Switching Maintenance Training

Switching Maintenance

1. System Integration Contents 1.1 Introduction to GSM System Elements....................................................................................... 2 1.2. GSM System Element ............................................................................................................... 7 1.3. Subsystem Functions and Integration ..................................................................................... 15

1BCCN2200 © 2007 Bintang CyberFall


1.1. Introduction to GSM System Elements



The basis for the standardization of a European cellular system was laid down in the mid 80s. A

team of the CEPT (today ETSI) worked on the standardization of this European cellular system.

The team was led under the name "Group Special Mobile" (GSM). This abbreviation was later

used as standard and changed to "Global System for Mobile Communications". The GSM or DCS

network is operated in a frequency range of 890 to 915 MHz and 835 to 960 MHz or 1710 to 1785

MHz and 1805 to 1880 MHz.

PLMN country (public land mobile network) Several PLMN network operators can appear in a "PLMN country".

A "PLMN country" is unambiguously specified via the selection of a so-called

"country code".

PLMN area A "PLMN area" is as a rule synonymous to PLMN network operator or a PLM network. Several

network operators who organize the "PLMN country" either regionally (e.g. North and South) or

overlapping appear as a rule in a "PLMN country". A PLMN area is unambiguously addressable

via the "network destination code" (NDC) which can be dialed.

MSC area (mobile services switching center) A PLMN normally contains several "MSCareas". An MSC is a "switching center" or switching

equipment for mobile subscribers and has one or several connections to the base station system"

or radio system. An "MSC Area" is unambiguously addressable via dialing information; it cannot

however be dialed by the calling subscriber, as it does not know the location of the subscriber.

Location area A "location area" is an administrative area within an "MSC area" (e.g. an emergency service

number per "location area") and covers several cell broadcast channels (CBCH). A "location area"

is internationally addressable, but it can not be dialed.

Cell A "cell" is the smallest functional area and is covered by a "base station"(BS), i.e. radio station. It

is the physical location of a mobile subscriber. In case of the cell is covered by an omni directional

BS (coverage 360 degrees) the cell contains one frequency pair (one up- and one downlink) and

therefore up to 8 traffic channels.

In case of the cell is subdivided into sectors up 8 X number of sectors traffic channels are possible.

A cell is also internally addressable.



Figure 1.1. GSM Service Area

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GSM Evolution (Phase) GSM was developed in he different phases described below.

GSM Phase 1 Phase 1 of the implementation of GSM Systems includes all central requirement for the

transmission of digital information. Speech data transmission is of core importance. Data

transmission is likewise defined at rates of 0.3 to 9,6 kbps.

GSM Phase 2 GSM Phase 2 was completed in 1995. Supplementary service is already in this phase, with

features comparable to ISDN were added to this standard. Technical improvements were also

specified such as half rate speech. An important aspect and terminal equipment must retain

compatibility with the Phase 1 networks and terminal equipment.

GSM Phase 2+ This phase relate to new supplementary services, services for special user groups, improved voice

codecs (Enhanced Full Rate) , IN applications and high data rate service (HSCSD, GPRS, EDGE)

GSM Phase 2 + (enhanced data service) 1997

GSM Phase 2 1995

GSM Phase 1 adopted 1990

Renaming : “Global System for Mobile

Communication”

1989

Groupe Special Mobile 1982

Events Year

Figure 1.2. GSM Evolution



BCCN2200 © 2007 Bintang CyberFall

Phase Phase Phase

Phase Phase Phase

Service

Figure 1.3. Phase of GSM

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Year 1990 1995 1997

Downward-compatible

Speech Connection : - Full Rate (FR)

Data Transfer : (9,6 kbps)

Speech Connection :

- Full Rate (FR)

- Half Rate (HR) Data Transfer : (9,6 kbps)

Supplementary Service

Speech Connection :

- Full Rate (FR)

- Half Rate (HR)

- Enhanced Full Rate (EFR) New Supplementary Service IN Application New Data Transfer :

- HSCSD

- GPRS

- EDGE

6


1.2. GSM System Element




Figure 1.4. Network Element

XNSS

Network Switching

SubSystem

GSM PLMNPLMN

Public Land Mobile Network RSS Radio

Subsystem

MS Mobile Station

PSTN

PDN

ISDN

Fixed

Networ

OSS Operation SubSystem

BSS Base Station SubSystem

8


GSM PLMN

GSM PLMN consists of :

• Network Switching Subsystem (NSS)

• Radio SubSystem (RSS)

• Operation SubSystem (OSS)

Network Elements The Network Switching Subsystem (NSS) consists of the following functional units :

• Mobile services Switching Center (MSC)

• Visitor Location Register (VLR)

• Home Location Register (HLR)

• Authentication Center (AC)

• Equipment Identity Register (EIR)

The Radio SubSystem (RSS) consists of the Mobile Station (MS) and the Base Station Subsystem

(BSS), which is composed of the following functional units.

• Base Station Controller (BSC)

• Base Transceiver Station (BTS)

• Transcoding and Rate Adaptation Unit (TRAU)

The Operation SubSystem (OSS) consists of :

• Operation & Maintenance Center for BSS

• Operation & Maintenance Center for SSS




Figure 1.5. GSM PLMN

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BTS

BSC

OMC-B OMC-S

VLR HLR

EIR AC

MSC

T R A U

PSTN

Radio SubSystem

Mobile

Station +

Base Station

Subsystem (BSS)

Operation SubSystem OSS

Network Switching

Subsystem

GSM PLMN

MS =

ME +

SIM

ISDN

Data

Network

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GSM PLMN Interfaces GSM Interfaces The following GSM Phase ½ interfaces are open interfaces:

• Um : MS – BSS

• A : MSC – BSC

• B : MSC – VLR

• C : MSC – HLR

• D : HLR – VLR

• E : MSC –MSC

• F : MSC – EIR

• G : VLR – VLR

The following interfaces are proprietary solutions:

• Asub : BSC – TRAU

• Abis : BSC –BTS

• T : BSC, BTS,TRAU – Local Maintenanace Terminal (LMT)

• O : BSC – OMC-B




GSM PLMN Interface

Figure 1.6. GSM PLMN Interfaces

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T

MS

BTS BSC TRAU

VLR

• Phase 1/2 • Without GPRS

AC

LM

LM

LM

OMC -

Um Abis Asub

C

B

F

EIR

D T T

O

AHLR MSC

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GPRS Interfaces The following GPRS interfaces :

• Gn : SGSN – SGSN

• Gs : SGSN – MSC/VLR

• Gb : SGSN – BSC

• Gc : GGSN – HLR

• Gf : GGSN – EIR

• Gp : SGSN – GGSN (other PLMN)



GPRS Architecture Interface


Figure 1.7. GPRS Interface

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MS BSS

SGS GGS PDN

GGSother PLMN

MSC /VLR

HLR/(GR)SGS

Gp

Gc

EIR Gf

Gi Gr

Gn

Gb Um

Gs

A

GnD

Signaling &

Signaling only Data transmission

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1.3. Subsystem Functions and Integration



Base Station Subsystem (BSS) The BSS consists of the following network elements :

• BSC : Base Station Controller

• BTS : Base Transceiver Station

• TRAU : Transcoding and Rate Adaptation Rate

Base Station Controller (BSC) The Base Station Controller(BSC) is the controlling element, the heart and center element of the

BSS.

BSC functions :

• Terminal Control Element (A & Abis Interface)

• Switched matrix between TRAU ⇔ BTS

• Central Module

• Collecting error messages in BSS

• Connection to the OMC-B

• Database storage




Figure 1.8. BSC

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TRAU

Base Station Controller BSC

• Terminal Control Elements (A & Abis Interface) • Switched matrix between TRAU ⇔ BTS • Central Module • Collecting error messages in BSS • Connection to the OMC-B

OMC- B

AsubAbis

BSC

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Base Transceiver Station (BTS) The BTS provides the physical connection of an MS to the network in from of the Air Interface. On

the other side, towards the NSS, the BTS is connected to the BSC via the Abis Interface.

Functions:

• Cell Configuration, Standard Cell, Umbrella Cell, Sectorized Cell

• Synchronization: Providing of mobile stations with frequency and time synchronization

information.

• Power Control : Control the power level of BTS and MS

• Timing Advance (TA): Calculation of the distance of the MS from the BTS, The MS are

informed of necessary transmission advance.



Um • Cell Configuration • Synchronization (time and frequency) • Power Control PC • Timing Advance TA

Base Transceiver Station (BTS)

BSC

Abis

Figure 1.9. BTS

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Transcoding and Adaption Rate (TRAU) The TRAU is used for speech compression (Transcoding) and adaptation of data to the

requirements of the air the interface (Rate Adoption). It lies between A and Asub interface.

Functions:

• Transcoding TC defines speech compression: compresses/decompresses the incoming

speech data from 64 kbps to 16 Kbps.

• Rate Adoption RA filters out the useful data (0.3 – 9.6 kbps in Phase ½) coming from the

MSC (64kbps) signal and forms a 16 kbps signal toward the BSC

• The user data sub multiplexed into 16 kbps sublots on the Asub interface.




Figure 1.10. TRAU

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• speech compression: 64 kbit/s ↔ 16 Kbps

• data transmission: 64 kbit/s ↔ 0.3 - 9.6 kbit/s

Transconding & Rate Adaption Unit (TRAU)

MSC TRAU BSC

BTS

64 Kbps 16 Kbps16 Kbps

TRAU Frame

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The Network Switching Subsystem (NSS)

The NSS plays the central part in every mobile network. While the BSS provides the radio access

for the MS, the various network elements within the NSS assume responsibility for the complete

set of control and database functions required to set up call connections using one or more of

these features. (Encryption, Authentication & Roaming)

To satisfy those tasks, the NSS consists of the following :

• Mobile Switching Center (MSC)

• Home Location Register (HLR)

• Visitor Location Register (VLR)

• Equipment Identification Register (EIR)

The Subsystems are interconnected directly or indirectly via the worldwide SS7 network. The

network topology of the NSS is more flexible than the hierarchical structure of BSS. Several MSC

may, for example, use one common VLR, the use of an EIR is optional and the required numbers

of subscribers determines the required number of HLR.

Mobile Switching Center (MSC) The MSC handles connection tasks in the PLMN, i.e. set up of circuit connections to the BSS,

between each other and other networks (PSTN). The MSC visited by a customer is described as a

Visitor MSC (VMSC). A MSC which represents an interface to other networks, is called Gateway

MSC (GMSC).

Functions:

• NSS Center

• Serve Several BSC

• Always associated with VLR

• Set-up & switching of user traffic & signaling

• Gateway MSC: Gateway to external networks




Figure 1.11. MSC

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• NSS Center

• Serves Several BSC

• Always associated with VLR

• Set-up & switching of user traffic & signaling

Mobile Switching Center (MSC)

VLR

Visitor Location Register

MSC

GMSC External

Network

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Visitor Location Register (VLR) The VLR is responsible to help the MSC with information on the subscriber, which are temporarily

in the MSC service area.

Examples of subscriber data information in the VLR :

• MSISDN : Mobile Subscriber ISDN Number

• IMSI : International Mobile Subscriber Identity

• TMSI : Temporary Mobile Subscriber Identity

• LMSI : Local Mobil Subscriber Identity

• MSRN : Mobile Station Roaming Number

• Triples : Security Parameter for Authentication

Functions:

• Temporary Mobile Subscriber Identity

• Subscriber data from HLR (MSISDN, IMSI, Service)

• Associated with MSC

• Mobile Station Roaming Number

• Authentication coordination

• Ciphering




Figure 1.12. VLR

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Temporary Mobile Subscriber Identity

Subscriber data from HLR (MSISDN, IMSI,

Service)

Associated with MSC

Mobile Station Roaming Number

Authentication coordination

Ciphering

Visitor Location Register (VLR)

MSC

VLR

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Home Location Register (HLR) The Home Location Register (HLR) is the main and semi permanent data base of the mobile

subscriber and central storage for data base subscriber.

The HLR is always associated with an Authentication Center (AC).

The HLR performs sends data to the VLR.

Authentication Center (AC) An Authentication Center (AC) contains all necessary means, keys and algorithms for the creation

of security related authorization parameters, the names is Triples.

The Triples are created on VLR request and delivered via HLR to the VLR. An AC is always

associated with HLR.




Figure 1.13. HLR – AC

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Home Location Register

• Central storage of subscriber data

• Send data to VLR (eg. Triples Request)

• Associated with AC

• Semi-permanent data : MSISDN, IMSI, &

Service

Authentication Center

• Generation of triples (VLR request) • Associated with HLR

Authentication Center (AC)

Home Location Register (HLR)

AC

HLR

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Equipment Identity Register (EIR) The Equipment Identity Register (EIR) contains the mobile equipment identity: International Mobile

Equipment Identity (IMEI). An IMEI clearly identifies a unique Mobile Equipment (ME) and contains

information about the place of manufacture, device type and the serial number of the equipment.

EIR are an optional feature in GSM.

There is having three lists to be observed and to be blocked equipment (WHITE – GRAY –

BLACK).

A Common EIR (CEIR) in Ireland enables the world-wide identification of stolen mobile equipment.




Figure 1.14. EIR

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EIR

Storage of ME data (IMEI)

Monitoring of IMEI: "white", "gray", "black" list

CEIR • Central, worldwide ME register

EIR

Equiptment Identity Register (EIR)

CEIR

IMEI = International Mobile Equipment

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Operation SubSystem (OSS) The functions of the OSS are performed:

• Subscriber and equipment data management

• Network operation, configuration & management

• Error detection & correction

• Security management

• Performance control




Figure 1.15. OSS

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• Subscriber and equipment data

management

• Network operation, configuration

& management

• Error detection & correction

• Security management

• Performance control

Operation SubSystem (OSS)

SSS Switchin

BSS Base Station

OMC

g

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2. Operation, Administration, and Maintenance Concept

Contents 2.1. Alarm Concept ........................................................................................................................... 2

2.1.1. Alarm and Message .......................................................................................................... 10 2.1.2. Alarm Clearance ............................................................................................................... 26 2.1.3. Escalation.......................................................................................................................... 30

2.2. Language and Communication................................................................................................ 32 2.2.1. Communication Interfaces ................................................................................................ 34 2.2.2. Commands and Syntaxes ................................................................................................. 36

2.3. Project Specific Documents..................................................................................................... 48 2.3.1. Tools and Documents ....................................................................................................... 51



2.1. Alarm Concept



A telecommunication network consists of different transmission and switching equipment and

devices. It offers different services to customers. ITU-T has specified the concept of a

Telecommunication Management Network (TMN) to provide management support for network

operators.

The simplified physical architecture of a TMN has two components:

• The operation systems (OS) provide the man-machine interface for conducting

management functions.

The functions are generally located in the Network Management Center (NMC).

• The Data Communication Network (DCN) connects the operation systems to the individual

network elements (NE) of the telecommunications network.



Figure 2.1. Telecommunication Management Network

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As with all other network elements, the Network Element Management includes all functions for

operating individual network elements.

The functions are implemented by operation, administration and maintenance (OAM) procedures

and are described in the system manual (Operation and Maintenance Manuals).

• Centrally executed OAM functions are generally the responsibility of the Network

Management Center (NMC) personnel.

It is provided by the NetManager (for fixed network applications) and the Switch

Commander (for mobile applications) as operation systems for system management in the

NMC.

The NMC comprises a LAN with workstations. The LAN has a TCP/IP server, which is

connected with all exchanges in the telecommunications network via a TCP/IP data

network.

• The Switch Commander is provided for the primarily decentralized OAM functions.

It is installed on a Windows NT-PC that is connected with the network elements by means

of TCP/IP data lines. A group of network elements can be accessed from the terminal.

• Local input/output devices are available for OAM functions to be run "on-site".

A BCT-Boot is provided in each of the network elements for this purpose. The BCT-Boot

software is installed on a Windows NT-PC. The PC is directly connected to

EWSD/D900/D1800 via a V.24 interface. The BCT-Boot provides a simple dialog interface

to the CP of the network element. It should be used mainly for commissioning/startup of the

network element SW and on-site fault clearance.

However, a combined BCT-Boot/CT may also be used locally for on-site OAM functions. In

this case, the PC can use both SW packages (Boot/Switch Commander) and is connected

to EWSD/D900/D1800 via V24 and TCP/IP interfaces.



Figure 2.2. TNM Components

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The training program has a modular structure and is oriented toward target groups.

The displayed assignment of the target groups to the NMC and regional OMCs can be modified by

specific solutions for individual network operators.

Centralized personnel in the NMC:

• NMC operator:

Performs alarm surveillance in the NMC and decides what department of the network

operator is to be notified of the alarm.

• Fault Management Expert (FME):

The fault management expert represents the technical assistance center TAC1 of the

network operator in the NMC. The FME is responsible for the central control function for all

maintenance activities in the network elements. He/she supports the field service and

performs special fault clearance if a fault cannot be resolved by the standard field service

fault clearance procedures. Moreover, this person is the single point of contact for the

network operator for support by the technical support center (TSC).

• Configuration Management Expert (CME):

The configuration management expert in the NMC is responsible for all configuration

functions in the network elements. This includes modification of the network element

database based on decisions taken by the planning department/service management as

well as clearance of malfunctions in the network (e.g., signaling problems).

