23 Abis Interface

M900/M1800 Base Station Subsystem Feature Description Manual Contents

Issue 08 (2006-08-20) Huawei Technologies Proprietary i

Contents

23 Abis Interface..........................................................................................................................23-1

23.1 Overview...................................................................................................................................................23-2

23.1.1 Protocol Model.................................................................................................................................23-2

23.1.2 Structure of Abis Interface ...............................................................................................................23-3

23.1.3 Functional Division between BSC and BTS....................................................................................23-5

23.2 Protocols on the Abis Interface .................................................................................................................23-7

23.2.1 Physical Layer..................................................................................................................................23-7

23.2.2 Data Link Layer ...............................................................................................................................23-8

23.2.3 Traffic Management of Layer 3 .......................................................................................................23-9

23.2.4 Operation and Maintenance Part of Layer 3 ..................................................................................23-11

23.3 Characteristics of Abis Interface .............................................................................................................23-14

23.3.1 Transmission Modes on the Abis Interface ....................................................................................23-14

23.3.2 Abis Interface Channel Assignment ...............................................................................................23-15

M900/M1800 Base Station Subsystem Feature Description Manual Figures

Issue 08 (2006-08-20) Huawei Technologies Proprietary iii

Figures

Figure 23-1 Protocol model of Abis interface ..................................................................................................23-2

Figure 23-2 Struction of Abis interface ............................................................................................................23-4

Figure 23-3 Abis interface layer 2 logical links................................................................................................23-5

Figure 23-4 Basic structure of management object ........................................................................................23-12

Figure 23-5 Networking of satellite transmission ..........................................................................................23-15

M900/M1800 Base Station Subsystem Feature Description Manual Tables

Issue 08 (2006-08-20) Huawei Technologies Proprietary v

Tables

Table 23-1 Distribution of services and functions between BTS and BSC ......................................................23-6

Table 23-2 Management status .......................................................................................................................23-13

Table 23-3 Operation status ............................................................................................................................23-14

Table 23-4 Availability status .........................................................................................................................23-14

Table 23-5 Sequence table under 10:1 mode ..................................................................................................23-17

Table 23-6 Sequence table under 12:1 mode ..................................................................................................23-18

Table 23-7 Sequence under 15:1 mode...........................................................................................................23-19

M900/M1800 Base Station Subsystem Feature Description Manual 23 Abis Interface

Issue 08 (2006-08-20) Huawei Technologies Proprietary 23-1

23 Abis Interface About This Chapter

The following table lists the contents of this chapter.

Title Description

23.1 Overview Introduces the protocols, structure, and functions of the Abis interface.

23.2 Protocols on the Abis Interface

Describes the protocols of various layers on the Abis interface.

23.3 Characteristics of Abis Interface

Describes the features of the Abis interface indlucing the transmission mode and network multiplexing.

23 Abis Interface M900/M1800 Base Station Subsystem

Feature Description Manual

23-2 Huawei Technologies Proprietary Issue 08 (2006-08-20)

23.1 Overview The Abis interface is the interface between Base Station Controller (BSC) and Base Transceiver Station (BTS). It is an internal interface of the BSS. At the beginning, ETSI hope to realize the complete standardization of Abis interface, so that the BTS can connect to the BSC of different supplier. However, the complete standardization of Abis interface has not been turned into reality. As a result ETSI only strictly define the service part of Abis interface in 08.52, 08.54, 08.56 and 08.58 of the GSM specification, and didn't define the O&M part. Therefore, the Abis interface can only be regarded as an internal interface. The interworking between different vendors' BTS and BSC has not been realized.

The terrestrial traffic channels on the Abis interface and the radio traffic channels on the Um interface are in one-to-one correspondence with one another.

23.1.1 Protocol Model

Protocol Model

The protocol model of the Abis interface is shown in Figure 23-1.

