nomi report

INTERNSHIP REPORT

SUBMITTED BY: MUHAMMAD HASEEB

STUDENT OF: BS (ELECTRONICS)

MUHAMMAD ALI JINNAH UNIVERSITYISLAMABAD

MUHAMMAD ALI JINNAH UNIVERSITY ISLAMABAD 0

Introduction to PTCL Network

SWITCHING NETWORK: Since the invention of the telephone, circuit switching has been the dominant technology for

voice communications, and it will remain so well into the ISDN era.

Local loop for switching network For transmission of data beyond a local area communication is typically achieved by

transmitting data from source to destination through a network of intermediate switching nodes. This switching networks design is sometimes used to implement LANs and MANs as well. Local loop connects Exchange and subscriber

Local loop types Copper wire loop

Optical Fiber Access Network (OFAN) Wireless local loop (WLL)

Copper wire local loopSubscriber is connected to exchange through copper cable. Copper loop is divided into three portions

Primary cable Secondary cable Drop wire

Local loop elements Telephone set or modem Drop wire Distribution point (DP) Secondary cable Cabinet Primary cable MDF

OFAN

It is a mixture of copper and optical fiber cable. The primary cable and MDF is replaced by OF cable. Access part of switch is shifted to the locality and connected to the switch vide OF cable and it is called ONU. Different ONU’S are connected to OLT and OLT is connected to switch. Star , ring and mesh topologies can be used for ONU network. V5.2 protocol is used which allows different vendors to interconnect their hardware and make it operational.


Wireless local loop

There is no fixed line Subscriber is connected to the switching office through radio interface. Different access techniques like CDMA, GSM, and Microwave can be used for WLL. No need to burry tons of copper wire just buys a bandwidth and deploy network. Minimum fault ratio. Mobility of subscriber can be controlled by not providing roaming facility and low radiation power of BTS. Economical compared to fixed line loop.

Why CDMA for WLL

More capacity for a fixed Bandwidth compared to GSM or AMPS. CDMA provides 4~6 times more capacity then GSM and 15 times more capacity to AMPS. More secure technique as it is very difficult to intercept... Large coverage area for example to cover 1000 sq km GSM requires 200 BTS sites whereas CDMA requires only 50 BTS sites. Less power resources required compared to other techniques.


Average transmitted power of GSM mobile phone is 2mW with a maximum transmitted power of 125mW BUT CDMA’s average transmitted power is 2 mW with a maximum transmitted power of 200 Mw.

Local Exchange Analogue Subscribers are connected through local loop. (Commercial and ordinary)Data lines are connected. ISDN lines (Digital subscribers and data lines)

DSB’S PABX’S End nodes

Functions of Local Exchange ACCESS CONCENTRATION BORSCHT DATA BASE (SCP) ROUTING SWITCHING(SSP) CHARGING SIGNALING Subscriber administration

BORSCHT B~ Battery O~Over voltage protection R~Ringing S~Supervision C~Coding H~Hybrid T~Testing

Access Part Subscribers are terminated. Subscribers are provided with BORSCHT. Subscribers are

concentrated. Analogue signals are converted to digital using PCM. Digital lines are also connected to access part.

Data Base (SCP) Consists routing data. Subscriber’s data authentication and facilities. Charging data. System

files (call records, exchange events and many other files data).

Routing Administration LE receives and evaluates digits and sends it to a particular direction. For example if someone dials a number 03331234567. He is directed to Ufone MSC via Transit exchange. Alternate routes are also provided in data base so that in case of failure of any route or congestion another route is available. Every route consists of trunks and hence called Trunk Groups.