In addition to the actual configuration management, the CME also implements the account

and security management functions.

• Performance Management Expert (PME):

Performs all performance management functions in the NMC.

Field service personnel in regional OMCs/exchanges:

• Network Element Manager (NEM):

Performs all standard functions for HW maintenance, SW safeguarding and routine testing.

Alarms are forwarded to the NEM from the NMC for this purpose. Should the NEM meet

with no success in clearing faults (e.g., major faults in emergency situations), he/she refers

to the fault management expert in the TAC1.



Moreover, the NEM can carry out simple database modifications according to instructions

by the CME.

• Network Element Assistant (NEA):

Supports the network element manager (NEM) during fault clearance (e.g., module

replacement) in exchanges.



Figure 2.3. Target Group for Training

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2.1.1. Alarm and Message

The system documentation is classified according to functions and target groups. It is available to

the network operator's personnel both in paper format as well as electronically (CD-ROM, BCT-

Common, Node Commander/OMC-B).



Figure 2.4. Operation and Maintenance Documentation

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The application used for alarm surveillance at the SC is called AMD (Alarm and Message Display).

List of main features You can use the AMD for the following purposes:

o Displaying of all alarms and messages, which are stored on the Alarm Data Server (ADS)

o Displaying the open alarms and the alarm summary of Network Elements

o Applying filters to the node and alarm list

o Sorting the node and alarm list

o Generating a work order

o Modifying the processing state of an alarm

o Customizing views, filters, columns, sorting, fonts colors and sound

o Supporting online and offline mode

o Displaying a processing state of an alarm

o Exporting of alarms and messages to text files

o Enabling acoustical alarm indications

o Printing of alarm and message lists as well as alarm and message details

o Starting of alarm handling as a display of alarm lists and starting the Interactive Document

Browser for alarm clearance using the corresponding procedure of the maintenance

manual (MMN)



Figure 2.5. Alarm and Message Display

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Monitoring network elements There are 4 services responsible for the alarm data handling:

• Q3 ADC - Q3 Alarm Data Collector (for NE's containing an MP)

• MML ADC - MML Alarm Data Collector (for NE's containing a CP)

• ASS - Alarm Store Service

• ANS - Alarm Notification Service

These services together are building the so-called ADS (Alarm Data Server).

The ADC collects the incoming alarms and transfers them to the ASS, which stores them in the

ORACLE database and triggers the ANS to update the view.

The advantage of this concept is the scalability. Each process could run on a different SC and

could be installed in a redundant configuration, which would guarantee more performance and

reliability.



Figure 2.6. Monitoring Network Element

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The different window parts of the AMD After the selection of the user group and the individual alarm view you will see the

window in below figure.

The AMD consists of 3 window parts:

1. Node Status window ( left window )

2. Alarm List window ( upper right window )

3. Alarm Details window ( lower right window )

Secondary Windows If you double click on a specific network element, a secondary window comes up which contains

the alarm list window and the alarm details window of this specific network element.

If you do a double click on a specific alarm, a secondary window comes up which contains the

alarm details window of this specific alarm.

You can open as many secondary windows as possible. If you close the main window, all

secondary windows are automatically closed.

The secondary windows contain the same menus and toolbars as the main window.



Figure 2.7. Windows of AMD

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Work order viewer Sometimes it is not possible for an operator to clear a specific alarm directly. (e.g. because a

module has to be replaced and the NE is located at a different place.)

In this case the operator has to inform somebody else to execute the necessary actions. This

information is given by a so-called work order.

A work order is a document containing the information necessary for the repair staff to start fault

clearance at the network element location.

To create a work order, select one or more alarms and click on the Create Work Order Icon of the

Alarm Message Display.

To view, edit and process work orders created for one or more alarms within the AMD application

the, SC application Work Order Viewer is used.

The main features of Work Order Viewer:

• Opening an existing work order document

• Printing a work order document

• Adding remarks to a work order

• Sending a work order document via electronic mail

Starting the Work Order Viewer Work Order Viewer can either be started from the AMD application or separately to edit already

existing work orders.

After starting the Work Order Viewer via the Windows NT Start button you have to open an already

existing work order document.

By starting the Work Order Viewer from the AMD application a work order is created for the

selected alarms and opened in the Work Order Viewer already.



Figure 2.8. Work Order Creation

Figure 2.9. Starting the “Work Order Viewer”

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Contents of work orders A Work Order contains all the information, which is necessary to start fault clearance at the

network element location.

1. Alarm list Displays all alarms contained in the work order. The list provides columns for alarm priority, alarm

type, object class, and object instance.

2. Board list Displays all faulty boards of a selected alarm. The list provides columns for module, location, rack,

shelf, and pitch. The display of faulty boards is not possible for network elements of type EWSD

Classic and therefore not supported in the current Switch Commander version.

3. Alarm Information page Shows detailed information of the selected alarm. You may enter or change the alarm specific

remarks.

4. Floor Plan page Shows the floor plan of the network element for which the work order has been created. A floor

plan is a document containing the graphical setup plan of a network element showing floors

(realized as floor plan pages), racks, and boards. One floor plan file exists per network element.

The assignment is part of the network element specification done with NE Administration

application and is stored in the communication database.

5. Rack View page Shows a schematic view of the rack selected in the Floor Plan page. The rack display is not

possible for network elements of type EWSD Classic and therefore not supported in the current

Switch Commander version.

6. Document Information page Shows information about the whole work order document. You may modify the work order author

and enter or change the work order specific remarks.



Figure 2.10. Contents of the Work Orders

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Interactive document browser for alarm clearance You can use the Work Order Viewer – as the Alarm Panel application – to show the detailed alarm

information and start the Interactive Document Browser for displaying the procedure for alarm

clearance in the maintenance manual.



Figure 2.11. Interactive Document Browser

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Editing a work order

Although Work Order Viewer basically is used to display work orders, you can add or change the

following information before saving or sending the work order as electronic mail:

• Name of the work order author,

• Work order specific, and

• Alarm specific remarks.

Work Orders are stored at a shared directory at the file server.

It can be found e.g. under:

1. Network Neighborhood

2. Fileserver (WIN NT machine name of the Fileserver)

3. SC Base

4. Alarm Surveillance

5. WorkOrderDir

Mailing a work order You can start the mail program configured for you in the Windows NT control panel (Mail icon): the

work order document is included as a mail attachment. You can use this feature within Work Order

Viewer only if your configured mail system supports MAPI (Messaging Application Program

Interface). MAPI enables you to send an electronic mail from within a Windows application and

attach the document you are working on to the mail note (e.g. Microsoft Exchange offers such an

interface).



Figure 2.12. Sending Work Order Using Email

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2.1.2. Alarm Clearance

Starting fault clearance At first you have to select the alarm you want to handle. Therefore you have to select the network

element in the Node Status Window and then you have to select the specific alarms in the Alarm List Window.

Stop Audible Alarm Stops the sound triggered by a new alarm.

Mute Audible Alarm Mutes or resumes audible alarms for the current AMD session.

Print With this button a dialog for printing the details of the selected alarms.

Confirm Alarm In the "Alarm List Window" select the desired alarms and click “Confirm”. The confirmation of

alarms in the AMD application leads the network element to update its database and send a

message containing the information of the new states.

Clear Alarm In the “Alarm List” dialog box select the alarms and click “Clear Alarm”. The clearance of alarms in

the Alarm Panel application leads the network element to update its database and send a

message containing the information of the new states. Most of the Alarms are automatically

cleared after successful fault clearance, setting the status to cleared in the AMD is only required

for Alarms which are not automatically cleared



Figure 2.13. Starting Fault Clearance

Figure 2.14. “Clear Alarm” Windows

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Maintenance Manual The alarm clearance with the help of the Interactive Document Browser is only possible for alarms,

which provide the information about the corresponding maintenance manual (MMN) procedure.

The Alarm Status of some CP Alarm Objects like "RECOV" or "SYOP" must be changed manually

via the Workbench.

To change the status to "in process" (confirmed):

SETALSTAT:MSGNO=<msg no.>,ALSTAT=IP;

To change the status to "cleared"

SETALSTAT:MSGNO=<msg no.>,ALSTAT=C;



Figure 2.15. Open the Maintenance Manual

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2.1.3. Escalation

Technical assistance centers TAC2 & TAC3 for network operator support are positioned in the

country-/project-specific and central technical service centers (TSC).

Generally, the fault management expert (also known as TAC1) is the network operator's partner of

the TAC.

The TAC2 personnel in the country-/project-specific TSC analyze queries/fault reports submitted

by the network operator and either respond themselves or transfer them to the TAC3 personnel in

the central TSC in Munich.

This after-sales service concept is named Performance Plus.

Performance Plus includes the following feature packages:

o Emergency Service It is provided a 24-hour hotline service to deal with serious faults in EWSD

systems. This refers principally to clearance of faults classified as so-called EWSD

emergency situations.

o Fault Report Processing All faults are reported by the network operator to the TSC.

If faults are independently cleared by the network operator fault management/field service,

the corresponding fault reports are used by the TSC for statistical purposes only.

In cases in which the network operator can't resolve faults (for example, software errors

requiring correction by patch), the network operator personnel is supported by the TSC .

o Field Service The regional field service provides support to the network operator's field service personnel

(network element manager, network element assistant) for onsite maintenance and fault

clearance if necessary.

o Repair and Replacement Service The network operator dispatches faulty hardware components to the TSC. There they are

repaired/replaced and afterwards returned.

Independent of these actions, network operators generally have their own pools of

replacement modules for fault clearance.

o Software/hardware update The TSC supplies customers with all necessary, up-to-date EWSD components (for

example, EPROM with updated firmware).



Figure 2.16. Support and Escalation

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2.2. Language and Communication



The command language used by the CP is called man-machine-language MML. It can be used for

the CP only and may be entered via switch commander or BCT-boot.

The switch commander also supports Q3 scripts. This is used to communicate with the SSNC.

Communication to the CP is based on MML commands, and communication to the SSNC is based

on Q3 commands. The BCT-Boot software does not support Q3.

o MML-commands => CP

o Q3 tasks => SSNC

Forms organized in a menu tree can be provided in the Switch Commander for the input of MML

and Q3 commands. It allows significantly simplified system command operations due to the menu

and form method used. Also, it allows the use of Q3 scripts for communication with the SSNC.



2.2.1. Communication Interfaces

The Craft Terminal is used for operation and maintenance of the exchanges. It replaces the old

text based local OMT with a modern graphical user interface.

Depending on the hardware and software the following terms are used:

BCT Basic Craft Terminal. Only the BCT/BOOT software is installed. Connection to the exchange via

V.24 interface.

CT Craft Terminal. Switch Commander software or/and BCT/COMMON software is installed.

Connection to the exchange via TCP/IP or X.25 interface.

(The X.25 interface can only be used for BCT/COMMON) The BCT/BOOT software can be

simultaneously installed on the same personal computer, again using V.24 interface for

connection.

BCT/BOOT Software for BCT. Only BMML commands can be entered.

BCT/COMMON Software for CT. The BMML and EMML modes are available.

Switch Commander Software for CT. Only the quick select mask input mode is available.

Connection to the exchange Two figures below show the connection methods of the BCT or CT hardware to the coordination

processor and SSNC of the exchange. The BCT/BOOT software is only used for direct

connections to the CP. BCT/COMMON software can be connected to the CP via X.25 software or

through the SSNC via TCP/IP. Switch Commander can be simultaneously connected to the CP

and SSNC of different exchanges via an TCP/IP network.

If a TCP/IP or X.25 connections are used, it is not possible to transfer or execute anything if these

links are not active, e.g. while the exchange is in installation or split operation mode! In this case

only the BCT/BOOT software can be used.



Figure 2.17. V.24 Connection of the BCT to Exchange

Figure 2.18. TCP/IP Connection of the CT to Exchange



2.2.2. Commands and Syntaxes

Basic MML Basic man machine language (BMML), the structure of which is based on an ITU

recommendation, was created for communication between the operators and the coordination

processor CP.

BMML contains all the rules to carry out standardized information exchange between the user

programs and the operating personnel. BMML is divided into 2 elements:

o BMML commands All possible entries of the operating personnel (Q3 and MML) are documented in

the task manual TML.

o Outputs of the CP All CP output masks are documented in the output manual OML.



Figure 2.19. BMML and Q3

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BMML command structure A BMML command contains the following components:

o The command code contains the action and the object.

The action indicates how the following object is handled, for example “display”,

“creation”, “configuration” etc.

The object indicates for which system unit or which call handling data object the

action is to be carried out. E.g. “LTG”, “SN”, “ROUTE”, “SUBscriber” etc.

o A colon, “:”, serves as a separation sign between the command code and the

following parameters.

o The parameters are not only identified by a certain position, but by their codes.

They can therefore be located at any position and are composed of the parameter name

and the parameter value.

o A comma, ”,”, serves as a separation sign between the individual parameters.

o The BMML command status usually ends with a semicolon ”;”.



Figure 2.20. BMML Command Structure

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Typical actions of a BMML command The most commonly used MML commands are for creating, deleting, changing and displaying call

processing database objects, and for the configuration, diagnosis and display of the configuration

status of hardware units.



Figure 2.21. BMML Command Actions

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Structure of the parameters of a BMML command As already mentioned, a parameter is divided into a parameter name and a parameter value.

A parameter value consists of one or more parameter arguments.

A parameter argument consists of one or more information units.

The following elements can be used as information units:

o Character string

e.g. for the parameter TGNO (name of a trunk line)

TGNO = JKT1

o Text sequence

e.g. for the parameter PRO (name of a processor)

PRO = “BCT-COMMON“

o Symbolic name

e.g. for the parameter SERV (services of an ISDN subscriber)

SERV = TELKOM2

o Numbers

e.g. for the parameter DN (directory number of a subscriber)

DN = 33301



Figure 2.22. Structure of Parameters

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Entry modes for BMML commands Various modes can be used for the input of basic MML commands:

Direct mode The basic MML command is entered and sent in its entirety including the parameter and

the end sign ”;”.

Prompting mode The basic MML command is only partially entered and sent. The entry can be sent after the

command code without “:” and after every parameter without ”,”. The system then switches

to an interactive mode and queries all possible parameters and finally the end sign “;”

individually. This interactive mode can be quit at any time by the user by entering the end

sign ”;”. Parameters which are not queried at this point can also be entered. To do so,

instead of or after entry of the queried parameter, enter the separator ”,” followed by a

parameter name and a parameter value.

Continuation mode Instead of ending a basic MML command with ”;”, it is also possible to fall into the so-called

continuation mode by entering an exclamation point “!”. This is only possible with a

sequence of basic MML commands with the same command codes.

After entering a command in continuation mode, the system expects the next command

beginning with the first parameter name without command code.

However, the last command of the sequence (i.e. before a command code which deviates

from the sequence is to be used) must be ended with ”;”.

Continuation mode is used in command files to improve speed because it is not necessary

to restart the user program when entering commands from the 2nd command to the last

command of a sequence. However, it is also used in MML commands which only fulfill

partial tasks after entry of the particular command and which do not complete the entire

task until after entry of the terminating ”;”.



Figure 2.23. Input Modes

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Q3 commands Unlike MML commands, are Q3 commands based on an ITU-T defined interface and are therefore

a standard language. Q3 commands are only used for communication with the SSNC. These

commands (or tasks) are translated to Q3 scripts by the switch commander software. These Q3

scripts are then sent to the SSNC, which provides the output.

The following differences can be identified between MML and Q3 commands.

Q3 is an ITU-T standard language, whereas MML is a specific language.

Q3 commands (or tasks) are translated to Q3 scripts and then sent to the SSNC. MML

commands are sent directly to the CP.

The input of Q3 commands can only be done by means if an input mask and not with an

input line.

Q3 commands do not use abbreviations; all parameters are full written text.

Q3 commands cannot be used in command files.



Figure 2.24. Q3 Commands Input Mask

Figure 2.25. Difference of Inputs to SSNC and CP

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2.3. Project Specific Documents



Viewer for online documentation All the documentation required for the operation of a D900/D1800/D1900 network node is

electronically available on CD-ROM. The documentation includes descriptions and manuals

assigned to specific function areas and tasks.

For displaying the different formats of electronic documentation (e.g. CML, MMN, OML,..) the

Interactive Document Browser (Application on SC) can start the Internet Explorer based on HTML

Documents and the Acrobat Reader for documents in Portable Document Format (PDF). Also the

Viewers can be started manually as shown in the next chapters.



Figure 2.26. Acrobat Reader

Figure 2.27. Internet Explorer

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2.3.1. Tools and Documents

Task Manual (TML) The Task Manual is a project-specific documentation package, which contains all tasks needed to

operate the system with the corresponding parameters.

The TML consists of the following components, the reason for the different names are the different

kinds of viewers:

• Introduction section

This contains an explanation on how to the use of the CML. An essential component is the

description of the depiction form of the command syntax in the CMD section.

• TASK or CMD section

The most important section of this manual.

• Cross reference list (called TAB at Acrobat Reader)

The TAB or cross-reference section contains a correlation table of all output masks

belonging to the corresponding MML command. Using these mask numbers (each output

mask has an unique number), one can branch to the “output manual” (OML), where all

layouts of the masks are described in detail.