Figure 23-1 Protocol model of Abis interface

LAPDm

Sign.Layer1

LAPD

Layer1

LAPD

Layer1

SCCP

MTP

BTSM

RR BSSAP

Abis

BTS

BSC

RR BTSM

BTSM: Base Transceiver Station Management LAPD: Link Access Procedure on the D Channel RR: Radio Resource LAPDm: Link Access Procedure on the Dm Channel SCCP: Signaling Connection Control Part MTP: Message Transfer Part BSSAP: Base Station Subsystem Application Part



z Layer 1 of the Abis interface is hardware-based and responsible for receiving and transmitting data to the physical link.

z The layer 2 protocol of the Abis interface is based on the LAPD. LAPD addresses TRX (or BCF) through TEI. Different logical links are used for traffic management message (RSL, Radio Signaling Link), network management message (OML, Operation & Maintenance Link), and L2 management messages (L2ML, Layer 2 Management Link).

z RR (Radio Resource Management) messages are mapped onto the BSSAP (BSS Application Part) in BSC. In BTS, most of RR messages are handled as transparent messages. However, some of them have to be interpreted and executed by BTS (for example, cipher, random access, paging and assignment), these messages are processed by the BTSM (BTS Management) entities in BSC and by BTS.

z BSC and BTS do not interpret CM (Connection Management) and MM (Mobility Management) messages. These messages are transferred over the A-interface by DTAP (Direct Transfer Application Part). At the Abis interface, DTAP messages are transferred as transparent messages.

Abis interface related protocols z GSM 08.52 defines the basic principles for the Abis interface specifications, and the

traffic function division between BSC and BTS.

z GSM 08.54 defines the physical structure of Abis interface.

z GSM 08.56 defines the data link protocol of Abis interface.

z GSM 08.58 defines the layer 3 procedures.

z GSM 12.21 defines the transmission mechanism of the OM message on the Abis interface.

z GSM 08.60 defines the in-band control protocol of the remote transcoder and rate adapters.

23.1.2 Structure of Abis Interface

The Abis interface can support three different internal BTS configurations (as illustrated in Figure 23-2):

z Single TRX.

z Multiple TRXs are connected with the BSC through a common physical connection.

z Multiple TRXs are connected with the BSC through different physical connections.




Figure 23-2 Struction of Abis interface

Abis

BTS3

BTS2

BTS1

A

Abis

MSCBSC

TRX

BCF

TRX

BCF

Abis

BSS

TRX

TRX

TRX

TRX

TRX

TRX

BCF

In Figure 23-2:

z TRX is the functional entity that supports 8 physical channels that belong to the same TDMA frame, which is defined in the PLMN.

z The BCF (Base Control Function) is the functional entity that performs common control functions including BTS initialization, software loading, channel configuration, operation and maintenance.

There are two types of channels at the Abis interface, which are:

z Traffic channels with the rates of 8 kbit/s, 16 kbit/s and 64 kbit/s respectively, carrying speech or data from radio channels.

z Signaling channels with rates of 16 kbit/s, 32 kbit/s or 64 kbit/s respectively, carrying signaling between BSC and MS, and between BSC and BTS.

Different Terminal Equipment Identifiers (TEI) are assigned to get unique addresses of TRXs. Three separate logical links are defined with each TEI (as shown in Figure 23-3).

z RSL: Radio Signaling Link used to support traffic management procedures, one for each TRX.

z OML: Operation & Maintenance Link used to support network management procedures, one for each SITE.

z L2ML, L2 management link, for transferring the management messages at L2.



Figure 23-3 Abis interface layer 2 logical links

TEI1L2ML SAPI=63

RSL SAPI=0OML SAPI=62

LAYER 2

TEI

MANAGE-MENT

TRX

TRX

TRX

BCF

L2ML SAPI=63


L2ML SAPI=63


BCF

BCF

BCF

BCF

L2ML SAPI=63OML SAPI=62

BSC BTS

TEI2

TEI3

TEI4

23.1.3 Functional Division between BSC and BTS

The BSS is composed of two functional entities, i.e. BSC and BTS. BTS is the radio part of the BSS under the control of the BSC, providing services for a specific cell. The BTS fulfills the interworking and mapping of the terrestrial channels and the radio channels, as well as the interworking of the MS and the network through the radio interface (Um interface). The BSC is the controlling part of the BSS, which manages the external and the internal interfaces, as well as the radio resource and radio interface parameters.

The specific function division between the BTS and the BSC is shown in Table 23-1.