Switching (SSP)


SwitchingAccess

DLU

DLUC

LTG

GP

LTGGP

Common ChannelSignaling

CCNCCCNP

Coordination

E M

SYP

SYPC

M B

MBCO M T

C C G

CP

S N 0

S N 1

S G C

S D C

S D C

S D C

S D C

Distributed controls in an EWSD exchange

- Digital Line Unit (DLU)

- Line Trunk Group (LTG)

- Switching Network (SN)

- Common Channel

Network Control (CCNC)

- Coordination Processor

(CP)

EWSD SUBSY STEMS

G C

SwitchingAccess

DLU

DLUC

LTG

GP

LTGGP

Common ChannelSignaling

CCNCCCNP

Coordination

E M

SYP

SYPC

M B

MBCO M T

C C G

CP

S N 0

S N 1

S G C

S D C

S D C

S D C

S D C

Distributed controls in an EWSD exchange

- Digital Line Unit (DLU)

- Line Trunk Group (LTG)

- Switching Network (SN)

- Common Channel

Network Control (CCNC)

- Coordination Processor

(CP)

EWSD SUBSY STEMS

G C

The actual matrix that provides cross connections is duplicated for redundancy purpose. Time and space switching are used in switching matrix.Since the processing workload is distributed over several microprocessors within the EWSD system, a common processor for Coordination tasks is extremely useful. These functions are handled by the Coordination Processor (CP).

The CP consists of the: Coordination Processor (CP) External Memory (EM) Operation and Maintenance Terminal (OMT) System Panel (SYP) Message Buffer (MB) Central Clock Generator (CCG)

Load DistributionIn order to reduce the workload of the Coordination Processor (CP) and to achieve faster

processing times, some processing functions are distributed over autonomous control devices.Since the EWSD subsystems independently execute all necessary tasks within their respective areas, they require their own control devices,

Such as the: DLU • Digital Line Unit Controller (DLUC) LTG • Group Processors (GP) SN • Switch Group Control (SGC) SYP • System Panel Control (SYPC) MB • Message Buffer Control (MBC) CCNC • Common Channel Network Processor (CCNP)


Digital Line Unit (DLU) Overview:DLU is responsible for terminating subscriber lines and concentrating subscriber line

traffic. Function of DLU UnitsSubscriber Line Module Analogue (SLMA)Every Subscriber Line Module Analogue (SLMA) has eight Subscriber Line Circuit Analogue (SLCA) which are controlled by a processor Subscriber Line Module Processor (SLMCP).

The Subscriber Line Module, Analogue provides:BORSCHT summarises the general tasks of subscriber line modules.

Battery Supply Over voltage Protection Ringing Signalling Coding Hybrid 2/4-Wire Testing

The Digital Interface Unit for the DLU (DIUD):

Receives and transmits speech information from and to the SLMs and distributes this information.

Extracts control information for the DLUC from the PDC that links the DLU to the LTGB.

uses signals from the PDC for pulse synchronisation

DLU Control (DLUC) The DLUC controls the DLU internal sequences of operation and distributes or concentrates

control signals between subscriber line circuits and the DLUC.

Test Unit (TU)

The Test Units test the following: analogue and digital subscriber lines, Subscriber line circuits Telephone Set of Analogue Subscriber.

Emergency Service

Even if all outgoing PDC links of a Remote DLU fails, it is still possible to establish calls between subscribers served by the same DLU. This is called Emergency Service.The DLU emergency operation is made possible through a combination of EMSP emergency units and specialized software modules.


Line/Trunk Group (LTG)

The Line/Trunk Groups (LTGs) are the interfaces between the digital Switching Network and the network environment of the exchange, which may be analogue or digital. For reasons of safety a LTG is always connected to both Switching Network (SN) plane. If the link between the LTG and the Switching Network, or even one plane of the Switching Network fails, call processing will continue without interruption.

LTG TYPES:

Line/Trunk Group (LTGA) Line/Trunk Group (LTGB) Line/Trunk Group (LTGC) Line/Trunk Group (LTGD)

Main Functional Units of LTG:

up to 8 line/Trunk Units (LTUs) signalling Unit (SU) Speech Multiplexer (SPMX) or Group Switch (GS) Link Interface Unit between LTG and Switching

The Line/Trunk Units (LTUs) can be connected to: Digital Line Units (DLUs) Other exchanges. Digital Switchboards (DSBs)An LTGB can interface 60 Digital Switchboards (DSBs) via digital access lines.