Figure 2.28. TML with Acrobat Reader

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The most frequently used part of the TML is the 'CMD' section with the project specific command

description. It contains all commands sorted alphabetically according to the Object. There one can

branch to all actions which are possible for this object. For every Command Code (Action +

Object), the following information is available (command description):

• general function description of the command

• the input format description of the command (maybe different input formats for one

command e.g. CR MSUB for GSM or GPRS Subscriber)

• description of the individual parameters and values. In case of multiple values the input

format is also described.

Basically there are two possibilities to find a command description:

1. The quicker variant is the FIND function. The search is done with the entered command

code (action + object). The action and object must be separated with a blank or underscore

(e.g. CONF LTG). Disadvantage: The complete command code must be known.

2. The easier possibility is to use the Navigation Pane (left column). When the desired Object

is found, one can click on the plus sign next to the object to open the branch with the

possible actions for this object. By clicking on one of this actions, the command description

is shown in the main window. Disadvantage: The Object in the Navigation Pane has to be

found manually as there is no search mechanism.



Figure 2.29. FIND Function

Figure 2.30. Navigation Plane

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Figure 2.31. Input Format Description

Figure 2.32. Example of an Input Format Box

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Output Manual (OML) The OML is a project-specific document describing all output layouts. It is available on CD-ROM.

For CP-printouts the mask number in the header of an output is used for entry into the OML.

SSNC (MP) printouts can not be found in the OML.

The OML consists of the following components:

• Contents section (only using Acrobat Reader)

The contents of the OML in the form of all output lists contained in it, including variants and

corrected versions.

• Introduction section

The introduction section corresponds to the one in the CML.

• Mask description section (MSK or Mask)

The OML describes every layout according to lines and columns. I.e. for every information

at a particular line/column position in the output mask, there is a corresponding description

in the OML.

• TAB section

In the TAB (tables) chapter of the OML, one can find the reference from the particular mask

number to the corresponding standard message group. The standard message group is

used if output messages are to be diverted to special output devices, files, etc.



Figure 2.33. OML with Acrobat Reader

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OML (mask description) using Acrobat Reader To find the desired mask description for a system output of a Network Element (NE), the Layout or

Message Number is needed.

With the Acrobat Reader, there are two possibilities to find this information:

• The already described ‘FIND’ function can be used to directly enter the number of the

system output.

• The navigation pane on the right. Open the section msk to open the branch with the mask

number ranges. Go through the tree to the matching output number. Use the '+' signs to

open branches.



Figure 2.34. Mask Number of the Output

Figure 2.35. Mask Description with Acrobat Reader

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Maintenance Manual (MMN) Standard HW maintenance is initiated on the basis of an alarm on the AMD / Alarm Surveillance or

other alarm displays in the OMC/NMC. The alarm displays branch to the maintenance manuals

which include procedures to control the fault clearance.

The guidelines for electrostatic sensitive devices have to be followed when executing HW

maintenance procedures. Furthermore the Exchange Configuration Documentation has to be used

to localize the faulty module in the exchange room.



Figure 2.36. Standard Hardware Maintenance

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The maintenance manuals are intended for use as guides to programmed standard HW

maintenance and for use as a reference. Maintenance manuals are available for all HW system

units for which the standard maintenance procedure applies. A maintenance manual on software

is also available but is not described in this section.

There are two different kinds of manuals used for maintenance applications:

1. Maintenance manuals for the different HW system units The maintenance manuals for the different hardware contains procedures for standard HW fault

clearance. It contains the following sections:

• Introduction

The introduction contains important general information such as how the manual fits into the

maintenance manual concept, how to interpret an alarm report, a description of the elements

which make up a fault clearance procedure and an explanation of symbols used.

• List of Procedures

This section lists the fault clearance procedures. The maintenance technician who branched to

the required maintenance manual on the basis of a system fault message starts the procedure

in the block designated as "1". The technician follows any further instructions in this procedure

which contain command inputs, queries from system responses, branches to other blocks and

module interchange.

• Tables

This section contains important reference information which is also used during a fault

clearance procedure. This section includes a list of suspect modules for fault clearance.

2. Construction manual The Construction Manual describes how the HW is embedded into the system. It contains the

following sections:

• Racks

This section contains information on how to combine frames to racks. Further it shows the

allocation of fuses to modules.



• Frames

This section contains all allowed modules for each frame including the mounting locations.

Additionally it shows the back plane and the cabling.

For LTG it comprises tables with LTU-types and LTU-numbers.

• Modules

For all modules which have maintenance relevant HW elements the front layout as

well as switches on the board itself (if any) are documented.



Figure 2.37. Open MMN with Acrobat Reader

Figure 2.38. Open MMN with IE

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MMN using Acrobat Reader Use the navigation pane on the left to find the right procedure for fault clearance. It can be

accessed directly in the tree by clicking through the branches, or by selecting the 'Procedures'

section, which opens the list of procedures in the main Window. Once the right procedure is found,

follow the instructions given.

Commands which have to be executed are linked to either the workbench of the Switch

Commander (command is loaded and has only to be filled with the right parameter values), or the

Task Manual to get the complete Command description (standard installation). This link

functionality can be changed manually if the right Acrobat Reader version is installed.



Figure 2.39. Using MMN with Acrobat Reader

Figure 2.40. Procedure Description

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Mechanical design The Exchange Configuration Documents in contrast to the Electronic Documentation describes the

site specific part of the documentation. Here, the complete hardware configuration, including

Racks, Frames and Modules is listed. Even the cabling and some database relevant information is

given.

Hardware definition The following terms are used for defining the hardware configuration:

• Rack row

It is possible to install one or more network elements of the same or different types in a single

installation room. The individual installation units are installed in rows. Such a row is referred to

as a rack row. Rack rows inside a room are assigned a rack row number to make it possible to

locate individual rows during maintenance.

• Rack

A rack is a single subunit inside a rack row. A rack has two doors on both the front and rear side

which provide access to HW modules or rack cabling. A rack is identified using the rack number.

To find the corresponding rack row and room (more than one room is possible, a special number

is used: The Rack Position Number (ROOM+ROW+RACK). • Frame

Frames are located inside a rack. A frame consists of a metal frame which serves as the

mechanical support, plastic shelves on the front side for holding the hardware modules, and a

multilayer backplane on the back side used for electric connections inside the frame and for

connecting cables to other frames or external equipment. Depending on the size of the

backplane, a frame can hold one or two horizontal rows of modules. A frame is identified by its

so-called "mounting unit" or MUT. The MUT numbers the individual horizontal sections inside a

rack from top to bottom consecutively.

• Module

HW modules are located inside a frame. Module rows inside an MUT are identified by the letter

A or C to facilitate the location of the modules even in frames containing multiple rows. Individual

modules inside a module row can be located using the "module location" or MOLOC number

stamped onto the metal frame supports.



To find the module in a rack and frame a special number is used: The Mounting position of Module Number (MUT+MODULE ROW+MOLOC).



Figure 2.41. Mechanical Design

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The different kinds of module frames As mentioned previously, module rows inside a frame are using letters. However the letter

designation used depends on whether the backplane structure is based on SIVAPAC or SIPAC

technology. Numbering of the module location (MOLOC) also depends on the structure of the

backplane.

SIVAPAC single row frame (e.g. LTG G) Module row is generally designated as A Module location is numbered from 1 to 126

SIVAPAC double row frame (e.g. DSU) The upper module row is designated as A and the lower module row as C Module location is

numbered from 1 to 126

SIPAC single row frames only (e.g. CP113C) Module row is always designated as C Module location is numbered from 101 to 349

This numbering makes more sense when looking at the plug positions on the backplane. The

SIVAPAC double row frame e.g. uses plug positions A and B for the upper row, C and D for the

lower row.



Figure 2.42. Types of Module Frames

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ECD/ESD for standard HW maintenance The Exchange Configuration Documentation (paper) or the Electronic Site Documentation (HTML)

includes information required for standard HW fault clearance. Always refer to this information

during fault clearance (e.g. to avoid plugging a HW module into the incorrect module slot which

could cause irreparable damage to the module or backplane)

Layout list rack, layout plan and equipment list rack are required for standard fault clearance. Laying List: Rack (LL:Rack)

The rack layout shows the application and numbering of individual racks inside one or more rack

rows of a network element. Refer to the REMARKS column for the system specific numbering of

HW units installed in individual racks. A six digit number has been entered in the RACK POS.NO

column which shows the position of a rack inside the system room and rack row. The RACK

POS.NO consists of the following:

digits 1 - 2 : room number

digits 3 - 4 : rack row number

digits 5 - 6 : rack number

Example: You receive an alarm message containing an error indication from DSU 10 / Module 0-1. You refer to the ECD for the corresponding network node and look for DSU 10 in the LL:Rack.

In the DESIGNATION column you find the designation R:DEVB/DSU/DLU. I.e. this is a combined

rack which contains special CP components (Magnetic Tape Device) and a unit DSU and DLU.

The RACK POS.NO column lists the location of the rack with the faulty DSU: 010101. You use this

location number to find the affected rack in the layout plan and to find the faulty module in the

equipment list rack (EL:R).

If the LL:Rack does not give enough information about e.g. the LTG numbering, the LL:Shelf can

be used additionally. There all the periphery units (LTG/DSU) are listed, sorted according to the

LTG/DSU numbers, with Rack Position Number and Mounting Unit.



Figure 2.43. LL: Rack

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Layout plan The layout plan shows the layout of a technical system room. It shows the building floor plan and

the location of the technical equipment installed in the system room. A layout plan is not true to

scale and shows only the approximate location of technical equipment. All technical devices can

be identified with the aid of a two dimensional number. This number consists of a two digit rack

row number and a two digit rack number.

Example: On the basis of the fault message, branch to the rack layout list (LL:Rack) for the

corresponding network node. The LL:Rack e.g. lists 010101 as the RACK POS.NO. I.e. the faulty

rack is clearly identifiable as room 01 in rack row 01 and rack number 01.

The double printed line in the Layout Plan shows the front of the racks, so the module side.



Figure 2.44. Layout Plan

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Equipment List Rack (EL:R)

The EL:R covers the contents of a single rack up to the module level. An exact location number

and a serial part number for HW and FW is listed for all rack units.

The rack itself, the fuse panel, the frames and frame modules. If modules have to be replaced,

note, that only modules with the same HW and FW version can be installed. Different numbers

should be used only after prior consultation of the responsible expert from the modification center.

The location number listed in the FIELD NO. column contains two to six characters. This number is

made up of the following components:

digits 1 - 2 : mounting unit

digit 3 : letter of mounting unit row

digits 4 - 6 : module location

Example: The six digit RACK POS.NO was determined by using LL:RACK. Each EL:R page lists

the EL:R Rack POS.NO with the corresponding number at lower right. In this example, the number

010101 was obtained from LL:RACK. With this number, the right page in the EL:R can be found.

They are sorted in the mounting unit sequence.

If a diagnostic was initiated or a status was interrogated during HW fault clearance and the DSU =10 / MODULE 0-1 was identified as faulty in accordance with the maintenance manual for this

DSU, it is possible to identify this module as M:IWE:HS (Interworking Equipment). In the same

line, in the FIELD NO. column, it is possible to obtain the exact location number for this module.

For the Module 0-1 in DSU 10 this is the number 03A021. This means that the module is in

mounting unit 03, mounting unit row A, mounting location 021.

Now we can continue the fault clearance with module replacement in accordance to the

corresponding maintenance procedure.



Figure 2.45. EL:R

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3. Switching Subsystem – Access Function Contents 3.1. Line Trunk Group....................................................................................................................... 2

3.1. 1. Function ............................................................................................................................. 3 3.1.2. Hardware and Location ....................................................................................................... 7

3.2. Data Service Unit..................................................................................................................... 28 3.2.1. Function ............................................................................................................................ 29 3.2.2. Hardware and Location ..................................................................................................... 31



3.1. Line Trunk Group



3.1. 1. Function

The line/trunk group (LTG) forms the interface between the digital environment of the node and the

digital switching network (SN).

The LTGs perform non-central control functions and thus relieve the coordination processor (CP)

of routine work. Several LTG types are available for optimal implementation of the various line

types and signaling methods. The LTG types essentially have the same basic structure and

operate according to the same principles. They differ only in a few hardware units and the specific

application programs in the group processor (GP).

The connection between the LTG and the duplicated switching network (SN) is made by a

secondary digital carrier (SDC). The transmission rate on the SDC from the LTG to the SN and

vice-versa is 8192kbps (abbreviated to 8Mbps). Each of these 8Mbps multiplex systems has 127

time slots, each with 64kbps for user and CCS7 information, and one 64kbps time slot (TS0) for

internal messages between LTGs, CP and CCNC..

The LTG always transmits and receives the speech information via both sides of the switching

network (SN0 and SN1). Both SN sides thus receive the same user information. The LTG only

assigns the speech information from the active switching network unit to the subscriber concerned.

The other SN side is designated as inactive and can transmit and receive the current user

information immediately if a fault occurs.



Figure 3.1. Functions of the LTG

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LTG types in D900 In the D900 switch all LTG applications belong to the functional type "B".

Depending on the application and age of the LTG the following hardware types may be used in the

D900 system:

• LTGM

• LTGN

• LTGP



Figure 3.2. LTG Types and Tasks

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3.1.2. Hardware and Location

The various LTG types basically have the same internal structure and consist of the following

physical or logical units. Depending on the LTG type, these units can be found on different

hardware modules:

Group Processor The group processor (GP) matches the incoming information from the surrounding network node

area to the internal message format of the system and controls all the parts within the LTG.

Link Interface Unit (LIU) The LIU connects the LTG to the duplicated SN (SN0 and SN1). The LIU converts the 8Mbps

multiplex highway arriving from the GS into two parallel 8Mbps SDCs to the SN. Conversely, it

receives the user information from the switching network-half designated as active via two parallel

SDCs and forwards it to the GS. The LIU synchronizes the information arriving over SDCs from

the SN with the LTG-internal clock system and feeds the node clock (8192kHz) to the group clock

generator of the LTG. It extracts the CP commands from the message channel (TS0) and forwards

them to the GP. In the opposite direction, the LIU transfers GP messages to the CP.

After each connection setup, the LIU verifies correct through-connection in the SN with the aid of

the cross-office check (COC). For this purpose, the calling LIU sends a test bit sequence that is

reflected by the LIU of the called side. If the transmitted and reflected bit patterns are identical, the

established connection is switched through to the subscriber.

Group Clock Generator (GCG) The GCG supplies the LTG with the required control clocks. The crystal oscillator in the GCG is

synchronized with a signal derived from the system clock in the LIU via a phase-locked loop.

Signaling Link Control (SILC) part The Signaling Link Control (SILC) part functions as an input/output processor. The SILC is used to

connect a number of signaling channels via which either the protocol for DLU access (DLU

protocol) or the ISDN D-channel protocol for the primary access (PA protocol) can be handled.

The transmission protocols are based on the HDLC procedure.

On the LTG side, the SILC completes the layer-2 functions of signaling protocols (synchronization,

error detection, error handling) and thereby guarantees securemessage exchange between

peripheral units and the GP.



Figure 3.3. Internal Structure of LTG

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Signaling Unit (SU) The SU is a logical unit of the LTG. Physically, the following subunits are possible:

• Code Receiver (CR)

The CR receives and detects multifrequency signals (DTMF, MFC-R2, MFC-R1,).

• Tone Generator (TOG)

The TOG generates the audible tones required for all line/trunk units (LTU) and the frequencies

needed for multifrequency dialing (MFC).

• Receiver Module for Continuity Check (RM:CTC)

The RM:CTC is necessary for testing CCS7 trunks.

Line/Trunk Unit (LTU) The LTU is a logical unit of the LTG. It contains different modules for special tasks.

Possible module types are:

• Digital Interface Unit (DIU)

The DIU is used to connect PDC systems like PCM30 or PCM24.

• Local DLU/DSU Interface (LDI) (1)

The LDI is used to connect a local DLU/DSU by a 4 Mbps carrier

• Conference Unit (COUC for LTGM/N)

Multiparty conferences require the conference unit. The COUB module can handle four

conferences with up to eight subscribers each, the new COUC module has 32 ports, which can

be used in any combination (e.g. one conference with 14 subscribers and two with 9 subscribers.

Additionally, the COUC has on board echo compensation.

• Digital Echo Compensator in D900 (DEC)

A DEC is necessary for connections between mobile and fixed networks to compensate the

reflection and delay occurring with these connections.

• Operationally Controlled Announcement Equipment (OCANEQ)



The OCANEQ is used for standard and individual announcements. It can be controlled by the

switch or by subscriber inputs (OCANEQ and Code Receivers as part of an User Interactive

Dialog UI LTG).

• Code Receiver

Additionally to the Signal Unit SU the LTU may also contain CR: Different CR types are possible,

e.g. for MFC:R2 or push-button dialing.

• MDTOG

This module is used to deliver the A-party number to analog wired subscribers of the exchange.

The used method is called Frequency Shift Key FSK. A MDTOG can be connected via SN to any

analog DLU port of the EWSD exchange (pool solution).

Group Switch The GS is a non-blocking space-time stage for 512 channels. The GS interconnects the LTU, SU,

LIU and optional the SILC. The speech data can be attenuated for each channel in eight stages.