Table 23-1 Distribution of services and functions between BTS and BSC

Location Remark Function BTS BSC/MSC

Channel allocation MSC-BSC channel

Blocking indication

Channel allocation

Terrestrial channel management

BSC-BTS channel

Blocking indication





Channel configuration management

Management Frequency hopping

Execution

Channel allocation

Link monitoring

Channel release

Idle channel observation

DCH management

Power control decision Note 1

System information management

System information broadcast

Random access check

Immediate assignment

DTX paging management

BCCH/CCCH management

DTX paging execution

Channel coding/decoding

Transcoding/rate adaptation

Uplink measurement

Processing measurement report

Note 2

Measurement

Traffic measurement

Radio channel management

Timing advance Calculation

Indication to MS during random access

Radio channel management

Timing advance

Indication to MS during handover




Indication to MS during session

LAPDm function

Management Ciphering

Execution

Management Handover

Handover access check

Mobility Management

Calling Control

z The support of power control in BTS is optional;

z The initial measurement data is reported by BTS to BSC through Abis interface. As an option, the BSC/BTS may support preprocessing of the initial data in BTS, which reduces the load of BSC.

23.2 Protocols on the Abis Interface

23.2.1 Physical Layer

Abis interface physical layer adopts the PCM link with the working rate at 2048 kbit/s to provide 32 channels at 64 kbit/s. The electro-technicial parameter at the physical layer conforms to the CCITT G.703 recommendations.

BSS is the connection point of the radio channel and terrestrial channel. Both kinds of channels have different transfer patterns and coding rates. In the radio channel of BSS, the transfer rate is 16 kbit/s while it is 64 kbit/s in the terrestrial channel. Therefore transcoding and rate adaptation is needed. This function is realized at the physical layer of Abis interface by the Transcoder & Rate Adaptation Unit (TRAU). TRAU can be located at BTS side, BSC side or MSC side. Given to the channel utilization at the Abis interface, M900/M1800 BTS does not support TRAU at BTS side, but the BSC or MSC instead.

Data coding is described in GSM 08.20. The in-band control protocol of TRAU is stipulated in GSM 08.60.




23.2.2 Data Link Layer

Overview

The data link layer of Abis uses LAPD protocol. It utilizes the service on the physical layer, and provides connection-oriented or connectionless services for layer 3. The data link Service Access Point (SAP) is the point that provides services for layer 3. SAP is identified by Service Access Point Identifier (SAPI). A data link connection endpoint is identified by a data link connection endpoint identifier as seen from layer 3 and by a data link connection identifier (DLCI) as seen from the data link layer.

For information exchange between two or more layer 3 entities, an association must be established between the layer 3 entities in the data link layer using a data link layer protocol.

The communication between data link layer entities is governed by a peer-to-peer protocol specific to the layer. Messages at the data link layer are transferred between entities at layer 2 through physical layer. Inter-layer service request is implemented with service primitive.

Function

The purpose of LAPD is to realize reliable end-to-end information transfer between layer 3 entities through the user-network interface by using the D-channel. To be specific, LAPD supports:

z Multiple terminal equipment between subscriber and interface,

z Multiple L3 entities.

Functions of LAPD includes:

z Establishes one or several data links on the D channel.

z Delimits, locates and transmits transparently frames so that a string of bits transmitted on the D channel in the form of frames can be identified.

z Implements sequence control to keep the order of the frames that pass the data link connections.

z Checks the transmission errors, format errors and operation errors in the data link connections.

z Makes recovery based on the detected transmission errors, format errors and operation errors.

z Notifies the management layer entities of the unrecoverable errors.

z Flow control.

Data link layer provides the means for information transfer between multiple combinations of data link connection points. The information may be transferred through point-to-point data link connections or through broadcast data link connections.



23.2.3 Traffic Management of Layer 3

The traffic management part of the Abis interface layer 3 is mainly described in GSM 08.58 specifications. The procedures defined in this specifications has two major functions:

z Realizing the interworking of the MS and BSS/NSS on the Um interface.

z Implementing part of the radio resource management functions under the control of BSC.

The traffic management message is divided into the transparent and non-transparent messages, as shown in Figure 23-4.

z The transparent message refers to the messages forwarded without interpretation or being processed by the BTS.

z The non-transparent message refers to the messages processed and structured by the BTS.