The SU is equipped with code receivers (CR) &Tone Generator (TOG) for generating audible tones

The SPMX is used if the LTG interfaces with trunk lines. The Group Switch (GS) is used if the LTG interfaces with subscriber lines. The GS also handles the 3 party conference calls. SPMX/GS is also multiplexed 4x2 Mbit/sec into 8 Mbit/sec and vice versa.

The Link Interface Unit (LIU) is the interface between the LTG and the Switching Network (SN). It:

duplicates the channels to both SN planes (SN0 and SN1).The Group Processor (GP) is an independent periphery controller.

GP functions are: controlling all functional units in the LTG exchange data with the Coordination Processor (CP) And other LTGs, self-diagnosis and safeguarding


Line/Trunk Group C & DAs the LTGC is used to terminate inter-office trunks while LTGD is used in International Gateway exchange. Switching Network (SN)The actual switching process that establishing a call connection between two subscribers takes place in the hardware subsystem called switching Network (SN). SN OverviewFor safeguarding reasons, the Switching Network (SN) is always duplicated.The External interface of the Switching Network is the same. They are Secondary Digital Carriers (SDCs) its data rate is 8 Mbit/s. SwitchingSN consists of Time Stages and Space Stages.A time stage consists of Time Stage Module (TSM) and space stage consist of Space Stage Module (SSM).Each stage consists of its own controller Switch Group Control (SGC)

Co-ordination Tasks In addition to the Co-ordination Processor (CP) with its External Memory (EM) and the Operation and Maintenance Terminal (OMT), the “Co-ordination” subsystem includes the following functional units:

the Message Buffer (MB) with its micro processor control (MBC), the central Clock Generator (CCG) the System Panel (SYP) with its micro processor control (SYPC)


SWITCHING NETWORK

A Sub.

B Sub.

T TS or SSS

The main components of a SN are :

Time Stages

In time stages octets to be switched change time slot and highway according to their destination

Space Stages

In space stages they change highway without changing time slots

Switch Group Control (SGC)

Connection paths through the time & space stages are switched by the SGC in accordance with the switching information from the CP.

SWITCHING NETWORK

A Sub.

B Sub.

T TS or SSS

The main components of a SN are :

Time Stages

In time stages octets to be switched change time slot and highway according to their destination

Space Stages

In space stages they change highway without changing time slots

Switch Group Control (SGC)

Connection paths through the time & space stages are switched by the SGC in accordance with the switching information from the CP.

CP MAIN FUNCTIONS: The CP performs the following functions

Call Processing Operation & MaintenanceSafeguarding

The Message Buffer (MB) serves as an interface adapter and transmission adapter for the internal information exchange between:· CP · SN · LTGs

OPERATION AND MAINTENANCE OF THE SYSTEM.

Operational Task Subscriber administration Routing administration Traffic administration Tariff and charging administration System administration

Maintenance Maintenance of subscriber lines Maintenance of inter-exchange trunks Hardware maintenance Software maintenance

Operator Guide Line (OGL)

Application and Organization

MUHAMMAD ALI JINNAH UNIVERSITY ISLAMABAD

Line/trunk Groups LTG Line/trunk Groups LTG Switching Network SN

Switching Network SN

Maintenance Alarm

Service Alarm

External equipmentCoordination Processor CPCoordination Processor CP

Processor Load

Central Units

Clock

Message buffer

Common Channel Signaling

Month Day

–Time

:

Entry Supervision

Fire

DC Powersupply

Power failure

Aircon-ditioning

External alarms

System PanelSYP

System PanelSYP

Update Test Accept

Trunk GroupalarmLine LockoutSignaling LinesCall Identification

Trunk GroupblockedCat. 1

Cat. 2

System Operator

External DLU AlarmsAdministrativeAlarmRecovery

Time Insecure

HW unitsSignalinglinks blockedAlarm indications suppressed

ERL

8

Communication between operating personnel and the EWSD system is made possible by the man-machine language (MML).The MML consists of:

The input language (commands) The output language (responses to inputs and alarms) The commands are entered in a man-machine dialog (Fig.1.1).

There are two versions of MML: The basic MML (BMML.) The extended MML (EMML)

Input LanguageThe input language describes the structure and meanings of the MML commands.

