trace > Trace the Message at BSC-CBCInterface. A dialog box is displayed, as shown in Figure 2-32.

Figure 2-32 Trace the Message at BSC-CBC Interface dialog box

Step 2 Set Tracing Mode and Color, and then click OK.

l If the Tracing Mode is set to Report, the BSC-CBC interface messages are traced in theReport mode.

l If the Tracing Mode is set to Save on GBAM. The BSC-CBC interface messages are tracedin the Save on Server mode. The LMT no longer displays the tracing messages.

----End

2.6 Tracing User MessagesThis describes how to trace signaling messages on the interfaces of the specified user throughthe LMT.





ContextTracing the user messages includes the following:l Tracing signaling messages on the A interface, Abis interface, Pb interface, Um interface,

and BSC-CBC interfacel Tracing messages on the specified interface

l Tracing the specified traced users through IMSI, IMEI, TMSI, MSISDN, or channel


Procedure

Step 1 On the Trace & Monitor tab page, choose Trace > Trace User Message. A dialog box isdisplayed, as shown in Figure 2-33.

Figure 2-33 Trace User Message dialog box

Step 2 Set Interface Type, and Color, type the IMSI, TMSI, MSISDN, IMEI, or channel of the userto be traced.

Step 3 Set the Tracing Mode to start the tracing.l If the Tracing Mode is set to Report, and click OK, the interface messages of the user are





Figure 2-34 Result of tracing user messages

l If the Tracing Mode is set to Save on Server, and click OK, the messages on the userinterface are traced in the Save on Server mode. The LMT no longer displays the tracingmessages.

----End



3 BSS System Information

About This Chapter

System information (SI) refers to the major radio network parameters on the Um interface suchas the network identification parameters, cell selection parameters, system control parameters,and network functional parameters.

3.1 BSS System Information TypeThe BSS system information consists of System Information Type 1 , System Information Type2, System Information Type 2bis, System Information Type 2ter, System Information Type2quater, System Information Type 3, System Information Type 4, System Information Type 5,System Information Type 5bis, System Information Type 5ter, System Information Type 6,System Information Type 7, System Information Type 8, and System Information Type 13.

3.2 Internal BSC Signaling Procedure of the System InformationThis describes the internal BSC signaling procedure of the system information.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 3 BSS System Information


3.1 BSS System Information TypeThe BSS system information consists of System Information Type 1 , System Information Type2, System Information Type 2bis, System Information Type 2ter, System Information Type2quater, System Information Type 3, System Information Type 4, System Information Type 5,System Information Type 5bis, System Information Type 5ter, System Information Type 6,System Information Type 7, System Information Type 8, and System Information Type 13.

3.1.1 System Information Type 1System Information Type 1 is sent on the BCCH by the network to all the MSs within the cell.It provides information about the Random Access Channel (RACH) control and the cellallocation (CA).

3.1.2 System Information Types 2, 2bis, 2ter, and 2quaterThis topic describes the functions and contents of System Information Types 2, 2bis, 2ter, and2quater.

3.1.3 System Information Type 3System Information Type 3 describes the location area identification, cell identity, RACHcontrol, and parameters of cell selection. It is mandatory and is sent on the BCCH.

3.1.4 System Information Type 4System Information Type 4 is sent on the BCCH by the network. It provides information aboutthe location area identification, RACH control, cell selection parameters, and available CBCHinformation.

3.1.5 System Information Types 5, 5bis, and 5terThis topic describes the functions and contents of System Information Types 5, 5bis, and 5ter.

3.1.6 System Information Type 6System Information Type 6 provides information about the location area identification, cellidentity, and other parameters of cell functions.

3.1.7 System Information Type 7System Information Type 7 is sent on the BCCH. It provides information about cell reselectionparameters.

3.1.8 System Information Type 8System Information Type 8 is mandatory and is sent on the BCCH. It provides information aboutcell reselection parameters.

3.1.9 System Information Type 13System Information Type 13 is sent on the BCCH by the network. It provides information relatedto GPRS in the cell.

3.1.1 System Information Type 1System Information Type 1 is sent on the BCCH by the network to all the MSs within the cell.It provides information about the Random Access Channel (RACH) control and the cellallocation (CA).

3 BSS System InformationHUAWEI BSC6000 Base Station Subsystem



Functions

System Information Type 1 is sent on the BCCH by the network to all the MSs within the cell.It provides information about the Random Access Channel (RACH) control and the cellallocation (CA).

Contents

SYS INFO 1l Cell Channel Desc.

l RACH Control Para.

l SI 1 Rest Octets.

l CA tableOne cell can be configured with a maximum of 64 frequencies. The actual configurationof cell frequencies is subject to the Table 3-1. The BSC selects a format of cell channeldescription based on the configuration of cell frequencies.The format of cell channel description is defined by octet 2, Format ID (Bit 128, Bit 127,Bit 124, Bit 123, and Bit 122) in the Table 3-2.

Table 3-1 Cell channel description

8 7 6 5 4 3 2 1

Cell Channel Description IEI octet 1

Bit Bit 0 0 Bit Bit Bit Bitoctet 2

128 127 Spare Spare 124 123 122 121

Bit Bit Bit Bit Bit Bit Bit Bitoctet 3

120 119 118 117 116 115 114 113

… … … … … … … … …

Bit Bit Bit Bit Bit Bit Bit Bitoctet 17

8 7 6 5 4 3 2 1

Table 3-2 Format of cell channel description

Bit 128 Bit 127 Bit 124 Bit 123 Bit 122 FormatNotation

0 0 X X X bit map 0

1 0 0 X X 1024 range

1 0 1 0 0 512 range

1 0 1 0 1 256 range



Bit 128 Bit 127 Bit 124 Bit 123 Bit 122 FormatNotation

1 0 1 1 0 128 range

1 0 1 1 1 variable bitmap

Different formats of cell channel description correspond to different numbers of availablecell frequencies. Assume that the number of available frequencies for a cell is n (except forduplicate and invalid frequencies). ARFCN(i) (i=1,…,n) represents the Absolute RadioFrequency Channel Number. The numbers of available frequencies for different formatsof cell channel description are as follows:– Bit map 0

The bit map 0 format is used for GSM 900 frequencies. The number of availablefrequencies is 64 if 1 ≤ARFCN(i) ≤ 124.

– 1024 rangeIf the 1024 range format is used, the number of available frequencies for a cell is equalto or smaller than 16. For a GSM 900 cell, 1 ≤ ARFCN (i) ≤ 124. For a GSM 1800cell, 512 ≤ ARFCN (i) ≤ 885.

– 512 rangeIf the 512 range format is used, the number of available frequencies for a cell is equalto or smaller than 18. The interval between any two frequencies must be less than 512.

– 256 rangeIf the 256 range format is used, the number of available frequencies for a cell is equalto or smaller than 22. The interval between any two frequencies must be less than 256.For example, in 128 range format, frequency 512 and frequency 812 cannot beconfigured together.

– 128 rangeIf the 128 range format is used, the number of available frequencies for a cell is equalto or smaller than 29. The interval between any two frequencies must be less than 128.For example, in 128 range format, frequency 512 and frequency 712 cannot beconfigured together.

– Variable bit mapIf the variable bit map format is used, the number of available frequencies for a cell isequal to or smaller than 64. The interval between any two frequencies must be 1–111.For example, in variable bit map format, you can configure 64 frequencies numberedfrom 512 to 575 with an increment of 1. However, you cannot configure 64 frequenciesnumbered from 512 to 638 with an increment of 2.NOTE

The early-mentioned restrictions are mainly for the GSM1800 frequencies.

l RACH Control Para.The RACH control parameters include the following:– MAX retrans

Maximum number of retransmissions (Max Retrans) defines the maximum number ofchannel request messages that can be resent before a MS receives an immediate




assignment message. Therefore, the number of channel request messages that an MScan send is M (Max Retrans) plus 1. The parameter has two bits, ranging from 0 to 3.The corresponding maximum numbers of retransmissions are 1, 2, 4, and 7.

– Tx_integerNumber of slots to spread transmission (Tx-integer) defines the number of timeslotsbetween two consecutive transmissions of channel request messages.

– CELL_BAR_ACCESSCell Bar Access (CBA) determines whether an MS can gain access to a cell. It has onlyone bit. Value 0 of this bit means that the MS can access the cell, and value 1 of this bitmeans the MS cannot access the cell. This parameter does not affect the handover accessof the MS.

– AC CNAccess Control Class N (AC CN) defines the access class for an MS. Each class isrepresented by a bit. N = 0, 1, … 9, 11, …, 15, totally 16 bits. If the AC CN bit is 1, theaccess of an MS with AC C = N is barred. Otherwise, the access of the MS with AC C= N is permitted. The MSs of classes 11–15 have a higher access priority than the MSsof classes 0–9. The MSs of classes 11-15 have the same priority. So do the MSs ofclasses 0–9.

– RECall reestablishment allowed (RE) determines whether call reestablishment is allowedwhen call drops occur. The parameter has one bit. Value 0 means that callreestablishment is allowed in the cell. Value 1 means that call reestablishment is notallowed in the cell.

– ECEmergency call allowed (EC) determines whether emergency calls are allowed whenthere is no SIM or the access is barred. The parameter has one bit. Value 0 means thatemergency calls are allowed in the cell to all MSs. Value 1 means that emergency callsare not allowed in the cell except for the MSs that belong to classes 11–15.

NOTE

A random value, which belongs to {S, S+1,....S+T-1}, is used as the time interval between twoconsecutive transmissions of channel request messages sent by an MS. The units of timeslotintervals are TDMA frames. "S" is subject to the configuration of common channels. "T" is Tx-integer.

Table 3-3 lists the relation between "S" and "T".

Table 3-3 Relation between "S" and "T"

Tx-Integer Non CombinedCCCH Combined CCCH

3, 8, 14, 50 55 41

4, 9, 16 76 52

5, 10, 20 109 58

6, 11, 25 163 86

7, 12, 32 217 115



NOTE

When satellite transmission is used, Huawei recommends that Max retrans is set to 4 and Tx-integer is set to 32 to reduce the delay caused by satellite transmission.

l SI 1 Rest OctetsThe SI 1 Rest Octets information element has eight bits. It contains indication informationabout the PCS 1900 and the DCS 1800 and spare bits.

3.1.2 System Information Types 2, 2bis, 2ter, and 2quaterThis topic describes the functions and contents of System Information Types 2, 2bis, 2ter, and2quater.

FunctionsSystem Information Type 2 is sent on the BCCH by the network to all MSs within the cell. Itprovides information about the RACH control, NCC Permitted, and the BCCH allocation (BA1)in the neighbor cells. Generally, System Information Types 2, 2bis, and 2ter describe differentparts of the BA1 list. The MS reads and decodes the BA1 list and then performs cell reselectionin idle mode. A GSM 900 MS in PHASE 1 recognizes only the neighbor cell frequenciesdescribed in System Information Type 2 and ignores the neighbor cell frequencies described inSystem Information Types 2bis and 2ter.

System Information Type 2bis is sent optionally on the BCCH by the network to all MSs withinthe cell. It provides information about the RACH control and the extension of the BCCHallocation in the neighbor cells (part of BA1). System Information Type 2 does not describe allthe frequencies in the BA1 list. Therefore, System Information Type 2bis describes the rest ofthe frequencies that are on the same frequency band.

System Information Type 2ter is sent optionally on the BCCH by the network to all MSs withinthe cell. It provides information about the extension of the BCCH allocation in the neighbor cells(part of BA1). It is read only by the dual-band MSs. The GSM 900 MSs and the GSM 1800 MSsignore this message because of band difference.

System Information Type 2quater provides information about the BCCH allocation in the 3Gneighbor cells under the condition that the inter-system handover is supported and the 3Gneighbor cells are configured. It is used for the reselection of 3G cells.

Contentsl SYS INFO 2

– Neighbor Cell Desc.

– NCC permitted

– RACH Control Para.

l SYS INFO 2 BIS– Neighbor Cell Desc.

– RACH Control Para.

l SYS INFO 2TER– Neighbor Cell Desc. (Extended)

l SYS INFO 2QUATER– SI 2quater Rest Octets.




l Neighbor Cell Description (BA1)The Neighbor Cell Description information element provides the absolute channel numbersof the BCCH carriers in the neighbor cells of the current cell. Currently, Huawei supportsa maximum of 32 neighbor cells per cell. Except for bit 5 (BA-IND) and bit 6 (EXT-IND)of octet 2, the Neighbor Cell Description information element is coded as the Cell ChannelDescription information element. For details, refer to the cell channel description in 3.1.1System Information Type 1 .The extension indication (EXT-IND) is sent in System Information Types 2 and 5. Itindicates whether there are extended neighbor cell frequencies sent in System InformationTypes 2bis and 5bis. If the EXT-IND bit is set to 0, System Information Types 2 and 5carry the complete BA. If the EXT-IND bit is set to 1, System Information Types 2 and 5carry only a part of the BA.The BA indication (BA-IND) is sent in System Information Types 2 and 5. It has one bitand is used by the MS to discriminate the changes in the BA1 or the BA2. If the adjacentcell relation and the BA2 are modified during the conversation, the BA-IND bit in SystemInformation Type 5 should be 1, indicating that the MS should decode the neighbor cellfrequencies again. The default of the BA-IND bit is 0.

l The NCC Permitted information element is sent in System Information Types 2 and 6. Ithas eight bits and provides all the NCCs required by MSs. If bit N is 0 (0 ≤ N ≤ 7), theMS does not measure the power level of the cell where the NCC is N, which means thatthe MS is not handed over to the network where the NCC is N. The NCC Permittedinformation element is mainly used for handovers and cell reselection.

l For details about the RACH Control Para. information element, refer to 3.1.1 SystemInformation Type 1 .

l The Neighbor Cell Description 2 information element is sent in System Information Types2ter and 5ter. Except for bit 5 (BA-IND) and bits 6 and 7 (Multiband_Reporting) of octet2, the Neighbor Cell Description 2 information element is coded as the Cell ChannelDescription information element. For details, refer to 3.1.1 System Information Type1 . The Multiband Reporting information element is sent in System Information Types 2terand 5ter. It has two bits and is used to request the dual-band MS to report information aboutneighbor cells of multiple bands. For details, refer to Table 3-4.

Table 3-4 Multiband reporting

Multiband Reporting (2bits)

Meaning

0 The MS reports six cells where the signal strength is thestrongest, irrespective of the band used.

1 The MS reports a neighbor cell that is on a differentband. It reports in the other five positions the neighborcells that are on the same band.

10 The MS reports two neighbor cells that are on a differentband. It reports in the other four positions the neighborcells that are on the same band.

11 The MS reports three neighbor cells that are on adifferent band. It reports in the other three positions theneighbor cells that are on the same band.



l SI 2quater Rest OctetsThe SI 2quater Rest Octets information element has the following parameters:– BA_IND, 3G_BA_IND, and MP_CHANGE_MARK

– 3G Neighbor Cell Description and Index_Start_3G

– UTRAN FDD Description and UTRAN TDD Description

– 3G MEASUREMENT PARAMETERS Description

3.1.3 System Information Type 3System Information Type 3 describes the location area identification, cell identity, RACHcontrol, and parameters of cell selection. It is mandatory and is sent on the BCCH.

FunctionsSystem Information Type 3 describes the location area identification, cell identity, RACHcontrol, and parameters of cell selection. It is mandatory and is sent on the BCCH.

ContentsSYS INFO 3l Cell Identity

l LAI

l Cell Option (BCCH)

l Cell Selection Para.


l SI 3 Rest Octets.

l CGICell Global Identification (CGI) consists of the Location Area Identification (LAI) and theCell Identity (CI). The LAI consists of the Mobile Country Code (MCC), the MobileNetwork Code (MNC), and the Location Area Code (LAC). System Information Types 3,6, and 4 contain all or part of the CGI information. Upon receiving the system information,the MS decodes the CGI. Based on the MCC and the MNC, the MS determines whether toaccess the network in the cell and whether the current location area has changed or not. Ifthe location area has changed, the MS initiates a location update procedure.The MCC is unique worldwide. It consists of three decimal numerals. For example, theMCC of China is 460. The MNC is unique nationwide. For example, the MNC of ChinaMobile is 00, and the MNC of China Unicom is 01. The LAC and the CI are planned byeach GSM network operator. Both the LAC and the CI have two octets. The CI ranges from0X0001 to 0XFFFE. 0X0000 and 0XFFFF are reserved.

l Control Channel Desc.The Control Channel Description information element has the following parameters:– MSCR

The MSC Release (MSCR) parameter indicates the release of an MSC. The parameterhas one bit. If the bit is 0, the MSC is released in 1998 or earlier. If it is 1, the MSC isreleased in 1999 or later.

– ATT




The Attach-Detach Allowed (ATT) parameter indicates whether the MS is allowed toinitiate an IMSI attach and detach procedure. The ATT has one bit. If it is 0, the MS isnot allowed. If it is 1, the MS is allowed.

– CCCH-CONFThe CCCH-CONF parameter determines the combination mode of the CCCH. TheCCCH-CONF has three bits. Table 3-5 describes the meaning of the CCCH-CONF.

Table 3-5 Meaning of the CCCH-CONF

CCCH-CONF(Three Bits)

Meaning Number of CCCHMessage Blocks in OneBCCH Multiframe

0 One basic physical channelused for CCCH, not sharedwith SDCCHs

9

1 One basic physical channelused for CCCH, shared withSDCCHs

3

10 Two basic physical channelsused for CCCH, not sharedwith SDCCHs

18

100 Three basic physical channelsused for CCCH, not sharedwith SDCCHs

27

110 Four basic physical channelsused for CCCH, not sharedwith SDCCHs

36

Others Reserved -

– BS_AG_BLKS_RES

The BS_AG_BLKS_RES parameter indicates the proportion of AGCH message blocksin the CCCH message blocks. If the CCCH-CONF is 001, the BS_AG_BLKS_RESranges from 0 to 2. If the CCCH-CONF is not 001, the BS_AG_BLKS_RES rangesfrom 0 to 7. After the CCCH-CONF is set, the BS_AG_BLKS_RES is actually used todetermine the proportions of AGCHs and PCHs on the CCCH. You can modify theBS_AG_BLKS_RES to balance the loading of AGCHs and PCHs.

– BS-PA-MFRAMSThe BS-PA-MFRAMS parameter indicates the number of multiframes contained in aperiod for the transmission of Paging Request messages to the same paging subgroup.It actually determines the number of paging subchannels contained in the paging channelof a cell. It has three bits. The value range is 0-7, representing 2-9 multiframes periodsfor transmission of Paging Request messages to the same paging subgroup respectively.

– T3212The timeout value of timer T3212 indicates the frequency of periodic location update.It has eight bits. The value range is 0-255. Each unit indicates six minutes. Value 0indicates that periodic location update is not performed.



l Cell Selection Para.The Cell Selection Para. affect the activities of an MS after it is switched on. Theseparameters include the following:– Cell Reselection Hysteresis

An MS can perform cell reselection only if the difference between the signal level ofthe neighbor cell (in a different location area) and the C2 of the local cell is greater thanthe value of Cell Reselection Hysteresis. This parameter has three bits, ranging from 0to 7. The range of the signal level is 0-14 dB.

– MS_TXPWR_MAX_CCHThe MS_TXPWR_MAX_CCH parameter indicates the transmit power the MS may usebefore it receives the power control command. The parameter has five bits, ranging from0 to 31. Each value corresponds to the output power of an MS.

– RXLEV_ACCESS_MINThe RXLEV_ACCESS_MIN indicates the minimum received signal level required forthe MS to access the system. It has six bits, ranging from 0 to 63. The range of the signallevel is from -110 dBm to -47 dBm.

– ACSThe ACS parameter indicates whether the MS uses C2 during cell reselection. It hasonly one bit. In System Information Type 3, this parameter is meaningless. In SystemInformation Type 4, value 0 of the bit indicates that the SI4 REST of System InformationType 4 is used to calculate the parameters related to C2. Other values indicate that theREST of System Information Types 7 and 8 are used to calculate the parameters relatedto C2.

– NECIThe NECI parameter indicates whether the current cell supports half rate services ornot. It has only one bit. Value 0 of the bit indicates that the current cell does not supporthalf rate services. Value 1 of the bit indicates that the current cell supports half rateservices.

l RACH Control Para.For details, refer to 3.1.1 System Information Type 1 .

l SI 3 Rest OctetsThe SI3 Rest Octets information element has the following parameters:– PI

This parameter indicates whether the MS uses C2 as the cell reselection parameter andwhether the parameter used to calculate C2 exists or not. It has only one bit. Value 0 ofthe bit indicates that the MS uses C1 as the cell reselection parameter. Value 1 of thebit indicates that the MS uses C2 that is derived from the system information as the cellreselection parameter.

– CBQThe Cell Bar Qualify (CBQ) parameter has only one bit. Along withCELL_BAR_ACCESS, it indicates the priority of a cell. For details, refer to Table3-6.




Table 3-6 Parameters affecting cell priority in cell selection

CBQ CBA Priority of CellSelection

Status of CellReselection

0 0 Normal Normal

0 1 Barred Barred

1 0 Low Normal

1 1 Low Normal

– CRO

The Cell Reselect Offset (CRO) parameter applies an offset to C2. It has six bits. Therange of the signal level is 0–126 dB. Along with TO and PT, the CRO is used to regulateC2 manually.

– TOThe value range of the TEMPORARY_OFFSET (TO) parameter is 0–7. Each levelrepresents 10 dB. For example, 0 refers to 0 dB, 1 refers to 10 dB, 6 refers to 60 dB,and 7 refers to infinity.

– PTThe value range of the Penalty Time (PT) parameter is 0–31. Each level represents 20seconds. For example, 0 refers to 20 s and 30 refers to 620 s. 31 is reserved to indicatethat CRO is subtracted from C2 and that TO is ignored.

– 2TIThis 2TI parameter indicates whether System Information Type 2quater can be obtainedor not.

– ECSCThe Early Classmark Sending Control (ECS) parameter indicates whether the ECS isallowed or not.

– GPRSThis GPRS parameter indicates whether the GPRS is supported or not.

– SI2quaterIThe SI2quaterI parameter indicates whether System Information Type 2quater can beobtained or not.

3.1.4 System Information Type 4System Information Type 4 is sent on the BCCH by the network. It provides information aboutthe location area identification, RACH control, cell selection parameters, and available CBCHinformation.