The traffic management messages can also be divided into four groups in terms of functions, which are:

z Radio link layer management message, used for the management of the data link layer on the radio channel.

z Dedicated channel management message used for the management of dedicated channels (SDCCH and TCH).

z Common control channel management message used for the management of common control channels.

z TRX management message used for TRX management.

Transparency and group of the message is determined by the message discriminator at the header of the message.

Step 1 Radio link layer management procedures

Radio link layer management procedures include:

z Link establishment indication procedure: BTS uses this procedure to indicate to BSC the success of setting up multi-frame link originated by the subscriber. BSC establishes a link from MSC to SCCP through the indication.

z Link establishment request procedure: This procedure is used by BSC to request the establishment of a link layer connection in multi-frame mode on the radio channel.

z Link release indication procedure: This procedure is used by BTS to indicate to BSC that a link layer connection on the radio channel has been released at the initiative of an MS.

z Link release request procedure: This procedure is used by BSC to request the release of a link layer connection on the radio channel.

z Transmission of a transparent L3-message on the Um interface in acknowledged mode: This procedure is used by BSC to request the sending of a transparent L3 message to MS on the Um interface in acknowledged mode.




z Reception of a transparent L3-message on the Um interface in acknowledged mode: This procedure is used by BTS to indicate the reception of a transparent L3 message on the Um interface in acknowledged mode.

z Transmission of a transparent L3-message on the Um interface in unacknowledged mode: This procedure is used by BSC to request the sending of a transparent L3 message to MS on the Um interface in unacknowledged mode.

z Reception of a transparent L3-message on the Um interface in unacknowledged mode: This procedure is used by BTS to indicate the reception of a transparent L3 message in unacknowledged mode.

z Link error indication procedure: Through this procedure BTS indicates BSC incase of any abnormality in the radio link layer.

Step 2 Dedicated channel management procedures

The dedicated channel management principle includes:

z Channel activation procedure: This procedure is used to activate a channel at BTS for an MS which later will be commanded to this channel by an Immediate Assignment, an Assignment Command, an Additional Assignment or a Handover Command message.

z Channel mode modification procedure: This procedure is used by BSC to request a change of the channel mode of an active channel.

z Handover detection procedure: This procedure is used between the target BTS and BSC to detect the accessing of the MS being handed over.

z Start of encryption procedure: This procedure is used to start encryption according to the procedure defined in Technical Specification GSM 04.08.

z Measurement report procedure: It includes the necessary basic measurement report procedure and measurement report preprocessing procedure. BTS reports all parameters related to handover decision to the BSC through this procedure.

z Deactivate SACCH procedure: This procedure is used by BSC to deactivate the SACCH at BTS according to the Channel Release procedure defined in Technical Specification GSM 04.08.

z Radio channel release procedure: This procedure is used by BSC to release a radio channel that is no longer needed.

z MS power control procedure: This procedure is used by BSS to set the MS power level or the parameters required by TRX. MS power control decision must be implemented in BSC, and as an optional procedure in BTS.

z BTS Transmission power control procedure: This procedure used between BSC and BTS to set the TRX transmission power level or the parameters required by TRX. The BTS transmission power control decision should be implemented in BSC, or in BTS.

z Connection failure procedure: This procedure is used by BTS to indicate to BSC that an active connection has been broken.

z Physical context request procedure: This is an optional procedure which allows the BSC to obtain information on the "physical context" of a radio channel just prior to a channel change.

z SACCH information modification procedure: BSC uses this procedure to instruct BTS to change the information (system information) filled in a specific SACCH channel.



Step 3 Common channel management procedures

Common channel management regulations include:

z Channel request by MS procedure: The procedure is initiated by TRX upon detection of a random access from an MS (Channel Request message from MS).

z Paging principle procedure: It is used to page an MS on the specified paging sub-channel. The paging of an MS is initiated by BSC sending a Paging Command message to BTS. BSC determines the paging group to be used according to the IMSI of the called MS. The value of this paging group together with the identity of the mobile station is sent to BTS.

z Immediate assignment procedure: When a mobile station accesses BTS, BSC uses this procedure to assign a dedicated channel for the mobile station immediately.

z Delete indication procedure: This procedure is used by BTS to indicate that due to overload on the AGCH, an Immediate Assign Command has been deleted.

z CCCH load indication procedure: This procedure is used by BTS to inform BSC the load on a designate CCCH. Indication period is also set by OM.

z Broadcast information modification procedure: This procedure is used by BSC to indicate to BTS the new information to be broadcast on BCCH.

z Short message cell broadcast procedure: Short Message Service Cell Broadcast messages are sent to BTS as SMS Broadcast Request messages.