Basic Structure of the MML CommandsA command consists of the command code and a number of command parameters (fig.1.1). The command code indicates the action and the object on which the action is performed. The command parameters contain the additional information required in order to execute the relevant command.

For example: DISP SUB: LAC = 0995, DN = 77332;DISPSUB DISPLAY subscriber dataLAC=0995 local area code 0995DN = 77332 directory number 77332

Explanation of the MML Syntax Command:Each command starts with the command code. The parameters are separated from the command code by a “ : ” (Colon) the end of the commands indicated by a “ ; ” (semicolon). A command may contain a maximum of 256 characters (blanks are not counted as character).

Command CodeThe command code comprises the action and the object. They may be separated by a blank. ParameterA parameter consists of the parameter name and its value. These two are separated by an “= “(equal sign). Parameters are separated from each other by a “,” (comma).

Parameter ValueThe Parameter value comprises one or more parameter arguments. A number of MML commands which differ only in the information units for a parameter argument can be combined to form a single command in which the various arguments are linked by “&” (ampersand) characters.

For example:DISP SUB: DN = 77332 & 77312;

(display subscriber data for directory numbers 77332 and 77312). If a parameter argument consists of a number, the commands for an entire range can be combined by linking the upper and lower values in the range by “&&” (double ampersand). For example:DISP SUB: DN = 77332&&77335; (display subscriber data for directory numbers 77332, 77333, 77334, and 77335).For compound numerical parameter arguments, the ranges for the last information units can be formed in the same way.

For example:DISP LTG: LTG=0-5 && 0-7; (Display data for the line/trunk groups with the numbers


0-5, 0-6 and 0-7DISP LTG: LTG=0-4&0-6; (Display data for the line/trunk groups with the numbers 0-4 and 0-6).

Parameter ArgumentsThere are three types of parameter argument: simple, compound and new/old. Simple parameter arguments comprise a single information unit, whereas compound parameter arguments consist of two to four information unit linked by a “-” (hyphen). For example:EQN = 1-5-3-8... (Equipment number = TSG number 1, LTG number 5, LTU number 3, channel number 8).New/old parameter arguments consists of two parameter arguments separated by a “/”. Atypical use is in modifying commands to indicate which new parameter value is to replace an old value.For example:MOD TAR: ... RATE = F1-25000/F1-20000...., (modify tariff F1 from 20s per charge unit to 25s).

Information Unit

Information units can be predefined character strings symbolic names, numbers or text strings.

SUBSCRIBER ADMINISTRATION Subscriber’s Facilities in Digital Exchanges (EWSD)

The subscriber who wants to have any of the following facilities, special push button (DTMF) telephone set will be provided to him. These facilities are provided on demand. Amount of Rs. 25/- per month is charged for each facility and amount of Rs. 100/- per month for the package of all facilities & Rs: 30 for CLI per month.

1. SECRET CODE DIALING (CODE BARING FACILITY)The STD subscriber having this facility is able to allow and prevent outgoing calls from his telephone set i.e. the STD subscriber can convert his telephone to Non-STD and vice versa.Procedure

*33* Key Word* 01# Block STD*33* Key Word* 02# Allow STD*33* Key Word* 04# All Block (eg Booking, local mobile, STD etc)(“Key Word” is the key word of four digits with any possible combination.)

MODSUB: LAC=0995, DN = 77332, TRARSTR = TRACLACT&TRACLMOD;ENTRKEYWORD: LAC=0995, DN=77332, KEY =1234, SECURE=Y;

2. CODE MODIFICATION:In addition to code baring facility the subscriber is allowed to modify his “key Word” from his own telephone set.Procedure:

*99* old code* New code #

3. ABBREVIATED DIALINGA subscriber can dial a code instead of dialing the complete telephone number. Maximum ten telephone numbers can be recorded (Codes 0 to 9). Code number is a digit (0,1,2....9) For


making a call to the required telephone number. In case, a subscriber wishes to modify a code, first he will deactivate the old code and then enter the new code.Procedure:

Activation: *51* Code Number *B-Telephone number #Deactivation: # 51*Code number #

To dial: ** Code number e.g. **1MODSUB: LAC=0995, DN = 77332, ABB=ABBD10&ABNMOD1; (For 10 numbers)