Up to 64 conferences (three subscribers and audible tones) are possible.

• GS for LTG with functional type B:

Beside the connection to LIU (8 Mbps), to the SU (2x2Mbps to TOG and 2Mbps to CR) and to

the SILC the GS offers 8x32 ports for 8 LTU. How many of the LTU0-7 can be equipped with HW

modules depends on the LTG HW type. The remaining LTUs can be used for specific

applications, which do not require HW.

• GS for LTG with functional type C:

Beside the connection to LIU (8 Mbps) and to the SU (2x2Mbps to TOG and 2Mbps to CR) the

GS offers 4x32 ports for 4 LTU. These LTU0-3 are normally used as DIU.



Figure 3.4. Internal Structure of LTG

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The LTGM The LTGM is one of old standard type for EWSD and D900 systems. It is used for all tasks except

OCANEQ. Only three modules are necessary for a complete LTGM with four PCM systems

connected.

• The 4 PCM are combined together with the current converter on the module DIU120A. Logically,

this module is treated as LTU0 to LTU3 with ordinary DIU30 modules. Optionally, this module

can be replaced by a DIU:LDIM module to connect to a DLU or DSU via a 4Mbps local DLU

interface.

• The GPL module (group processor for LTGM) holds the PMU and, if required, the SILC

functionality. Two different GP modules are used:

GPL, Group processor for LTGM without SILC function

GPLS, Group processor for LTGM with SILC function

• The GSM (group switch for LTGM) is a combination of GSL, TOG, RM:CTC, CR and GCG.

Depending on the available on board components, different GSM modules are used. The last

three digits of the GSMabc modules define the module type:

Additional fourth module in LTGM: the LTU:S of LTGM in B function D900: Additionally, a digital echo compensator (DEC120) or a large conference unit (COUC) can

be installed as LTU:S if the LTG is used for connecting the PSTN.



Figure 3.5. Example of LTGM Configuration

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Figure 3.6. Structure of LTGM

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The LTGN The LTGN is the a current standard type of the LTG.

Only one module makes up a complete LTGN for the basic tasks. The LTGN hardware combines

almost every possible functional unit and this single module, e.g. different code receivers in logical

LTU and SU positions.

Additional second module in LTGM: the LTU:S of LTGN in B function • D900: Additionally, a digital echo compensator (DEC120) or a COUC (Conference Unit C) can be

installed.

• EWSD:

Additionally, a PHMA can be installed as LTU5 if the LTG is used for connecting an Access

Network AN via V5.2 interface. Additionally, a MDTOG can be installed as LTU5 if the LTG is

used for supporting the feature CLIP for analog subscribers.

Additionally, a COUC can be installed as LTU3 to support large conferences Additional LTU:S

modules, like OCANEQ is available.



Figure 3.7. Different Types of LTGN

Figure 3.8. Structure of LTGN

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The LTGP The successor of the LTGN is the LTGP, which replaces the LTGN for the existing mobile core

applications and supports the same functionality as the LTGN. In the LTGN it was possible to

integrate one LTG functionality on one board. Now, with the LTGP technology, four LTG functions

are concentrated on one board, but nevertheless, they continue to perform like 4 separate LTG's.

It is downwards compatible to older software releases up to and including SR8.

General benefits of LTGP are: • Cost reduction due to high density packaging by use of most modern technology

• Footprint reduction to one quarter by increasing the channel capacity of 1 LTG module by a

factor of 4 (4LTGs on one board)

• Assurance of further deliverability by replacement of older component types.

As default, each LTG operates with its own GP software and handles its own dedicated message

channel via its own SDC connection to the SN. Each LTG has its own set of PCM periphery. This

concept is also implemented in the LTGP, but the hardware realization of the LTGP internal

functions is different. The low access and high process time of the new technology allows firmware

resources to be shared between the four LTGP functions.

The other LTG functions (e.g. GS, DIU, CR, TOG, and SILC) are on the same board and are

controlled by a single IOP processor doing the job for all four LTGP functions.

In some applications, the basic LTG functionality has to be extended with special features, such as

conference unit, echo cancellation, etc. These extra functions for the LTGP are implemented on

the functional unit LTU:S. Since DEC120 and COUC are not released for LTGP, the new DEC480

and the ATCO must be used.

Each LTGP board is provided with only one supplementary board LTU:S. By using the special

feature boards from the LTGN, only one of the four LTGP functions on one board (i.e. LTGP#1)

has access to the feature board that offers the extended functionality. In the other three LTGP

functions only the basic LTG functions can be used. An exception to this rule is the DEC480,

providing echo cancellation for all four LTG functions (480 channels).

It is possible to load different load types in the LTGP functions of one GPP board.

If an LTGN module has a failure, 120 ports are lost. With LTGP, 480 ports are lost.



This quantity is still acceptable because with the new technology the MTBF was increased.

The LTGP is prepared to be connected

• electrically via copper lines to the TSG of SN B

• electrically via copper lines to SNMUX A of SN D

• via fiber optics to SNMUX B of SN D (additional backplane-module SNOPT required)



Figure 3.9. Connection LTGP to SN

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LTGP hardware - M:GPP The basic LTG functionality of such 4 LTGP functions is implemented on one baseboard named

Group Processor, type P (GPP). There is big impact to the GP-unit, because only one GP-processor is used, which executes the

GP-SW of the four LTG-units during individually assigned time slots.

The realization of this concept is covered by a new ASIC A:GPCP and a modification in special

parts of the GP-FW.

HW architecture: • Concentration of 4 "classic" LTG-function-units (LTGN) into one module GPP (2 new ASIC's )

• LTGP with GPP module covers PCM30- applications (LTGS with GPS module is planned to

cover SDH-applications, STM1 interface)

• Support of electrical (SN B) and optical (SN D) interface to SN

• All basic peripheral functions are controlled by one single microprocessor

• All CR + MDTOG functions are concentrated in two DSPs on board

• All optional functions are implemented on separate modules (i.e. LTU:S)

• The base module and only one optional module form the base LTGP core (LTGP unit)

The following module types are possible, but only M:GPPYG is released for mobile applications:



Figure 3.10. LTGP

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DEC 480 In SR 10 the LTGN may be replaced by the new LTGP. The GPP-board has four times the number

of traffic channels than the formerly used GPN-board: 480 channels instead of 120.

Since echo compensation is a must in many applications in mobile networks, it is necessary to

have a new DEC module that can serve all 480 channel of one GPP board.

The existing module DEC120 can NOT be plugged into the LTU:S position and work together with

LTGP.

In order to supply all 480 channels of the LTGP with echo cancellers, a new board DEC480 was

developed.

DEC480 may be used in LTGP as echo canceller for 480 channels with a maximum echo delay of

about 63 msec. It may also be used for 120 channels in LTGN or even LTGM.

The DEC480 hard- and firmware is basically the same as for DEC120, implemented four times on

one board. Thus, it behaves exactly as the old DEC120.

No new MML commands were introduced for DEC480.



Figure 3.11. Interface Between M:GPP and M:DEC480

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Frame layouts There are a lot of possible rack types for combining different LTGs with other equipment like the

switching network. Please refer to the maintenance manuals and site-specific documentation for

details.

Frame for LTGM As the LTGM has only three modules (four with the optional LTU:S), five LTGs use one frame

(F:LTGM(A)). Up to 30 LTGM can be installed in one rack. Each LTG has its own current

converter, located on the DIU120A or DIU:LDIM module.

Frame for LTGN There are two different frame types for the LTGN. If the LTU:S function is not needed (ordinary

PCM systems to other network nodes), 16 LTGN can be installed in one frame (F:LTGN(A)). Up to

64 LTGs can be installed in a rack. When the LTU:S is necessary (e.g. DEC or COUC), only eight

LTGs are possible (F:LTGN(B)). Each LTGN has its own on-board current converter.



Figure 3.12. Frame for LTGM and LTGN

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Frame F:LTGP There are two types of frames for the LTGP namely F:LTGP(A) and F:LTGP(B).

F:LTGP(A) will be used for an 'ordinary' LTG while F:LTGP(B) has the UI-LTG functionality.

The frame F:LTGP(A) houses the modules for 2x 16 LTG functionalities (on 2x 4x M:GPP and

LTU:S). It also provides adaptation systems for external interfaces (power supply, SDC interface,

M:SNOPT).

The backplane of the new F:LTGP(A) is split into 2 separated parts. Each of the two parts takes 4

LTGP units (GPP + LTU:S) and the redundant interface module SNOPT. The modules M:SNOPT

are plugged into SIPAC-HS adaptation systems on the cable side. The advantage is a better

reliability and handling (service, maintenance) in case of a failure in one backplane half.

In this way, the entire frame provides a total of 32 LTG functions. Eight of them provide the

complete functionality range while the remaining 24 are restricted to the basic LTG functions with

exception to the DEC480 that serves for all LTGs on one board.

Due to the high number of cables in a rack only 8-fold PCM cables will be used to the MDF at a

full rack with up to 6x F:LTGP(A). For enlargement of an existing exchange with only a few

F:LTGP a single or double PCM cable may be used too.

Due to the estimated power consumption of the frames a forced cooling is necessary.



Figure 3.13. Frame for LTGP

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3.2. Data Service Unit



3.2.1. Function

The Data Service Unit is needed for data and fax calls to and from mobile subscribers. The DSU

converts the different protocols used to transfer data between personal computers (V.32, V.42,

FAX G3 etc.) to the GSM specific transmission method. The maximum bit rate is 9600bps.

When performing any kind of data call, it is first routed through the DSU and then to the called

subscriber.

For the MSC, the DSU is an external equipment connected to LTGs. For redundancy reasons, a

DSU is usually connected to two LTGs via two PCM cables to each LTG.



Figure 3.14. Path Through MSC for Data Call

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The DSU is divided into the following functional units:

The central functional units are duplicated for redundancy reasons and form the DLU

systems 0 and 1. They consist of:

• Digital Line Unit Controller (DLUC)

The DLUC controls all internal functions of the DSU. A DLUC controls 60 channels on two

PDCs.

• Digital Interface Unit for DLU (DIUD)

The interface between DSU and LTG is the DIUD. Two PDCs can be connected. Instead of the

DIUD, a Digital Interface Unit for local DLU interface, module D (DIU:LDID) can be used. This is

a interface for only one cable using a special 4Mbit/s transmission method, but can only be used

with cables shorter than 120 meters.

• Central Clock Generator

Provides the system clock for the DSU. It is located on the module BDCG.

Signal Distribution Communication between the central and peripheral units takes place with the bus distributors via

the duplicated internal bus systems 0 and 1. The bus distributors include:

• Bus Distributor and Clock Generator (BDCG, only for basic frames)

• Bus Distributor Basic Module (BDB, only for basic frames)

• Bus Distributor Extension Module (BDE, only for extension frames).

Peripheral units The peripheral units comprise:

• Interworking Equipment (IWE)

The IWE consists of a Main module, IWEx, and a Submodule, IWESx, where the "x" is the

module variant (currently A,B,C...F). For each simultaneous call, one pair of these modules is

necessary. FAXG3 calls can be handled without additional equipment (external data modems).

• External Modems for data calls with different protocols.



Figure 3.15. Structure of DSU

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Frames, shelves and racks Frames The DSU consists of three different frame types:

Module Frame A for DSU, F:DLU(A) (Basic Frame) Contains the two DLU systems, the bus distributor modules BDB and BDCG and up to

11 IWEs.

Module Frame B for DSU, F:DLU(B) (Extension Frame) Contains the bus distributor modules BDE and a maximum of 16 IWEs

Module Frame for Modems, F:Modem Holds in-rack modems for data calls. 12 from Dr. Neuhaus or 14 from GPT Frame type

A is mandatory and only installed once for each DSU. Depending on the necessary call

capacity, frame type B can be installed once, twice or not at all. The maximum number

of IWEs per DSU is 43 (11+16+16). Each IWE can handle one FAXG3 call without an

external modem or one data/fax call with an external modem.

Shelves Each frame has two module rows called shelves. Each module of a DSU can be

identified by its shelf position, the mounting location (MOLOC). In a DSU frame, the

upper shelf has mounting locations starting with an "A", the lower shelf modules start

with "C". Many of the MML commands for the DSU need module numbers, but these

numbers are not the mounting locations, they are referenced with the DLUMOD

number, e.g.

Another special term for DSU modules is the DLUEQ (DLU equipment). These

modules are the current converters, which have to be configured by MML commands.



Figure 3.16. DSU Frame

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Racks The rack for the DSU (R:DSU) holds one DLU(A) frame and up to two DLU(B) frames.

Additionally, two modem frames can be installed. If necessary, additional modems can be installed

in another rack (R:Modem).

Every frame has a number, the mounting unit (MUT). Located on the top of each rack is the fuse

panel, which has a MUT number, too. The numbers start with 1 for the fuse panel, 2 for the

DLU(A) frame and so on.

There is a gap after the frame in mounting unit 3, the next frame counts as MUT 5! The MUT

numbers are printed on a label on the frame.



Figure 3.17. R:DSU and R:Modem

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4. Switching Subsystem – Switching Function

Contents 4.1. Switching Network ..................................................................................................................... 2




4.1. Switching Network



4.1. 1. Function

The switching network SN is the link inside a node for:

• traffic connections between LTGs (temporary through connections)

• the D900 internal message exchange between LTG, SSNC and CP control units via fixed

message channels MCH

• CCS7 signaling messages between CCS7 signaling channels in PCM links connected to

the LTG and the SSNC (fixed connections set by command).

The switching network is fully duplicated (SN0 and SN1). For traffic connections, one is the active,

the other one the standby side. All calls are always simultaneously through connected via both SN

sides while the LTG only through connects user channel information received from the active SN

to the PCM links. If the active SN fails the system switches to the standby SN without any loss.

Through connection in the SN occurs in accordance with the "time – space – time" principle

(change of time slot – change of space slot – change of time slot). Each through connection

ensures a transparent bi-directional 64kbit/s path through the SN.

In addition to temporary through connections (transient calls), the following nonswitched

connections also apply:

• nailed-up connections (NUC) set by MML command

• through connection of message channels between LTG control units and the message buffer

(permanently specified by CP software).

Most connections between the SN and other functional units use secondary digital carrier lines

(SDC) with a bit rate of 8192kbps (mostly called 8Mbit system or highways), carrying 128 standard

64kbps time slots (numbers 0-127).

When using the LTG-P, the SDC:LTG of 16 LTGPs each may be realized as fiber optics with a

transmission rate of 184 Mb/s using one module SNOPT to connect the F:LTGP to SNMUXB.



Figure 4.1. Switching Network in D900

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SN(B) The SN(B) for D900 systems is available in different capacity stages. With the exception of the

small switching network for a maximum of 63 LTGs (combined space-time stages), each SN

consists of the subunits time stage group (TSG) and space stage group (SSG).

Time Stage Group (TSG): Each TSG connects the SDC to/from the LTG and MB. 64 of this SDCs can be connected to each

TSG. An SN is made of a maximum of 8 duplicated TSG. Each TSG contains a switch group

control (SGC) which is connected to the CP via the message buffer (MB) with an own SDC line.

The SGC receives setting instructions for temporary or fixed bi-directional 64kbps through

connections from the CP. The SGC implements through connections by setting the individual time

stage modules (TSM) in a TSG. Inside a TSG each TSM can change the position in time and

space of any time slot arbitrarily for a group of 8 connected SDC.

Space Stage Group (SSG): The SSG through connects a call between TSM inside the same or different TSG. An SN consists

of a maximum of 4 duplicated SSG. Inside the SSG is a switch group control (SGC) connected to

the CP via the message buffer (MB). The SGC receives setting instructions for temporary or fixed

bi-directional 64kbps through connections from the CP. The SGC implements through connections

by setting the individual space stage modules (SSM) in an SSG. Each SSM can change the space

slot of the time slot for connected SDC arbitrarily.

External and internal connections The following types of secondary digital carriers (SDC) with 8Mbps form the internal and external

interfaces of the SN:

• SDC:LTG between TSG and maximum 63 LTG for circuit connections (time slots 1-127)

and for message exchange between the LTG GP control unit and the CP (message

channel to time slot 0). Any TSG port can be used except 0, which is reserved for the

SDC:TSG to the message buffer.

• one SDC:TSG between TSG and MB to transfer the message channel for all LTG in this

TSG to the CP. Always connected to port 0 of every TSG.



• one SDC:SGC between the SGC control unit in a TSG/SSG and the MB to transfer the

CP setting instructions to TSG/SSG

• The individual TSG and SSG are connected to each other via SDC:SSG



Figure 4.2. Interfaces and Internal Structure of SN

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Capacity stages As the SN is available in different increments the actual size of the switching network can be

matched to the expected traffic volume in an exchange. The volume of traffic to be through

connected measured in Erlangs is used as the dimensional size.

In addition to the increments listed the special implementation of SN for 31 LTG and for 63 LTG is

also available for small D900.

Capacity / space requirements for SN increments: • If a CCNC is connected, 1 or 2 SDC:CCNC are added depending on the number of CCS7

signaling channels; the number of SDC:LTG is reduced accordingly.