FunctionsSystem Information Type 4 is sent on the BCCH by the network. It provides information aboutthe location area identification, RACH control, cell selection parameters, and available CBCHinformation. The optional IEs CBCH Channel Description and CBCH Mobile Allocation areused when the system supports cell broadcast. These IEs describe the configurations of theCBCH and the related frequency information.



ContentsSYS INFO 4l LAI

l Cell Selection Para.


l CBCH Channel Desc. (optional)

l CBCH Mobile Allocation (optional)

l SI4 Rest Oct.

l LAIFor details, refer to 3.1.3 System Information Type 3 .

l Cell Selection Para.For details, refer to 3.1.3 System Information Type 3 .

l RACH Control Para.For details, refer to 3.1.2 System Information Types 2, 2bis, 2ter, and 2quater.

l CBCH Channel Description and CBCH Mobile AllocationBoth CBCH Channel Description and CBCH Mobile Allocation are optional. If the systemsupports cell broadcast, CBCH Channel Description indicates the configuration of theCBCH. If the CBCH is in frequency hopping mode, CBCH Mobile Allocation is mandatory.

l SI4 Rest Oct.If the cell selection parameter ACS is set to No, the SI4 Rest Oct. is used to calculate thecell reselection parameter C2.The criteria for cell reselection are as follows:– When PENALTY_TIME = 31, C2 = C1 - CELL_RESELECT_OFFSET

– When PENALTY_TIME is not equal to 31, C2 = C1 + CELL_RESELECT_OFFSET- TEMPORARY_OFFSET x H(PENALTY_TIME-T)For a non-serving cell, if x < 0, H (x) = 0; if x 0, H (x) = 1. For a serving cell, H (x) =0.

The SI4 Rest Oct. information element has the following parameters:– PI

For details, refer to 3.1.3 System Information Type 3 .– CBQ

For details, refer to 3.1.3 System Information Type 3 .– CRO

For details, refer to 3.1.3 System Information Type 3 .– TO

For details, refer to 3.1.3 System Information Type 3 .– PT

For details, refer to 3.1.3 System Information Type 3 .

3.1.5 System Information Types 5, 5bis, and 5terThis topic describes the functions and contents of System Information Types 5, 5bis, and 5ter.




FunctionsSystem Information Type 5 provides the frequency information of the neighbor cells (BA2). Itis mandatory and is sent on the SACCH. Different from System Information Type 2, the MScan read the frequency information described in System Information Type 5 when it is in theconversation state and report the information about the neighbor cells in the measurement report.Such information is used for handovers. A GSM 900 MS in PHASE 1 recognizes the neighborcell frequencies described only in System Information Type 5 and ignores the neighbor cellfrequencies described in System Information Types 5bis and 5ter.

System Information Type 5bis provides the frequency information of the neighbor cells (part ofBA2). It is optional and is sent on the SACCH. System Information Type 5 does not describeall the frequencies in the BA1 list. Therefore, System Information Type 5bis describes the restof the frequencies that are on the same frequency band.

System Information Type 5ter provides the frequency information of the neighbor cells (part ofBA2). It is sent on the SACCH. Only the dual-band MSs read this message. The GSM 900 MSsand the GSM 1800 MSs ignore this message.

ContentsSYS INFO 5- - Neighbor Cell Desc.l SYS INFO 5- - Neighbor Cell Desc.

l SYS INFO 5TER - - Neighbor Cell Desc. (Extended)

l Neighbor Cell Desc.For details, refer to 3.1.2 System Information Types 2, 2bis, 2ter, and 2quater.

l Neighbor Cell Description (Extended)For details, refer to 3.1.2 System Information Types 2, 2bis, 2ter, and 2quater.

3.1.6 System Information Type 6System Information Type 6 provides information about the location area identification, cellidentity, and other parameters of cell functions.

FunctionsSystem Information Type 6 provides information about the location area identification, cellidentity, and other parameters of cell functions. It is mandatory and is sent on the SACCH.

ContentsSYS INFO 6l Cell Identity

l LAI

l Cell Option (BCCH)

l NCC Permitted

l CGIFor details, refer to 3.1.3 System Information Type 3 .

l Cell OptionFor details, refer to 3.1.3 System Information Type 3 .



l NCC PermittedFor details, refer to 3.1.2 System Information Types 2, 2bis, 2ter, and 2quater.

3.1.7 System Information Type 7System Information Type 7 is sent on the BCCH. It provides information about cell reselectionparameters.

FunctionsSystem Information Type 7 is sent on the BCCH. It provides information about cell reselectionparameters.

ContentsSI 7 Rest Octets

The SI 7 Rest Octets information element contains the cell reselection parameters used by theMS. It may also contain the Power Offset parameter used by the DCS1800 Class 3 MS.

The coding scheme of SI 7 Rest Octets is the same as that of SI 4 Rest Octets. For details, referto 3.1.4 System Information Type 4 .

3.1.8 System Information Type 8System Information Type 8 is mandatory and is sent on the BCCH. It provides information aboutcell reselection parameters.

FunctionsSystem Information Type 8 is mandatory and is sent on the BCCH. It provides information aboutcell reselection parameters.


The SI 8 Rest Octets information element contains the cell reselection parameters used by theMS. It may also contain the Power Offset parameter used by the DCS1800 Class 3 MS.

The coding scheme of SI 8 Rest Octets is the same as that of SI 4 Rest Octets. For details, referto 3.1.4 System Information Type 4 .

3.1.9 System Information Type 13System Information Type 13 is sent on the BCCH by the network. It provides information relatedto GPRS in the cell.

FunctionsSystem Information Type 13 is sent on the BCCH by the network. It provides information relatedto GPRS in the cell.





The SI 13 Rest Octets information element has the following parameters:l BCCH_CHANGE_MARK

The BCCH_CHANGE_MARK parameter has three bits. It changes according to themessages sent on the BCCH.

l SI_CHANGE_FIELDThe SI parameter is binary and indicates that the last bit of the BCCH_CHANGE_MARKparameter has changed. It has four bits and ranges from 0 to 15.

l SI13_CHANGE_MARKThe SI13_CHANGE_MARK parameter ranges from 0 to 3.

l RACThe RAC parameter is binary and indicates the routing area code. It has eight bits.

l SPGC_CCCH_SUPThe SPGC_CCCH_SUP parameter indicates whether the CCCH supports theSPLIT_PG_CYCLE parameter or not. Value 0 indicates that the CCCH does not supportSPLIT_PG_CYCLE. Value 1 indicates that the CCCH supports SPLIT_PG_CYCLE.

l PRIORITY_ACCESS_THRThe PRIORITY_ACCESS_THR parameter indicates whether packet access is supportedor not. It has three bits. Value 000 indicates that packet access is not supported. Values 001and 010 are reserved, indicating by default that packet access are not supported. Values011, 100, 101, and 110 indicate that users of priorities 1, 1 and 2, 1 to 3, and 1 to 4,respectively, support packet access. Value 111 is reserved, indicating that packet access issupported.

l NETWORK_CONTROL_ORDERThe NETWORK_CONTROL_ORDER parameter has two bits. Value 00 indicates that thecell controls cell reselection and no measurement reports are sent. Value 01 indicates thatthe cell controls cell reselection and the MS sends the measurement reports. Value 10indicates that the network controls cell reselection and the MS sends the measurementreports. Value 11 is reserved.

l PSI1_REPEAT_PERIODThe PSI1_REPEAT_PERIOD parameter indicates the retransmit period of the PSI2. It hasfour bits. Value 0000 indicates that the retransmit period is one multiframe. Value 0001indicates that the retransmit period is two multiframes. Value 0010 indicates that theretransmit period is three multiframes. By analogy, value 1110 indicates that the retransmitperiod is 15 multiframes and value 1111 indicates that the retransmit period is 16multiframes.

l System Information Type 13 also include parameters such as the GPRS Mobile Allocation,GPRS Cell Options, GPRS Power Control, Parameters struct, and PBCCH Descriptionstruct.

3.2 Internal BSC Signaling Procedure of the SystemInformation

This describes the internal BSC signaling procedure of the system information.



System Information Type 1You can obtain the Cell Frequency in System Information Type 1 in the Cell Attributeswindow. Table 3-7 lists the RACH control parameters in System Information Type 1 and thecorresponding parameters on the BSC6000 Local Maintenance Terminal.

Table 3-7 RACH control parameters in System Information Type 1 and the correspondingparameters on the BSC6000 Local Maintenance Terminal

RACH Control Parameters inSystem Information Type 1

Parameters on the BSC6000 LocalMaintenance Terminal

Max Retrans MS MAX Retrans

Tx_interger Tx_interger

Cell Bar Access Cell_Bar_ Access

AC Common Access Control Class and SpecialAccess Control Class

RE Call Reestablishment Forbidden

EC Emergent Call Disable

To configure the parameters listed in the table on the BSC6000 Local MaintenanceTerminal, do as follows:l In the dialog box shown in Figure 3-1, click Call Control. Then set MS MAX retrans,

Common Access Control Class, Special Access Control Class, and Emergent CallDisable.

l In the dialog box shown in Figure 3-1, click Idle Mode. Set Tx-integer (RACH Timeslotthat equals to a TDMA frame, 4.615ms) and Cell_Bar_Access.

l In the dialog box shown in Figure 3-1, set Call Reestablishment Forbidden.




Figure 3-1 Set Cell Attributes dialog box

NOTE

If cell flow control is enabled, the MAX Retrans and Tx_interger parameters in System Information Type1 are automatically regulated according to the current flow control system.

System Information Types 2, 2bis, and 2terl The information on neighbor cell frequencies in System Information Types 2, 2bis, and

2ter is obtained from the 2G BA1 Table. The Ncc Permitted parameter in SystemInformation Type 2 is obtained from the Ncc Permitted field in the Idle Mode. The RACHControl Parameters in System Information Types 2 and 2bis are the same as that in SystemInformation Type 1. For details, see Table 3-7.

l The information in System Information Type 2quater is obtained from the UTRAN SystemMessage, UTRAN FDD Cell BA1, and UTRAN TDD Cell BA1.

l To configure the parameters listed in the table on the BSC6000 Local MaintenanceTerminal, do as follows:– In the dialog box shown in Figure 3-1, click Idle Mode, select Advanced, and then set

the neighbor cell frequency in 2G BA1 Table.– In the dialog box shown in Figure 3-1, click Idle Mode. Then set NCC Permitted.



– In the dialog box shown in Figure 3-1, click Call Control, and then click Advanced.Then set the UTRAN system message in UTRAN System Message.

– In the dialog box shown in Figure 3-1, click Idle Mode, and then click Advanced.Then set the UTRAN neighbor cell frequency in UTRAN FDD Cell BA1.

– In the dialog box shown in Figure 3-1, click Idle Mode, and then click Advanced.Then set the UTRAN neighbor cell frequency in UTRAN TDD Cell BA1.

System Information Type 3The CGI in System Information Type 3 is obtained from the Cell Attributes window. Table3-8 lists the control channel parameters in System Information Type 3 and the correspondingparameters on the BSC6000 Local Maintenance Terminal.

Table 3-8 Control channel parameters in System Information Type 3 and the correspondingparameters on the BSC6000 Local Maintenance Terminal

Control Channel Parameters inSystem Information Type 3


ATT ATT

CCCH-CONF CCCH Conf

BS_AG_BLKS_RES BS_AG_BLKS_RES

BS-PA-MFRAMS BS-PA-MFRARMS

T3212 Period of Periodic Location Update (6 minutes)

To configure the parameters listed in the table on the BSC6000 Local MaintenanceTerminal, do as follows: In the dialog box shown in Figure 3-1, click Idle Mode. Set ATT,CCCH-CONF, BS_AG_BLKS_RES, BS-PA-MFRAMS, and T3212.

Table 3-9 lists the cell option parameters in System Information Type 3 and the correspondingparameters on the BSC6000 Local Maintenance Terminal.

Table 3-9 Cell option parameters in System Information Type 3 and the correspondingparameters on the BSC6000 Local Maintenance Terminal

Cell option parameters in SystemInformation Type 3


PWRC PWRC

DTX UL DTX

Radio Link Timeout Radio Link Timeout

To configure the parameters listed in the table on the BSC6000 Local MaintenanceTerminal, do as follows:




l In the dialog box shown in Figure 3-1, click Other Attributes, and then clickAdvanced. On the Public Channel Control tab page, set PWRC.

l In the dialog box shown in Figure 3-1, set UL DTX.

l In the dialog box shown in Figure 3-1, click Call Control. Set Radio Link Timeout(SACCH period (480ms)).

Table 3-10 lists the cell option parameters in System Information Type 3 and the correspondingparameters on the BSC6000 Local Maintenance Terminal.

Table 3-10 Cell selection parameters in System Information Type 3 and the correspondingparameters on the BSC6000 Local Maintenance Terminal

Cell Selection Parameters in SystemInformation Type 3


Cell Reselection Hysteresis CRH

MS_TXPWR_MAX_CCH MS_TXPWR_MAX_CCH

RXLEV_ACCESS_MIN RXLEV_ACCESS_MIN

ACS PI

NECI Support Half Rate

To configure the parameters listed in the table on the BSC6000 Local MaintenanceTerminal, do as follows:l In the dialog box shown in Figure 3-1, click Idle Mode. Set CRH and ACS.

l In the dialog box shown in Figure 3-1, click Other Attributes, select Advanced andCommon Channel Control, and then set MS_TXPWR_MAX_CCH and Half ratesupported.

l In the dialog box shown in Figure 3-1, set RXLEV_ACCESS_MIN.

The RACH Control Parameters information element in System Information Type 3 is the sameas that in System Information Type 1. For details, refer to Table 3-7.

System Information Type 4The Location Area Identification in System Information Type 4 is obtained from the CellAttributes window. For the Cell Selection Parameters, see Table 3-10. The RACH ControlParameters information element in System Information Type 4 is the same as that in SystemInformation Type 1. For details, see Table 3-7.

Table 3-11 lists the Rest Oct parameters in System Information Type 4 and the correspondingparameters on the BSC6000 Local Maintenance Terminal.



Table 3-11 Rest Oct parameters in System Information Type 4 and the corresponding parameterson the BSC6000 Local Maintenance Terminal

Rest Oct Parameters in SystemInformation Type 4


PI PI

CBQ Cell Bar Quality Cell_Bar_Qualify

CRO CRO (2dB)

TOTO

TO, TEMPORARY_OFFSET

PT PT (s)


l In the dialog box shown in Figure 3-1, click Idle Mode. Set PI, CBQ, and CRO (2 dB).

l In the dialog box shown in Figure 3-1, click Idle Mode, and then click Advanced. On theIdle Parameter tab page, set TO and PT.

Other System Informationl The information on neighbor cell frequencies in System Information Types 5, 5bis, and

5ter is obtained from the 2G BA2 Table, UTRAN FDD Cell BA1, and UTRAN TDD CellBA1.


– Click HO Data, and then select Advanced and 2G BA2 Table. Then set thecorresponding parameters.

– In the dialog box shown in Figure 3-1, click HO Data, and then select Advanced andUTRAN FDD Cell BA1. Then set the corresponding parameters.

– In the dialog box shown in Figure 3-1, click HO Data, and then select Advanced andUTRAN TDD Cell BA1. Then set the corresponding parameters.

l The CGI in System Information Type 6 is obtained from the Cell Attributes window. TheCell Options information element in System Information Type 6 is the same as that inSystem Information Type 3. For details, see Table 3-9. The procedure for configuringNCC Permitted is the same as that for configuring NCC Permitted in System InformationType 2.

l The Rest Oct in System Information Type 7 is the same as that in System Information Type4. See Table 3-11.

l The Rest Oct in System Information Type 8 is the same as that in System Information Type4. See Table 3-11.

l System Information Type 13 is not processed in the BSC and is directly forwarded to theBTS.




4 Immediate Assignment

About This Chapter

This topic describes immediate assignment including its internal BSC signaling procedure andabnormal cases.

4.1 Immediate Assignment ProcedureThe purpose of immediate assignment is to establish a Radio Resource (RR) connection betweenan MS and the network on the Um interface. The immediate assignment procedure is initiatedby the MS.

4.2 Internal BSC Signaling Procedure of Immediate AssignmentThis topic describes the internal BSC signaling procedure of immediate assignment.

4.3 Abnormal Immediate Assignment CasesThis topic describes the abnormal immediate assignment cases.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 4 Immediate Assignment


4.1 Immediate Assignment ProcedureThe purpose of immediate assignment is to establish a Radio Resource (RR) connection betweenan MS and the network on the Um interface. The immediate assignment procedure is initiatedby the MS.

Figure 4-1 shows the immediate assignment procedure.

Figure 4-1 Immediate assignment procedure

Channel Request(1)

RACH

Channel Required(2)

Channel Activation(3)

MS BTS BSC

Channel Activation Acknowledge(4)

Immediate Assignment Command(5)

AGCH

Start T3101SABM(6)

main DCCH

UA(7)

main DCCHEstablish Indication(8)

Stop T3101

1. The MS sends the BTS a Channel Request message on the RACH.

The Channel Request message contains the Establish Cause and Random Referenceparameters. It has eight bits. Bits 3 to 6 indicate the access cause, and bit 5 to 2 carry theidentifier. Based on a Channel Request message, a maximum of 32 MSs are discriminated.The UA response messages on the Um interface are used to discriminate more MSs.

2. The BTS sends the BSC a Channel Required message.

The Channel Required message contains the Request Reference and Access Delayparameters. The Request Reference parameter contains the random access reference valueand the absolute frame number of the received access burst. The Access Delay is the delayof the access burst.

3. Upon receiving the Channel Required message, the BSC assigns a signaling channel andsends the BTS a Channel Activation message to activate a radio channel. The ChannelActivation message carries the activation type, channel mode, level, and TA.

4 Immediate AssignmentHUAWEI BSC6000 Base Station Subsystem



4. Upon receiving the Channel Activation message, if the channel type is correct, BTS2 turnson the power amplifier on the specified channel to receive information in the uplinkdirection and sends a Channel Activation Acknowledge message to the BSC.

5. The BSC sends through the BTS to the MS an Immediate Assignment Command message.

The Immediate Assignment Command message is sent on the AGCH. It carries theImmediate Assignment Extend message and the assignment information of two MSs. TheImmediate Assignment Command message has the following information elements:

l Dedicated mode or TBF

The Dedicated mode or TBF information element requests the MS to decode the rest ofthe message to an Immediate Assignment message or to allocate a Temporary BlockFlow.

l Page Mode

The Paging Mode information element controls the action of the MSs in a paging group.

l Channel Description

The Channel Description information element describes an assigned channel and thecorresponding SACCH. It carries the Channel Type, TDMA offset, timeslot, andabsolute RF channel number.

l Request Reference

The Request Reference information element contains the random access reference valueand the absolute frame number of the received access burst. The Access Delay is thedelay of the access burst.

l Time Advance

This Time Advance information element provides the initial timing advance value.

NOTE

If the BSC has no available channels, it sends the MS an Immediate Assignment Reject messageor an Immediate Assignment Extend Reject message.

l After receiving the Immediate Assignment Reject message, the MS starts timer T3122 uponreceiving one of the last three channel requests. Before timer T3122 expires, the MS is notpermitted to access the network nor initiate access attempts except emergency calls in thesame cell. It returns to idle mode and waits on the paging channel.

l If the Immediate Assignment Reject message is received for the first time, the MS starts timerT3126. Timer T3126 starts when the number of Channel Request messages sent by the MSreaches the maximum value. When timer T3126 expires, the immediate assignmentprocedure fails.

6. The MS sends an SABM frame on the main DCCH.

The SABM is a frame in the LAPDm protocol at the data link layer. It is the first frame toestablish a multiple frame acknowledged mode.

The messages on the Um interface come in two types, signaling messages and shortmessages. They are identified by the Service Access Point Identifier (SAPI). The serviceaccess point is the point at which the data link layer provides services to layer 3. SAPI 0supports the transfer of signaling, and SAPI 3 supports the transfer of short messages. Inthe GSM network, an SABM frame carries a signaling message, the layer 3 service requestmessage. The layer 3 service request message contains the identity of MS and indicateswhich service MS is requesting. The layer 3 service request messages are categorized intoCM service requests, location update requests, IMSI detach, and paging responses. Thesemessages contain the IMSI, detailed access cause, and classmarks.



NOTE

The main DCCH is the primary signaling channel and is generally the SDCCH, FACCH, andSACCH.

7. The BTS responds with a UA frame on the main DCCH.The UA frame is an unnumbered acknowledge frame of the LAPDm protocol at the datalink layer. It confirms the SABM frame.When the Channel Request messages sent by two MSs have the same contents, the twoMSs may be assigned the same dedicated channel. Upon receiving the SABM frame, theBTS sends the MS a UA frame that contains the same information as the received SABMframe. If the IMSI contained in the SABM frame is different from that in the UA frame,the MS leaves this channel and starts another access attempt. If the IMSI contained in theSABM frame is the same as that in the UA frame, the MS stays on the assigned channel.

8. The BTS sends the BSC an Establish Indication message.This Establish Indication message indicates the establishment of a radio connection inmulti-frame mode and contains parameters Link Identifier and L3 Information. The LinkIdentifier parameter identifies the signaling channel type and the message priority of SAPIand SAPI 0. The L3 Information parameter is a complete L3 message.

4.2 Internal BSC Signaling Procedure of ImmediateAssignment

This topic describes the internal BSC signaling procedure of immediate assignment.

l Upon receiving the Channel Required message from the BTS, the BSC assigns a signalingchannel according to the specified channel type and channel algorithm.

l During random access, upon receiving the Establish Indication message from the BTS, theBSC sends the MSC a CM Service Request message that carries the target CGI based onthe MCC, MNC, LAC, and CI parameters in the Cell Attributes window.

4.3 Abnormal Immediate Assignment CasesThis topic describes the abnormal immediate assignment cases.

4.3.1 Failure in Receiving an Establish Indication Message After Channel ActivationThis topic describes the fault, probable causes, and handling suggestions.

4.3.2 BSC Sending an Immediate Assignment Reject MessageThis topic describes the fault, probable causes, and handling suggestions.

4.3.1 Failure in Receiving an Establish Indication Message AfterChannel Activation

This topic describes the fault, probable causes, and handling suggestions.

FaultThe BSC sends the MS an Immediate Assignment Command message but does not receive anEstablish Indication message from the BTS.

4 Immediate AssignmentHUAWEI BSC6000 Base Station Subsystem



Probable CausesThe probable causes are as follows:

1. The design of the MS does not comply with the protocols. The MS sends the ChannelRequest message for many times and the BSS assigns and activates multiple signalingchannels.