Step 4 TRX management procedures

This type of procedure is used for TRX management. There are:

z SACCH filling information modify procedure: This procedure is used by BSC to indicate to BTS the new information to be used as filling information on SACCHs.

z Radio resources indication procedure: This procedure is used to inform BSC on the interference levels on idle channels of a TRX.

z Flow control procedure: This procedure is defined to give some degree of flow control. It can be used for TRX processor overload, downlink CCCH overload and ACCH overload.

z Error reporting procedure: This procedure is used by BTS to report detected downlink message errors, which cannot be reported by any other procedure.

----End

23.2.4 Operation and Maintenance Part of Layer 3

Operation and maintenance information model z Managed objects

There are four types of management objects: site, cell, carrier and channel. The basic structure is illustrated in Figure 23-4.




Figure 23-4 Basic structure of management object

SITE

CELL 0 CELL nCELL 1

TRX mTRX 0 TRX 1

CH0 CH1 CH7

TRX

z Object addressing

Addressing of network management messages is realized by means of managed object types and cases. For each object case in BTS there is a complete L2 connection description. The setup of the first connection uses one (semi-) permanent default TEI. Subsequent connections use the TEIs provided when setting up TEI procedures. Object cases can also use layer 3 addresses. The mixed use of layer 2 and layer 3 addressing enables one BTS site have one or multiple physical links.

z Managed object state

Management status includes management status, operation status and availability status. See Table 23-2, Table 23-3 and Table 23-4. The management state of managed objects is only controlled by BSC, and available state is the specific explanation of operative state.

Table 23-2 Management status

State Description Locked BSC has disconnected all calls through this managed object, and no new

calls can be connected to this object. Shut down New services can not be connected to this managed object, but those

existing calls will be maintained. Unlocked New calls can be connected to this managed object.

Table 23-3 Operation status

State Description Disabled Resources are completely unavailable, and can no longer provide services

to the users.



State Description Enabled All or part of resources are available and can be used.

Table 23-4 Availability status

State Description ln test The resource is being tested. Its operational state is disabled. Failed The source/object is not working due to some internal error. Its

operational state is disabled. Power off The resource needs power supply. Its operational state is disabled. Off line The resource needs manual or automatic operations. Its operational state

is disabled. Dependency Services provided by this resource are degraded in a certain sense, such

as rate or operational capacity. Its operational state is disabled. Degraded Services provided by this resource are degraded in a certain sense, such

as rate or operational capacity. Its operational state is disabled. Not Installed Hardware or software of the managed objects is not installed. Its

operational state is disabled.

Basic procedures

All procedures are based on formatted O&M messages. Most formatted O&M messages initiated by BSC or BTS require the peer layer 3 endpoint to give response or acknowledgment in the form of formatted O&M messages. Single formatted O&M messages that need not be responded are called a basic procedure. All formatted O&M messages are sent on layer 2 in the form of I frames. A group of procedures, called as structured procedures, are based on the combination of some basic procedures.

For a specific object, if a certain basic procedure is not completed, the system will not start its subsequent basic procedures. When there is no response to the formatted operation and maintenance message from the peer layer 3 before L3 timeout, the basic procedure is regarded as not completed. When the previous basic procedure has not received any response (ACK or NACK) before layer 3 timeout, then no subsequent basic procedure is sent to this object case. The default timeout for layer 3 is 10s. If part of an original message is not understood or supported, the whole message is discarded. A ACK message returned by the object indicates affirm response, it is used to notify the message sender that the command has been executed or will be executed. A NACK message returned by the object indicates disaffirm response, it is used to notify the message sender that the command executed unsuccessfully and the corresponding failure cause.