• Space requirements inside a rack:

Each TSG requires only one frame inside a rack. Each SSG requires only a half of a frame

inside a rack. The remaining space inside the rack can be used for LTG.

In a TSG rack it is possible to install a maximum of 4 LTG module frames.

In an SSG rack it is possible to install a maximum of 4 LTG module frames.

In the SN:63LTG rack it is possible to install a maximum of 4 LTG module frames.

The SN:31LTG is stored inside the CP rack.

Mobile systems are not fully equipped with all possible LTGs. Because of the much higher

signaling load in a PLMN, the amount of internal messages would be too high for the message

buffer. Figure below shows the capacity stages of D900 and D900 systems.



Figure 4.3. Capacity Stages of the SN

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SN(B) functional units and modules The SN(B) is divided into the following functional units:

• Time switch circuit (TSC)

A TSC can connect each incoming time slot belonging to one of the 4 connected SDC:LTG to a

random outgoing time slot on any of the 4 connected SN internal SDCs. As each of the SDCs is

always bi-directional a TSC is divided into TSC incoming and TSC outgoing.

• Link interface to LTG (LIL)

The LIL is the interface to the LTG. It is responsible for propagation time equalization of the

SDC:LTG.

• Space switch SS16|16

An SS16|16 can connect any incoming time slot belonging to one of the 16 connected SDC to

the outgoing time slot with the same number belonging to any of these 16 SDC.

• Space Switch SS8|15

An SS8|15 is connected to 8 SDC on one side and 15 SDC on the other side.

Each SS8|15 is divided into two subunits. One unit can connect any incoming time slot belonging

to one of the 8 SDC on one side to the outgoing time slot with the same number belonging to

one of the 15 SDC on the other side. The other subunit can connect any incoming time slot

belonging to one of the 15 SDC on one side to the outgoing time slot with the same number

belonging to one of the 8 SDC on the other side.

• Link interface between TSG and SSG (LIS)

The SDC:SSG (TSG – SSG) are connected to SSG and TSG via the LIS. These act as

interfaces for propagation time equalization of the individual SDC. In addition the LIS specifies

which TSG (SN0 or 1) will interoperate with which SSG (SN0 or 1). In this sense it can be

compared to the LIU function inside the LTG.

• Switch group control (SGC)

Each SGC controls the functional units in its TSG/SSG. To do this it interacts with the CP via its

SDC:SGC.



• Link Interface to message buffer (LIM)

The interface function for the SDC:SGC to the message buffer is implemented by means of the

LIM component.

In the SN(B) the individual functional units are assigned to modules as follows:

• 2 TSC including LIL function are implemented in one TSMB module

• in the TSG the LIS function for 16 SDC is implemented in one LISB module

• the LIS function of the SSG is implemented with 2 SS8|15 in one SSM8B module

• 8 SS16|16 are implemented in one SSM16B module

• LIM and SGC functions are implemented in one SGCB



Figure 4.4. Internal Structure of TSG and SSG

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SN(B) rack and module frames

Each SN rack always contains 2 SN module frames. These can be installed inside

the rack at the top or bottom. The remaining space inside the rack can be used for

LTG and/or MB.

A rack always contains one of the following module frame types for redundant units

from SN0 and SN1:

• TSG(B) frame with one TSG

• SSG(B) frame with one or two SSG belonging to the same SN plane

• TSG(B) frame with one SN:63LTG plane



Figure 4.5. Frame for SN(B)

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Figure 4.6. Example of Rack for SN

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SND With SND, a new type of switching network is offered for D900/1800/1900. It adopts and expands

upon the functions of the SN B:

• Connection of up to 1008 LTGs (planned for 2016 LTGs, but only 1008 realized in

SR10)

• Non-blocking design (every path can be used at any time independently of the other

paths)

• Compatible to all LTG types

• Permanent supervision of the traffic channel paths via parity bits

• Suitable for use in both small as well as large exchanges with small growth gradation

(16 LTG)

The SND is designed redundantly for security reasons (SND0 and SND1). Each connection is

always switched over both SND sides at the same time. If one SND side fails, the redundant

switching of connections through the two SND sides ensures that no call data are lost and that the

SND retains all of its functionality. The LTGs send to both SN sides but when receiving from the

SN, only the channels arriving from the active SN side are forwarded.

In addition to the transient user channel connections, the following fixed connections can be

switched:

• Long-term connections ("nailed-up connections", NUC) are activated by means of

an MML command,

• Message channels between LTG control units and the message buffer (specified by

the CP software as long-term connections).

All connections between the SN and the directly connected functional units MBD and LTG are

made via secondary digital carriers SDC at a bit rate of 8192 kbps, each with 128 standard time

slots at 64 kbps (numbers 1-127). (The SDC are generally referred to as 8Mbit systems or

"highways")

• The SDC:LTG between the SN D and the LTGs includes user channel connections

/ permanently connected SS7 links (time slots 0-127) as well as the LTG message

channel (MCH in time slot 0)

• An SDC between SN D and MB D is used to forward the communication paths of

65 LTGs each to the MBD.



• SDCs of the type MBD-S1 and MBD-S3 are used to transmit the CP setting

commands (via MB D) to the SND.

When using the LTG-P, the SDC:LTG of 16 LTGPs each may be realized as fiber optics with a

transmission rate of 184 Mb/s using one module SNOPT to connect the F:LTGP to SNMUXB.



Figure 4.7. SND Connection

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Capacity stages Thanks to its modular design, an operational SND can be extended on site beyond the limits of the

originally configured capacity stage if it has to be expanded to accommodate planning changes.

The different capacity stages of the SND are realized by the number of switching network

multiplexers (SNMUX) used.

SND for up to 126 LTG Only one switching network multiplexer is needed for an SND for up to 126 LTGs. In this

configuration, the SNMUX has a switching function.

SND for up to 252 LTG Two switching network multiplexers (SNMUX1 and SNMUX2) are used in the case of an SND for

up to a maximum of 252 LTGs. In this constellation, the SNMUX1 implements the switching

function and the SNMUX2 the multiplexer/demultiplexer function. Both SNMUX are directly

connected with each other by optical waveguides at 920 Mbit/s in this capacity stage.

SND for up to 1008 LTG Additional switching network multiplexers (up to a maximum of 8 SNMUX) and a switching network

matrix (SNMAT) are used in capacity stages for more than 252 LTGs (up to maximum 1008

LTGs). All SNMUX are connected directly with the SNMAT using 920-Mbit/s optical waveguides. In

this case the SNMUX implements the multiplexer function and the SNMAT the switching function.



Figure 4.8. SND for Up to 126 LTG


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SND hardware layout The following diagrams illustrate only the major functional units of the SND modules.

The interfaces are greatly simplified and the redundancy of the SND is not shown.

Switching Network Multiplexer (SNMUXA) The switching network multiplexer (SNMUXA) comprises the following:

• interface module type D for LTG, (LILD)

• multiplexer controller module (MUXC)

• transceiver module for optical connections (OML920).

The LILD and MUXC together comprise the multiplexer/demultiplexer for the connection to the

LTGs. Depending on the capacity stage of the SND, the MUXC can also perform switching

functions.

The interfaces to the SNMAT are implemented using OML920 as optical links. Up to 2 OML920s

can be plugged into the rear of the module frame for each SNMUXA. A maximum of 16 OML920s

are possible for a maximum configuration of 8 SNMUXAs. The optical connections are bi-

directional lines. Data are transmitted at 920 Mbit/s in each direction.

Switching Network Multiplexer (SNMUXB) The switching network multiplexer (SNMUXB) comprises the following:

• optical fiber connectors (M:OFC)

• interface module type E for LTG, (LILE)

• multiplexer controller module (MUXC)


The OFC form the optical interface to the F:LTGP at 184 Mbit/s. The LILD and MUXC together

comprise the multiplexer/demultiplexer for the connection to the LTGs.

MUXC and OML920 have the same function as in SNMUXA.

Switching Network Matrix (SNMAT) The switching network matrix (SNMAT, Fig. 3.6) comprises the following:

• matrix modules (MATM)

• matrix controller module (MATC)




Each matrix module (MATM) is assigned four transmit and receive modules (OML920). These

each convert the serial optical data streams fed from the switching network multiplexer (SNMUXA)

into four 184 Mbit/s data signals. Each of these four signals is then split into eight output signals

and routed to each of the eight MATMs.

The blocking-free switching network matrix structure obtained in this way is controlled, supervised

and clocked in the SNMAT by the MATC and MATM.

The SNMAT is connected with the MBD (MBDH) via an 8-Mbit/s HDLC interface (to the MATC

module).



Figure 4.11. SND Functional Units

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Frames of SND F:SNMUXA comprises the following modules:

• M:LILD: LTG Switching Interface Module Type D

M:LILD forms the interface to LTG and MBDH (LTG - MCH interface). To do so, 16 8-

Mbit/s SDC inputs from the LTGs are combined into one high-speed ATM connection at

184.32 Mbit/s. To these 16 * 128 user channels (payload) another 256 test and

synchronization channels are added. Within the SND, all 8-bit time slots are monitored by

means of 2 parity bits.

• M:MUXC: Multiplex Control Module

M:MUXC controls the eight M:LILD and the two M:OML920 via 2 Mbit/s HDLC connections.

Depending on the configuration of the SND, the MUXC can be used as a "switch" (SND for

up to 252 LTG) or as a pure "multiplexer" (SND for more than 252 LTGs and thus with

SNMAT).

The M:MUXC receives/sends the 184.32 Mbit/s highway data from/to the M:LILD modules.

In an SND for up to 252 LTG, the MUXC module is additionally connected via M:OML920

to the MUXC of the other SNMUX.

In an SND for more than 252 LTG, each MUXC module is connected via two M:OML920 to

the SNMAT.

• M:OML920: Optical Multiplexer Switching Module for Serial Data Rates of 920 Mbit/s

In SND with more than 126 LTG, the OML920 enables data transmission via fiber optic

cables between the frames. The OML920 is a transceiver module on the rear panel of the

module frame, transparent to the transmitted data.

Four electrical data streams, each at 184.32 Mbit/s are united and sent from one OML920

module to other OML920 modules via fiber optic cables. This bidirectional data connection

can be used over a distance of up to 200 m.

For technical reasons, the bit rate increases by a ratio of 5/4 compared with 4*184Mbps.



Figure 4.12. F:SNMUXA

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F:SNMUXB comprises the following modules:

• M:OFC: Optical Fiber Connector

M:OFC is the counterpart of M:SNOPT and transforms the optical 184 Mbit/s signals from

F:LTGP into electrical 184Mbit/s signals for the M:LILE.

• M:LILE: LTG Switching Interface Module Type E

The M:LILE forms the interface to the new environment LTGP. It receives the data from/to

MBUL0-0, MBUL 0-1, and up to 15 LTGs as electrical 8,192 Mbit/s interfaces. For LTG 1-

15 an optical interface is provided as well but if the electrical interfaces are plugged they

overwrite the optical interfaces. Additionally 8 bidirectional optical interfaces (184.32

Mbit/s), each holding 16x 8,192 Mbit/s SDCs links are provided. It performs an alignment

by equalizing clock and cable length

differences and multiplexes them to the internal 184.32 Mbit/s links. Furthermore 2 parity

bits for each time slot and an additional maintenance overhead is inserted and evaluated.

• M:MUXC: Multiplex Control Module

Depending on the configuration of the SND, the MUXC can be used as a "switch" (SND for

up to 252 LTG) or as a pure "multiplexer" (SND for more than 252 LTGs and thus with

SNMAT). The M:MUXC receives/sends the 184.32 Mbit/s highway data from/to the M:LILD

modules. In an SND for up to 252 LTG, the MUXC module is additionally connected via

M:OML920 to the MUXC of the other SNMUX. In an SND for more than 252 LTG, each

MUXC module is connected via two M:OML920 to the SNMAT.

• M:OML920: Optical Multiplexer Switching Module for Serial Data Rates of 920 Mbit/s

In SND with more than 126 LTG, the OML920 enables data transmission via fiber optic

cables between the frames. The OML920 is a transceiver module on the rear panel of the

module frame, transparent to the transmitted data. Four electrical data streams, each at

184.32 Mbit/s are united and sent from one OML920 module to other OML920 modules

via fiber optic cables. This bi-directional data connection can be used over a distance of up

to 200 m. For technical reasons, the bit rate increases by a ratio of 5/4 compared with

4*184Mbps.

• M:SNOPT: Optical Interface to SN

The module M:SNOPT provides optoelectrical signal conversion and a MUX/DEMUX

to/from the SDC signals to the different M:GGPPs. Although it is located at the backplane

of F:LTGP, it belongs to the SND and is controlled via M:LILE.



Figure 4.13. F:SNMUXB

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Frame F:SNMAT The switching network matrix SNMAT is required only if more than 252 LTG are connected.

F:SNMAT comprises the following modules:

• M:MATM Switching Matrix Module In F:SNMAT, the switching matrix is made up from a maximum of eight modules M:MATM

(only four M:MATM for up to 1008 LTG). Each M:MATM has 128 inputs and 16 outputs,

each at 184.32 Mb/s. Thus the full configuration of an SNMAT with eight M:MATM provides

a 128/128 matrix allowing connection of up to 2016 LTGs (in SR 10 just 1008 realized).

Four OML920 modules are permanently assigned to one MATM module. In the direction

from the SNMUXA to SNMAT, the four OML920 modules of one MATM convert the serial

920-Mbit/s optical data streams received into four 184 Mb/s data signals. Each of the four

signals is then split and fed to each of the MATM modules.

In the opposite direction, the OML920 modules combine the 4 electrical 184-Mbit/s data

streams into one 920-Mbit/s data stream that is routed to the OML920 modules of the

SNMUXA, which may be situated up to about 200 m away.

In smaller SND not all MATM are required (e.g. 4 SNMUX for 504 LTGs means 8 OML920

and only 2 MATM).

• M:MATC Switching Matrix Control Module The M:MATC controller implements the preprocessing of the commands for path setup,

which are received from the CP via the MBD interface (MBD-S3 interface) and distributes

this information to the M:MATM modules via a 2-Mbit HDLC connection.

In addition, the pulse generator and the 5V-power supply for the whole module frame are

located on the M:MATC.



Figure 4.14. F:SNMAT

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5. Switching Subsystem – Coordination Function

Contents 5.1. Coordination Processor ............................................................................................................. 2


5.2. Message Buffer........................................................................................................................ 33 5.2.1. Function ............................................................................................................................ 34 5.2.2. Hardware and Location ..................................................................................................... 36

5.3. Clock........................................................................................................................................ 45 5.3.1. Function ............................................................................................................................ 46 5.3.2. Hardware and Location ..................................................................................................... 48

5.4. Operation and Maintenance Console ...................................................................................... 54 5.4.1. Configuration and Interfaces ............................................................................................. 55 5.4.2. Function ............................................................................................................................ 58

5.5. Storages .................................................................................................................................. 60 5.5.1. Function ............................................................................................................................ 61 5.5.2. Hardware and Location ..................................................................................................... 62 5.5.3. Procedures........................................................................................................................ 67



5.1. Coordination Processor



5.1. 1. Function

The Coordination Processor is the heart of a the exchange. It controls all other functional units, does the main call processing tasks and processes MML inputs. The CP is divided into several subunits:

• two base processors (BAP) for maintenance and call processing tasks • two ATM Bridge Processors (AMP) as interface to the SSNC • up to 6 call processors (CAP) for call processing only • up to 4 input/output controllers as interfaces to input/output processors • a duplicated common memory (CMY) • a duplicated bus system (BCMY) between the BAPs, CAPs, IOCs and CMY • several input/output processors for connecting external equipment

The CP performs the following functions in a network node: Call processing

• digit translation • routing • zoning • path selection through the switching network • call charge registration • traffic data administration • network administration

Operation and maintenance

• input and output from/to external memories (EM) • communication with the operation and maintenance terminals (OMT /BCT) • communication with the operation and maintenance center (OMC)

Safeguarding • self-supervision • error detection • error handling




CP113C/CR The CP113C/CR comprises the following hardware functional units:

• base processors (BAP)

• ATM bridge processors (AMP)

• call processors (CAP)

• input/output controls (IOC)

• bus for common memory (BCMY)

• common memory (CMY)

• input/output processors (IOP):

o IOP:MB (input/output processor for message buffer)

o IOP:TA (input/output processor for time and alarms)

o IOP:LAU (input/output processor for line adaption unit)

o IOP:UNI (input/output processor unified for O&M devices)

o IOP:AUC (input/output processor for authentication center), only for use in mobile

communication network nodes (D900)

There are two BAPs in the CP113, one is called the master, performing all the maintenance tasks

and, if necessary, call processing. The other one is called spare, which does only call processing.

The master/slave status of the BAPs can be changed. Either manually with the MML command

COM BAP; or automatically by the system itself. This automatic change is normally done once a

day. If a BAP fails, his functionality will be replaced by the remaining BAP.

The optional call processors can not replace the functionality of the BAPs.

The basic configuration of the CP113C can be expanded as necessary by adding similar functional

units. This is true for computing and memory capacity, and also for the connection of call

processing plus operation and maintenance peripherals.