2. Even when the BSS is functional, the MS may send several Channel Request messagesduring one RR connection attempt. The BSS activates multiple signaling channels, but theMS uses only one of them. The BSC cannot receive the Establish Indication messages fromother channels and therefore releases the channel after timer T3101 expires. If the numberof slots for spread transmission (Tx-integer) is set properly, the reason may be that the BTSreceives the uplink signals correctly but the MS cannot receive the downlink signals.Meanwhile, as indicated in the signaling tracing on the Um interface on the MS side, theBSC does not receive a response message from the BTS after sending a Channel Requestmessage.

3. The Tx-integer and the CCCH are not set correctly. The settings of the Tx-integer and theCCCH affect the interval at which an MS resends the Channel Request messages.

Handling Suggestionsl Use another MS to determine whether the problem lies in the MS itself.

l Check whether the received level and received quality on the uplink and downlink arenormal. If the MS is near the BTS, but the received level and received quality is low, checkwhether the antenna system, MS antenna, and MS battery are functional.

l Check whether the Tx-integer and the CCCH are set correctly.

4.3.2 BSC Sending an Immediate Assignment Reject MessageThis topic describes the fault, probable causes, and handling suggestions.

FaultUpon receiving the Channel Required message, the BSC sends the MS an Immediate AssignmentReject message.


1. The BSC finds no suitable signaling channel, that is, a SDCCH or a TCH, to assign to theMS. This is because that the channels are busy or blocked.

2. Upon receiving a Channel Activation message, the BTS sends the BSC many ChannelActivation Negative Acknowledge messages.

Handling Suggestionsl Check whether the channels are busy or blocked and whether the TRXs are functional. Add

TRXs to the BTS, modify the access threshold, and enable the directed retry.

l Check whether the channel states on the BSC and the BTS are the same. If not, you caninfer that the transmission on the Abis interface is unstable. Check also the BTS boards.



5 Classmark Update

About This Chapter

The MS classmark specifies the service capability, supported frequency bands, power capability,and ciphering capability of an MS in the GSM network. It is categorized into classmark 1,classmark 2, and classmark 3.

5.1 Classmark Update ProcedureThis topic describes the classmark update procedure.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 5 Classmark Update


5.1 Classmark Update ProcedureThis topic describes the classmark update procedure.

Signaling ProcedureFigure 5-1 shows the classmark update procedure.

Figure 5-1 Classmark update procedure

System Information Type3

BCCH

SABM

Complete Layer 3 Inforamtion

MS BSS MSC

main DCCH

main DCCH

SDCCH

Classmark Change(1)

SDCCHClassmark Update(2)

Classmark Request(3)Classmark Enquiry(4)

Classmark Change(5)

Classmark Update(6)

If the ECSC is allowed in System Information Type 3, an MS, for example, a dual-band MS ora vehicle mounted MS, can initiate a classmark update procedure by sending a Classmark Changemessage on the dedicated channel assigned by the network. The Classmark Change messagecarries the updated classmark 2 information element or even a classmark 3 information element.

1. Upon receiving the Classmark Change message, the BSS sends the MSC a ClassmarkUpdate message. The Classmark Update message carries the classmark 2 and classmark 3information elements. It is a bi-directional message.

2. When an MM connection is established between the MS and the MSC, the MSC initiatesa classmark update procedure by sending the BSS a Classmark Request message on anSCCP.

3. Upon receiving the Classmark Request message, the BSS:

l Sends the MSC a Classmark Update message

l Sends the MS a Classmark Enquiry message

l Takes no action

5 Classmark UpdateHUAWEI BSC6000 Base Station Subsystem



4. Upon receiving the Classmark Enquiry message, the MS sends the BSS a ClassmarkChange message. The Classmark Change message has the same contents as the ClassmarkChange message described in 1.

Procedure Descriptionl Figure 5-1 is divided by the broken lines into three parts, in which the upper part indicate

whether the ECSC is supported.l The middle part in Figure 5-1 shows the classmark update procedure initiated by the MS

when the ECSC is allowed in System Information Type 3.l The lower part in Figure 5-1 shows the classmark update procedure initiated by the MSC.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 5 Classmark Update


6 Location Update

About This Chapter

In the GSM system, MS location information is stored in the HLR, the VLR, and the MS. Whenthe location information changes, relevant information in the HLR, the VLR, and the MS mustbe changed accordingly, which can be realized through the location update procedure.

6.1 Location Update ProcedureThe location update procedure is a general procedure and is used for generic location update,periodic update, and IMSI attach.

6.2 Internal BSC Signaling Procedures of Location UpdateThis describes the internal BSC signaling procedures of location update.

6.3 Abnormal Location Update CasesThis topic describes the abnormal location update cases.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 6 Location Update


6.1 Location Update ProcedureThe location update procedure is a general procedure and is used for generic location update,periodic update, and IMSI attach.

6.1.1 Periodic Update ProcedurePeriodic update is used to periodically notify the network of the MS availability.

6.1.2 IMSI Attach ProcedureThe IMSI attach procedure is the complement of the IMSI detach procedure. It is used to indicatethe IMSI as active in the network.

6.1.3 Generic Location Update ProcedureThis topic describes the generic location update procedure.

6.1.1 Periodic Update ProcedurePeriodic update is used to periodically notify the network of the MS availability.

Periodic update is used to periodically notify the network of the MS availability. The locationupdate type information element in the Location Updating Request message indicates periodicupdate.

The periodic location update procedure is controlled by timer T3212 in the MS. If the timer isnot started, it is started each time the MS enters the Normal Service or Attempting to Updatestate of the MM Idle state. When the MS leaves the MM Idle state, timer T3212 continues runninguntil it expires. The MM Idle state indicates that the MS is not activated, is in the interceptionstate, and does not process any call procedure.

Timer T3212 is stopped (is set to its initial value 0 for the next start) when:

l A Location Updating Accept or Location Updating Reject message is received.

l An Authentication Reject message is received.

l The first MM message such as the Location Updating Accepted and the CM Service Acceptmessage is received, or ciphering mode setting is complete when the MM connection is setup, except when the most recent service state is Limited Service.

l The MS has responded to paging and has received the first correct layer 3 message exceptthe RR message.

l Timer T3212 expires.

l The MS is deactivated, that is, the MS is switched off or the SIM is removed.

When timer T3212 expires, the following cases might occur:

l The location update procedure is started and the timer shall be set to its initial value for thenext start.

l If the MS is in other states than MM Idle, the location update procedure is delayed untilthe MS enters the MM Idle state.

l If the MS is in the No Cell Available, Limited Service, PLMN Search, or PLMN Search-Normal Service state, the location update procedure is delayed until the MS leaves theservice state.

6 Location UpdateHUAWEI BSC6000 Base Station Subsystem



l If the system information indicates that periodic location update shall not be used, theprocedure is not started. The timeout value is carried by the Control Channel DescriptionIE in the System Information Type 3 message.

The T3212 timeout value is not changed in the No Cell Available, Limited Service, PLMNSearch, or PLMN Search-Normal Service states.

When the timeout value is changed during serving cell change and the timer is running, the MSrestarts the timer with the value t modulo t1. t1 is the new T3212 timeout value, and t is thecurrent timer value.

When timer T3212 stops, the MS restarts the timer with a random value between between 1 andt1.

6.1.2 IMSI Attach ProcedureThe IMSI attach procedure is the complement of the IMSI detach procedure. It is used to indicatethe IMSI as active in the network.

The System Information Type 3 message carries an ATT flag that indicates whether the attachand detach procedures are required to be used or not.

If the IMSI attach and detach procedures are required by the network, the MS will trigger theIMSI attach procedure during IMSI activation. When the MS activates the IMSI within thenetwork coverage area or moves into the coverage area, the IMSI attach procedure is triggeredonly when the Update Status is Updated and the stored LAI is the same as that broadcast on theBCCH of the current serving cell. Otherwise, a generic location update procedure is triggered,which is independent of the ATT flag indication.

IMSI attach is performed through the generic location update procedure. The location updatetype information element in the Location Updating Request message must in this case indicateIMSI attach.

6.1.3 Generic Location Update ProcedureThis topic describes the generic location update procedure.

The generic location update procedure is as follows:l Network requesting additional MS capability information

The network may initiate a classmark interrogation procedure to obtain the MS capabilityinformation such as the encryption capability and the short message transmission andreception capability.

l Network requesting for identificationThe network may initiate an identification request procedure if it cannot get the IMSI fromthe TMSI and LAI or it requires the IMEI.

l Authentication by the networkThe authentication procedure may be initiated by the network upon receipt of the LocationUpdating Request message from the MS.

l Ciphering mode setting by the networkThe ciphering mode setting procedure may be initiated by the network if a new TMSI hasto be allocated.

l Attempt counter



To limit the number of location update attempts, when a location update fails, an attemptcounter is used. The counter counts the number of consecutive unsuccessful location updateattempts and increases by 1 when a location update fails.The attempt counter is reset when:– The MS is switched on.

– A SIM is inserted.

– A location update is complete.

– A location update with the cause value 11 (PLMN not Allowed), 12 (Location Area notAllowed), 13 (Roaming not Allowed in This Location Area), or 15 (No Suitable Cellsin Location Area) is complete.

– The service state changes from Attempting to Update.

– The MS enters a new location area.

– Timer T3212 expires.

– The location update is triggered by the CM sublayer requests.

The attempt counter is used to decide whether a location update needs to be initiated aftertimer T3211 expires.

l Location update not accepted by the networkIf the location update is not accepted, the network sends a Location Updating Rejectmessage to the MS. The MS receiving a Location Updating Reject message stops timerT3210, stores the reject cause, starts timer T3240, enters state Location Updating Rejected,and awaits the release of the RR connection triggered by the network. It deletes theEquivalent PLMNs list when the reject cause is not #12, #14, or #15.Upon the release of the RR connection, the MS takes the following actions depending onthe stored reject cause:– # 2 (IMSI Unknown in HLR)

– # 3 (Illegal MS)

– # 6 (Illegal ME)

If the reject value is #2, #3, or #6, the MS sets the update state to Roaming Not Allowed,deletes any TMSI, stored LAI, and ciphering key sequence number, and considers the SIMas invalid until it is switched off or the SIM is removed.– # 11 (PLMN not Allowed)

– # 12 (Location Area not Allowed)

– # 13 (Roaming not Allowed in This Location Area)

– # 15 (No Suitable Cells in Location Area)

If the reject value is #11, #12, #13, or #15, the MS deletes any LAI, TMSI, and cipheringkey sequence number stored in the SIM, resets the attempt counter, and sets the update stateto Roaming Not Allowed. The MS stores the LAI and the PLMN identity in a suitableforbidden list, for example, in the Forbidden PLMN List for cause #11, in the list ofForbidden Location Areas for Regional Provision of Service for cause #12, in the list ofForbidden Location Areas for Roaming for cause #13 (The MS performs a PLMN selectioninstead of a cell selection when it returns to the MM Idle state), and in the list of ForbiddenLocation Areas for Roaming for cause #15 (The MS searches a suitable cell in a locationarea of the same PLMN).Other reject values are considered as abnormal cases.




l Release of the RR connection after location update

When the location update procedure is complete, the MS (except when it has a follow-onapplication request and has received the proceed indication from the network) sets timerT3240 and enters the Wait For Network Command state, expecting the release of the RRconnection. The network may keep the RR connection for a network-initiated MMconnection, or may allow a mobile-initiated MM connection.

Any release of the RR connection is initiated by the network. If the RR connection is notreleased within a given time controlled by timer T3240, the MS aborts the RR connection.Then the MS enters the MM Idle state.

When the MS enters the Normal Service or Attempting to Update state, either timer T3212or timer T3211 is started.

6.2 Internal BSC Signaling Procedures of Location UpdateThis describes the internal BSC signaling procedures of location update.

On receiving the Channel Required message from the BTS, the BSC assigns a signaling channel.

During random access, on receiving the Establish Indication message from the BTS, the BSCsends the MSC a Location Updating Request message that carries the target CGI based on theMCC, MNC, LAC, and CI parameters in the Cell Attributes window.

NOTE

You can find the periodic location update time in the Periodic Location Update Time Limit by selectingIdle Mode in the Cell Attributes window. The periodic location update time is delivered to the MS in theSystem Information Type 3 message.

6.3 Abnormal Location Update CasesThis topic describes the abnormal location update cases.

6.3.1 Location Update Not Started or Aborted on the MS SideThis topic describes the fault, probable causes, and handling suggestions.

6.3.2 Location Update Failure on the Network SideThis topic describes the fault, probable causes, and handling suggestions.

6.3.1 Location Update Not Started or Aborted on the MS SideThis topic describes the fault, probable causes, and handling suggestions.

FaultThe location update procedure is not started or is aborted.


l Access barred because of access class control



The location update procedure is not started. The MS stays in the current serving cell andstarts the normal cell reselection procedure. It starts the location update procedure as soonas it gains access or at cell change.

l Receiving an Immediate Assignment Reject message during random access (in A/Gb modeonly)The location update procedure is not started. The MS stays in the chosen serving cell andstarts the normal cell selection procedure. The waiting timer T3122 is reset when a cellchange occurs. The location update procedure is started as soon as timer T3122 expires.

l Random access failure (in A/Gb mode only)Timer T3213 is started when random access fails. When it expires, the procedure isattempted again if still necessary. If two successive random access attempts fail, the locationupdate procedure attempt is aborted.

l RR connection failureThe location update procedure is aborted.

l T3212 expiryThe location update procedure and the RR connection are aborted.

l RR release before the normal end of procedureThe location update procedure is aborted.

l RR connection establishment failure (in Iu mode only)

Handling SuggestionsRefer to 4.1 Immediate Assignment Procedure. Based on the cause values carried by theLocation Updating Rejected message, you can also refer to the following suggestions:l Cause values #2, #3, #6, #11, #12, and #13

Check whether the subscription information in the HLR and the subscriber data in the VLRis correct.

l Cause value #15Check whether the CGI and the LAC are consistent and correct on the MSC and the BSC.

6.3.2 Location Update Failure on the Network SideThis topic describes the fault, probable causes, and handling suggestions.

FaultLocation update fails, and the network sends a Location Updating Reject message.


1. RR connection failureIf an RR connection fails during a common procedure integrated with the location updateprocedure, the behavior of the network is the same as that in a common procedure.If an RR connection fails when a common procedure does not exist, the location updateprocedure towards the MS is aborted.

2. Location update not accepted by the network




If the Location Updating Request message is received with a protocol error, the networkreturns a Location Updating Reject message with one of the following reject causes:l #03 (Illegal MS)

l #97 (Message Type Non-Existent or not Implemented)

l #98 (Message Type not Compatible with the Protocol State)

l #111 (Protocol Error, Unspecified)

Upon sending the response, the network starts the channel release procedure.3. Network failure

If the MSC, VLR, or HLR is faulty, the network sends a Location Updating Reject messagewith the cause value #17 (Network Failure).Generally, if the CGI or the LAC are not consistent on the MSC and the BSC, the causevalue may also be #17.

Handling SuggestionsRefer to 4.1 Immediate Assignment Procedure.

If the cause value is #17, refer to the following suggestions:

1. Check whether the CGI and the LAC are consistent on the MSC and the BSC, especiallywhether the both the LAC and the CI are decimal or hexadecimal.

2. Check the hardware of the MSC, VLR, or HLR.



7 Authentication

About This Chapter

The purpose of authentication is to permit the network to check whether the identity providedby the MS is acceptable or not and to prevent the private information of the legal subscribersfrom being stolen.

7.1 Authentication PrinciplesThe authentication procedure is always initiated and controlled by the network.

7.2 Authentication ProcedureThis topic describes the authentication procedure.

7.3 Authentication FailureDifferent ways of identification used by the MS may lead to different unsuccessful authenticationprocedures.

7.4 Internal BSC Signaling Procedure of AuthenticationThis topic describes the internal BSC signaling procedure of authentication.

7.5 Abnormal Authentication CasesThis topic describes the abnormal authentication cases.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 7 Authentication


7.1 Authentication PrinciplesThe authentication procedure is always initiated and controlled by the network.

The network initiates the authentication procedure in the following cases:l The MS applies to change the subscriber information in the VLR or the HLR.

l Service access is initiated. For example, when the MS originates a call, is called, activated,or deactivated, or the supplementary service is initiated.

l The MS accesses the network for the first time after the MSC/VLR restarts.

l The ciphering key Kc on the network does not match that on the MS.

The purpose of authentication twofold:l To permit the network to check whether the identity provided by the MS is acceptable or

notl To provide parameters that enable the MS to calculate a new ciphering key

The authentication procedure uses an Authentication Triplet, namely RAND, Kc, and SERS.The Authentication Triplet is calculated in the authentication center of the GSM network. Whenregistering in a GSM network, each subscriber is assigned a Mobile Station International ISDNNumber (MSISDN) and an International Mobile Subscriber Identity (IMSI). The IMSI is writteninto the SIM through a SIM writer. The SIM writer also generates an authentication parameterKi, which is stored in the SIM and the authentication center as well. The IMSI and Ki arepermanent information.

A pseudo-random number generator is used in the authentication center to generate anunpredictable pseudo random number RAND. In the authentication center, the RAND and Kigenerate a signed response (SRES) through algorithm A3 and a ciphering key Kc throughalgorithm A8. The three parameters RAND, Kc, and SERS constitute an Authentication Triplet,which are stored as part of the subscriber data in the HLR.

Generally, the authentication center sends five groups of Authentication Triplet to the HLR atone time. The HLR automatically stores them. The HLR can store ten groups of AuthenticationTriplet. Upon request, the HLR sends five groups of Authentication Triplet to the MSC/VLR atone time. The MSC/VLR uses the Authentication Triplet one by one. When only two groups areleft, the MSC/VLR requests the HLR for the Authentication Triplet again.

7.2 Authentication ProcedureThis topic describes the authentication procedure.

Figure 7-1 shows the authentication procedure.

7 AuthenticationHUAWEI BSC6000 Base Station Subsystem



Figure 7-1 Authentication procedure

MS BTS MSC

SDCCH

BSC

Authentication Request(1)

Start T3260

StopT3260

SDCCH

Authentication Response(2)

The authentication procedure is as follows:

1. The network initiates an authentication procedure by sending an Authentication Requestmessage to the MS and starts timer T3260. The Authentication Request message carries a128-bit RAND that is used to calculate the response parameters. It also carries the CipheringKey Sequence Number (CKSN) assigned to the ciphering key.

2. Upon receiving the Authentication Request message, the MS calculates the SRES requiredby the Authentication Response message and the new ciphering key Kc. The SRES iscalculated based on the RAND and Ki through algorithm A3. After writing the newciphering key Kc and the CKSN in the SIM, the MS sends the network an AuthenticationResponse message.Upon receiving the Authentication Response message, the network stops timer T3260 andcompares the stored SRES with the SRES in the Authentication Response message. If theSRESs are the same, the authentication procedure is complete, and the successiveprocedures, for example, the ciphering procedure, start.

7.3 Authentication FailureDifferent ways of identification used by the MS may lead to different unsuccessful authenticationprocedures.

If authentication fails, that is, if the response is not valid, the network may distinguish betweenthe following two ways of identification used by the MS:

1. If the TMSI is used, the network initiates the identification procedure.If the IMSI given by the MS differs from that in the network, the network restarts theauthentication procedure. If the IMSI given by the MS is the expected one, the networkreturns an Authentication Reject message.

2. if the IMSI is used, the network sends an Authentication Reject message.Figure 7-2 shows the unsuccessful authentication procedure.



Figure 7-2 Unsuccessful authentication procedure

MS BTS MSC

SDCCH

BSC


SDCCH

Authentication Response(2)

Authentication Reject(3)

SDCCH

If the Authentication Reject message is received when the MS is in the IMSI Detach Initiatedstate, timer T3220 will be stopped when the RR connection is released. The MS, if possible,starts the local release procedure after the normal release procedure or timer T3220 expiry. Ifnot possible, for example, during IMSI detachment at MS power-down, the RR sublayer on theMS side is aborted.

If the Authentication Reject message is received in any other state, the MS aborts any MMconnection establishment or call re-establishment procedure, stops all the timers T3210 orT3230, releases all the MM connections, starts timer T3240, and enters the Wait For NetworkCommand state, expecting the release of the RR connection. If the RR connection is not releasedwithin a given time controlled by timer T3240, the MS aborts the RR connection.

In both cases, either after an RR connection release triggered from the network or after an RRconnection abort requested by the MS, the MS enters the No IMSI substate of the MM Idle state.

7.4 Internal BSC Signaling Procedure of AuthenticationThis topic describes the internal BSC signaling procedure of authentication.

The authentication is initiated and controlled by the MSC, and the BSC does no specialprocessing.

7.5 Abnormal Authentication CasesThis topic describes the abnormal authentication cases.

7.5.1 RR Connection FailureThis topic describes the fault, probable causes, and handling suggestions.

7.5.2 Timer T3260 ExpiryThis topic describes the fault, probable causes, and handling suggestions.

7.5.3 SIM UnregisteredThis topic describes the fault, probable causes, and handling suggestions.

7 AuthenticationHUAWEI BSC6000 Base Station Subsystem




FaultThe authentication procedure fails, and the network releases all the MM connections.

Probable CausesUpon detecting an RR connection failure before an Authentication Response message isreceived, the network releases all the MM connections (if any) and aborts any ongoing MM-specific procedure.

Handling SuggestionsCheck whether interference exists on the Um interface.

7.5.2 Timer T3260 ExpiryThis topic describes the fault, probable causes, and handling suggestions.

FaultThe authentication procedure fails.

Probable CausesIf timer T3260 expires before an Authentication Response message is received, the networkreleases the RR connection and all the MM connections, aborts the authentication procedure andall the ongoing MM connections (if any), and starts the RR connection release procedure.

Handling SuggestionsCheck whether the timeout value of timer T3260 is appropriate.

7.5.3 SIM UnregisteredThis topic describes the fault, probable causes, and handling suggestions.

FaultThe network directly responds to the MS with an Authentication Reject message.

Probable CausesIf the SIM of an MS is not registered in the network, the network returns an AuthenticationReject message to the MS.

Handling SuggestionsRegister the SIM correctly.



8 Ciphering

About This Chapter

Ciphering is used to secure the information exchange between an MS and a BTS. The informationconsists of the signaling information and the subscriber information. The subscriber informationconsists of the subscriber data and the subscriber voice.