4. DO NOT DISTURBSAn announcement will be made to all those subscribers who make calls to the subscribers having this facility.Procedure:

Activation: *26# Deactivation: # 26#

MODSUB: LAC=0995, DN = 77332, DIV=DIVND;5. CALL WAITINGA subscriber “A” having this facility when in conversation with another subscriber “B” is informed of an incoming call from a third subscriber “C” by a peptone. He can then:Refuse the call from subscriber “C” by ignoring the peptones. After one minute busy tone will be sent to subscriber “C”.Accept the call by pressing the cradle switch once to receive the dial tone. Then he Dials digit “2” to be connected to subscriber “C” and hold Subscriber “B”.Return to subscriber “B” by pressing the cradle switch one again to receive the dial tone. Then he dials digit “2” to be connected to subscriber “B”.

Activation: *43# Deactivation: # 43#

MODSUB: LAC=0995, DN = 77332, COS=CWACT&ACTCW ;6 CALL DIVERSION ON IMMEDIATEA subscriber having this facility can transfer his all-incoming calls immediate to a pre-recorded number; the number may be of another exchange also.

Procedure:For Activation: *21* 77332# For Deactivation: # 21#

MODSUB: LAC=0995, DN = 50001, DIV=DIVI & DIVI MOD;

NOTE: DIVIMOD EXTEND THE AUTHORISATION TO THE SUB.Subscriber input,For Activation: *21* 77332For Deactivation #21#

7 CALL DIVERSION ON DON’T ANSWERFor Activation: *06* 77332# For Deactivation: # 06#

MODSUB: LAC=0995, DN = 77332, DIV=DIVDA & DIVDA MOD;

NOTE: DIVIMOD EXTEND THE AUTHORISATION TO THE SUB

8 CALL DIVERSION ON BUSY LINE


For Activation: *09* 77332# For Deactivation: # 09#

MODSUB: LAC=0995, DN = 77332, DIV=DIVBY & DIVBY MOD;

NOTE: DIVBYMOD EXTEND THE AUTHORISATION TO THE SUB

9. CONFERENCE FACILITY

This is an exchange-controlled facility. With the help of this facility a subscriber with a call in progress may use his telephone to ring a third party to set up 3 party conference call.

Procedure:If a subscriber “A” talking with subscriber “B” wishes to include subscriber “C” he presses the cradle switch once to get dial tone and dials subscriber “C” number. The call is set up from subscriber “A” to subscriber “C” and the subscriber “B” is placed on hold position.If subscriber “A” wishes to talk with subscriber “B” again he presses the Cradle switch to get dial tone and dials digit”2”, Call “A-B” is set up and “C” is placed on hold position. If “A” desires again to talk with “C” he will get dial tone by pressing his cradle switch again and will dial digit “2”. Call “A-C” is set up and “B” is placed on hold position.To make a three party conference call. Subscriber “A” dials “B” subscriber’s number to set up a call “A-B”. Then “A” will press his cradle switch, after getting dial tone he will dial “C” subscriber’s number to establish a call “A-C”. After that subscriber “A” will press his cradle switch once again to get dial tone and will dial digit “3” to establish 3 party conference call together.

MODSUB: LAC=0995, DN = 77332, COS=CONF3;

10. DELAY HOT LINE

A subscriber having this facility can make a call with a pre-recorded number without dialing the # number. When a subscriber lifts his hand set after delay of 10 seconds he is connected to a pre-recorded number.

Procedure: Activation: *53* B-Number # Deactivation: # 53#

MODSUB: LAC=0995, DN = 77332, COSDAT=HOTLDEL- 77311 & DNHLMOD;

11. WAKE UPThis is an exchange-controlled facility. Subscriber having a special telephone (DTMF) set is able to activate makes up function. Wake up time is a four-digit number i.e. 0830, 0900....2330 etc. There are two types of wake-up facility.

Wake-up for casual time:Procedure: Activation: *55* wake up time #

Deactivation: # 55#Wake-up for up to 99 days.