The operation and maintenance periphery (O&M periphery) and data communication periphery

can be expanded as required for the CP113C/CR. The following devices can be attached:

o magnetic disk device (MDD)

o magneto-optical disk device (MOD)

o operation and maintenance terminal (OMT or BCT)



o data links to data communication devices or to data terminal equipment with V.24, V.35,

V.36 interfaces and with the BX.25/X.25 protocol maintenance panel (used only by TAC

staff for special fault clearance procedures).



Figure 5.1. Hardware Structure of the CPCP113C/CR

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BAP,CAP and IOC

The base processors, call processors and input/output controls are built using identical hardware

components and can therefore be described together.

Each processor comprises the following:

o two processing units (PU)

o a local memory (LMY)

o a common interface (CI)

o an interface to the bus system for input/output control (BIOC)

The interface to the BIOC is part of the CI and thus physically present in all processors. However,

it is only activated when used as an IOC.

Processing Unit The processing unit (PU) is duplicated. Mutual checking by the two PUs allows fast error detection

and handling, thus preventing the effects of errors from spreading.

The PU0 is always the master unit in normal operation. During write cycles to the memories, the

data are always sent by the master PU, while in read cycles both Pus receive the data. The core of

the processing unit is a microprocessor. The programs of the system-specific software and

function-oriented user software run on this microprocessor.

Local Memory Dynamically important programs and data only required by a particular processor are stored in the

local memory (LMY) of the processor. This memory can only be addressed by the processor itself

or, in the IOC, also by the IOPs.

In addition to the local memory, a flash EPROM is also available. It includes the firmware for the

hardware recovery, the loader, the diagnosis programs and also the IOC firmware.

Common Interface The processor is connected to both buses of the common memory (BCMY) by means of the

common interface (CI). All accesses to the common memory (CMY) and the inter processor

communication are performed via this interface. It is also possible to connect a maintenance panel

for system checks and special fault clearance to the common interface .



Interface to the Bus System for Input/ Output Control The interface to the bus system for input/output control (BIOC) is only active when the processor is

used as an input/output control (IOC). The interface is part of the common interface. The interface

to the BIOC connects the local bus of the IOC with the bus system for input/output control. A

maximum of 12 input/output processors (IOP) can be connected to the BIOC.



Figure 5.2. Structure of BAP, CAP, and IOP

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Input/Output Processors (IOP) Different types of input/output processors (IOP) connect the CP113C/CR with the other units in the

network node, the external memories, the operation and maintenance terminal or basic craft

terminal, the operation and maintenance center (OMC, via data lines) and computer centers (also

via data lines).

Input/Output Processor for Message Buffer The input/output processors for the message buffer (IOP:MB) are the CP113C/CR interfaces to

the functional units in the network node. All subsystems and functional units are supplied via two

IOP:MBs for reasons of operational reliability. If one of the two IOP:MBs fails, the remaining

processor takes over the data exchange functions by itself. The following units are connected to

the IOP:MB:

• the message buffer groups (MBG),

• the central clock generators (CCG),

The number of IOP:MBs used depends on the size of the switching network.

Input/Output Processor for Time and Alarms The input/output processor for time and alarms (IOP:TA) contains the hardware clock of the

CP113C/CR and interfaces for accepting external alarms. The duplicated hardware clock of the

IOP:TA is synchronized by a clock supplied by the central clock generator (CCG). The hardware

clock generates the date as well as the time in hours, minutes and seconds. The time is displayed

on the front panel of the module.

Alarms occur in racks of the CP area which cannot be assigned to specific functional units, e.g. fan

alarms. The IOP:TA accepts these alarms and reports them to the safeguarding software in the

BAP. The IOP:TA has alarm interfaces to a maximum of 5 racks.



Figure 5.3. Structure of the CP113C/CR input/output system

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Input/Output Processor Unified for O&M Devices The following devices or lines can be connected via the input/output processor unified for O&M

devices (IOP:UNI):

• magnetic tape device (MTD),

• magnetic disk device (MDD),

and optionally:

• one O&M terminal (OMT or BCT) and 2 data lines or

• 3 data lines,

• magneto-optical disk unit (MOD).

The magneto-optical disk unit is used as a storage medium instead of or in addition to the

magnetic disk, to improve the operating activities, particularly to reduce the start up and backup

times. The MOD can be connected on the same SCSI bus as the MTD and MDD. At the interface

to the CP, the MOD is driven like an MTD. The maximum number of MOD/MTDs which can be

connected is 2 per IOP:UNI.

Three connections are provided for OMT/BCTs and data lines. One OMT and 2 data lines, or

alternatively 3 data lines, can be connected to them directly or via a Modem.

Input/Output Processor for Line Adaption Unit The input/output processor for line adaption unit (IOP:LAU) is used for connecting X.25-equipment

to the exchange, such as OMC or craft terminal. It consists of just a single module, the line control

unit module B, LCUB. The line adaption unit module B (module LAUB) is used for connecting the

IOP:LAU to the interface. The LAUB module is controlled by the line control unit. The two modules,

LCUB and LAUB, which are used together, are configured as follows:

• the LCUB module as IOPLAU (e.g. CONF IOP: IOP=IOPLAU-0, OST=ACT; )

• the LAUB module as LAU (e.g.: CONF LAU: LAU=0, OST=ACT; ).

The IOP:LAU is always used in pairs, with the two LCUBs being cross-connected to the two

LAUBs for reasons of operational reliability. A pair of IOP:LAUs is connected on one side to two

different BIOCs, and on the other side has 2 x 2 = 4 serial interfaces with BX.25/X.25 protocol, for

the connection of 4 data lines (X25LINK 0...3) using the LAPB data transmission procedure (Link

Access Procedure Balanced). The maximum data transmission rate is 64 kbit/s.



Input/Output Processor for Authentication Center The input/output processor for authentication center (IOP:AUC) is only available when the

CP113C is used in authentication centers (AC) in a mobile communication system. In a mobile

communication system, the authorization rights of the mobile subscriber are checked whenever a

call is set up between a mobile station and the network, with the objectives of protecting

• the mobile network against unauthorized access at user and customer level, and

• the authorized mobile subscriber against impermissible access to the mobile network by

unauthorized persons or by a subscriber attempting to pass off an invalid authorization as valid.

All important security functions are executed by the IOP:AUC in the AC. The IOP:AUC generates

the authentication triple required for the authentication process during call setup. This function is

particularly security-sensitive, and requires corresponding security measures. The IOP:AUC is

therefore also known as the security box.

To administer the subscriber data, the AC communicates with the personalization center for

subscriber identity module (PCS). Files containing the subscriber data are generated in the PCS

and transferred to the AC by means of a data line or magnetic tape. The files are encrypted to

ensure security during transmission. From a smartcard, the encoding parameters are loaded via a

serial interface to one IOP:AUC and are distributed to the other IOP:AUCs in the AC.



Racks and frames The racks for the CP113 are different for the C and CR version. Frames for the CP113C are

located in standard racks with a height of 2450mm. The rural version of the CP uses racks with a

height of 2130mm and can be installed in a container.

CP113C rack An additional rack is required to accommodate additional equipment (Modems, magnetic tape

drive).

CP113C module frames Two types of module frames and a device frame are used in the CP113C:

• a module frame for processors (BAP, CAP), bus for common memory and common memory

(F:PBC)

• a module frame for processors (IOC, CAP) and input/output processors (F:PIOP)

• a device frame for accommodating magnetic disk units, magneto-optical disk units and power

supply units (F:DEV(F)). The devices are pushed in the same way as modules. Each device

requires a plug-in converter.



Figure 5.4. Rack CP113C with frame F:PIOP (B)

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Figure 5.5. Rack CP113C with frame F:PIOP

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The following table shows the modules in the CP113C/CR and their assignments to the functional

units:



Figure 5.6. Module frame F:PBC

DCCx Direct current converter

PEX Program execution part

PIA Processor interface and arbiter

BCM Bus clock generator and maintenance controller

CMYC Common memory control

MTI Memory and tracer interface

CMYM Common memory medium

BAP Base processor

CAP Call processor

BCMY Bus for common memory

CMY Common memory

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Figure 5.7. Module frame F:PIOP



IOPTA Input/output processor for time and alarms

IOPMB Input/output processor for message buffer

LAUB Line adaption unit, module B, BX.25- or X.25-interface

LCUB Line control unit, module B

IOPUNI Input/output processor unified for O&M devices

IOPAUC Input/output processor for authentification center, available when using CP113 in

authentication centers (AC) of mobile systems D900/D1800.

CAP Call processor

IOC Input/output control

IOPG Input/output processor group

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Figure 5.8. Module frame F: PIOP (B)

DCCM C/D Direct current converter



IOPTA Input/output processor for time and alarms

IOPMB Input/output processor for message buffer

LAUB Line adaption unit, module B, BX.25- or X.25-interface

LCUB Line control unit, module B

IOPUNI Input/output processor unified for O&M devices

IOPAUC Input/output processor for authentification center, available when using CP113 in

authentication centers (AC) of mobile systems D900/D1800.

CAP Call processor

AMP ATM Bridge processor

IOC Input/output control

IOPG Input/output processor group

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Advantages of new CP113E • call processors (CAP): performance improved by factor 5

• base processors (BAP): performance improved by factor 3,5

• ATM bridge processors (AMP): performance improved by factor 1,5

• input output controllers (IOC): performance improved by factor 2

• traffic handling capacity of more than 16 million busy hour call attempts (BHCA) possible

• no need for B:CMY what was the bottleneck in CP-internal communication

• can be adapted to network nodes of any size

• smaller footprint

• reduced power consumption

• CP113E has no effect on the system functions switching and operating (OAM). The interface to

the call processing SW and maintenance periphery remains unmodified.

• IOPs are directly taken over from the CP113C ; their performance is improved by a faster access

to CMY.

Capacity stages In the basic configuration the CP113E has only two base processors (BAP) and two input/output

controls (IOC). Up to sixteen input/output processors (IOP) can be connected to each IOC. For an

expansion, two more input/output controls (IOC) with additional IOP can be added. In its maximum

configuration the CP113E is equipped with 16 processors: two BAPs, four IOCs and 10 call

processors (CAP). Depending on the system configuration, up to four ATM bridge processors

(AMP) can also be used as an alternative to CAP.

In future configurations it will be possible to expand the CP113E by eight additional CAPs in order

to have a total of 24 processors. Of the eight additional processors, four can also be used as

AMPs.

The CP113E is connected via the input/output processors (IOP) to the message buffer D (MBD)

and to the OA&M equipment of the network node. There is a direct interface to the signaling

system network control (SSNC) via the ATM bridge processor (AMP). The asynchronous transfer

mode (ATM) is used at this interface. It reduces the CP load when distributing messages in the

network node.



Figure 5.9. Performance comparison



Redundancy The following functional units of the CP113E are duplicated:

• Base processor (BAP)

One of the two base processors (BAP) operates as “master” (BAPM), the other as “spare”

(BAPS). the BAPM processes operation and maintenance tasks as well as some of the call-

processing tasks. The BAPS processes call-processing tasks only. The two BAPs operate in

task and load sharing mode. If the BAPM fails, the BAPS takes over the tasks of the BAPM.

• Call processor (CAP)

The call processors (CAP) in CP113E handle call-processing tasks only. They work in load

sharing mode. Together with the BAPS and BAPM, the CAPs form a pool redundancy. As a

result, even if one processor fails (BAP or CAP), the CP113E can continue to handle the full

nominal load (n+1 redundancy).

• Input/output control (IOC)

The input/output controls (IOC) are duplicated. If one IOC fails, the other IOC carries out the

tasks of its partner unit.

• ATM bridge processor (AMP)

The AMPs are always operated in pairs in the CP113E. An AMP pair operates in working/spare

mode, i.e. both AMPs receive the same messages at the same time. However, only the active

AMP sends messages.

• Common memory (CMY)

The CMY is duplicated. Both CMYs (CMY0 and CMY1) can be reached by all processors and

input/output controls (IOC) as well as by the IOPs. In normal operation the two CMYs perform all

read and write cycles synchronously. However, the two CMYs can also be operated separately

(splitting mode). Access to the CMY by the processors is realized via High Speed Serial Links

(HSSL) that can transport data faster than the formerly used BCMY.

• Input/output processor (IOP)

The input/output processors (IOP) are grouped into two IOP groups in order to perform the tasks

of each other if an IOP in one IOPG should fail. The same IOP modules as in CP113C are used.

• Operation, administration and maintenance periphery



The redundant OA&M periphery units are always connected to two different IOCs. If one IOC or

the associated input/output processor (IOP) fails, inputs and outputs to/from the redundant

OA&M unit are carried out via the other IOC in the pair.



Figure 5.10. CP113E, possible configurations

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All the hardware in the CP113E is modularly designed, i.e. the functional units are implemented in

modules. One module corresponds to one hardware functional unit in this respect. In case of the

IOP:SCDP the hardware functional unit includes two modules. As already said, all IOPs are the

same as in CP113C.

Two new module types are introduced:

• Program Execution Board for CP113E (PEXE) for BAP, CAP, IOC, AMP and

• Common Memory for CP113E (CMYE)



Rack The CP113E is housed in a new rack R:CP113E.

The upper half of this rack is reserved for the IOP-frames, the lower half for the processor frames.

Figure 5.11. Module types



Figure 5.12. R:CP113E

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Frames Basic processor frame F:BPCE The F:BPCE comprises two backplane halves that are interconnected via a connection element

M:CONE. With SR10, only two AMPs are possible and a maximum of 10

Extension processor frame F:EPCE The F:EPCE houses the MODs, MDDs and (optionally) eight more CAPs or four more AMPs. But

these are not yet needed / possible with SR10.



Figure 5.13. Module frame F:BPCE (modules in brackets are not used in mobile applications)

Figure 5.14. Module frame F:EPCE (CAPs and AMPs not used in mobile applications)

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Extension IOP frame In mobile applications, the so called "extension frame" will be used as "basic", i.e. first, frame for

IOPs.

The shown layout is the standard configuration for switches with SSNC and MBD only.

Basic IOP frame This frame layout can only be used in combination with the smallest SN (SN63) and without SSNC

and MBD. Mounting unit is MUT05 Therefore the F:BIOP will not be used in mobile applications.

It is shown here for the sake of completeness only.



Figure 5.15. Module frame F:EIOP for mobile applications with SSNC and MBD

Figure 5.16. Module frame F:BIOP (not for use in mobile applications)

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5.2. Message Buffer



5.2.1. Function

The Message Buffer is part of the coordination area of the network node.

The main function of the MB consists in managing various types of interface and switching

through information to these interfaces:

• Message channels are connected to/from the LTG via serial synchronous 8Mbps

SDC: The individual LTG message channels therefore have 64 Kpbs. They contain

switching messages for the setup of the user channel connections, administrative

and security messages and maintenance messages. The MBD evaluates the

routing label that is the address information in the packets of the internal exchange

signaling. Messages from one LTG to another do not encumber the CP bus system,

but are forwarded directly.

• Signaling channels to/from the individual SN controller components are likewise in

the SDC. The transmission rate per channel is 64 kbps.

• SSNC interface with AMX (ATM Multiplexer) via ATMB (ATM Bridge) for forwarding

all input information ("orders") via a direct interface between MBD and AMX/SSNC.

Using this interface to the SSNC, CCS7 ISUP messages can be directly forwarded

between LTG and SSNC.

• The IOP:MB are connected via redundant, asynchronous, bit-parallel

("handshaking") interfaces.

The MB is completely redundant and includes a MB0 and a MB1. These function

redundantly and in a load-sharing manner. About half of the LTG currently have the active

message channel on one MB side.

Since there is no redundant connection between the MB and the SN, in the event of a

failure of the corresponding MB unit, particular components are not available in one SN

half ("nac").



Figure 5.17. MBD in D900 environment

Figure 5.18. Message Flow through MBD

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The MBD is set up in the form of two redundant halves, which work independently of each other in

the load-sharing mode.

The MBD comprises four different module types:

The MBDH module takes over the processing of the HDLC interfaces concerning the LTGs and

SN. Each module provides LTG message channels to a maximum of four TSGs and six SGC

interfaces. The maximum number of LTGs that can be connected with an individual MBDH is 252.

The smallest possible MBD configuration with 63 LTGs based on one single MBDH, in which only

one SDC:TSG interface and two SDC:SGC interfaces are used. The MBD expansion stages 252,

504, ... 2016 are achieved in stages of 252 LTGs by connecting additional MBDH modules. The

maximum is 8 MBDH, i.e. a total of 2016 LTGs are therefore possible (SN D).

The MBDA module is connected with the SSNC via two ATM lines, each at a speed of 207 Mbit/s.

Each module can process approximately 24,000 #7 messages (ISUPMSU) per second (including

additional asymmetric load). One MBDA is the intended minimum, five MBDA modules is the

planned maximum.

Both the ATM bridges per MBDA are implemented in the form of fiber optic cables.

Per bridge, there are two FOTX modules on the rear panel of MBD module frame behind the

MBDA slot. They connect the two sides of the SSNC-ATM switching network. The fiber optic cable

transceiver module FOTX implements the electrical/optical conversion (Rx and Tx) of an ATM200

channel on the fiber optic cable connection.

The MBDC module has a maximum of seven interfaces with IOP:MB pairs on the CP113C. In

SR9, a maximum of two IOP:MB interfaces are used. Alongside its task as a CP message

transferor, this module takes over the control of the MBD in the case of a recovery and with regard

to a complete system reset. The MBDC can transfer up to 38,000 messages.