8.1 Ciphering ProcedureWhether ciphering is used or not is determined by the radio resource management entity. Theciphering procedure is initiated by the network and is performed in the BTS. To cipher the userdata, you must enter the corresponding parameters in the ciphering program. The ciphering keyKc is generated by the AUC, is stored in the MSC/VLR, and is sent to the BTS before ciphering.

8.2 Ciphering Mode ChangeThe MSC sends a Ciphering Mode Change command, and the BTS performs the ciphering modechange.

8.3 Internal BSC Signaling Procedure of CipheringThis topic describes the internal BSC signaling procedure of ciphering.

8.4 Abnormal Ciphering CasesThis topic describes the abnormal ciphering cases.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 8 Ciphering


8.1 Ciphering ProcedureWhether ciphering is used or not is determined by the radio resource management entity. Theciphering procedure is initiated by the network and is performed in the BTS. To cipher the userdata, you must enter the corresponding parameters in the ciphering program. The ciphering keyKc is generated by the AUC, is stored in the MSC/VLR, and is sent to the BTS before ciphering.

Signaling ProcedureFigure 8-1 shows the ciphering procedure.

Figure 8-1 Ciphering procedure

MS BTS MSC

SDCCH

BSC

Ciphering ModeCommand(1)Encryption

Mode Command(2)

SDCCH

Ciphering ModeCommand(3)



The ciphering procedure is as follows:

1. The MSC sends the BSC a Ciphering Mode Command message. The Ciphering ModeCommand message carries the required ciphering algorithms including A5/0, the cipheringkey Kc, and whether the Ciphering Mode Complete message sent by the MS must carrythe IMEI.

2. According to the ciphering algorithm in the Ciphering Mode Command message, theciphering algorithm allowed by the BSC, and the ciphering algorithm supported by the MS,the BSC determines the algorithm to be used and notifies the BTS.

3. The BTS sends the Ciphering Mode Command message to notify the MS of the cipheringalgorithm.

4. Upon receiving the Ciphering Mode Command message, the MS starts sending theciphering mode and then responds the BSC with a Cipher Mode Complete message.

5. Upon receiving the Ciphering Mode Complete message from the MS, the BSC notifies theMSC of the ciphering completion.

Procedure DescriptionFor details about the ciphering procedure, refer to the following:l A5 ciphering algorithm

As specified in the GSM protocol, there are eight ciphering algorithms, A5/0–A5/7, inwhich A5/0 indicates Not Ciphered. The ciphering mode setting procedure is initiated by

8 CipheringHUAWEI BSC6000 Base Station Subsystem



the network. The required ciphering algorithm is specified in the Ciphering Informationelement of the Ciphering Mode Command message.

l Ciphering algorithm selection

When an MS initiates a call, it sends a CM Service Request message that carries classmark2, classmark 3, and the ciphering algorithm supported by the MS. When the ECSC is setto 1, classmark 3 is carried in the CM Service Request message. When the ECSC is set to0, classmark 3 can only be carried in the CM Service Request message through classmarkchange or update. Therefore, set the ECSC to 1 when ciphering is used. According to theciphering algorithm in the Cipher Mode Command message, the ciphering algorithmallowed by the BSC, and the ciphering algorithm in the CM Service Request message, theBSC determines the algorithm to be used. In a reverse order, the BSC selects an applicablealgorithm from the intersection of the early-mentioned three algorithms. The priority of thealgorithms is A5/7 > A5/6 > A5/5 > A5/4 > A5/4 > A5/3 > A5/2 > A5/1 > A5/0.

l Ciphering during handover

The Handover Request message carries an Ciphering Information element. The CipheringInformation element specifies the required ciphering algorithm and the ciphering key. Ifone of the two A interfaces of the two BSSs is in PHASE I, because of the defects in theETSI GSM PHASE I protocol (no ciphering mode setting information unit is included inthe Handover Command message), the two BSSs interoperate only when they use the sameciphering algorithm such as A5/0 or A5/2. Otherwise, special processing (modifying theinter-BSC handover command) is required in the target MSC or the target BSC (or theserving MSC or the serving BSC).

During the interconnection on the A interface in ciphering mode, to avoid unsuccessfulhandovers, you must know whether additional data configuration is required on the BSCsand MSCs from different manufacturers.

8.2 Ciphering Mode ChangeThe MSC sends a Ciphering Mode Change command, and the BTS performs the ciphering modechange.

The BTS performs and manages ciphering. The BSC does no processing.

If the ciphering mode is changed,

1. The BTS performs the sending configuration in old mode and the receiving configurationin new mode.

2. The MS is configured in a completely new mode, including transmission and reception.

3. The BTS is configured in a completely new mode.

8.3 Internal BSC Signaling Procedure of CipheringThis topic describes the internal BSC signaling procedure of ciphering.

The internal BSC signaling procedure of ciphering is as follows:

1. Upon receiving the Ciphering Mode Command message from the MSC, the BSC checksthe classmarks of the MS and the settings of the Ciphering Algorithm in the CellAttributes dialog box.



2. According to the ciphering algorithm in the Ciphering Mode Command message, theciphering algorithm allowed by the BSC, and the ciphering algorithm in the CM ServiceRequest message, the BSC determines the algorithm to be used.

3. In a reverse order, the BSC selects an applicable algorithm from the intersection of theearly-mentioned three algorithms. The priority of the algorithms is A5/7 > A5/6 > A5/5 >A5/4 > A5/4 > A5/3 > A5/2 > A5/1 > A5/0. The determined ciphering mode is carried inthe Cipher Mode Command message that is sent to the BTS.

8.4 Abnormal Ciphering CasesThis topic describes the abnormal ciphering cases.

8.4.1 BSS Sending a Cipher Mode Reject MessageThis topic describes the fault, probable causes, and handling suggestions.

8.4.2 MS Doing No ProcessingThis topic describes the fault, probable causes, and handling suggestions.

8.4.1 BSS Sending a Cipher Mode Reject MessageThis topic describes the fault, probable causes, and handling suggestions.

FaultThe BSS sends the MSC a Cipher Mode Reject message.


1. The BSS does not support the ciphering algorithm specified in the Ciphering ModeCommand message. It sends the MSC a Cipher Mode Reject message with the cause valueCiphering Algorithm Not Supported.

2. If the BSS has initiated ciphering before the MSC requires changing the cipheringalgorithm, the BSS sends the MSC a Cipher Mode Reject message.

Handling Suggestionsl Check whether the BSS supports the ciphering algorithm specified in the Ciphering Mode

Command message.l Check whether the BSS has initiated ciphering.

8.4.2 MS Doing No ProcessingThis topic describes the fault, probable causes, and handling suggestions.

FaultUpon receiving the Ciphering Mode Command message, the MS does no processing.

Probable CausesThe Ciphering Mode Command message is considered valid when:

8 CipheringHUAWEI BSC6000 Base Station Subsystem



l It carries an Algorithm Identifier and is received by the MS in No Ciphering mode.

l It carries No Algorithm Identifier and is received by the MS in No Ciphering mode.

l It carries No Algorithm Identifier and is received by the MS in Ciphering mode.

The Ciphering Mode Command message received in other cases, for example, when it carriesan Algorithm Identifier and is received in Ciphering mode, is considered erroneous. In this case,the MS sends an RR Status message with the cause value Protocol Error and does no furtherprocessing.

Handling SuggestionsCheck the mode that the MS is in and the Ciphering Mode Command message.



9 TMSI Reallocation

About This Chapter

The TMSI reallocation takes place in ciphering mode. It is generally related to another procedure,such as location update or call establishment.

9.1 TMSI Reallocation ProcedureThe purpose of the TMSI reallocation procedure is to provide identity confidentiality, that is, toprotect a user against being identified and located by an intruder. Usually, the TMSI reallocationis performed at least at each change of a location area. It can be initiated at any time by thenetwork if an RR connection exists between the network and an MS.

9.2 Internal BSC Signaling Procedure of TMSI ReallocationThis topic describes the internal BSC signaling procedure of TMSI reallocation.

9.3 Abnormal TMSI Reallocation CasesThis topic describes the abnormal TMSI reallocation cases.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 9 TMSI Reallocation


9.1 TMSI Reallocation ProcedureThe purpose of the TMSI reallocation procedure is to provide identity confidentiality, that is, toprotect a user against being identified and located by an intruder. Usually, the TMSI reallocationis performed at least at each change of a location area. It can be initiated at any time by thenetwork if an RR connection exists between the network and an MS.

Figure 9-1 shows the TMSI reallocation procedure.

Figure 9-1 TMSI reallocation procedure

MS BTS MSC

SDCCH

BSC

TMSIReallocation Command(1)

Start T3250

StopT3250

SDCCH

TMSIReallocation Complete(2)

The TMSI reallocation procedure is as follows:l The network initiates the TMSI reallocation procedure by sending a TMSI Reallocation

Command message to the MS and starts timer T3250. The TMSI Reallocation Commandmessage carries a new combination of TMSI and LAI allocated by the network or an LAIand the IMSI if the used TMSI is deleted. Usually, the TMSI Reallocation Commandmessage is sent to the MS using an RR connection in ciphering mode.

l Upon receiving the TMSI Reallocation Command message, the MS stores the LAI in theSIM. If the received identity is the IMSI of the relevant MS, the MS deletes any TMSI. Ifthe received identity is a TMSI, the MS stores the TMSI in the SIM. In both cases, the MSsends a TMSI Reallocation Complete message to the network.Upon receiving the TMSI Reallocation Complete message, the network stops timer T3250.If a TMSI is sent to the MS, the network considers the new TMSI as valid. If an IMSI issent to the MS, the network considers the old TMSI as deleted.

9.2 Internal BSC Signaling Procedure of TMSI ReallocationThis topic describes the internal BSC signaling procedure of TMSI reallocation.

The network initiates and controls the TMSI reallocation procedure and the BSC does no specialprocessing.

9 TMSI ReallocationHUAWEI BSC6000 Base Station Subsystem



9.3 Abnormal TMSI Reallocation CasesThis topic describes the abnormal TMSI reallocation cases.

9.3.1 TMSI Reallocation Caused by RR Connection Failure on the Network SideThis topic describes the fault, probable causes, and handling suggestions.

9.3.2 TMSI Reallocation Caused by T3250 ExpiryThis topic describes the fault, probable causes, and handling suggestions.

9.3.1 TMSI Reallocation Caused by RR Connection Failure on theNetwork Side


FaultThe TMSI is reallocated due to RR connection failure on the network side.

Probable Causes

If the RR connection fails before the TMSI Reallocation Complete message is received, all MMconnections should be released and both the old and the new TMSIs should be considered asoccupied for a certain recovery time.

During this period the network may:l Use the IMSI for paging if the MS is the called party. Upon response from the MS, the

TMSI reallocation is restarted.l Consider the new TMSI as valid if the MS is the calling party.

Initiate an identification procedure followed by a new TMSI reallocation if the MS uses the oldTMSI.

Handling SuggestionsNo handling is required.

9.3.2 TMSI Reallocation Caused by T3250 ExpiryThis topic describes the fault, probable causes, and handling suggestions.

FaultThe network releases the RR connection.

Probable CausesThe TMSI reallocation is supervised by the timer T3250 in the network. At the first expiry oftimer T3250, the network releases the RR connection. In this case, the network aborts thereallocation procedure, releases all MM connections, and follows the rules for RR connectionfailure.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 9 TMSI Reallocation


Handling SuggestionsThe BSC does no special processing.

9 TMSI ReallocationHUAWEI BSC6000 Base Station Subsystem



10 Speech Channel Assignment

About This Chapter

The speech channel assignment is the procedure for assigning TCHs to the MS according to theservice requests.

10.1 Speech Channel Assignment ProcedureThis topic describes the speech channel assignment procedure.

10.2 Channel Mode Modification ProcedureThis topic describes the channel mode modification procedure.

10.3 Internal BSC Signaling Procedure of Speech Channel AssignmentThis describes the internal BSC signaling procedure of speech channel assignment.

10.4 Abnormal Speech Channel Assignment CasesThis topic describes the abnormal speech channel assignment cases.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 10 Speech Channel Assignment


10.1 Speech Channel Assignment ProcedureThis topic describes the speech channel assignment procedure.

Figure 10-1 shows the speech channel assignment procedure.

Figure 10-1 Speech channel assignment procedure


Channel ActivationAcknowledge(3)

MS BTS BSC

Assignment Command(4)

Start T10

SABM(5)

main DCCH

UA(6)

FACCH Establishment Indication(7)

BTS

AssignmentRequest(1)

Start T3107

FACCH

AssignmentComplete(8)

FACCH

Stop T3107AssignmentComplete(9)

Stop T10

The speech channel assignment procedure is as follows:

1. The MSC requests the radio resources from the BSS through the SCCP connection andstarts timer T10. The Assignment Request message carries the Channel Type, Priority,Circuit Identity Code, and Downlink DTX Flag.

l The Channel Type parameter has five to ten bytes. The third byte "speech / dataindicator" indicates speech, data, or signaling. The fourth byte "channel rate and type"indicates the number of half-rate channels or full-rate channels and the number of relatedphysical channels. The remaining bytes indicate speech versions 1–5.

l The Priority parameter indicates different priority levels and whether queuing and pre-emption is performed.

10 Speech Channel AssignmentHUAWEI BSC6000 Base Station Subsystem



l The Circuit Identity Code parameter is used for the physical connection between theBSC and the MSC.

l The Downlink DTX Flag parameter indicates whether discontinuous transmission isallowed.

2. For details about the Channel Activation message, refer to 4 Immediate Assignment.3. For details about the Channel Activation Acknowledge message, refer to 4 Immediate

Assignment.4. Upon receiving the Channel Activation Acknowledge message, the BSC sends the MS an

Assignment Command message on the SDCCH and starts timer T3107. The AssignmentCommand message carries the Channel Description, Power Command, and Channel Mode.For details about these parameters, refer to the immediate assignment procedure.

5. Upon receiving the Assignment Command message from the BTS, the MS adjusts thesignaling to the TCH and sends the SABM frame on the FACCH. The SABM frame is thefirst frame during the setup of multi-frame verification mode and does not carry layer 3messages.

6. Upon receiving the SABM frame, the BTS responds to the MS with a UA frame on theFACCH. The UA frame does not carry layer 3 messages.

7. Then the BTS sends the BSC an Establishment Indication message. The EstablishmentIndication message does not carry layer 3 messages. The system responds with a UAAcknowledgement frame.

8. Upon receiving the UA frame, the MS sends an Assignment Complete message on theFACCH to notify the BSC of the channel assignment completion. Then it stops TimerT3107.

9. The BSC sends the MSC the Assignment Complete message and stops timer T10. TheAssinment Complete message carries the Chosen Channel, Circuit Pool, and Speechversion. The meanings of the parameters are as follows:l Chosen Channel

Inidicates the type of the assigned channell Circuit Pool

Indicates the circuit pool informationl Speech Version

Indicates the speech coding algorithm

10.2 Channel Mode Modification ProcedureThis topic describes the channel mode modification procedure.

Figure 10-2 shows the channel mode modification procedure.



Figure 10-2 Channel mode modification procedure

MS BTS MSCBSC


Start T10

main DCCH

Mode Modify(2)

Mode ModifyAcknowledge(3)

ChannelMode Modify(4)

Channel ModeModify Acknowledge(5)

main DCCHAssignment

Commplete(6)

StopT10

The channel mode modification procedure is as follows:

1. For details about the Assignment Request message, refer to 10.1 Speech ChannelAssignment Procedure.

2. Upon receiving the Assignment Request message, the BSC sends the BTS a Mode Modifymessage. The Mode Modify message carries the Channel Mode parameter.

3. If the channel mode is changed, the BTS sends the BSC a Mode Modify Acknowledgemessage to the BSC. If the channel mode cannot be changed, the BTS sends the BSC aMode Modify Negative Acknowledge message.

4. Upon receiving the Mode Modify Acknowlege message, the BSC sends the MS a ChannelMode Modify message. The Channel Mode Modify message carries the information of thechannel to be changed and the mode of channel after change.

5. If the channel mode is changed, the MS sends the BSC a Channel Mode ModifyAcknowledge message. If the MS does not support the specified mode, it stays in theoriginal mode. The Channel Mode Modify Acknowledge message carries the modeinformation.

6. For details about the Assignment Complete message, refer to 10.1 Speech ChannelAssignment Procedure.

10.3 Internal BSC Signaling Procedure of Speech ChannelAssignment

This describes the internal BSC signaling procedure of speech channel assignment.

The internal BSC signaling procedure of speech channel assignment is as follows:

1. On receiving the Assignment Request message from the MSC, the BSC checks the channeltype. Choose Other Attributes > Advanced > Other Parameters. Check whether the




Data Service Allowed is enabled. If not, the BSC responds with an Assignment Failuremessage.

2. Based on the CIC in the Assignment Request message, the BSC checks the E1 timeslotson the A interface and confirms the existence of CIC. It also checks whether the circuitpool of the configured CIC, the channel type in the Assignment Request message, and thecapacity of the GDPUT are collided. If they are collided, the BSC responds with anAssignment Failure message.

3. On receiving the Assignment Complete message from the MS, the BSC fills the messagewith the A Interface Tag and sends the message to the MSC. You can choose BSCProperty > Basic Data to display the A Interface Tag.

10.4 Abnormal Speech Channel Assignment CasesThis topic describes the abnormal speech channel assignment cases.

10.4.1 BSC Sending an Assignment Failure MessageThis describes the fault, probable causes, and handling suggestions.

10.4.2 BSC Receiving a Connection Failure Indication MessageThis topic describes the fault, probable causes, and handling suggestions.

10.4.3 BSC Receiving an Error Indication MessageThis topic describes the fault, probable causes, and handling suggestions.

10.4.1 BSC Sending an Assignment Failure MessageThis describes the fault, probable causes, and handling suggestions.

DescriptionUpon receiving the Assignment Request message, the BSC responds with an Assignment Failuremessage.

AnalysisThe probable causes are as follows:

1. Radio Interface Message FailureThe MS fails to access the speech channel. It sends an Assignment Failure message on thesignaling channel. Due to the particularity of the transmission on the Um interface, thiscase happens the most frequently and cannot be solved.

2. Equipment FailureThe BSC hardware is faulty.

3. No Radio Resource AvailableThe BSC has no appropriate speech channels for assignment. The possible reason is thatall the speech channels are busy or that the speech channels are blocked.

4. Requested Terrestrial Resource Unavailable5. Requested Transcoding/Rate Adaption Unavailable6. Terrestrial Resource Already Allocated7. Invalid Message Contents



8. Radio Interface Failure - Reversion To Old Channel9. Requested Speech Version Unavailable10. Timer T3107 expiry

Handling SuggestionsThe respective handling suggestions are as follows:l Check the access-related parameters of the antenna system, BTS boards, and BSC data

configuration.l Check the following:

– Communication between modules and subracks in the BSC

– Communication on the A interface, for example, the cable connections betweenGEIUAs and subracks

l Add TRXs to the BTS, modify the access threshold, and enable the directed retry.

l The circuits on the A interface on the BSC side are abnormal, for example, the CIC in theAssignment Request message is not available. Check the consistency of the A interfacedata on the MSC and the BSC. Check also the CIC state.

l Check the transmission on the A interface.

l Check whether the CIC configuration on the BSC and the MSC is consistent. If not,manually reset the CIC on the BSC6000 Local Maintenance Terminal.

l Check whether the message conforms to the protocols.

l Check the environment quality on the Um interface. For example, check the quality of thelevel.

l Check whether the BSC supports the requested speech version.

l Check whether the timeout value of timer T3107 is appropriate.


FaultDuring the assignment procedure, the BSC receives a Connection Failure Indication message.

Probable CausesThe probable causes are as follows:l Radio link failure

l Hardware failure

Handling SuggestionsThe handling suggestions are as follows:l Check the resources on the Um interface.

l Check the following:– Communication between subracks




– Communication on the A interface, for example, the cable connections betweenGEIUBs and subracks

10.4.3 BSC Receiving an Error Indication MessageThis topic describes the fault, probable causes, and handling suggestions.

FaultDuring the assignment procedure, the BSC receives an Error Indication message.


l Protocol disconformity

l Link layer failure

l Timer T200 expiry

l MS failure in receiving a UA frame

Handling SuggestionsThe respective handling suggestions are as follows:

l Check the contents of the frames at the data link layer.

l Check the status of the data link layer.

l Check the timeout value of timer T200.

l Check the contents of the SABM frame.



11 Mobile Originating Call Establishment

About This Chapter

Mobile originating call refers to an MS calling another MS or a fixed phone.

11.1 Mobile Originating Call Establishment ProcedureIn terms of the assignment type, the mobile originating call establishment procedure iscategorized into the early assignment procedure, late assignment procedure, and very earlyassignment procedure. The MSC determines the early assignment procedure and the lateassignment procedure. The BSS determines the very early assignment procedure based on theradio resources.

11.2 Internal BSC Signaling Procedure of Mobile Originating Call EstablishmentThis describes the internal BSC signaling procedure of mobile originating call establishment.

11.3 Abnormal Mobile Originating Call Establishment CasesThis topic describes the abnormal mobile originating call establishment cases.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 11 Mobile Originating Call Establishment


11.1 Mobile Originating Call Establishment ProcedureIn terms of the assignment type, the mobile originating call establishment procedure iscategorized into the early assignment procedure, late assignment procedure, and very earlyassignment procedure. The MSC determines the early assignment procedure and the lateassignment procedure. The BSS determines the very early assignment procedure based on theradio resources.

11.1.1 Early Assignment ProcedureThis topic describes the early assignment procedure, namely the mobile originating callestablishment without OACSU procedure.

11.1.2 Late Assignment ProcedureThis topic describes the late assignment procedure, namely the mobile originating callestablishment with OACSU procedure.

11.1.3 Very Early Assignment ProcedureThis topic describes the very early assignment procedure, namely the Mobile Originating CallEstablishment with OACSU procedure.

11.1.1 Early Assignment ProcedureThis topic describes the early assignment procedure, namely the mobile originating callestablishment without OACSU procedure.

Figure 11-1 shows the early assignment procedure.