There are mainly the following types of basic procedures:




z Software loading management procedure

z Abis interface management procedure

z Transmission management procedure

z Air interface management procedure

z Test management procedure

z State management and event reporting procedure

z Equipment state management procedure

z Other procedure

23.3 Characteristics of Abis Interface Huawei's Abis interface supports various services. It also supports the control over BTS and the allocation of frequency. Abis interface has the following characteristics:

z Supporting all the services as stipulated in the GSM 02 series.

z Supporting smooth expansion of BTS capacity.

z Three types of multiplexing modes on Abis interface: 10:1, 12:1 and 15:1, meaning the ability to simultaneously transmit 10, 12 or 15 TRX data on the same E1 respectively.

z Transmission modes on the Abis interface can be terrestrial, satellite, microwave or optical fiber.

23.3.1 Transmission Modes on the Abis Interface

The transmission modes on the Abis interface can be terrestrial or satellite. These two types of transmission mode are selected in the BSC data configuration. For thinly populated and scattered areas where ordinary transmission technology is expensive and difficult to implement, Huawei offers connectivity through satellite. Figure 23-5 shows a typical example of networking through satellite.



Figure 23-5 Networking of satellite transmission

Satelite

Earth ReceivingStation BTS

BTS

E1

E1 SDH/PDH/HDSL/Microware/E1

MSC Earth Station

BSC

BTS

BTS

Earth ReceivingStation

The networking implementation through satellite transmission is different from the land transmission due to long transmission delay. To get good quality transmission, following measures are taken:

z LAPD protocol is modified to overcome the impact of delay.

z The adjustment algorithm of the TRAU frame is modified from fixed cycle adjustment to self-adaptive adjustment.

z The BTS clock works in internal clock mode.

23.3.2 Abis Interface Channel Assignment

Abis interface has three types of channels, including Traffic Channel (TCH), Radio Signaling Link (RSL) and Operation & Maintenance Link (OML). Each site corresponds to an OML, each TRX corresponds to an RSL, and a radio traffic channel corresponds to the traffic channel at the Abis interface.

There are three multiplexing modes for Abis interface: 10:1, 12:1 or 15:1, respectively meaning that the data of 10, 12 or 15 TRXs can be simultaneously transmitted on one E1.

In the following description, the row is the timeslot No., and the column is the sub-timeslot No. which is calculated by 8 kbit/s rate. Ti.j refers to the No. j sub-timeslot of the No. i TRX which occupies a 16 kbit/s sub-timeslot on E1.

Step 1 Timeslot distribution of E1 in 10:1 multiplexing




Table 23-5 Sequence table under 10:1 mode

Sub-TS

TS Sub-TS 0 Sub-TS1 Sub-TS2 Sub-TS3

0 Synchronization 1 T0.0 T0.1 T0.2 T0.3 2 T0.4 T0.5 T0.6 T0.7

3 RSL0 4 T1.0 T1.1 T1.2 T1.3

5 T1.4 T1.5 T1.6 T1.7 6 RSL1

7 T2.0 T2.1 T2.2 T2.3 8 T2.4 T2.5 T2.6 T2.7

9 RSL2 10 T3.0 T3.1 T3.2 T3.3

11 T3.4 T3.5 T3.6 T3.7 12 RSL3

13 T4.0 T4.1 T4.2 T4.3 14 T4.4 T4.5 T4.6 T4.7

15 RSL4 16 T5.0 T5.1 T5.2 T5.3

17 T5.4 T5.5 T5.6 T5.7 18 RSL5

19 T6.0 T6.1 T6.2 T6.3 20 T6.4 T6.5 T6.6 T6.7

21 RSL6 22 T7.0 T7.1 T7.2 T7.3

23 T7.4 T7.5 T7.6 T7.7 24 RSL7

25 T8.0 T8.1 T8.2 T8.3 26 T8.4 T8.5 T8.6 T8.7

27 RSL8

28 T9.0 T9.1 T9.2 T9.3 29 T9.4 T9.5 T9.6 T9.7

30 RSL9 31 OML



In 10:1 multiplexing, each E1 carries 10 TRXs. Each signaling link occupies a 64 kbit/s timeslot on the E1. If some sites cascade on one E1, , the E1 can carry 4 sites/9 TRXs or 7 sites/8 TRXs.