The MBDCG module receives its reference clock from the CCG and distributes these further to the

SN modules. Simultaneously, it also provides the individual MBD modules with the MBD system

clock. With regard to the SND, the MBDCG multiplexes multiple SN signaling channels to a single

8 Mbit/s interface ("S3").

The MBDH modules can be installed into a frame during operation ("hot plug-in").



With regard to installation, the continuous ascending sequence (MBDH0, MBDH1, ... MBDH7)

must be observed.



Figre 5.19. Hardware of the MBD

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All modules are connected to one another via a serial high-speed interface, the so called IBUS (Internal Bus). IBUS takes over the entire communications transfer in the MBD and a module is

also connected with its redundant counterpart in the second MBD half via an IBUS connection. In

this way, the connection of a module with its communications partner can be performed directly, if

they are both located in the same MBD half. If the destination is located in the redundant part of

the MBD, this is carried out via an indirect connection, which can be routed via either of two

different communication paths. It can either first be sent to the partner module of the receiver in

the same MBD half, from where it is forwarded to the receiver on the other MBD side, or the

message is sent to the appropriate partner module of the sender in the other MBD half and

transferred from there to the receiver. As standard, the former method is chosen (after module

reset).



Figure 5.20. MBD IBUS

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Module frames The planned maximum MBD configuration is intended to be eight MBDH, five MBDA, one MBDC

and one MBDCG. These modules are all located together in a single frame. The duplicated MBD

thus comprises two identical frames.

The MBD frame F:MBD is installed in the LTGN rack frame.



Figure 5.21. Frame of the MBD

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Expansion stages The number of required MBDH modules depends on the number of LTS to be connected. All

modules of the redundant MBD frame work according to the load sharing principle.

The number of required MBDA modules depends on the scope of the message (MSUs) being

exchanged between the MBD and the SSNC. For the highest expansion stage of SSNC (F:SCB

and 7xF:SCE), five 5 MBDA modules are required.

Each ATM bridge (2 per MBDA module) is "in service" on one side of a MB and "hot standby" on

the other.

The distribution of the ten ATMB interfaces (five modules with two ATM functions) must be

performed in accordance with the load sharing principle. Details regarding this can be found in the

handbook.

No MBDA module is required without SSNC or for emulation of MBB.

The number of IOP-MB modules required is determined by the traffic volume between the MBD

and CP. The MBDC module supports up to seven IOP:MB interfaces, so that one single MBDC

module suffices for all the expansion stages.

Currently, a maximum of 4 IOP:MB interfaces are used.

With the objective of uniform load sharing, there is an automatic allocation by the IOP:MB to

MBDH. In addition, an IOP:MB transmits the maintenance information flow to the MBDC module.



Figure 5.22. Expansion Stages

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5.3. Clock



5.3.1. Function

In order to be able to switch and transmit digital information, the operating sequence must be

synchronous for all available system components. In order to do this, a totally operationally

dependable, accurate and consistent clock generator is required for all the network nodes within

the digital network.

Due to its extremely important role, the central clock generator CCG is redundant. One of the two

clock generators is always active and performs a master function; the other is in standby and

performs a slave function. In this manner, in the event of a functional fault or a failure of the master

CCG it is guaranteed that the master / slave allocation is immediately and automatically changed

and the clock generator of the connected subsystems can continue uninterrupted.

The CCG itself is generally synchronized with an external reference frequency, i.e. an atomic clock

signal, a 2MHs clock signal derived from a conventional 2 Mbps PCM30 system or another

frequency signal. It is essential that the input frequencies tally with those of the adjacent network

nodes to a very high degree of accuracy.



Figure 5.23. Location of the CCG in the D900 system

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The central clock generator comprises up to four module types, of which only one is

compulsorily required:

• the CCGES module contains the actual clock generator with oscillator and external master clock

input. The outgoing and monitored frequency signal from this module is used as the input clock

for the MB, IOP:TA, CCGED and, if necessary, the SSNC

• the CCGERB module may be used if no external reference frequencies can/should be used. It

contains a rubidium atom clock • the CCGE:GPS/DCF module is used, if satellite or special radio

frequency signals are to be received as a reference

• up to 4 optional CCGED modules for the distribution of the system clock to external systems, if

required the CCG can function in two operating modes:

• Synchronous operating mode (with at least one external reference signal)

• Plesiochronous operating mode (no external reference frequency "holdover").

Even if a reference frequency from the rubidium module is used, the term plesiochronous is used

because this reference does not come from a synchronization network.

In the synchronous operating mode, the CCG generates the clock using the built-in high-quality

oscillator and synchronizes it with one of the four possible external reference frequencies. The

active (master) CCG transmits the generated system to:

• the redundant message buffer (MB 0 and MB 1)

• the communication processor (time of day generator on the IOP:TA in the CP113x)

• the inactive (slave) CCG for the synchronization of the two CCG

• the external master clock distributor (CCGED), if desired

• the SSNC (ACCGs in the ASN)

The optionally available CCGED modules (external clock distributors) can be used in order to

output a 2048 kHz synchronous system clock to external systems, e.g. SDH transport systems.

Four modules can be installed, each with 32 outputs.



Figure 5.24. Structure of the CCGE

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Clock distribution Clock Generation In normal operation, the oscillators of the two redundant units CCGE0 and CCGE1 receive

different references for the clock generation. In the event of the failure of all the external

references, e.g. only on the CCGE0, it is received from the other CCG with an external reference

via an internal crossover (e.g. CCGE1).

The phase of the oscillators is not constant in normal operation when using different reference

signals. In order to simplify the switchover, the CCG standby output signals are synchronized for

the D900 internal clock users independently of the oscillators of the two units. To do this, the

output signal of the active unit is transferred to the standby unit via a further crossover connection.

Every clock receiver within the D900 network node (MB, CP, SSNC, external), which takes a

reference clock from the CCGE, is provided with the clock of the CCG, the respective other CCG

(standby) does not provide a clock.

The clock distribution in the network node is set up hierarchically. The clocks are generated,

synchronized and transmitted in several consecutive stages.

The pieces of hardware have their own clock generators at the respective levels.

These unit-specific oscillators are synchronized using the input clock coming from the

superordinate level. In the event of a failure of the clock signal of the superordinate level, the

subordinate clock generators continue in free-running operation. In this way, the operation of the

system can be continued to a certain extent. In this case, however, the quality of the interoffice

trunks to other network nodes is reduced. In the worst-case scenario, this can result in the failure

of user or signaling channels.

Self-monitoring CCGES self-monitoring detects all hardware faults with great accuracy. The CCGE outputs are not

individually monitored, but such faults must rather be detected by the connected clock receivers.

A control signal is sent from the active CCG to the standby. If this signal from the active redundant

partner unit is not transmitted, a switchover from standby to active is performed for the internal

D900 outputs without involving the CP.



Figure 5.25. Hierarchical levels of the clock generator in the D900 system

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CCG module and module frame utilization The clock generators share one module frame, which accordingly consists of two halves with

identical modules.

The CCGED, CCGERB and CCGE:GPS are optional modules.



Figure 5.26. Module frame for the CCG

Figure 5.37. CCGE Module

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5.4. Operation and Maintenance Console



5.4.1. Configuration and Interfaces

The BCT/BOOT software is only used for direct connections to the CP. BCT/COMMON software

can be connected to the CP via X.25 software or through the SSNC via TCP/IP. Switch

Commander can be simultaneously connected to the CP and SSNC of different exchanges via an

TCP/IP network.

If a TCP/IP or X.25 connections are used, it is not possible to transfer or execute anything if these

links are not active, e.g. while the exchange is in installation or split operation mode! In this case

only the BCT/BOOT software can be used.

The structure of the man machine language (MML) is based on an ITU recommendation. It was

created for communication between the operators and the coordination processor CP.

In contrast to MML, organizations and companies who work traditionally at the telecommunication

world, have standardized the Q3 standard. The Q3 standard is used for the communication

between the operator and the MP. The MP's are the main processors of the SSNC.

In SSS solutions from SR9 on it is possible to combine a classic MSC (using MML commands)

and a SSNC (using Q3 scripts). For both interface types (MML/Q3), the so-called Switch

Commander is used. Since the Q3 standard looks more like a programming language, a

simplification for the operator was necessary. The input syntax described in the Task Manual and

the system responses of the MP illustrated in the OML resemble the conventional MML syntax.

The Switch Commander converts the entered MP command into a Q3 request before it is sent to

the MP. The response of the MP, so-called Q3 confirmations, will be converted into a readable

format.

In contrast to Q3, the Switch Commander sends MML commands for the CP without modification

to the MP, where the command is just forwarded to the CP. Responses from the CP are shown

directly on the Switch Commander.



Figure 5.28. Q3 Task and MML Command principles

Figure 5.29. V.24 connection of the BCT to the exchange

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Figure 5.30. TCP/IP connections of the CT to the exchange

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5.4.2. Function

Functions of the BMML window Executing commands and login to the exchange Enter any command in the Command Input Line and press the ENTER key or use the execute

function of the Menu or Icon Bar. If there is no existing CP session, a dialogbox appears

requesting the Userid. After that, another dialog box with the password request is displayed.

Response of the system when parameters are missing If the user enters an incomplete command, the Input Request dialog box is used to request

missing parameters. It is possible to ignore a parameter by pressing ENTER.

If the parameter is requested again, it is mandatory. Otherwise the next parameter is prompted. To

finish a command, use the semicolon at any time.

BMML-window contents after command execution After a successful execution the BMML-window areas have the following contents:

Output Area

Output mask responded from the exchange depending on the executed command.

BMML-Command Input Line

The last entered command, again without parameters entered using the Input Request

dialog box.

Command History Area

The last up to 1024 commands in exactly the way they were entered in the BMML-Input

Line, without parameters entered with the aid of the Input Request dialog box!

The logging function The contents of the Output Area are automatically stored in a cyclic logfile on disk.

The size of this file can be changed by an administrator (e.g. 10MByte). When the file is full, older

entries are overwritten. Each of the two possible BMML-Windows has its own logfile. The name of

the logfile is BMMLlogX.txt where X is 1 for COM1 and 2 for COM2. The location on disk depends

on the installation, e.g. D:\bctboot\Logging\BMMLlog1.txt. This logfiles can be opened with a

simple text editor, but only an administrator can change or delete them.



Regardless of the size of this cyclic file, the maximum size of the Output Area is 500kByte, but

everything is still stored on disk.

Content of switch commander Switch Commander tree consists of multiple O&M software applications. These are:

• Alarm Console

• BMML

• Floor Plan Editor

• Interactive Document Browser

• Log Viewer

• Network Layer Manager

• Q3 Event Presentation Service

• Q3 Trace

• Refresh Status

• Switch Commander Administration

• Switch Commander Alarm and Message Display

• Switch Commander Information

• Switch Commander NE Administration

• Switch Commander Process Administration

• Scenario Wizard

• Task Analyzer

• Task Browser

• Trace Configuration

• Work Order Viewer

• Work Bench



5.5. Storages



5.5.1. Function

MDD stores APS for the system. The Applications Program System (APS) comprises the whole

Software (SW) and Firmware (FW), which is necessary for the Operation of the Switching System

EWSD/D900/D1800.

The APS comprises SW and FW as well and is programmed with e.g. CHILL (CCITT High Level

Language), C or Assembler. The APS runs and is stored in different locations. The following

overview shows the most important SW an FW locations.

• The SW in the Coordination Processor comprises data, resident SW and reloadable SW

as well. The resident SW is used for programs, which are more or less time critical (Call

processing, Operating System etc.). The reloadable SW is stored on the magnet disk an

reloaded if necessary. It is used for non time critical applications like Administration,

Configuration etc. The MDD also stores the SW for all other D900 Units except SSNC. The

FW in the Coordination Processor (CP) is used e.g. for the Boot of the System, i.e. the

situation when no SW is loaded yet.

• The Signaling System Network Control and its MDDs contain FW and SW with code and

data only for itself. The data is mainly consisting of the SS7- MTP and - SCCP information

necessary for the routing function and the message distribution to the corresponding user

parts.

• The Switching Network contains FW, which is necessary for e.g. the HW self supervision,

the through connection of the speech path etc.

• The LTG comprises SW and FW as well. The SW is stored on the magnetic disk and

loaded during the LTG Configuration and LTG Recoveries. The SW contains code to run

the LTG and data e.g. the application of ports, LTUs etc.. Similar to the CP the FW is e.g.

necessary to boot the LTG.

• The DLU/DSU contains SW and FW. The SW is used e.g. for the storage of the DLU Port

data. The FW is necessary for the DLU start up and for the Call Processing in the

emergency stand-alone.




Connection between MDD and CP+MP are described below:

Figure 5.31. APS Location and MDD Connection

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Figure 5.32. Module MDDE – CP

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Figure 5.33. Frame F:DEV(F) MDD-CP

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Figure 5.34. MDD – MP

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Figure 5.35. Frame F:SCB MDD-MP

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5.5.3. Procedures

An APS generation is a set of system files, which are necessary to run a switching system.

One (valid) generation in the CP is belonging to a "partner"-generation in the SSNC and vice

versa. Such a pair is normally created at the same time and linked together by a number called

generation compatibility sign "gcs".

An APS generation can be used as a current generation (the generation files are currently used

for the switching system) or as a fallback generation (the generation is kept on an external

memory: magnetic disk, magneto optical disk or magnetic tape) for a fallback in case of an

emergency situation. The current generations in CP and SSNC always have the same gcs. Also

each valid fallback generation has a partner with the same gcs.

New Generation after Data base extension

In case of the size of certain database tables is not sufficient any more (e.g. no Trunk Groups can

be created any more) or after implementation of a new APS the size of the data tables is to be

expanded with the Office Data Generator (ODAGEN). In this case the corresponding data tables

are expanded in a copy of the current APS. After successful expansion of the APS, the system

starts up with this new APS (ODAGEN Generation). Fallback Generations Routine and quarterly Saving

In some unusual emergency situations the system may not be able to work successfully with the

current APS, it will automatically (or by operator request) fall back to an older APS (fallback-

generation). This happens at the same time in CP and SSNC. Automatic Fallback cannot use

generations on MOD or invalid, locked or disabled generations on MDD.

In other cases it might happen, that there is no more generation on disk, which is able to start-up:

By operator-request, a generation on magneto optical disk will be used to reload the system.

Therefore the current generations of CP and SSNC are copied to MDD and MOD, inclusive the

current database, at least in an interval of two weeks and all three month with an additional start

up test in the CP (Backup Generation and Golden Generation). After APS Change In case of the introduction of a new APS version, a copy of the new APS is saved after run in of

the database. This APS copy can also be used for recoveries with a fall back (Golden Generation)



6. Switching Subsystem – Signaling Function

Contents 6.1. CCS7 Introduction ..................................................................................................................... 2

6.1. 1. Protocol Stack.................................................................................................................... 3 6.1.2. Sample of Procedure ........................................................................................................ 12

6.2. Signaling Component .............................................................................................................. 18 6.2.1. Function ............................................................................................................................ 19 6.2.2. Hardware and Location ..................................................................................................... 21



6.1. CCS7 Introduction



6.1. 1. Protocol Stack

The purpose of signaling system is to transfer control information (signal units) between elements

in telecommunication network. The elements are switches, operations centers, and databases.

Originally, signaling systems were designed to setup connections between telephone offices and

customer premises equipment (CPE) in order to transport only voice traffic through a voice-

oriented, analog network. Today, they are designed to set up connections between service

provider offices and CPE in order to transport not only voice but also video or data signals through

either analog or a digital network.

CCS7 is a successor of Common Channel Signaling number 6. CCS7 serves telecommunication

standards for years, and still can be used for next telecommunication system, e.g: IP based

telecommunication.

In GSM system signaling functions in CCS7 are distributed among the following parts:

• message transfer part (MTP)

• function-specific user parts (UP) The message transfer part represents a user-neutral means of transport for messages between

the users. These parts build lower levels of the signaling that support many kind of user parts. The

term user is applied here for all functional units which use the transport capability of the message

transfer part. Each user part encompasses the functions, protocols and coding for the signaling via

CCS7 for a specific user type (e.g. telephone service, data service, ISDN). In this way, the user

parts control the set-up and release of circuit connections, the processing of facilities as well as

administration and maintenance functions for the circuits. The functions of the message transfer

part and the user parts of CCS7 are divided into 4 levels. Levels 1 to 3 are allotted to the message

transfer part while the user parts form level 4.

Message Transfer Part

The message transfer part (MTP) is used in CCS7 by all user parts as a transport system for

message exchange. Messages to be transferred from one user part to another are given to the

message transfer part (Fig. 10 Functional CCS7 levels). The message transfer part ensures that

the messages reach the addressed user part in the correct order without information loss,

duplication or sequence alteration and without any bit errors.



Functional levels of MTP Level 1 (signaling data link) defines the physical, electrical and functional characteristics of a

signaling data link and the access units. Level 1 represents the bearer for a signaling link. In a

digital network, 64-kbit/s channels are generally used as signaling data links.