11 Mobile Originating Call EstablishmentHUAWEI BSC6000 Base Station Subsystem



Figure 11-1 Early assignment procedure

MS BTS MSC

Setup(5)

BSC

FACCH

SDCCH

Immediate Assignment Procedure

Establish Indication(CM Service Request)(1)

CC(3)

CR(L3:CMService Request)(2)

CM Service Accepted(4)

Call Proceeding(6)SDCCH

TCH Assignment Procedure

FACCH

Alerting(7)

FACCH

Connect(8)

Connect Acknowledge(9)SDCCH

Talking(10)

Release Procedure

The early assignment procedure is as follows:

1. The BTS sends the BSC an Establishment Indication message. The EstablishmentIndication message accurately indicates the reason for the access of an MS, for example,the cause values for mobile originating call establishment and for IMSI detach are different.The message also carries the content of the CM Service Request message.

2. The BSC establishes an SCCP link connection on the A interface and sends the MSC a CMService Request message.

3. The MSC sends the BSC a Connect Confirm message.4. The MSC sends the MS a CM Service Accepted message on the SDCCH on the Um

interface.



5. The calling MS sends a Setup message on the SDCCH. The Setup message carries all theinformation required on the network side for processing the call, including the number ofthe called MS.

6. The MSC sends the calling MS a Call Proceeding message on the SDCCH on the Uminterface. The Call Proceeding message indicates that a call is being processed and themobile originating call processing procedure is initiated.

7. The MSC sends the MS an Alerting message on the FACCH on the Um interface. Thenthe calling MS hears a ringing tone.

8. The MSC sends the calling MS a Connect message on the FACCH on the Um interface.The Connect message is used to notify the MS that the connection is established.

9. The calling MS responds to the MSC with a Connect Acknowledge message on theFACCH.

10. The calling and the called MSs enter the session state.

11.1.2 Late Assignment ProcedureThis topic describes the late assignment procedure, namely the mobile originating callestablishment with OACSU procedure.

Figure 11-2 shows the late assignment procedure.




Figure 11-2 Late assignment procedure

MS BTS MSC

Setup(5)

BSC

SDCCH

SDCCH



CC(3)



Call Proceeding(6)SDCCH


SDCCHAlerting(7)

FACCH

Connect(8)

Connect Acknowledge(9)SDCCH

Talking(10)

Release Procedure

For details about the late assignment procedure, refer to 11.1.1 Early Assignment Procedure.

1. The difference between the late assignment procedure and the early assignment procedureis that the assignment procedure of the former takes place after the Alerting message issent.

2. The late assignment saves the seizure time of speech channels.3. The disadvantage of the procedure shown in Figure 11-2 is that if the subsequent

assignment is unsuccessful, the called MS can only hear the ring tone but cannot makecalls.Therefore, in actual application, the early assignment procedure is used instead of the lateassignment procedure.



11.1.3 Very Early Assignment ProcedureThis topic describes the very early assignment procedure, namely the Mobile Originating CallEstablishment with OACSU procedure.

Figure 11-3 shows the very early assignment procedure.

Figure 11-3 Very early assignment procedure

MS BTS MSC

Setup(5)

BSC

FACCH

FACCH

Immediate Assignment TCH Procedure


CC(3)



Call Proceeding(6)FACCH

TCH Mode Modify

FACCHAlerting(7)

FACCH

Connect(8)

Connect Acknowledge(9)FACCH

Talking(10)

Release Procedure

For details about the very early assignment procedure, refer to 11.1.1 Early AssignmentProcedure.

1. The difference between the very early assignment procedure and the 11.1.1 EarlyAssignment Procedure is that in the former, the TCH is assigned as a signaling channelduring the immediate assignment procedure. Therefore, no TCH needs to be assignedduring the assignment procedure, and the assigned TCH is adjusted to a speech channelthrough the Mode Modify message.




2. During the immediate assignment procedure, if no idle SDCCHs but TCHs are availableand TCH immediate assignment is allowed in the BSC data configuration, the very earlyassignment procedure will take place.

11.2 Internal BSC Signaling Procedure of MobileOriginating Call Establishment

This describes the internal BSC signaling procedure of mobile originating call establishment.

The internal BSC signaling procedure of mobile originating call establishment is as follows:

1. On receiving the Channel Required message from the BTS, the BSC assigns a signalingchannel according to the channel type and channel assignment algorithm in the ChannelRequired message. The TCH Immediate Assignment Allowed in the Cell Attributeswindow may be involved in the channel assignment.

2. During random access, on receiving the Establish Indication message from the BTS, theBSC sends the MSC a CM Service Request message that carries the target CGI based onthe MCC, MNC, LAC, and CI.

3. On receiving the Assignment Request message from the MSC, the BSC checks the channeltype. Choose Other Attributes > Advanced > Other Parameters. Check whether DataService Allowed is supported.

4. If the data service is not supported, an Assignment Failure message is returned. Based onthe CIC in the Assignment Request message, the BSC checks the E1 timeslots on the Ainterface and confirms the existence of CIC. It also checks whether the circuit pool of theconfigured CIC, the channel type in the Assignment Request message, and the capacity ofthe GDPUC are collided. If they are collided, the BSC responds with an Assignment Failuremessage.

5. On receiving the Assignment Complete message from the MS, the BSC fills the messagewith the A Interface Tag and sends the message to the MSC. You can choose BSCProperty > Basic Data to display the A Interface Tag.

11.3 Abnormal Mobile Originating Call EstablishmentCases

This topic describes the abnormal mobile originating call establishment cases.

11.3.1 Calling MS Cannot Be HeardThis topic describes the fault, probable causes, and handling suggestions.

11.3.2 MSC Releasing the Call after Sending a CM Service Reject MessageThis topic describes the fault, probable causes, and handling suggestions.

11.3.3 Abnormal Procedure Caused by MS in Busy StateThis topic describes the fault, probable causes, and handling suggestions.

11.3.4 MSC Sending a Disconnect Message Instead of an Assignment Request MessageThis topic describes the fault, probable causes, and handling suggestions.

11.3.5 Abnormal Procedures Caused by MS HangupThis topic describes the fault, probable causes, and handling suggestions.



11.3.6 Abnormal Procedures Caused by MSC Sending a Clear Command Message or aDisconnect MessageThis topic describes the fault, probable causes, and handling suggestions.

11.3.7 LAPD Reporting an Error Indication Message During Call EstablishmentThis topic describes the fault, probable causes, and handling suggestions.

11.3.1 Calling MS Cannot Be HeardThis topic describes the fault, probable causes, and handling suggestions.

FaultWhen late assignment is enabled, the called MS cannot hear the calling MS.

Probable CausesTCH assignment fails.

Handling SuggestionsDisable the late assignment.

11.3.2 MSC Releasing the Call after Sending a CM Service RejectMessage


FaultAfter sending a CM Service Reject message, the MSC sends a Clear Command message torelease the call.


l The MSC cannot find the subscriber information and considers that the subscriber is illegal.

l Authentication or encryption fails.

l The MSC does not support the applied service in the CM Service Request message.

l The MSC has no sufficient resources for the access, for example, no idle CICs.

Handling SuggestionsThe handling suggestions are as follows:

l The MS makes a subscription under the MSC.

l Check the subscriber information.

l Hand over the MS to a cell under another MSC.

l Wait for the MSC to release the resources, or expand the MSC transmission capability onthe A interface.




11.3.3 Abnormal Procedure Caused by MS in Busy StateThis topic describes the fault, probable causes, and handling suggestions.

FaultAfter the assignment success of the calling MS, the network sends a Disconnect message withthe cause value User Busy. The onhook by the calling MS or a Clear Command message sentby the MSC triggers the release of the BSC resources.

Probable CausesThe MS is busy.

Handling SuggestionsWait for the onhook of the called MS and make a second call.

11.3.4 MSC Sending a Disconnect Message Instead of anAssignment Request Message


FaultThe MSC does not send an Assignment Request message. It sends a Disconnect message to clearthe call.

Probable CausesThe A interface may be faulty.

Handling SuggestionsCheck the following:

l The state of the A interface circuit on the MSC side

l The consistency of the A interface data on the MSC and the BSC, especially the circuitpool data

11.3.5 Abnormal Procedures Caused by MS HangupThis topic describes the fault, probable causes, and handling suggestions.

FaultThe call establishment procedure is terminated.

Probable Causesl The MS hangs up.

l The calling or the called MS hangs up during a procedure, which causes abnormality in thesubsequent procedures. For example, after the BSC receives an Assignment Request



message from the MSC, the MS suddenly hangs up. In that case, the call establishmentprocedure may be terminated before the BSC responds to the MSC with an AssignmentComplete message or an Assignment Failure message. As a result, the procedure is neithera successful assignment procedure (The BSC sends an Assignment Complete message.)nor an unsuccessful assignment procedure (The BSC sends an Assignment Failuremessage.).

Handling Suggestions

No handling is required.

11.3.6 Abnormal Procedures Caused by MSC Sending a ClearCommand Message or a Disconnect Message


Fault

The MSC sends a Clear Command message or a Disconnect message.

Probable Causes

Check the following:

l The cause value in the Clear Command messageIf a call terminates normally, the cause value in the Clear Command message is CallControl. Otherwise, the cause value may be Protocol Error or Equipment Failure.

l The time difference between the previous message and the Clear Command message or theDisconnect messageCheck whether the abnormal procedure is triggered by timeout.

Handling Suggestionsl If the cause value in the Clear Command message is Call Control, no abnormality exists.

If the cause value in the Clear Command message is Protocol Error, refer to the relatedprotocols. If the cause value in the Clear Command message is Equipment Failure, checkthe related BSC hardware:– Connection on the Ater interface

– GEIUA in the GTCS

l Check the timeout values of the related timers.

11.3.7 LAPD Reporting an Error Indication Message During CallEstablishment


Fault

The LAPD reports an Error Indication message during call establishment.





l Inconformity with protocols

l LAPD link failure

l Timer T200 expiry

l MS failure in receiving a UA frame


l Check the contents of the frames at the data link layer.

l Check the status of the data link layer.

l Check the timeout value of timer T200.

l Check contents of the SABM frame.



12 Mobile Terminating Call Establishment

About This Chapter

Mobile terminating call refers to an MS called by another MS or a fixed phone.

12.1 Mobile Terminating Call Establishment ProcedureThis topic describes the mobile terminating call establishment procedure. For details, refer toGSM Rec. 24008, 24080, 48008, 48018, and 48058.

12.2 Internal BSC Signaling Procedure of Mobile Terminating Call EstablishmentThis describes the internal BSC signaling procedure of mobile terminating call establishment.

12.3 Abnormal Mobile Terminating Call Establishment CasesThis topic describes the abnormal mobile terminating call establishment cases.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 12 Mobile Terminating Call Establishment


12.1 Mobile Terminating Call Establishment ProcedureThis topic describes the mobile terminating call establishment procedure. For details, refer toGSM Rec. 24008, 24080, 48008, 48018, and 48058.

Figure 12-1 shows the mobile terminating call establishment procedure.

Figure 12-1 Mobile terminating call establishment procedure

MS BTS MSC

Setup(9)

BSC

PCH


Paging(1)


Alerting(11)

Call Confirmmed(10)

FACCH

Talking(14)

Release Procedure

Paging Command(2)Paging Request(3)

ChannelRequest(4)

Establish Indication(Paging Response)(5)

RACH

CR(CL31)(6)

CC(7)

CM Service Accepted(8)SDCCH

SDCCH

SDCCH

Connect(12)

FACCH ConnectAcknowledge(13)

FACCH

The mobile terminating call establishment procedure is as follows:

1. When the paged MS is in the service area of the MSC, the MSC sends the BSC a Pagingmessage. The Paging message can also be sent to the BSC by the SGSN through the PCUon the Gb interface. It carries a list of paging cells (optional), TMSI, and IMSI.

12 Mobile Terminating Call EstablishmentHUAWEI BSC6000 Base Station Subsystem



2. The BSC sends the BTS a Paging Command message that carries the number of theoccupied timeslot and the number of the paging sub-channel.

3. Upon receiving the Paging Command message from the BSC, the BTS sends the pagedMS a Paging Request message on the paging sub-channel. The Paging Request messagecarries the IMSI or TMSI of the paged MS.

4. After decoding the Paging message, if the MS finds itself the paged MS, it sends the BTSa Channel Request message to trigger an Initial Channel Assignment procedure.

5. For details about other messages, refer to 11.1 Mobile Originating Call EstablishmentProcedure.

12.2 Internal BSC Signaling Procedure of MobileTerminating Call Establishment

This describes the internal BSC signaling procedure of mobile terminating call establishment.

The internal BSC signaling procedure of mobile terminating call establishment is as follows:

1. On receiving the Paging message, the BSC forwards the message to the service module inthe BM subrack that is configured with SS7. Based on the CGI in the Paging message, theservice module checks the information of the paged cell. If the paged cell is in the BMsubrack where the service module is located, the service module directly sends the Pagingmessage to the cell. If the paged cell is in another BM subrack, the service module forwardsthe Paging message to the service module in that BM subrack.

2. The service module in the BM subrack first checks whether the Allow eMLPP is set toYes in Call Control of > Cell Attributes. Then the service module determines the pagingpacket based on the BS_AG_BLKS_RES, CCCH_CONF, and BS_PA_MFRAMES inIdle Mode of > Cell Attributes. After that, it sends the Paging message to the BTS.

12.3 Abnormal Mobile Terminating Call EstablishmentCases

This topic describes the abnormal mobile terminating call establishment cases.

12.3.1 No Paging Message on the A InterfaceThis topic describes the fault, probable causes, and handling suggestions.

12.3.2 No Paging Message on the Abis InterfaceThis describes the fault, probable causes, and handling suggestions.

12.3.3 No Paging Response on the Abis InterfaceThis describes the fault, probable causes, and handling suggestions.

12.3.4 No Paging Response on the A InterfaceThis topic describes the fault, probable causes, and handling suggestions.

12.3.1 No Paging Message on the A InterfaceThis topic describes the fault, probable causes, and handling suggestions.



FaultThe MSC does not send a Paging message to the BSC, as indicated in the signaling tracing onthe A interface.

Probable CausesThe probable cause lies on the NSS side.

Handling SuggestionsCheck the data configuration and subscriber information in the MSC/VLR and the HLR. Poweroff the called MS and then power it on to make test calls.

l Check whether the subscriber data in the VLR is correct.When an MS is called, the MSC determines the current state of the MS based on thesubscriber data in the VLR. The subscriber data includes the the active state, registeredlocation area, and registered cells. Then the MSC determines whether and how to send aPaging message.If the state of the MS changes, for example, the MS is switched off or moves to anotherlocation area, but it has not registered in the network or the subscriber data in the VLR isnot updated, the paging may fail.In this case, the MS needs to originate a location update procedure to ensure that thesubscriber data in the VLR is correct. On the BSC side, the system information indicatesthe location update period of the MS. For details, refer to 6.1 Location UpdateProcedure. On the MSC side, there is also a location update period. The location updateperiod on the BSC side is shorter than that on the MSC side. Therefore, the MS mustoriginate a location update within the period specified by the MSC.

l Check whether the parameters of location areas and cells on the MSC side are correct.Incorrect parameter configuration of location areas and cells on the MSC side may lead tounsuccessful transmission of the Paging message. For example, if the target BSC isincorrectly configured, the Paging message is sent to the wrong BSC.

12.3.2 No Paging Message on the Abis InterfaceThis describes the fault, probable causes, and handling suggestions.

DescriptionUpon receiving the Paging message from the MSC, the BSC does not send a Paging Commandmessage to the BTS, as indicated in the message tracing on the Abis interface.

AnalysisThe probable cause lies on the BSC side.

Handling Suggestionsl Check whether the flow control procedure is triggered.

– Check whether the PCH or AGCH is overloaded due to a sharp increase in shortmessages or a burst of access requests.




You can verify the change by comparing the values of the counters ImmediateAssignment Requests and MSC Paging Requests (Circuit Service) before and afterthe problem occurs.

– Choose BSC Property > Flow Control Data. Check whether the flow controlparameters are consistent with those described in the Version Matching Guide.

l Check whether the data is correct.– Check whether the CGI on the BSC side is consistent with that in the LAC carried in

the Paging message.Check whether the configuration data of the cell is correct on the BSC6000 LocalMaintenance Terminal.Incorrect parameter configuration of location areas and cells on the MSC side may leadto unsuccessful transmission of the Paging message. For example, if the target BSC isincorrectly configured, the Paging message is sent to the wrong BSC.

– Check whether the paging-related parameters on the BSC side are configured correctly.Choose Cell Attributes > Idle Mode. Check whether the parametersBS_AG_BLKS_RES, CCCH_CONF, and BS_PA_MFRAMES are set correctly.

l Check the communications between the subracks in the BSC.On receiving the Paging message from the MSC, the BSC starts paging based on thelocation area and cell information in the Paging message. Huawei BSC has multiplesubracks. The Paging Command message sent from the BSC to the BTS may be forwardedbetween subracks. If the communication between the subracks is abnormal, the PagingCommand message may not be forwarded, and no Paging Command message is sent onthe Abis interface.You can view the BSC alarms to check the communication between the modules.

12.3.3 No Paging Response on the Abis InterfaceThis describes the fault, probable causes, and handling suggestions.

DescriptionAfter sending the BTS a Paging Command message, the BSC does not receive an EstablishmentIndication (Paging Response) message, as indicated in the message tracing on the Abis interface.

AnalysisThe probable causes are incorrect data configuration and poor radio coverage.

Handling Suggestionsl Check whether the PCH or AGCH is overloaded due to a sharp increase in short messages

or a burst of access requests.You can verify the change by comparing the values of the counters Immediate AssignmentRequests and MSC Paging Requests (Circuit Service) before and after the problemoccurs.

l Check whether the problem lies in the mobile equipment or in the SIM.Faulty mobile equipment or faulty SIM may lead to the problem.– Insert another SIM into the mobile equipment to check whether the problem lies in the

SIM.



– Insert the SIM into another mobile equipment to check whether the problem lies in themobile equipment.

l To check whether the problem lies in the BTS, make test calls in the following locations:– Other cells under the same BTS

– Other sites of the same site type

– Other sites of a different site type

– Sites from other manufacturers

l Check whether the data is correct.– Check whether the paging-related parameters on the BSC side are configured correctly.

Choose Cell Attributes > Idle Mode. Check whether the parametersBS_AG_BLKS_RES, CCCH_CONF, BS_PA_MFRAMES, and TX-Integer(RACH Timeslot (Equals to a TDMA Rrame, 4.615 ms) are set correctly.Choose Cell Attributes > Call Control. Check whether the parameters such as theMS MAX Retrans are set correctly.

– Check whether the values of the Location Update Period on the BSC and the MSCare set correctly.Choose Cell Attributes > Call Control. Check whether the parameters such as thePeriod of Periodic Location Update (6 minutes) are set correctly.The location update period on the BSC side is shorter than that on the MSC side.For details, refer to 6.1 Location Update Procedure.

l Check the radio coverage.Poor radio coverage may lead to the existence of dead zones where an MS cannot receivethe Paging Request message. Therefore, it cannot be paged. This case does not existglobally.

12.3.4 No Paging Response on the A InterfaceThis topic describes the fault, probable causes, and handling suggestions.

FaultUpon receiving the Establishment Indication (Paging Response) message from the BTS, theBSC does not send any message to the MSC, as indicated in the message tracing on the Abisinterface and the A interface.

Probable CausesThe SS7 is faulty.

Handling SuggestionsTroubleshoot the SS7 signaling intermittence.




13 BSC Release

About This Chapter

BSC release consists of the normal release and the local release.

13.1 Normal Release ProcedureNormal release is originated by the MS or the MSC. Upon onhook, the calling MS sends aDisconnect message to the MSC. Then the corresponding MSC sends the Disconnect messageto the called MS.

13.2 Local Release ProcedureThe local release procedure is initiated by the BSC.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 13 BSC Release


13.1 Normal Release ProcedureNormal release is originated by the MS or the MSC. Upon onhook, the calling MS sends aDisconnect message to the MSC. Then the corresponding MSC sends the Disconnect messageto the called MS.

Signaling ProcedureAfter the access of the MS, the BSC initiates the release procedure upon service requests, forexample, MS onhook. Figure 13-1 shows the BSC normal release procedure.

13 BSC ReleaseHUAWEI BSC6000 Base Station Subsystem



Figure 13-1 Normal release procedure

MS BTS MSC

Release Complete(3)

BSC

Disconnect(1)

FACCH

Stop T3109

Stop T3109

Start T305

Release(2)FACCH

Start T308

Start T305

Stop T308

FACCH

Clear Command(4)Channel Release(5)

FACCH

Deactivate SACCH(8)DISC(6)

FACCH

UA(7)FACCH

Release Indication(9)

Start T3111

Stop T3111

RF Channel Release(10)Clear Complete(11)

RF Channel ReleaseAcknowledge(12)

RLSD(13)

RLC(14)

The BSC normal release procedure is as follows:

1. Upon onhook, the calling MS sends a Disconnect message to the MSC and starts timerT305. The Disconnect message carries the cause for disconnection.



2. The MSC sends the calling MS a Release message and at the same time sends the calledMS a Disconnect message. The network starts timer T308.

3. Upon receiving the Release message, the calling MS stops timer T305, releases the MMconnection, and sends the MSC a Release Complete message.

4. Upon receiving the Release Complete message, the MSC stops timer T308, releases theMM connection, and sends the BSC a Clear Command message. The Clear Commandmessage notifies the BSC of releasing the resources on the A interface and the Um interface.

5. The BSC sends a Channel Release message and starts timer T3109. The Channel Releasemessage carries the RR cause filed and notifies the MS and the BTS of releasing the logicchannels on the Um interface.

6. Upon receiving the Channel Release message, the MS disconnects the uplink signaling linkand sends the BTS a DISC frame, indicating that the logic channels are released.

7. The BTS sends the MS a UA frame. Upon receiving the UA frame, the MS returns to theCCCH and enters the idle state.

8. The BSC sends the BTS a Deactivate SACCH message, deactivates the associated channels,and releases the downlink channel associated signaling.

9. Upon receiving the DISC frame, the BTS sends the BSC a Release Indication message,stops timer T3109, and starts timer T3111. The Release Indication message indicates thatthe MS has released the logic channels on the Um interface.

10. Upon timer T3111 expiry, the BSC sends the BTS an RF Channel Release message. TimerT3111 is used to reserve a period for the acknowledgement of disrupted connection.

11. The BTS sends the BSC an RF Channel Release Acknowledge message, indicating that theRF channels on the radio interface are released and can be used for re-assignment.

12. The BSC responds to the MSC with a Clear Complete message.13. The MSC sends the BSC an RLSD message to release the SCCP connection.14. The BSC responds to the MSC with an RLC message, indicating that the SCCP connection

is released.