Table 23-6 Sequence table under 12:1 mode

Sub-TS


0 Synchronization 1 T0.0 T0.1 T0.2 T0.3 2 T0.4 T0.5 T0.6 T0.7

3 RSL0, RSL1 4 T1.0 T1.1 T1.2 T1.3

5 T1.4 T1.5 T1.6 T1.7 6 T2.0 T2.1 T2.2 T2.3

7 T2.4 T2.5 T2.6 T2.7 8 RSL2, RSL3

9 T3.0 T3.1 T3.2 T3.3 10 T3.4 T3.5 T3.6 T3.7

11 T4.0 T4.1 T4.2 T4.3 12 T4.4 T4.5 T4.6 T4.7

13 RSL4, RSL5 14 T5.0 T5.1 T5.2 T5.3

15 T5.4 T5.5 T5.6 T5.7 16 T6.0 T6.1 T6.2 T6.3

17 T6.4 T6.5 T6.6 T6.7 18 RSL6, RSL7

19 T7.0 T7.1 T7.2 T7.3 20 T7.4 T7.5 T7.6 T7.7

21 T8.0 T8.1 T8.2 T8.3 22 T8.4 T8.5 T8.6 T8.7

23 RSL8, RSL9 24 T9.0 T9.1 T9.2 T9.3

25 T9.4 T9.5 T9.6 T9.7 26 T10.0 T10.1 T10.2 T10.3

27 T10.4 T10.5 T10.6 T10.7 28 RSL10, RSL11

29 T11.0 T11.1 T11.2 T11.3




Sub-TS


30 T11.4 T11.5 T11.6 T11.7

31 OML

In 12:1 mode, each E1 carries 12 TRXs, and every two RSLs share a 64 kbit/s timeslot of E1. If some site cascaded on one E1, then the E1 can carry 3 sites/11 TRXs or 6 sites/10 TRXs.


Table 23-7 Sequence under 15:1 mode

Sub-TS


0 Synchronization 1 V1 V2 V3 V4

2 V5 V6 V7 V8 3 V9 V10 V11 V12

4 V13 V14 V15 V16 5 V17 V18 V19 V20

6 V21 V22 V23 V24 7 V25 V26 V27 V288 V29 V30 V31 V32 9 V33 V34 V35 V36

10 V37 V38 V39 V40 11 V41 V42 V43 V44

12 V45 V46 V47 V48 13 V49 V50 V51 V52

14 V53 V54 V55 V56 15 V57 V58 V59 V60

16 V61 V62 V63 V64 17 V65 V66 V67 V68

18 V69 V70 V71 V72 19 V73 V74 V75 V76

20 V77 V78 V79 V80 21 V81 V82 V83 V84

22 V85 V86 V87 V88 23 V89 V90 V91 V92



Sub-TS


24 V93 V94 V95 V96

25 V97 V98 V99 V100 26 V101 V102 V103 V104

27 V105 V106 V107 V108 28 RSL11, 12, 13, 14

29 RSL7, 8, 9, 10 30 RSL3, 4, 5, 6

31 OML+RSL0, 1, 2

In 15:1 mode, each E1 carries 15 TRXs, and timeslots 1 to 27 contain 108 sub-timeslots of 16 kbit/s for the use by traffic channels of 15 TRXs. Vi refers to the ith traffic channel of the site. The E1 can be configured with 16 signaling links, every 4 of which share a 64 kbit/s timeslot. If all cascaded sites have the same 15:1 configuration, then a single E1 can carry 2 sites/14 TRXs or 4 sites/12 TRXs.

----End

ContentsFiguresTables23 Abis InterfaceAbout This Chapter23.1 Overview23.1.1 Protocol Model23.1.2 Structure of Abis Interface23.1.3 Functional Division between BSC and BTS

23.2 Protocols on the Abis Interface23.2.1 Physical Layer23.2.2 Data Link Layer23.2.3 Traffic Management of Layer 323.2.4 Operation and Maintenance Part of Layer 3

23.3 Characteristics of Abis Interface23.3.1 Transmission Modes on the Abis Interface23.3.2 Abis Interface Channel Assignment

Documents

23 Abis Interface