Procedure: Activation: *56* wake up time *99# Deactivation: # 56* wake up time #

12. CALLER LINE IDENTIFICATION: (CLI)

MODSUB: LAC=0995,DN=77332,COS=CLIP & FSK;

Standard Command Action: A c t i o n M e a n i n gDisplay (DISP)

DISP display the specified in a command for the relevant command object in edited form (generally table or matrix form). If selected data are to be displayed the SEL (semi permanent data) or SRCH (transient data) commands should be used instead of DISPExample: DISP SUB: DN = 12134;

Status (STAT)

STAT displays the operating states of the specified object in edited form.Example: STAT TRUNK:TGNO=BHRP;

Create (CR)

CR (opposite: CAN) creates a memory map of an object either to unknown to the system. Additional associated data can then be incorporated with ENTR.Example: CR SUB:DN=77332, CAT=MS,EQN=10-0-0-0;

Modify (MOD)

MOD modifies the semi permanent data for an existing or creates a new entry for the object specified in the command.Example: MOD CPT: CODE-089, DEST=BHRP;

Activate(ACT)

ACT activities an existing object or system functionExample: ACT OUTSUP;

Configure (CONF) CONF modifies the operating state of the specified object. For this to be done it must be possible to configure the object and the state transition must be allowedExample; CONF SN: SN=1, OST = MBL;

Diagnose (DIAG) DIAG is used to test the specified object for possible errors. For this to be done the object must be MBL.Example DIAG MB: MB=0, TA=ALL;

Deactivate (DACT) DACT deactivates object or system function previously activated. However, it does not cancel the object.Example DACT OUTSUP: LOCDEV=SYSTEMDEVICE=FUOMT;

Cancel (CAN)

CAN cancels the existing semi permanent entry designated by the command object.Example: CANSUB: DN = 1234, INCEPT = CHANGEDN;

Introduction to Digital Switching System EWSD (Electronic Switching System Digital)

Siemens manufactures the EWSD equipment installed in the PTCL exchanges. This technology was introduced in Pakistan for the first time in 1989. Its maiden installation was in Haripur Training School and then in the PTCL Complex Satellite Town Branch, Rawalpindi.


Components of the EWSD The primary components of the EWSD are listed as under:

1. Access Center DLU (Digital Line Unit) LTG (Line Trunk Group) TE (Test Equipment)

2. Switching Center Switching Network

3. Control Center CCG (Central Clock Generator) CP (Coordination Processor) SYP (System Panel) MB (Message Buffer)

4. Signaling CCNC (Common Channel Network Controller) CCS7

5. Power Supply Introduction to PTCL WLL (Wireless Local Loop):

PTCL Wireless is a WLL (Wireless Local Loop) operator operating in the major cities and also in some remote areas of Pakistan via the CDMA Technology. The MSC (Mobile Switching Centre) and HLR (Home Location Register) equipment is manufactured and installed by HUAWEI, which is a Chinese company, while the BSC (Base Station Controller) and BTS (Base Transceiver Station) equipment is manufactured and installed by ZTE.

Components of the MSC The MSC (Mobile Switching Centre) is composed of two major components namely

Media Gateway (UMG8900) Soft Switch (CSOFTX3000)

MEDIA GATEWAY UMG8900 The Media Gateway is further subdivided into

Trunk Gateway Signalling Gateway


Trunk Gateway: The Trunk Gateway (TG) section provides interface to the Copper Cable in the form of E1’s,

optical fiber in the form of STM, Fast Ethernet (FE) and Gigabit Ethernet (GE). The computer snapshot of a shelf, which provides the TG functionality, is shown below:

All E1’s coming from any side (such as BSC or any other network) is terminated in the Media Gateway on the ME32 card. One ME32 card provides interface for 32 E1’s. BSC and MSC are interconnected to each other with copper cables. MS2L card provides interface to the optical fiber cable. One MS2L card provides 2STM -1 interface. The Media Gateway IP based data goes into the Soft Switch via the MNET Card. MG10 Card provides GIGA BIT interface.