Procedure Descriptionl Steps 1 through 3 shown in Figure 13-1 is the call connection release.

NOTE

Figure 13-1 shows the MS originating release procedure. For the network originating releaseprocedure, the directions of only the three transparent transmission messages are opposite.

l Steps 4 through 14 shown in Figure 13-1 is the radio resource release.After the connections at the CC layer and at the MM layer are released, the network sendsthe BSC a Clear Command message to request the release of the SCCP signaling link. TheClear Command message carries the clear causes such as the Handover Successful or CallControl. If the release is caused by radio interface message failures, radio link failures, orequipment failures, the BSC sends a Clear Request message to the system. Then, the MSCdelivers the Clear Command message.

13.2 Local Release ProcedureThe local release procedure is initiated by the BSC.

Figure 13-2 shows the local release procedure.

13 BSC ReleaseHUAWEI BSC6000 Base Station Subsystem



Figure 13-2 Local release procedure

Deactivate SACCH (1)

Release Request (2)

RF Channel Release(4)

RF Channel Release Acknowledge (5)

BTS BSC

Release Confirm (3)

l The BSC sends the BTS a Deactivate SACCH message to deactivate the associatedchannels.

l The BSC sends the BTS a Release Request message with the cause value Local End Release.In this case, the release procedure has nothing to do with the MS.

l Upon receiving the Release Request message with the cause value Local End Release, theBTS responds to the BSC with a Release Confirm message. If the Release Request messagecarries other cause values, the BTS sends a DISC frame to the MS. Only after receivingthe UA frame or DM frame from the MS, the BTS sends the Release Confirm message tothe BSC.

l The BSC sends an RF Channel Release message to the BTS.

l The BTS sends an RF Channel Release Acknowledge message to the BSC.



14 Handover

About This Chapter

Handover is one of the basic functions of the GSM. It enables calls to be set up in better cellsand reduces call drops. Handover also lowers cross interference. The handover procedureconsists of handover triggering, handover preparation, handover decision, and handoverexecution.

14.1 Handover ProcedureThe handover procedure is categorized into the intra-BSC handover procedure, inter-BSChandover procedure, inter-MSC handover procedure, and inter-system handover procedure.

14.2 Internal BSC Signaling Procedure of HandoverThe internal BSC signaling procedure of handover is categorized by intra-BSC handover, inter-BSC handover, inter-MSC handover, and inter-system handover.

14.3 Abnormal Handover CasesThis topic describes the abnormal handover cases.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 14 Handover


14.1 Handover ProcedureThe handover procedure is categorized into the intra-BSC handover procedure, inter-BSChandover procedure, inter-MSC handover procedure, and inter-system handover procedure.

14.1.1 Intra-BSC Handover ProcedureThis topic describes the intra-BSC handover procedure.

14.1.2 Inter-BSC Handover ProcedureThis topic describes the inter-BSC handover procedure.

14.1.3 Inter-MSC Handover ProcedureThis topic describes the inter-MSC handover procedure.

14.1.4 Inter-System Handover ProcedureThis topic describes the inter-system handover procedure.

14.1.1 Intra-BSC Handover ProcedureThis topic describes the intra-BSC handover procedure.

Figure 14-1 shows the intra-BSC handover procedure.

14 HandoverHUAWEI BSC6000 Base Station Subsystem



Figure 14-1 Intra-BSC handover procedure

MS BTS2 BTS1BSC


EstablishIndication(10)

SACCH

MS MSC

MeasurementReport(1)Measurement

Result(2)

HandoverCommand(5)


FACCHStart T3103

HandoverAccess(6)

FACCH

Start T3124

HandoverAccess

FACCHHandover Detect(7)

PHY INFO(8)

FACCH

Stop T3124

SABM(9)

FACCH

UA(11)

FACCH HandoverComplete(12)

FACCH

Stop T3103Handover

Perfomed(13)

1. The MS sends BTS1 a measurement report on an SACCH on the Um interface.

2. BTS 1 forwards the measurement report to the BSC.

3. Based on the measurement report, the BSC determines whether to hand over the MS toanother cell. If a handover is required, the BSC sends BTS 2 a Channel Activation message.

4. Upon receiving the Channel Activation message, if the channel type is correct, BTS 2 turnson the power amplifier on the specified channel to receive information on the uplink, andsends a Channel Activation Acknowledge message to the BSC.

5. Upon receiving the Channel Activation Acknowledge message, the BSC sends BTS 1 aHandover Command message. Then BTS 1 forwards the command to the MS. The messageis sent on an FACCH on the Um interface. BTS 1 starts timer T3103. The HandoverCommand message has all the information to be transferred on the new channel and thedata required for accessing the MS. It also indicates whether the handover is synchronousor asynchronous.

6. Upon receiving the Handover Command message, the MS attempts the access and sendsBTS 2 a Handover Access message on the FACCH.



7. Upon receiving the Handover Access message, BTS 2 sends the BSC a Handover Detectmessage.

8. Whether a PHY INFO message is sent or not depends on the handover type.l Asynchronous handover

After the channels of BTS 2 are activated, BTS 2 waits for the access of the MS on adedicated channel until timer T3103 expires. Upon detecting the Handover Accessmessage from the MS, BTS 2 sends the BSC a Handover Detect message and at thesame time to the MS a PHY INFO message on an FACCH. The PHY INFO messagecarries the new TA calculated by BTS 2. Upon receiving the PHY INFO message, theMS sends BTS 2 an SABM frame.

l Synchronous handoverBTS2 does not send the PHY INFO message. Upon sending the Handover Accessmessage, the MS sends BTS 2 the SABM frame.

9. When the PHY INFO message is sent depends on the handover type.l Asynchronous handover

The MS starts timer T3124 upon sending the Handover Access message for the firsttime. It stops timer T3124 upon receiving the PHY INFO message, and sends BTS 2an SABM frame on an FACCH.

l Synchronous handoverUpon sending the Handover Access message, the MS sends BTS 2 an SABM frame.

10. Upon receiving the first SABM frame, BTS 2 sends an Establishment Indication messageto notify the BSC of radio link establishment.

11. At the same time, BTS2 sends a UA frame on an FACCH to notify the MS of radio linkestablishment.

12. The MS sends BTS 2 a Handover Complete message on the FACCH. BTS 2 forwards themessage to notify the BSC of the handover success. The Handover Complete messagecarries only the handover complete indication. The MS does not return to the old channelafter sending this message. If the MS does not receive the PHY INFO message or the UAframe from the target cell, it sends a Handover Failure message on the old channel.

13. Upon receiving the Handover Complete message, the BSC stops timer T3103 and sends aHandover Performed message to notify the MSC of the handover completion. TheHandover Performed message carries the handover type. At the same time, the BSC sendsan RF Channel Release message to notify BTS 1 of channel release. The target cell forwardsto the BSC the Handover Complete message it receives from the MS. Upon receiving theHandover Complete message, the BSC sends an RF Channel Release message to notifyBTS 1 of channel release. Upon receiving the RF Channel Release message, BTS 1 sendsan RF Channel Release Acknowledge message. The message indicates that the radiochannel is released and ready for reallocation.

14.1.2 Inter-BSC Handover ProcedureThis topic describes the inter-BSC handover procedure.

Figure 14-2 shows the inter-BSC handover procedure.




Figure 14-2 Inter-BSC handover procedure

MS BTS1 MSCBSC1 BSC2 BTS2

MeasurementReport from MS(1) Handover

Required(2)SACCH

FACCH

MS

HandoverRequest(3) Channel

Activation(4)Start T7 Channel Activation

Acknowledge(5)Handover RequestAcknowledge(6)Handover

Command(7)

Stop T7

HandoverCommand(8)

Start T8

HandoverCommand(9)

HandoverAccess(9)

StartT3124

HandoverAccess(10)

FACCH

HandoverDetect(11)Handover

Detect(12)PHY

INFO(13)

FACCH

SABM(14)

FACCH

StopT3124


UA(16)

FACCH

FACCH

HandoverComplete(17)Handover

Complete(18)HandoverComplete(19)Clear

Command(20)

Stop T8

ClearComplete(21)

The inter-BSC handover procedure involves more A-interface signaling procedures than theintra-BSC handover procedure. These signaling procedures are described subsequently. Fordetails about other signaling messages, refer to 14.1.2 Inter-BSC Handover Procedure.

1. When an MS needs to be handed over to a cell controlled by BSC 2, BSC 1 sends the MSCa Handover Required message and starts timer T7. This message carries the CELL IDs ofthe target cell group and the serving cell, and the handover cause.

2. Upon receiving the Handover Required message, if the MSC finds that the location area ofthe target cell is under itself, it sends BSC 2 a Handover Request message. The HandoverRequest message carries the information, transmission mode, MS classmark, and requiredchannel classmark of the serving and the target cells. Upon receiving the Handover Requestmessage, BSC 2 sends the MSC an SCCP Connection Confirm message, indicating that its



connection to the MSC is established. The A interface messages are sent through this SCCPconnection.

3. BSC 2 activates a new channel and sends a Handover Request Acknowledge message tonotify the MSC that the channel is now available. The Handover Request Acknowledgemessage carries the information of the allocated handover resources and the handovercommand indicating that the BSC is ready.

4. Upon receiving the Handover Request Acknowledge message, the MSC sends BSC 1 aHandover Command message. Then BSC 1 stops timer T7. BSC 1 sends the MS a HandoverCommand message and starts timer T8, requesting the MS to access the new channel. TheHandover Command message carries the cell ID, channel type, and handover reference.

5. Upon receiving the Handover Complete message from BSC 2, the MSC sends BSC 1 aClear Command message. The Clear Command message carries the clearance causes. BSC1 stops timer T8, initiates a channel release procedure, and sends the MSC a Clear Completemessage.

NOTE

If the serving cell and the target cell are in different location areas, the MS initiates a location updateprocedure after a call is complete.

14.1.3 Inter-MSC Handover ProcedureThis topic describes the inter-MSC handover procedure.

Figure 14-3 shows the inter-MSC handover procedure.




Figure 14-3 Inter-MSC handover procedure

MS BTS1 MSC1BSC1 MSC2 BSC2

MeasurementReport

from MS(1) HandoverRequired(2)

SACCH

FACCH

BTS2

PerformHandover(3) Channel

Activation(5)

Channel ActivationAcknowledge(6)Handover Request

Acknowledge(7)

HandoverCommand(12)

HandoverAccess(13)

FACCHHandoverDetect(14)Handover

Detect(15) PHYINFO(16)

FACCH

SABM(18)

FACCHEstablish

Indication(19)

UA(20)

FACCH

FACCH

HandoverComplete(21)Handover

Complete(22)HandoverComplete(23)Send

End Signal(24)

ClearComplete(26)

MS

HandoverRequest(4)

RadioChannel Ack(8)

IAM(9)

ACM(10)HandoverCommand(11)

PHYINFO(17)

FACCH

ClearCommand(25)

For the inter-MSC handover procedure, refer to 14.1.1 Intra-BSC Handover Procedure and14.1.2 Inter-BSC Handover Procedure.

The messages on the E interface are as follows:

1. Perform Handover: MAP layer message. It contains the CGI of the serving cell and thetarget cell and the required channel type. It informs MSC2 that a handover will be initiated.

2. Radio Channel Acknowledge: MAP layer message. It carries the information of the newchannel in the target cell and the handover number.

3. IAM: initial address message. It is a TUP/ISUP message.4. ACM: address complete message. It is a TUP/ISUP message.5. Send End Signal: MAP layer message.

14.1.4 Inter-System Handover ProcedureThis topic describes the inter-system handover procedure.



Figure 14-4 shows the inter-system handover procedure.

Figure 14-4 GSM-to-UMTS handover procedure

MS BSS RNCMSC

Handover Required(1)

FACCH

MS

Inter System to UTRANHandover Command(2)

Start T3121 Handover toUTRAN Complete(4)

HandoverCommand(3)

HandoverComplete(5)

Stop T3121

Clear Command(6)

Clear Complete(7)

FACCH

Figure 14-5 UMTS-to-GSM handover procedure

MS BSS RNCMSC MS

HandoverCommand(4)

FACCH

HandoverRequest(1)

FACCHHandoverAccess(7)

FACCH

Handover Detect(6)

Handover RequestAcknowledge(2) Handover Request

Acbowledge(3)HandoverAccess(5)

HandoverComplete(8) Handover

Complete(9)

The GSM-to-UMTS handover procedure is as follows:

1. The BSS sends a Handover Required message to the MSC.2. Upon receiving the Handover Required message, the MSC sends the BSS an Inter System

To UTRAN Handover Command message and starts timer T3121.3. Upon receiving the Inter System To UTRAN Handover Command message, the BSS sends

the MS a Handover Command message on an FACCH.4. After the connection is successfully established, the MS sends the RNC a Handover to

UTRAN Complete message on a UTRAN channel.




5. The RNC forwards the Handover Complete message to the MSC.6. Upon receiving the Handover Complete message, the MSC stops timer T3121 and initiates

a channel release procedure.

NOTE

For the UMTS-to-GSM handover procedure, refer to the GSM-to-UMTS handover procedure mentionedearlier.

14.2 Internal BSC Signaling Procedure of HandoverThe internal BSC signaling procedure of handover is categorized by intra-BSC handover, inter-BSC handover, inter-MSC handover, and inter-system handover.

14.2.1 Internal BSC Signaling Procedure of the Intra-BSC HandoverThis topic describes the internal BSC signaling procedure of the intra-BSC handover.

14.2.2 Internal BSC Signaling Procedure of the Inter-BSC HandoverThis topic describes the internal BSC signaling procedure of the inter-BSC handover.

14.2.3 Internal BSC Signaling Procedure of the Inter-MSC HandoverThis topic describes the internal BSC signaling procedure of the inter-MSC handover.

14.2.4 Internal BSC Signaling Procedure of the Inter-System HandoverThis describes the internal BSC signaling procedure of the inter-system handover.

14.2.1 Internal BSC Signaling Procedure of the Intra-BSC HandoverThis topic describes the internal BSC signaling procedure of the intra-BSC handover.

1. If the BSC considers that the call meets the handover conditions, it selects a candidate cellfrom the candidate cell list based on the priority in a descending order. If the candidate cellis internal BSC, the BSC notifies the candidate cell of initiating an intra-BSC handoverprocedure, and the candidate cell will be the target cell.

2. The target cell allocates a channel and notifies BTS 2 of channel activation.3. After BTS 2 activates the channel, BTS 1 sends the MS a Handover Command message.

Then BSC 2 starts timer T3103 to wait for the Handover Detect message.4. After receiving the Handover Detect message, BTS 2 continues to wait for the

Establishment Indication message and the Handover Complete message.5. After BTS 2 receives the Handover Complete message, BSC 2 stops timer T3103 and

considers that the call is set up in the target cell.6. BSC 1 notifies BTS 1 of initiating a local release procedure. At the same time, it sends a

Handover Performed message to notify the MSC of the handover completion.

14.2.2 Internal BSC Signaling Procedure of the Inter-BSC HandoverThis topic describes the internal BSC signaling procedure of the inter-BSC handover.

1. If the BSC considers that the call meets the handover conditions, it selects a candidate cellfrom the candidate cell list based on the priority in a descending order. If the candidate cellis an external cell, the inter-BSC handover procedure is directly triggered. For the servingcell, the external cell is the target cell, and the BSC where the target cell is located is thetarget BSC, namely BSC 2.



2. Upon handover initiation, BTS 1 sends the MSC a Handover Required message and startstimer T17 to wait for a Handover Command message.

3. Upon receiving the Handover Ruest message from the MSC, BSC 2 allocates and activateschannels according to the target cell ID in the message. After channel activation, BTS 2sends the MSC a Handover Request Acknowledge message that carries the HandoverCommand message.

4. BTS 1 forwards to the MS the Handover Command message that BSC 1 receives and atthe same time starts timer T8 to wait for the handover completion. If the Clear Commandmessage with the cause value Handover Success is received before T8 expires, BSC 1considers that the handover is successful. If the MS returns to the old channel before timerT8 expiry, BSC 1 stops timer T8 and sends the MSC a Handover Failure message. If timerT8 expires, BSC 1 considers that the call drops and sends the MSC a Clear Request message.

5. BTS 2 forwards the Handover Detect message to the MSC and continues to wait for theEstablishment Indication message and the Handover Complete message.

6. Upon receiving the Handover Complete message, BTS 2 sends a Handover Completemessage to notify the MSC of handover completion.

7. Upon receiving the Clear Command message, BTS 1 releases the radio resources the calloccupies and returns the MSC a Clear Complete message.

14.2.3 Internal BSC Signaling Procedure of the Inter-MSCHandover

This topic describes the internal BSC signaling procedure of the inter-MSC handover.

The internal BSC signaling procedure of the inter-MSC handover is the same as that describedin 14.2.2 Internal BSC Signaling Procedure of the Inter-BSC Handover.

14.2.4 Internal BSC Signaling Procedure of the Inter-SystemHandover

This describes the internal BSC signaling procedure of the inter-system handover.

Compared with the internal system handover, the BSC in the inter-system handover procedureperforms more actions as described subsequently:

l Obtaining the UTRAN neighbor cell information and the UTRAN system parameters fromthe Idle Mode, Handover Data, and Other Attributes in the Cell Attributes window.

l Recording the capability of the MS

The internal BSC signaling procedure of the inter-system handover is the same as that describedin 14.2.2 Internal BSC Signaling Procedure of the Inter-BSC Handover.

14.3 Abnormal Handover CasesThis topic describes the abnormal handover cases.

14.3.1 No Available Channels in the Target CellThis describes the fault, probable causes, and handling suggestions.

14.3.2 Old BSS Not Receiving a Specified Message upon T8 ExpiryThis describes the fault, probable causes, and handling suggestions.




14.3.3 Inter-Cell Handover Failure (MS Returning to the Old Channel)This topic describes the fault, probable causes, and handling suggestions.


14.3.5 Forced Handover FailureThis topic describes the fault, probable causes, and handling suggestions.

14.3.6 Handover Failure Caused by CIC MalfunctionThis topic describes the fault, probable causes, and handling suggestions.

14.3.7 Handover Failure Caused by MS Access FailureThis topic describes the fault, probable causes, and handling suggestions.

14.3.1 No Available Channels in the Target CellThis describes the fault, probable causes, and handling suggestions.

Description

No channels are available in the target cell.

Analysis

The probable causes are as follows:

l During an inter-cell handover, no TCHs are available in the target cell.

l During a cross-cell handover, no SDCCHs are available in the target cell.

l During an intra-cell handover due to bad quality, no TCHs are available in the cell.


The handling suggestions are as follows:

l Check whether the target cell is congested. If yes, add TRXs to the target cell.

l On the Cell Attributes tab page, click Channel Management. In the displayed dialog box,click Advanced. On the Huawei Channel Allocation Algorithm II and Radio ChannelManagement and Control tab page, check whether TCH Traffic Busy Threshold (%)is set properly.

l On the Cell Attributes tab page, click Channel Management. In the displayed dialog box,check whether Enhanced TCH Adjust Allowed is set properly.

14.3.2 Old BSS Not Receiving a Specified Message upon T8 ExpiryThis describes the fault, probable causes, and handling suggestions.

Description

The old BSS does not receive a Clear Command message from the MSC or a Handover Failuremessage from the MS upon T8 expiry.



AnalysisIf the old BSS does not receive a Clear Command message from the MSC or a Handover Failuremessage from the MS upon T8 expiry, it will release the dedicated channels and send the MSCa Clear Request message with the cause value Radio Interface Message Failure. Before a ClearCommand message is received, the terrestrial resources on the old BSS side remain allocated.On receiving the Clear Command message, the old BSS changes the state of the terrestrialresources to idle and sends a Clear Complete message to the MSC. Then the MSC releases theSCCP connection to the old BSS and thus terminates the connection with the BSS.

Handling SuggestionsOn the Cell Attributes tab page, click Other Attributes. Then click Advanced. On the CellTimer tab page, check whether T8 is set properly.

14.3.3 Inter-Cell Handover Failure (MS Returning to the OldChannel)


FaultThe MS returns to the old channel after inter-cell handover failure.

Probable CausesThe probable causes are that the MS cannot access the old channel due to bad transmissionquality on the Um interface, low level, or incorrect data configuration of the external cells.

Handling SuggestionsCheck the transmission quality on the Um interface.


FaultCalls drop.


l Radio link failure

l Hardware faults

Handling Suggestionsl Check the resources on the Um interface.

l Check the antenna system and the power amplifier.




14.3.5 Forced Handover FailureThis topic describes the fault, probable causes, and handling suggestions.

Fault

Forced handover fails.

Probable Causesl No neighbor cell

l Incorrect configuration of the neighbor cell

l No resources in the neighbor cell

l Bad radio conditions in the neighbor cell


Check the data configuration and the radio conditions of the neighbor cell, for example, the level.

14.3.6 Handover Failure Caused by CIC MalfunctionThis topic describes the fault, probable causes, and handling suggestions.

Fault

Handover fails. The cause value of the Handover Failure message is Requested TerrestrialResource Unavailable.

Probable Causes

If the CIC allocated in the Handover Request message received by the target BSC is marked asBLOCK, the target BSC will respond to the MSC with a Handover Failure message with thecause value Requested Terrestrial Resource Unavailable.


Check the state of the CIC.

14.3.7 Handover Failure Caused by MS Access FailureThis topic describes the fault, probable causes, and handling suggestions.

FaultThe MS cannot be handed over.

Probable CausesRefer to the handling suggestions.



Handling Suggestionsl Check whether the handover trigger conditions are met.

l Check whether there is a neighbor cell list in the measurement report.

l Check whether the neighbor cell has available channels.

l Check whether the data of the neighbor cell is incorrect, for example, whether there isinconsistency in CGI.




15 Call Re-Establishment

About This Chapter

The call re-establishment procedure allows an MS to resume a connection after a radio linkfailure. It may take place in a new cell or a new location area.

15.1 Call Re-Establishment ProcedureThis describes the call re-establishment procedure.

15.2 Internal BSC Signaling Procedure of Call Re-EstablishmentThe call re-establishment is controlled by the MSC, and the BSC does no special processing.

15.3 Abnormal Call Re-Establishment CasesThis topic describes the abnormal call re-establishment cases.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 15 Call Re-Establishment


15.1 Call Re-Establishment ProcedureThis describes the call re-establishment procedure.

Signaling ProcedureFigure 15-1 shows the call re-establishment procedure.