Level 2 (signaling link) defines the functions and procedures for a correct exchange of user

messages via a signaling link. The following functions must be carried out in level 2:

• delimitation of the signal units by flags and elimination of superfluous flags

• error detection using check bits and error correction by retransmitting signal units

• restoration of fault-free operation, for example, after disruption of the signaling data link

Level 3 (signaling network) defines the interworking of the individual signaling links.

A distinction is made between the two following functional areas:

• message routing, message discrimination and message distribution

• signaling network management



Figure 6.1. Functional CCS7 Levels

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Signal Units The message transfer part transports messages in signal units of varying length. A signal unit is

formed by the functions of level 2. In addition to the message it also contains control information

for the message exchange. There are three different types of signal units:

• message signal units (MSU)

• link status signal units (LSSU)

• fill-in signal units (FISU) Using message signal units the message transfer part transfers user messages, i.e. messages

from user parts (level 4) and messages from the signaling network management (level 3). The link

status signal units contain information for the operation of the signaling link (e.g. for the alignment)

and the fill-in signal units are used to maintain the acknowledgment cycle when no user messages

are to be sent in one of the two directions of the signaling link. The figure on the opposite page

illustrates the structure of the signal units.



Figure 6.2. Message Signal Unit (MSU)

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Figure 6.3. Link Status Signal Unit (LSSU)

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Figure 6.4. Fill-in Signal Unit (FISU)

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Flag (F) The signal units are of varying length. In order to clearly separate them from one another, each

signal unit begins and ends with a flag. The flag is also used for the purpose of alignment. The bit

pattern of a flag (F) is 01111110.

Backward sequence number (BSN) It contains the forward sequence number of a signal unit in the opposite direction whose reception

is being acknowledged.

Backward indicator bit (BIB) With this bit, faulty signal units are requested to be retransmitted for error correction.

Forward sequence number (FSN) A forward sequence number (FSN) is assigned consecutively to each signal unit to be transmitted.

The numbers 0 to 127 are available as forward sequence number.

Forward indicator bit (FIB) It indicates whether a signal unit is being sent for the first time or whether it is being retransmitted.

Length indicator (LI) The length indicator (LI) is used to differentiate between the three signal units:

• 0 = fill-in signal unit

• 1 or 2 = link status signal unit

• greater than 2 = message signal unit.

Service information octet (SIO) The service information octet (SIO) only exists in message signal units. It contains the service

indicator and the network indicator.

The service indicator is used for addressing the corresponding CCS7 user. This means the level 3

function distributes the message, with help of the service indicator, to the corresponding user parts

(distribution). As a rule, the ISUP (ISDN user part), TUP, TUP + or SCCP user parts are used

here. If link status information is sent, this also is displayed via the service indicator.

The network indicator cites the corresponding network in which the transmitter and receiver of the

message are located. There are four options:



• NAT0 = own network

• NAT1 = common communication network with another network

• INAT0 = common international network for networks with international network access

• INAT1 = not used.

Figure 6.5. Service Information Octet

NI: • NAT0 • NAT1 • INAT0 • INAT1

SI: • SCCP • TUP • TUP+ • ISUP • Link Status

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Signaling information field (SIF) The signaling information field (SIF) only exists in message signal units. It contains the actual user

message.

Check bits (CK) The check bits (CK) are formed on the transmission side from the contents of the signal unit and

are added to the signal unit as redundancy.

Status field (SF) The status field (SF) only exists in link status signal units. It contains status indications for the

alignment of the transmit and receive directions.



Signaling System #7

Physical & electrical attributes

Signaling Data Link

Signaling Network functions

MTP Message Transfer

ISUP ISDN

User Part

TUP Telephone

User Part

DUP Data

User Part

SCCP

7

4 - 6

3

2

1

3

2

1

4

Level

TCAP

MAP Mobile

OSI Layer

Figure 6.6. Signaling System Number 7 Protocol Stack

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6.1.2. Sample of Procedure

BTS

BSC

BTS

HLR VLR VLR EIR

SSP

SSP

GMSC MSCMSC

PSTN

BTS

A-bis

A-b

is

A-bis

Um

SS7/ISUP

SS7/ISUP

E

D G

C

C

B F

A

Database

Switching

Radio System

Figure 6.7. GSM Architecture



Location Registration / Location Update Information of the current location of a mobile subscriber are necessary to built up a connection to

the subscriber, i.e. to start a Mobile Terminating Call MTC. To keep track of the users current

location the Location Registration / Update procedures are used. Always the MS is responsible to

initiate this Location Registration / Update procedures. It informs the network on its current

Location Area. The Location Area information is stored in the currently responsible VLR. The

identity of this VLR is stored in the users HLR.

If a MS is "new" in a PLMN a Location Registration is performed. "New" is defined as the very first

usage of a SIM card or a first access after changing the PLMN.

In case of a Location Registration the network needs the IMSI of the MS, because either no TMSI

has been allocated before to the MS (in case of first SIM usage) or it is impossible to regenerate

the IMSI from the TMSI, because the new VLR is not able to get into contact with the old VLR (e.g.

in case of PLMN changes). After Location Registration, in the following Location Updates are used

to update the location information in the PLMN. In a Location Update only the TMSI is transmitted

via Um.

There are three reasons to perform a Location Update Procedure LUP:

Location Update with "IMSI Attach": If a MS is switched on / off, the network is informed about

the change of the current MS state, i.e. whether to be reachable or not. Therefore, when being

switched on / off, the MS performs an "IMSI Attach" / "IMSI Detach" procedure. The information

whether the MS is Attached / Detached is stored in the VLR. If an "IMSI Attach is performed it is

connected with a LUP.

Normal Location Update: Normally a LUP is performed after the MS has recognized that it has

crossed the boarder between two different Location Areas.

The MS is able to recognize the LA change, because it always listens around to the broadcast

information of all cells in its environment, which include the CGI (and so the LAI). If the LAI of the

strongest cell changes, a LUP is performed.

Periodical Location Update: A periodic LUP is initiated by a MS at regular intervals. If the VLR

does not receive the LUP after a certain time, a "Mobile Station not reachable" flag is set.

The LUP is not performed during the duration of a connection. In this case, the LUP is performed

after call release.



Location Update Procedure LUP without change of the MSC area

1. The MS recognizes that the LAI has changed. It requests a LUP, identifying itself with the

TMSI or IMSI. The request and the identity are forwarded to the VLR.

2. The VLR re-identifies the IMSI from the TMSI. If no / no more Triples are available in the

VLR, it requests triples from the AC via the HLR.

3. The AC generates a set of Triples and delivers them via HLR to the VLR.

4. The VLR stores the Triples and initiates the Authentication, then gives the cipher start

command and initiates an IMEI check (optional).

5. If the Authentication, cipher start and IMEI check are successful, the VLR needs for call

setups the subscriber data. In case of a LR, they are have not been stored before in the

VLR and so they have to be requested from the HLR. Together with this request, the VLR

delivers its identity and the information, where this subscriber is stored in the VLR, i.e. the

Local Mobile Subscriber

1. Identity, to the VLR.

6. The HLR stores the VLR identity and LMSI and transmits the requested subscriber data to

the VLR.

7. The VLR stores the subscriber data and assigns a TMSI (LR: mandatory) or a new TMSI

(LUP: only with MSC/VLR change) to the MS. This TMSI is transmitted together with the

VLRs acknowledgement, that the LUP has been successful, to the MS. There, the new

TMSI and LAI are stored on the SIM card.



Figure 6.8. Location Update in Same MSC/VLR

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Mobile Originating Call MOC

1. Channel Request: The MS requests for the allocation of a dedicated signaling channel to

perform the call setup.

2. After allocation of a signaling channel the request for MOC call setup, included the TMSI

(IMSI) and the last LAI, is forwarded to the VLR

3. The VLR requests the AC via HLR for Triples (if necessary).

4. The VLR initiates Authentication, Cipher start, IMEI check (optional) and TMSI Re-

allocation (optional).

5. If all this procedures have been successful, MS sends the Setup information (number of

requested subscriber and detailed service description) to the MSC.

6. The MSC requests the VLR to check from the subscriber data whether the requested

service an number can be handled (or if there are restrictions which do not allow further

proceeding of the call setup)

7. If the VLR indicates that the call should be proceeded, the MSC commands the BSC to

assign a Traffic Channel (i.e. resources for speech data transmission) to the MS

8. The BSC assigns a Traffic Channel TCH to the MS

9. The MSC sets up the connection to requested number (called party).

Remark: This MOC as well as the MTC described in the following describes only the principles

of an MOC / MTC, not the detailed signaling flow.



Figure 6.9. Mobile Originating Call

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6.2. Signaling Component



6.2.1. Function

To control the SS7 signaling system, the Signaling System Network Controller (SSNC) is used in

D900. It provides the protocol functions of the message transfer part (MTP) and parts of the

signaling connection control part (SCCP). The open architecture of the SSNC is based on Solution

O.N.E (optimized network evolution) technology, i.e. message transfer within the SSNC is based

on ATM.

Connection to the CP113 is done via a CP processor, the AMP. The signaling channels are

supplied by means of PCM30/24 via LTGs or directly by the network.

Communication with users in the LTGs is provided directly via high-speed interfaces over the

MBD.

The SSNC has its own OAM platform "Switch Commander". For operation, it is provided with

V24/LAN interfaces for the connection of NM systems.

Thanks to its own OAM platform, the SSNC can also be used as a standalone network element

(i.e. without D900 environment).

This document only describes the functionality of the SSNC as signaling network controller. It does

not describe special signaling interfaces like the signaling on the Iu interface for UMTS or on the

Gb interface for GPRS. These interfaces are discussed in the corresponding UMTS and GPRS

courses.

The SSNC implements the functions of the message transfer part MTP and parts of the SCCP

(SCCP global title translation and SCCP management). This is shown in the following diagram,

using a protocol stack.

Signaling System No.7 is divided into two main parts so that it can be adapted optimally to the

diverse requirements of its various users:

• The message transfer part MTP and the

• User parts UP.

Message Transfer Part The message transfer part (MTP) is used in CCS7 by all user parts as a transport system for

message exchange. Messages to be transferred from one user part to another are given to the

message transfer part which ensures that the messages reach the addressed user part in the

correct order, without information loss, duplication or sequence alteration and without any bit

errors.



Functional levels of the MTP Level 1 defines the physical, electrical and functional characteristics of a signaling data link and

the access units. Level 1 represents the bearer for a signaling link. In a digital network, 64-kbit/s

channels are generally used as signaling data links.

Level 2 defines the functions and procedures for a correct exchange of user messages via a

signaling link. The following tasks must be carried out in level 2:

• delimitation of the signal units by flags and elimination of superfluous flags

• error detection using check bits and error correction by retransmitting signal units

• restoration of fault-free operation, e.g. after disruption of the signaling data link.

Level 3 defines the interworking of the individual signaling links. A distinction is made between the

two following functional areas:

• message routing and message distribution

• signaling network management

In the SSNC these functional levels are mapped on the functional units MP:SLT (signaling link

terminal) and MP:SM (signaling manager). The MP:SLT performs MTP-level 1 (message transfer),

MTP-level 2 (error correction) and MTP-level 3 (message handling incl. allocation). These SLT

functions are logically combined and are performed by one or more MPs. Depending on system

usage of the network node, the SSNC can be provided with up to 47 MP:SLT. Per SLT up to 60

signaling channels (64kbit/s) may be connected, but not more than 1500 links in total!

The MP:SM functional unit supports MTP-Level 3 network management and hosts the routing

database for the signaling network. Thus, each MP:SLT has an internal connection to the MP:SM.

User Parts The function, structure, format and coding of the messages as well as the connection sequences

and the procedures for cooperating with other signaling systems (interworking) are stipulated in

the user parts. The user parts therefore control the setup and release of circuit connections, the

handling of service features as well as administration and maintenance functions for the signaling

channels (SCCP management). The ISDN- and telephone user parts (ISUP/TUP) are located in

the LTGs. The SCCP is located in the SSNC and is the only user part in case the SSNC is

operated as Signaling Relay Point (SRP).




Figure 6.10. Connection Possibilities for SS7 Links to SSNC

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Figure 6.11. SSNC in the System

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The SSNC consists of a number of main processors (MPs) which perform various functions for

processing signaling messages and other tasks. The MPs are connected by an ATM switching

network (ASN) which can link up to 50 MPs based on the same hardware platform. The interface

to signaling links is provided by Line Interface Cards (LICs) shown in the diagram on the following

page.

The SSNC has standard ATM connections (optical fiber) with the D900 components MB and CP,

and 2Mbit/s PCM30 to the LTGs or to other network nodes.

Main Processor MP: The Main Processor (MP) is the central component of the SSNC.

Each MP-function consists of 2 HW-modules MPUC or MPUD (for redundancy reasons).

In general there are 2 types of MP:

1. MP:SA (main processor with standalone capabilities) used as MP:OAM and MP:OAMD. The

MP:OAM performs safeguarding functions, connects the external memories (MDD and MOD) and

the Ethernet interface to the SC.

The optional MP:OAMD also has an external harddisk (but no MOD) and an Ethernet interface.

This processor is responsible for handling charging data.

The MP:OAM is additionally equipped with an ALIB for stand-alone configurations. The ALIB

makes it possible to display the alarm status or generate audible alarms in the rack and via

operator devices. In the opposite direction, events in the environment (e.g. fire, flooding, and door

contacts) can be detected via contact loops and reported centrally to the operator.

2. MP:AP (main processor used for application SW processing)

In the MP:AP different software functions can be performed. The loaded SW is depending of the

application. The following types are usual (but some mixed versions are also existing):

• One MP:SM for all signaling management functions e.g. link testing, LSSUs

• One MP:STATS for SS7 traffic measurement, if used

• MP:SLTs to process the L2 and L3 tasks (Message Transfer Part). Each pair of

MPUCs can handle up to 60 SS7 signaling links (64kbps) or 2 High-Speed-Links

(2 Mbps). If MPUD is used each pair may connect up to 127 SS7 links or 4 HSL.

• MP:GTTs if Global Title Translation is performed (e.g. VLR,HLR,SRP)

• (MP:NP if the number portability feature of the SSNC is used)



Line Interface Card LIC: The Line Interface Card forms the interface between the SSNC units and the SS7 network. It is

made by 2 redundant LIC-cards.

Up to 8 PCM lines can be connected to a pair of LIC modules. The LIC converts the message

stream coming from the SS7 networks from synchronous transfer mode (STM) at 2 Mbit/s to a

stream going to the ASN in asynchronous transfer mode (ATM) at 207 Mbit/s and vice versa.

Additionally, special high speed SS7 link types can be connected. An ATM type and a STM type,

both with 2Mbit/s.

ATM Switching Network (ASN) The ASN is the redundant central element of the internal transport system in the SSNC. It provides

the connections between all the processors and equipment in the SSNC. The ATM Switching

Network (ASN) function itself consists of two different ATM Multiplexers/Demultiplexers (AMXE

and GMX) and the ATM Switching Module for ASN40 (ASMG16/16 or 8/8).

The AMX consists of an ATM multiplexer AMXE and ASN controller and clock generator (ACCG).

The AMXE is used as a concentration level to the ASN. To connect the SSNC units to the ASN,

each AMXE provides 32 ports each with 207 Mb/s. The ACCG monitors the AMXE and supports

the clock generator.

The ASMG16/16 is required for the switching network ASN40 (40Gbit/s).

Alternatively the ASMG8/8 can be used for a smaller switching network size ASN20 (20 Gbit/s).

Depending of the ASMG module 8 or 16 GMXE modules can be connected, each with 32 port for

AMX connection.



Figure 6.12. ASN Parts

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Frame and rack layout The SSNC has 4 different shelf-types (HW-frames)

1. SCB: Basic Shelf

2. SCE: Extension Shelf

3. ASN: ATM Switching Network or ASN(H)

4. SXCB: For MP:OAMD (Charging Processor)

SCB The Basic Shelf contains the minimum HW needed for SSNC-operation:

The MP: OAM (MP:SA) with SC-connection, the external memories (MDDs, MODs), the MP:SM,

one pair of LICs and the AMXEs/ACCGs for supervision, synchronization and ASN connection

(both sides). With some modifications (e.g. no MOD is used), this shelf type can be used for a

MP:OAMD too.

SCE Up to 7 SCE shelves in max. 3 racks can be used, depending on how many MPs/LICs are used. It

contains a maximum of 8 MP- or LIC-pairs and the AMXEs/ACCGs for supervision,

synchronization and ASN connection (both sides).

ASN Contains the HW-modules for the ATM switching network.

Two different versions are existing:

• ASN 0/1 also called ASN(40) or ASN(E) where the different sides of the ASN are in 2

different shelves or

• ASN(H) also called ASN(20) or "compact ASN" where both ASN-sides are in the same

shelf. Due to this a second SCE is possible in the rack. Another type of ASMG may be

used.

SXCB The F:SXCB can be used for the MP:OAMD for charging purposes only and is located on MUT07

of the basic rack, or on MUT09 of an extension rack. It is not allowed to install the F:SXCB for the

MP-OAMD on any other position.

An Extension Rack is not shown in the following pictures. It is only used for SCE or

SXCB shelf types.



Figure 6.13. ASN40 Rack

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Figure 6.14. ASN20 Rack

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