Figure 15-1 Call re-establishment procedure

ChannelRequest(5)

Clear Request(2)

Cipher ModeComplete(11)

Cipher ModeCommand(10)


Status Enquiry(14)

Status(15)

CM Re-establishmentRequest(7)

CC(8)CM Service Accepted (9)

MS BSS RNCMSC

Connection FailureIndication(radio link failure)(1)

RACHEstablish Indication(CM

Reestablishment Request)(6)

Clear Command(3)


FACCH

RACH

StartT3230

StopT3230

StartT322

FACCHStopT322

1. After a radio link failure is detected, the BTS sends the BSC a Connection Failure Indicationmessage, which contains the cause value for radio link failure.

2. The BSC sends the MSC a Clear Request message, which contains the cause for theabnormal release.

3. On receiving the Clear Request message, the MSC sends the BSC a Clear Commandmessage, requesting the release of radio resources.

4. The BSC initiates a release procedure, releases the channel resources on the Um interface,and returns a Clear Complete message to the MSC.

15 Call Re-EstablishmentHUAWEI BSC6000 Base Station Subsystem



5. The MS sends the BTS a Channel Request message and initiates an immediate assignmentprocedure.

6. The BTS initiates a call re-establishment procedure by sending the BSC a CM Re-establishment Request message. In addition, the MM entity of the MS starts timer T3230,gives an indication to all CM entities that are being re-established, and remains in the MMsublayer state Wait For Reestablish. The CM Re-Establishment Request message containsthe IMSI (or TMSI), classmark 2, and Ciphering Key Sequence Number (CKSN).

7. The BSC establishes an SCCP link connection on the A interface and sends the MSC a CMService Request message.

8. The MSC sends the BSC a Connect Confirm message.

9. The MSC sends the MS a CM Service Accepted message on the SDCCH on the Uminterface.

10. The MSC initiates the ciphering mode setting procedure by sending a Cipher ModeCommand message. For details, refer to the ciphering procedure. Once the cipheringprocedure is complete or the CM Service Accept message is received, the MS stops timerT3230 and enters the MM sublayer state MM Connection Active.

11. The BSC returns a Cipher Mode Complete message to the MSC.

12. The MSC sends the BSC an Assignment Request message and initiates a signalingprocessing procedure. For details about the signaling procedure, refer to the mobileoriginating call establishment procedure.

13. The BSC returns an Assignment Complete message to the MSC.

14. The MSC initiates the status enquiry procedure by sending the MS a Status Enquirymessage. At the same time, timer T322 is started.

15. The MS reports its call state or attach state to the MSC. The MSC stops timer T322accordingly.

Procedure Description

For details of the call re-establishment procedure, refer to the following:

1. Steps 1 through 4 shown in Figure 15-1 is radio resource release procedure, which is thesame as the normal release procedure.

2. Steps 5 through 9 shown in Figure 15-1 is the immediate assignment procedure, namely,the signaling channel seizure procedure.

3. Steps 10 and 11 shown in Figure 15-1 is the ciphering procedure.

4. Steps 12 and 13 shown in Figure 15-1 is the assignment procedure.

5. Initiation of the call re-establishment procedure

If a cell is required to support call re-establishment, Call Re-Establishment in CellAttributes must be selected, and the cell cannot be in barred state.

Upon detection of a link failure, the MS sends a Channel Request message with the causevalue Call Re-Establishment in the selected cell. The previous channel resources arereleased by the BSC after the timer on the BTS side expires.

Upon detection of a link failure, the BTS sends the BSC a Connection Failure message withthe cause value Radio Link Failure. Then the BSC releases the corresponding radioresources and waits for the call re-establishment request from the MS.

6. Mode of the MS in the call re-establishment procedure



The MS cannot return to idle mode during a call re-establishment procedure. Therefore, ifthe cell selected for call re-establishment is not the location area, the MS cannot performlocation update until the call re-establishment procedure is complete.

15.2 Internal BSC Signaling Procedure of Call Re-Establishment

The call re-establishment is controlled by the MSC, and the BSC does no special processing.

15.3 Abnormal Call Re-Establishment CasesThis topic describes the abnormal call re-establishment cases.

15.3.1 Network Sending a CM Service Reject MessageThis topic describes the fault, probable causes, and handling suggestions.

15.3.2 Call Re-Establishment Not Allowed or Re-Establishment FailureThis describes the fault, probable causes, and handling suggestions.


15.3.1 Network Sending a CM Service Reject MessageThis topic describes the fault, probable causes, and handling suggestions.

Fault

After the MSC receives a CM Re-Establishment Request message, if the RR sublayer sends anindication that the ciphering mode setting procedure is complete, or if a CM Service Acceptmessage is received, you can infer that the MS accepts the services. The MS re-enters the MMsublayer state MM Connection Active.

If the re-establishment request from the MS does not correspond to its current call state, thenetwork returns the MS a CM Service Reject message.

Probable Causes


l IMSI Unknown in VLR

l Illegal MS

l Network Failure

l Congestion

l Service Option not Supported

l Service Option Temporarily out of Order

Irrespective of the reject cause, upon receiving a CM Service Reject message, the MS releasesthe MM connection and the relevant RR connection.




Handling SuggestionsThe respective handling suggestions are as follows:

l Check whether the location update procedure is performed successfully to ensure that theIMSI is loaded to the VLR. In addition, check whether the IMSI exists in the HLR.

l Check whether the MS can access the network and can perform location update. If not,replace the MS with a new one that can access the network.

l Modify the configuration that corresponds to call re-establishment on the network side.

l Configure more channels.

l Modify the configuration that corresponds to call re-establishment on the network side.

l Modify the configuration that corresponds to call re-establishment on the network side, forexample, the CM service related functions.

l If the early-mentioned measures do not work, analyze the values of the correspondinginformation elements to find out in which network element the fault takes place. Thenperform detailed analysis in the located network element.

15.3.2 Call Re-Establishment Not Allowed or Re-EstablishmentFailure

This describes the fault, probable causes, and handling suggestions.

DescriptionWhen an MM connection is established, the MM layer sends an indication to the CC layer. Ifthe MM layer is disconnected, the connection may be re-established through a CC request.

AnalysisThe probable causes are as follows:

l If re-establishment is not allowed, and the call is initiated within the establishment orclearing period, the CC layer releases the MM connection.

l If re-establishment is unsuccessful, the MM connection is released, and a release indicationis sent to the CC layer.

Handling SuggestionsCheck whether the Call Reestablishment Forbidden parameter of the cell where the re-establishment procedure is initiated is set properly and whether the cell is barred.


FaultUpon detection of a random access failure or an RR connection failure, the MS stops timerT3230, aborts the call re-establishment procedure, and releases all active MM connections.

Upon detection of an RR connection failure, the MSC aborts the call re-establishment procedureand releases all active MM connections.



Probable CausesThe probable causes can be found out through signaling tracing.


l If the transmission quality on the Um interface is poor, use a test MS to measure thesignaling quality on the uplink and downlink and the power level. Improve the transmitand receive quality and reduce the interference.

l If the channels are congested, register and observe the relevant traffic statistics to determinethe severity congestion. Exapnd the system capacity if the congestion rate is high.

l If the problem lies in the network, make adjustments on the network side to locate thephases in which response delay happens.




16 Directed Retry

About This Chapter

Directed retry is a special type of handover. It refers to the process of assigning an MS to a TCHin a cell other than the serving cell when no radio resources are available. It is triggered by theassignment procedure and employs internal or external handover procedures.

16.1 Directed Retry ProcedureThe directed retry procedure is categorized into the intra-BSC directed retry procedure, inter-BSC directed retry procedure, and inter-MSC directed retry procedure.

16.2 Internal BSC Signaling Procedure of Directed RetryThe internal BSC signaling procedure of directed retry is categorized by intra-BSC directedretry, inter-BSC directed retry, and inter-MSC directed retry.

16.3 Abnormal Directed Retry CasesThis topic describes the abnormal directed retry cases.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 16 Directed Retry


16.1 Directed Retry ProcedureThe directed retry procedure is categorized into the intra-BSC directed retry procedure, inter-BSC directed retry procedure, and inter-MSC directed retry procedure.

16.1.1 Intra-BSC Directed Retry ProcedureThis topic describes the intra-BSC directed retry procedure.

16.1.2 Inter-BSC directed retry procedureThis topic describes the inter-BSC directed retry procedure.

16.1.3 Inter-MSC directed retry procedureThis topic describes the inter-MSC directed retry procedure.

16.1.1 Intra-BSC Directed Retry ProcedureThis topic describes the intra-BSC directed retry procedure.

Figure 16-1 shows the intra-BSC directed retry procedure.

16 Directed RetryHUAWEI BSC6000 Base Station Subsystem



Figure 16-1 Intra-BSC directed retry procedure


Handover Command(17) Handover

Access(18)HandoverDetect(19)

PHY INFO(20)

SABM(22)


UA(24)HandoverComplete(25)


ChannelRequest(1) Channel

Required(2)Channel

Activation(3)Immediate

AssignmentCommand(5)

UA(7)

SABM(6)

Establish Indication(CM ServiceRequest)(8)

CR(Complete L3 Information)(9)

CC(10)


MS BTS1 MSCBSC BTS2 MS


StartT3103

FACCH

RACH

AGCH

SDCCH

CM ServiceAccepted(11)

SDCCH

Setup(12)SDCCH Call Proceeding(13)

SDCCH FACCH

PHY INFO(21)

FACCH

FACCH

FACCH

StopT3103

1. The MS sends the BTS a Channel Request message on the RACH.

2. The BTS sends the BSC a Channel Required message.

3. Upon receiving the Channel Required message, the BSC assigns a signaling channel andsends the BTS a Channel Activation message.



4. Upon receiving the Channel Activation message, if the channel type is correct, the BTSenables the power amplifier on the AGCH, starts receiving the uplink information, andsends the BSC a Channel Activation Acknowledge message.

5. Upon receiving the Channel Activation Acknowledge message, the BSC sends anImmediate Assignment Command message on the AGCH to notify the MS of channelaccess.

6. After the MS successfully accesses the channel, the MSC sends the BSC an AssignmentRequest message requesting for TCH radio resources. The Assignment Request messagecarries the information on the circuits between the MSC and the BSC. If no TCH is availablein the serving cell, the BSC attempts to hand over the MS to a neighbor cell that providesvoice services. If the target cell and the serving cell are controlled by the same BSC, thedirected retry is an intra-BSC directed retry.

The intra-BSC directed retry procedure is as follows:

1. Steps 1 through 8 in the procedure shown in Figure 16-1 are the random access andimmediate assignment procedures, in which the BSS assigns a signaling channel to the MS.

2. Steps 14 through 24 in the procedure shown in Figure 16-1 are TCH directed retryprocedure, in which the BSS assigns a speech channel to the MS.

16.1.2 Inter-BSC directed retry procedureThis topic describes the inter-BSC directed retry procedure.

Figure 16-2 shows the inter-BSC directed retry procedure.




Figure 16-2 Inter-BSC directed retry procedure

AssignmentRequest(14)Handover

Required(15)Handover

Request(16)

ChannelActivation(17)

HandoverRequest

Acknowledge(19)HandoverCommand(20)

HandoverCommand(21)

HandoverComplete(31)Clear

Command(32)

ChannelRequest(1) Channel

Required(2)Channel

Activation(3)

ImmediateAssignment

Command(5)

SABM(6)EstablishIndication

(CM ServiceRequest)(8)

CM ServiceAccepted(11)

Setup(12)Call

Proceeding(13)

MS BTS1 MSCBSC1 BSC2 BTS2

RACH

AGCH

MS

Start T10

Start T8


SDCCH

UA(7)CR (Complete

Layer3Information)(9)

CC(10)

SDCCH

SDCCH

SDCCH

SDCCH

HandoverAccess(22)

FACCHPHY

INFO(25)

FACCH

SABM(27)

FACCHUA(29)

FACCH

FACCH

HandoverComplete(30)

PHYINFO(26)

FACCHEstablish

Indication(28)

Stop T10

Stop T8

ClearComplete(33)



The inter-BSC directed retry procedure involves more A-interface signaling procedures than theintra-BSC directed retry procedure. These signaling procedures are described subsequently. Fordetails about other signaling messages, refer to 16.1.1 Intra-BSC Directed Retry Procedure.

1. When the MS must be handed over to a cell under BSC 2, BSC 1 sends the MSC a HandoverRequired message requesting the MS to initiate an outgoing inter-BSC handover.

2. Upon receiving the Handover Required message, the MSC sends BSC 2 a HandoverRequest message.

3. BSC 2 activates a new channel and sends a Handover Request Acknowledge message tonotify the MSC that the channel is now available.

4. Upon receiving the Handover Request Acknowledge message, the MSC sends BSC 1 aHandover Command message. BSC 1 forwards the Handover Command message on a TCHto notify the MS of channel access.

5. Upon receiving the Handover Complete message from BSC 2, the MSC sends BSC 1 aClear Command message. BSC 1 initiates a local release procedure and sends the MSC aClear Complete message.

16.1.3 Inter-MSC directed retry procedureThis topic describes the inter-MSC directed retry procedure.

Figure 16-3 shows the inter-MSC directed retry procedure.




Figure 16-3 Inter-MSC directed retry procedure

AssignmentRequest(1)Handover

Required(2) PerformHandover(3) Handover

Request(4)

ChannelActivation(5)

ChannelActivation

Acknowledge(6)

HandoverRequest

Acknowledge(7)Radio ChannelAcknowledge(8)

IAM(9)

ACM(10)Handover Command(11)

HandoverDetect(17)

Send EndSignal(23)

Clear Command(24)

HandoverAccess(13)Handover

Detect(14)

PHY INFO(15)

SABM(18)EstablishIndication(19）

UA(20）HandoverComplete(21)

MS BTS1 MSC1BSC1 MSC2 BSC2

Start T10

FACCH

SDCCH

FACCH

PHY INFO(16)

FACCH

FACCH

FACCH

BTS2 MS

Start T8

FACCHStop T10

HandoverComplete(22)

Stop T8

ClearComplete(25)

HandCommand(12)

For details about the inter-MSC directed retry procedure, refer to 16.1.2 Inter-BSC directedretry procedure.

16.2 Internal BSC Signaling Procedure of Directed RetryThe internal BSC signaling procedure of directed retry is categorized by intra-BSC directedretry, inter-BSC directed retry, and inter-MSC directed retry.

16.2.1 Internal BSC Signaling Procedure of the Intra-BSC Directed RetryThis describes the internal BSC signaling procedure of the intra-BSC directed retry.

16.2.2 Internal BSC Signaling Procedure of the Inter-BSC Directed RetryThis describes the internal BSC signaling procedure of the inter-BSC directed retry.



16.2.3 Internal BSC Signaling Procedure of the Inter-MSC Directed RetryThis topic describes the internal BSC signaling procedure of the inter-MSC directed retry.

16.2.1 Internal BSC Signaling Procedure of the Intra-BSC DirectedRetry

This describes the internal BSC signaling procedure of the intra-BSC directed retry.

After the BSC receives the Assignment Request message from the MSC, if the cell where thecall is originated has no available TCHs or Assignment Cell Load Judge is enabled, and theDirected Retry Allowed in the Cell Attributes window is selected, a directed retry procedureis triggered.

NOTE

Directed retry is a special type of handover.

1. If the BSC considers that the call meets the handover trigger conditions, it selects acandidate cell from the candidate cell list based on the priority in a descending order. If thecandidate cell is under the same BSC as the serving cell, the BSC notifies the candidatecell of initiating an intra-BSC directed retry procedure, and the candidate cell will be thetarget cell.

2. A channel in the target cell is assigned and the BTS2 that serves the target cell is notifiedto activate the channel.

3. After BTS2 activates the channel, the BSC notifies the MS to send a Handover Commandmessage to BTS1. Meanwhile, BSC2 starts timer T3103 to wait for the Handover Detectmessage.

4. On receiving the Handover Detect message, BTS2 continues to wait for the EstablishmentIndication message and the Handover Complete message.

5. After BTS2 receives the Handover Complete message, BSC2 stops timer T3103 andconsiders that the call is set up in the target cell.

6. The BSC sends an Assignment Complete message to notify the MSC of the assignmentcompletion. The Assignment Complete message carries the information of the target cell.At the same time, BSC1 notifies BTS1 to initiate a local release procedure.

16.2.2 Internal BSC Signaling Procedure of the Inter-BSC DirectedRetry

This describes the internal BSC signaling procedure of the inter-BSC directed retry.

After the BSC receives the Assignment Request message from the MSC, if the cell where thecall is originated has no available TCHs or Assignment Cell Load Judge is enabled, and theDirected Retry Allowed in the Cell Attributes window is selected, a directed retry procedureis triggered. If the target cell of the directed retry is an external cell, the inter-BSC directed retryprocedure is triggered.

NOTE

Directed retry is a special type of handover.

The BSC starts an eight-second timer awaiting the Handover Detect message from the BTS. Atthe same time, it initiates a forced handover procedure.

1. If the BSC considers that the call meets the handover trigger conditions, it selects acandidate cell from the candidate cell list based on the priority in a descending order. If the




candidate cell is an external cell, the outgoing BSC directed retry procedure, namely theinter-BSC handover procedure is triggered.

2. Upon handover initiation, BTS1 sends the MSC a Handover Required message and startstimer T17 to wait for a Handover Command message.

3. On receiving the Handover Request message from the MSC, BSC1 allocates and activatesa channel according to the target cell ID in the message. After channel activation, BTS2sends the MSC a Handover Request Acknowledge message that carries the HandoverCommand message.

4. BTS1 forwards to the MS the Handover Command message that BSC1 receives and at thesame time starts timer T8 to wait for the handover completion. If the Clear Commandmessage with the cause value Handover Success or Call Control is received before T8expires, BSC 1 considers that the handover is successful. If the MS returns to the old channelbefore T8 expires, BSC1 stops T8 and sends the MSC a Handover Failure message. If T8expires, BSC1 considers that the call drops and sends the MSC a Clear Request message.

5. BTS2 forwards the Handover Detect message to the MSC and continues to wait for theEstablishment Indication message and the Handover Complete message.

6. On receiving the Handover Complete message, BTS2 stops timer T3103B2 and sends aHandover Complete message to notify the MSC of handover completion.

7. On receiving the Clear Command message, BTS2 releases the radio resources the calloccupies and returns the MSC a Clear Complete message.

16.2.3 Internal BSC Signaling Procedure of the Inter-MSC DirectedRetry

This topic describes the internal BSC signaling procedure of the inter-MSC directed retry.

The internal BSC signaling procedure of the inter-MSC directed retry is the same as that of theinter-BSC directed retry.

16.3 Abnormal Directed Retry CasesThis topic describes the abnormal directed retry cases.

16.3.1 No Available Channels in the Target CellThis topic describes the fault, probable causes, and handling suggestions.

16.3.2 Channel Activation FailureThis topic describes the fault, probable causes, and handling suggestions.

16.3.1 No Available Channels in the Target CellThis topic describes the fault, probable causes, and handling suggestions.

FaultWhen no channels are available in the target cell, BSC 2 sends BSC 1 a handover failure message,and BSC 1 sends the MSC an Assignment Failure message.

Probable CausesNo TCHs are available in the target cell.



Handling SuggestionsCheck whether the target cell is congested. If yes, add TRXs to the target cell.

16.3.2 Channel Activation FailureThis topic describes the fault, probable causes, and handling suggestions.

FaultWhen channel activation in the target cell fails, BSC 2 sends the MSC an Assignment Failuremessage.

Probable CausesThe desired channel in the target cell fails to be activated due to TRX failure.

Handling SuggestionsLocate the channel number in the Channel Activation Negative Acknowledge message, andcheck whether the corresponding TRX fails. If the TRX fails, replace it.




17 BSC Re-Assignment

About This Chapter

BSC re-assignment refers to a TCH assignment procedure initiated by the BSC after the BSCreceives an Assignment Failure message from the MS on the SDCCH. BSC re-assignment raisesthe rate of assignments on the Um interface.

17.1 BSC Re-Assignment ProcedureThis topic describes the BSC re-assignment procedure.

17.2 Internal BSC Signaling Procedure of BSC Re-AssignmentThis topic describes the internal BSC signaling procedure of BSC re-assignment.

17.3 Abnormal BSC Re-Assignment CasesThis topic describes the abnormal BSC re-assignment cases.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 17 BSC Re-Assignment


17.1 BSC Re-Assignment ProcedureThis topic describes the BSC re-assignment procedure.

Figure 17-1 shows the BSC re-assignment procedure.

Figure 17-1 BSC re-assignment procedure

Assignment Failure


Assignment Command

Channel ActivationAcknowldge(2)

Assignment Command(3)

UA(5)

Assignment Complete(7)

SABM(4)

Establish Indication(6)

MS BTS MSCBSC

SDCCH

SDCCH

SDCCH

FACCH

Start T3107

……

……

Stop T3107

Start T3107

FACCH

FACCH

Stop T3107

1. After the BSC receives the Assignment Failure message from the MS, the network stopstimer T3107. After internal processing, the BSC sends the BTS a Channel Activatemessage.

2. Upon receiving the Channel Activation Acknowledge message from the BTS, the BSCdoes internal processing.

3. The BSC sends the MS an Assignment Command message on the SDCCH that is notreleased.

4. The MS sends the BTS an SABM frame on the main DCCH specified in the AssignmentCommand message.

17 BSC Re-AssignmentHUAWEI BSC6000 Base Station Subsystem



5. The BTS sends the MS a UA frame on the main DCCH.6. The BTS sends the BSC an Establish Indication message.7. Upon accessing the speech channel, the MS sends the BSC an Assignment Complete

message on the main DCCH.8. Upon successful assignment of a TCH and a terrestrial circuit, the BSC sends the MSC an

Assignment Complete message on the occupied TCH, indicating that the call enters thesession state.

17.2 Internal BSC Signaling Procedure of BSC Re-Assignment

This topic describes the internal BSC signaling procedure of BSC re-assignment.

The BSC sends the BTS an Assignment Command message and starts timer T3107. Before timerT3107 expires, the BSC receives an Assignment Failure from the BTS.

1. Based on the Assignment Request message, the BSC selects an appropriate carrier, activatesa channel, and sends the BTS an Assignment Command message. The AssignmentCommand message carries the information about the new channel.

2. The BSC records the information on the first assignment, such as the channel assignmentrequirements, voice version supported by the MSC, TRX number, band attributes, MSmaximum and minimum power, call type, handover type, indexes of neighbor cells,requirements for downlink DTX, classmark 2, classmark 3, and cell number.

3. Based on the circuit pool number in the first assignment, the BSC obtains the circuitcapability and attaches the channel type parameter in the Channel Assignment Commandmessage.

4. Based on the channel priority in the Assignment Request message from the MSC, the BSCfills the channel priority in the Assignment Command message.

5. Based on the cell type in the first assignment, the BSC fills cell type in the AssignmentCommand message.

6. After all relevant requirements are specified, the BSC assigns a channel as required. Thesubsequent procedure is the same as that of the first assignment.

17.3 Abnormal BSC Re-Assignment CasesThis topic describes the abnormal BSC re-assignment cases.

17.3.1 BSC Failure in Initiating a Re-Assignment ProcedureThis topic describes the fault, probable causes, and handling suggestions.

17.3.1 BSC Failure in Initiating a Re-Assignment ProcedureThis topic describes the fault, probable causes, and handling suggestions.

FaultAfter sending an Assignment Command message, the BSC does not initiate a re-assignmentprocedure although re-assignment is enabled.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 17 BSC Re-Assignment


Probable CausesUpon receiving the Channel Activation Acknowledge message, the BSC sends the MS anAssignment Command message on the SDCCH and starts timer T3107. If timer T3107 expires,the BSC does not initiate a re-assignment procedure.

Upon receiving a Connect Failure message from the BTS, the BSC does not initiate a re-assignment procedure. When timer T3107 expires or a Connect Failure message is received, theBSC releases related resources.

NOTE

For details, refer to GSM Rec. 0858 and 0808.

Handling SuggestionsIf the BSC receives a Connect Failure message from the BTS, the transmission quality on theA interface should be improved. To improve the transmission quality on the A interface and toreduce interference, perform a drive test to check the signaling level on the downlink and uplinkchannels.

17 BSC Re-AssignmentHUAWEI BSC6000 Base Station Subsystem



18 Queuing and Preemption

About This Chapter

This topic describes queuing and pre-emption.

18.1 Queuing ProcedureIf no TCHs are available and queuing is allowed, the assignment requests are placed in a waitingqueue. When the TCHs are available, they are assigned in the queuing sequence.

18.2 Preemption ProcedurePreemption refers to handing over a subscriber with a lower priority to another speech channelor cell so that a subscriber with a higher priority acquires the speech channel resources.

18.3 Internal BSC Signaling Procedure of Queuing and PreemptionThis topic describes the internal BSC signaling procedure of queuing and pre-emption.

18.4 Abnormal Queuing and Preemption CasesThis topic describes the abnormal queuing and pre-emption cases.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 18 Queuing and Preemption


18.1 Queuing ProcedureIf no TCHs are available and queuing is allowed, the assignment requests are placed in a waitingqueue. When the TCHs are available, they are assigned in the queuing sequence.

Figure 18-1 shows the queuing procedure.

Figure 18-1 Queuing procedure


Setup

Queuing Indication

AssignmentComplete

MS BTS MSCBSC

SDCCH


Call ProceedingSDCCH

TCH Assignment Procedure(2)

Release Procedure

Start T11

StopT11

Start Tqho

StopTqho

TALKING

1. The MSC sends the BSC an Assignment Request message and finds that no speech channelis available. If queuing is allowed, the assignment request is placed in a queue, and timerT11 is started.

2. When a speech channel is assigned, the queuing procedure is complete, and timer T11 stops.

18 Queuing and PreemptionHUAWEI BSC6000 Base Station Subsystem



18.2 Preemption ProcedurePreemption refers to handing over a subscriber with a lower priority to another speech channelor cell so that a subscriber with a higher priority acquires the speech channel resources.

Figure 18-2 shows the pre-emption procedure.

Figure 18-2 Preemption procedure

AssignmentRequest

Preemption Start (1)Release Procedure or

Handover Procedure(2)

AssignmentComplete

LowPriority MS

HighPriority MS BSCBTS


Start T11

StopT11

BSC

Talking

Start Tqho

StopTqho

TALKING

Release Procedure

1. The MSC sends the BSC an Assignment Request message and finds that no speech channelis available. If pre-emption is allowed and the priority of the subscriber is higher than thepriority of the subscriber that occupies the speech channel, the preemption procedure isinitiated.

2. The subscriber with a lower priority is handed over to another speech channel or cell.3. The subscriber with a higher priority seizes the speech channel and the pre-emption

procedure is complete.



18.3 Internal BSC Signaling Procedure of Queuing andPreemption

This topic describes the internal BSC signaling procedure of queuing and pre-emption.

1. Internal BSC signaling procedure of queuingThe BSC processes the requests from the MSC, manages the queuing, and determineswhether queuing is allowed. Only assignment requests and inter-cell handover requests canbe queued.Upon receiving an Assignment Request message, the BSC searches for an availablechannel. If no channel is available, the BSC sends the MSC a Queuing Indication messageand starts timer T11. The timeout value of timer T11 is configurable.The BSC places the Assignment Request message in a queue and starts the message whenappropriate. Upon assigning a TCH, the BSC stops timer T11 and sends the MSC anAssignment Complete message.

2. Internal BSC signaling procedure of pre-emptionIf no TCH is available, the BSC checks the pre-emption settings and starts a pre-emptionprocedure.Among all occupied TCHs, the BSC searches for a TCH that has comparatively lowerpriority and that meets the pre-emption requirements. If no such TCHs are available, thequeuing procedure is triggered.The BSC checks whether eMLPP is enabled. If eMLPP is enabled, the preempted call isforced to perform an outgoing cell handover. The call with a higher priority preempts thereleased TCH.If eMLPP is not enabled, the call with a lower priority is directly released, and the call witha higher priority preempts the TCH.

18.4 Abnormal Queuing and Preemption CasesThis topic describes the abnormal queuing and pre-emption cases.

18.4.1 BSC Sending the MSC a Clear Request MessageThis topic describes the fault, probable causes, and handling suggestions.

18.4.1 BSC Sending the MSC a Clear Request MessageThis topic describes the fault, probable causes, and handling suggestions.

DescriptionThe BSC sends the MSC a Clear Request message.

Probable CausesIf the BSC finds no available TCH after timer T11 expiry, the BSC removes the AssignmentRequest message from the queue and sends the MSC a Clear Request message with the causeNo Radio Resource Available.

18 Queuing and PreemptionHUAWEI BSC6000 Base Station Subsystem



After a TCH allocation fails, the BSC sends the MSC an Assignment Failure message. Then,the MSC stops timer Tqho.

Handling SuggestionsCheck whether there is an allocable TCH inside the BSC.



19 Short Message Service

About This Chapter

For an idle MS, short messages are transferred on the SDCCH. For a busy MS, however, shortmessages are transferred on the SACCH. The point-to-point short message procedure comprisestwo fundamental procedures: mobile originating short message transfer procedure and mobileterminating short message transfer procedure.

19.1 Short Message Transfer ProcedureThe short message transfer procedure comprises the short message sending and receivingprocedures initiated by an idle or a busy MS.

19.2 Internal BSC Signaling Procedure of Short Message TransferThis describes the internal BSC signaling procedure of short messages transfer.

19.3 Abnormal Short Message Transfer CasesThis topic describes the abnormal short message transfer cases.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 19 Short Message Service


19.1 Short Message Transfer ProcedureThe short message transfer procedure comprises the short message sending and receivingprocedures initiated by an idle or a busy MS.

19.1.1 Short Message Sending Procedure Initiated by an Idle MSThis topic describes the short message sending procedure initiated by an idle MS.19.1.2 Short Message Receiving Procedure Initiated by an Idle MSThis topic describes the short message receiving procedure initiated by an idle MS.19.1.3 Short Message Sending Procedure Initiated by a Busy MSThis topic describes the short message sending procedure initiated by a busy MS.19.1.4 Short message receiving procedure initiated by a busy MSThis topic describes the short message receiving procedure initiated by a busy MS.

19.1.1 Short Message Sending Procedure Initiated by an Idle MSThis topic describes the short message sending procedure initiated by an idle MS.

Figure 19-1 shows the short message sending procedure initiated by an idle MS.

Figure 19-1 Short message sending procedure initiated by an idle MS

Authentication Request

Authentication Response

Ciphering Mode Command

Ciphering Mode Complete

CP DATA(5)

CP Acknowledge(6)

CP Acknowledge(8)

CP DATA(7)

CM Service Accepted (1)

SABM (SAPI 3)(2)

UA(4)

Establish Indication(SAPI)(3)

MS BTS MSCBSC


SDCCH

Release Procedure

SDCCH

SDCCH

SDCCH

SDCCH

SDCCH

SDCCH

SDCCH

SDCCH

SDCCH

SDCCH

19 Short Message ServiceHUAWEI BSC6000 Base Station Subsystem



l Steps 1 through 4 in the procedure are the random access and immediate assignmentprocedures, in which the BSS assigns a signaling channel to the MS.

l Steps 5 through 8 is the short message sending procedure.

The following describes the short message sending procedure initiated by an idle MS:

1. The MS sends an SABM frame again, requesting the network to establish the SMS.2. The BSC provides a transparent-transmission channel for short message exchange between

the MS and the MSC.

In this procedure, the MSC, if possible, sends the BSC an Access Request message for channelallocation. The time for sending the Access Request message is the same as that for an ordinarycall. The BSC provides the SMS either by allocating a new channel or by using the originalSDCCH.

The protocol on Point to Point SMS covers four layers, which are the connection managementlayer (CM), relay layer (RL), transport layer (TL), and application layer (AL). Both the CPDATA message and the CP Acknowledge message shown in Figure 19-1 are transferred at theCM layer. The CP_DATA message carries the contents of the messages at the RL and AL layers.The CP Acknowledge message is the acknowledgement message of the CP DATA message.

19.1.2 Short Message Receiving Procedure Initiated by an Idle MSThis topic describes the short message receiving procedure initiated by an idle MS.

Figure 19-2 shows the short message receiving procedure initiated by an idle MS.



Figure 19-2 Short message receiving procedure initiated by an idle MS

MS BTS MSC

CR(CompleteLayer3 Information(3)

BSC

Paging(1)

PCH

SABM(SAPI 3)(11)

UA(12)

Release Indication(9)

Paging Command(2)Paging Request

Immediate Assignment Prcedure

CC(4)


SDCCHAuthentication Response(6)

SDCCHCipherding Mode Commnd(7)

SDCCHCipherding Mode Complete(8)

SDCCH CP DATA(9)Establis Request(SAPI 3)(10)

SDCCH

SDCCHEstablish

Confirm(SAPI 3)(13)

CP DATA(14)SDCCH

CP Acknowledge(15)

SDCCH CP DATA(16)SDCCH

SDCCH

CP Acknowledge(17)

Release Procedure

In Figure 19-2,

l Steps 1 through 3 is the paging response and immediate assignment procedure.The MSC sends a Paging Command message. The MS requests for an SDCCH channeland returns a Paging Response message.

l Steps 14 through 17 is a connection establishment and short message sending procedure.During the short message mobile terminating procedure, the BSC sends the MS anEstablishment Request message, requesting for connection establishment. If the BSC




receives an Establishment Confirm message from the MS, the channel for SMS isestablished. The BSC transfers short messages on the transparent channel until theprocedure is complete.

19.1.3 Short Message Sending Procedure Initiated by a Busy MSThis topic describes the short message sending procedure initiated by a busy MS.

Figure 19-3 shows the short message sending procedure initiated by a busy MS.

Figure 19-3 Short message sending procedure initiated by a busy MS

CM Service Request(1)

SABM (SAPI 3)(3)

UA(5)

Establish Indication(4)

CP DATA(6)

CP Acknowledge(7)

CP DATA(8)

MS BTS MSCBSC

FACCH

ACTIVE CALL

FACCH

ACTIVE CALL


FACCH

FACCH

SACCH

SACCH

SACCH

SACCH

CP Acknowledge(9)

The following describes the short message sending procedure initiated by a busy MS:

1. The MS sends the MSC a CM Service Request message on the FACCH. If the MSCresponds with a CM Service Accepted message, a link at the CC layer is established.

2. A link at the CC layer is established on the SACCH for sending short messages.

19.1.4 Short message receiving procedure initiated by a busy MSThis topic describes the short message receiving procedure initiated by a busy MS.

Figure 19-4 shows the short message receiving procedure initiated by a busy MS.



Figure 19-4 Short message receiving procedure initiated by a busy MS

EstablishRequest(SAPI 3)(2)

CP DATA(6)

CP Acknowledge(9)

CP Acknowledge(7)

CP DATA(8)

SABM (SAPI 3)(3)

UA(5)

CP DATA(1)

MS BTS MSCBSC

ACTIVE CALL

SACCH

FACCH

FACCH

EstablishConfirm (SAPI 3)(5)

SACCH

SACCH

SACCH

ACTIVE CALL

The following describes the short message receiving procedure initiated by a busy MS:

1. Upon receiving a CP DATA message from the MSC, the BSC establishes a link forreceiving short messages at the RR layer.

2. Upon receiving a CP Acknowlege message from the MS, the MSC sends short messages.

19.2 Internal BSC Signaling Procedure of Short MessageTransfer

This describes the internal BSC signaling procedure of short messages transfer.

1. Based on the classmark reported by the MS, the BSC checks whether the MS supportsSMS.

2. On receiving the short messages from the MS, the BSC checks the value of the parameterShort Message Uplink Disabled. You can set the parameter through the followingprocedure: On the Cell Attributes tab page, click Call Control. In the displayed dialogbox, click Advanced. Then click the Call Control tab and set the parameter. If theparameter is set to Yes, short message cannot be sent.

3. On receiving the short messages from the MS, the BSC checks the value of the parameterShort Message Downlink Disabled. You can set the parameter through the followingprocedure: On the Cell Attributes tab page, click Call Control. In the displayed dialogbox, click Advanced. Then click the Call Control tab and set the parameter. If theparameter is set to Yes, short messages cannot be sent.




19.3 Abnormal Short Message Transfer CasesThis topic describes the abnormal short message transfer cases.

19.3.1 Short Message Sending Failure due to Authentication and Ciphering DisabledThis topic describes the fault, probable causes, and handling suggestions.

19.3.1 Short Message Sending Failure due to Authentication andCiphering Disabled


FaultSome MSs fail to send short messages because the authentication and ciphering function isdisabled.

Probable CausesThe short message procedure specified in the GSM protocols involves the authentication andciphering procedure. For some MSs, short message sending fails if no authentication andciphering procedure is involved in the short message procedure.

Handling SuggestionsThe MSC initiates an authentication and ciphering procedure.



20 Short Message Service Cell Broadcast

About This Chapter

The short message service cell broadcast (SMSCB) is similar to the paging station broadcastservice. The operators broadcast messages to the subscribers in the specified areas. Thesubscribers that subscribe to the service receive the messages broadcast by the operators.

20.1 SMSCB ProcedureThe SMSCB procedure comprises the CBC-BSC SMSCB procedure and the BSC-BTS SMSCBprocedure.

20.2 Internal BSC Signaling Procedure of the SMSCBThis describes the internal BSC signaling procedure of the SMSCB.

20.3 Abnormal SMSCB CasesThis topic describes the abnormal SMSCB cases.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 20 Short Message Service Cell Broadcast


20.1 SMSCB ProcedureThe SMSCB procedure comprises the CBC-BSC SMSCB procedure and the BSC-BTS SMSCBprocedure.

20.1.1 CBC-BSC SMSCB ProcedureThis topic describes the CBC-BSC SMSCB procedure.

20.1.2 BSC-BTS SMSCB ProcedureThis topic describes the BSC-BTS SMSCB procedure.

20.1.1 CBC-BSC SMSCB ProcedureThis topic describes the CBC-BSC SMSCB procedure.

Procedure for Sending or Replacing a Message

Figure 20-1 shows the procedure for sending or replacing a message.

Figure 20-1 Procedure for Sending or Replacing a Message

Write Replace Request1

CBC BSC

Report Response2

1. The CBC sends the BSC a Write Replace Request message.

l If the message is new, the BSC saves the message in the message library.

l If the message is sent for replacing the existing message, the BSC deletes the existingmessage and saves the new message in the message library.

2. The BSC sends the CBC a response message.

l If the parameters in the Write Replace Request message are legal, the CBC sends aReport Response message.

l If the parameters in the Write Replace Request message are illegal, the CBC sends aReject Response message.

Deleting an Existing Message

Figure 20-2 shows the procedure for deleting an existing message.

20 Short Message Service Cell BroadcastHUAWEI BSC6000 Base Station Subsystem



Figure 20-2 Procedure for deleting an existing message

Kill Request1

Report Response2

CBC BSC

1. The CBC sends the BSC a Kill Request message.2. The BSC sends the CBC a response message.

l If the parameters in the Kill Request message are legal, the BSC deletes the existingmessage and sends the CBC a Report Response message.

l If the parameters in the Kill Request message are illegal, the BSC sends the CBC aReject Response message.

Querying the CBCH Status

Figure 20-3 shows the procedure for querying the CBCH status.

Figure 20-3 Procedure for querying the CBCH status

Status CBCH Query Request(1)

Status CBCH Query Response(2)

CBC BSC

1. The CBC sends the BSC a Status CBCH Query Request message.2. The BSC sends the CBC a response message.

l If the parameters in the Status CBCH Query Request message are legal, the BSC sendsthe CBC a Status CBCH Query Response message.

l If the parameters in the Status CBCH Query Request message are illegal, the BSC sendsthe CBC a Reject Response message.

Querying the Message Status

Figure 20-4 shows the procedure for querying the message status.



Figure 20-4 Procedure for querying the message status

Status Message Query Request(1)

Status Message Query Response(2)

CBC BSC

1. The CBC sends the BSC a Status Message Query Request message.2. The BSC sends the CBC a response message.

l If the parameters in the Status Message Query Request message are legal, the BSC sendsthe CBC a Status Message Query Response message.

l If the parameters in the Status Message Query Request message are illegal, the BSCsends the CBC a Reject Response message.

Resetting a Cell

Figure 20-5 shows the procedure for resetting a cell.

Figure 20-5 Procedure for resetting a cell

Reset Request(1)

Restart Indication Response(2)

CBC BSC

1. The CBC sends the BSC a Reset message.2. The BSC sends the CBC a response message.

l If the CBCH of the specified cell is normal, the BSC responds with a Restart IndicationResponse message.

l If the CBCH of the specified cell is abnormal, the BSC responds with a FailureIndication Response message.

Setting the DRX

Figure 20-6 shows the procedure for setting the discontinuous reception (DRX).




Figure 20-6 Procedure for setting the DRX

Set DRX Request(1)

Set DRX Response(2)

CBC BSC

1. The CBC sends the BSC a Set DRX Request message.2. The BSC sends the CBC a response message.

l If the parameters in the Set DRX Request message are legal, the BSC sends the CBC aSet DRX Response message.

l If the parameters in the Kill Request message are illegal, the BSC sends the CBC aReject Response message.

20.1.2 BSC-BTS SMSCB ProcedureThis topic describes the BSC-BTS SMSCB procedure.

The BSC sends the BTS the CBS information through an SMS Broadcast Command message,which specifies the channel to be used. See Figure 20-7.

Figure 20-7 BSC Sending an SMS Broadcast Command Message

SMS Broadcast CommandSMS 1(1)

BSC BTS MS

SMS 2(2)

CBCH

CBCH

……

SMS n(3)

CBCH

The BTS reports the load status of the CBCH to the BSC through a CBCH Loading Indicationmessage and requests the BSC to perform flow control. See Figure 20-8.



Figure 20-8 BTS Sending the BSC a CBCH Loading Indication Message

CBCH Loading Indication(1)

BSC BTS

20.2 Internal BSC Signaling Procedure of the SMSCBThis describes the internal BSC signaling procedure of the SMSCB.

1. The CBIP in the GXPUT obtains the IP addresses of the CBC and the CBIP from thedatabase and establishes communication through a SOCKET link.

2. The CBIP obtains the cell information from the database, filters the cells without CBCHs,and writes in the cell information library the information of the cells with CBCHs .

3. The CBIP obtains the contents of the SMS to be broadcast from the CBC and writes thecontents in the message library. The contents include the number of retransmissions andthe retransmission interval.

4. The GXPUT receives the messages from the CBC, and the CBPI processes the messages.5. Upon expiry of the SMSCB timer, the CBIP checks every cell for messages to be broadcast.

l If there are messages to be broadcast, the CBIP sends the messages to the correspondingGXPUM, and the GEIUB forwards the messages to the corresponding BTS. TheGXPUT manages the SMSCB of the entire BSC.

l If there are no messages to broadcast, no processing is required.

NOTE

The delivery of the cell broadcast messages is triggered by SMSCB timer expiry.

Figure 20-9 SMSCB procedure

GXPUT

GXPUM

GTNU

GEIUB

GXPUM

GTNU

GEIUB

GMPS

GEPS

20.3 Abnormal SMSCB CasesThis topic describes the abnormal SMSCB cases.




20.3.1 MS Failure in Receiving Cell Broadcast MessagesThis describes the fault, probable causes, and handling suggestions.

20.3.2 CBCH Not Configured in a CellThis describes the fault, probable causes, and handling suggestions.

20.3.1 MS Failure in Receiving Cell Broadcast MessagesThis describes the fault, probable causes, and handling suggestions.

Description

The MS fails to receive call broadcast messages.

Analysis


1. The SMSCB switch of the MS is turned off, and the relevant channel number is notconfigured.

2. The setting of the IP address in the GXPUT and that in the CBC are different.

3. The communication between the GXPUT and the CBC is disrupted. For example, the CBCCommunication Disrupted alarm with the ID 102 is generated.


Locate the problem through message tracing and on the Site Maintenance System.

1. Check whether SMS Broadcast Command messages exist on the Abis interface of therelevant cell.

2. Send the system information of the relevant cell on the Site Maintenance System and checkwhether the IE CBCH DESP message in System Information Type 4 is correct.

20.3.2 CBCH Not Configured in a CellThis describes the fault, probable causes, and handling suggestions.

Descriptionl The cell is abnormal.

l The CBC cannot perform any operation or the operation is performed unsuccessfully.

l No cell broadcast messages are sent.

l No cell broadcast messages are received.

Analysis

The cause value of the failed signaling is Specified Cell Not Found. The problem lies in that theCBCH of the cell is not configured.



Handling SuggestionsCheck whether the CBCH of the cell is configured. If not, add the CBCH on the BSC6000 LocalMaintenance Terminal.




Documents

Huawei Sig Guide