Signaling Gateway: The Signaling Gateway (SG) section provides signal processing, signaling conversion and interacts with the Soft Switch. H 248 Protocol is used between Media Gateway and the Soft switch. The computer snapshot of a shelf, which provides the SG functionality, is


shown below: All signaling information goes into the MSPF Card. It processes the signaling and using SIGTRAN, converts the circuit switch based signaling into IP based Signaling. One MSPF converts 16 MTP-2 links into 4 M2UA links. Then this IP based data goes into the SOFT SWITCH through the MNET card. MOMU card provides the operation and maintenance of the Media Gateway. It gathers all alarms in the Media Gateway and through a LAN switch network; these alarms are displayed on the 3 or 4 interconnected LMT’s (Local Maintenance Terminal).

SOFT SWITCH CSOFTX3000 The Soft Switch is considered as the brain of the Mobile Switching Center (MSC). It is

purely IP based. It receives signaling data in IP form from the Media Gateway. Only the signaling data goes into the Soft Switch. The main cards used in Soft Switch are shown below:


The IP packets from the Media Gateway first come to the WIFM card in the Soft Switch and then go to the WBSG card. The WBSG card decides which IP Based Signaling data should go on which card. Normally it goes into the WCCU card. WVDB is a VLR (Visitor Location Register) based card.

All the shelves in the Soft Switch communicate with each other via the LAN switch. WCCU is the most vital card in the Soft Switch. It is responsible for providing and maintaining the call between different users. BAM (Back Administration Module) is also present in Soft Switch rack. All the alarms of the Soft Switch are stored in BAM, which are then displayed on the LMT’s connected to the BAM via a LAN switch. IGWB (Gateway Billing Server) present in the Soft Switch rack is used for Pre-Paid and Post paid Billing.

Coding Techniques used in CDMA

WLL uses Code Division Multiple Access (CDMA) as a medium of access control. The advantage of CDMA is that all users share same bandwidth at the same time by using different codes.Three different types of codes are used which are listed as under:

Long PN Codes Short PN Codes Walsh Codes

LONG PN CODES: These codes are used on reverse channels from MS (Mobile Station) to BTS (Base Transceiver

Station) and distinguish each user separately.

SHORT PN CODES :These codes are used to determine each sector of a cell. There are two short PN sequences I

and Q and each of these is 32,768 chips long.

WALSH CODES : These codes are used on a forward channel from BTS (Base Transceiver Station) to MS (Mobile Station). Total 64 different Walsh codes are present. Each code is 64 chips (bits) long and each code is orthogonal to each other. A chip is a binary digit having a value of either a ‘1’ or a ‘0’. MS and BTS are connected via the air Interface. BTS connects to the BSC through cooper cables or air interface. BSC connects to the MSC via copper cables. BSC racks are interconnecting with each other through optical fiber cables. Voice and signaling data both reach on MG but only signaling data goes into the Soft Switch Internet.

Router is a device, which decides that on which output line an incoming packet data is to be transmitted. So the router routes the data towards packet data switch network (PDSN). Router and PDSN are connected with each other through optical fiber cables. In BSC, Packet Data Control Function (PCF) card is used for handling the Internet data.

Advantages of CDMA : There are numerous factors of using the CDMA technique some of which are listed below:

Frequency re-use Factor High Privacy


High Spectrum Capacity Large Coverage Area Soft Handoff Power Control Good Voice Quality

INTERFACES USED IN THE NETWORK:

Source/Destination Interface MS to BTS Um Interface BTS to BSC Abis Interface BSC to MSC A1, A2 interface MSC to PSTN Ai Interface MSC to PSTN Di Interface MSC to ISDN B Interface MSC to VLR C Interface MSC to HLR D Interface HLR to VLR E Interface MSC to EIR F interface BSC to BSC T1 Interface BSC to PDSN A3, A7 Interface PDSN to AAA Server A10, A11 Interface

ABBREVIATIONS:

MS Mobile Subscriber or Mobile Station BTS Base Transceiver Station BSC Base Station Controller BSS Base Station sub system MSC Mobile Switching Center PDSN Packet Data Switch Network HLR Home Location Register VLR Visitor Location Register PSTN Public Switched Telephone Network ISDN Integrated Service Digital Network PN Pseudo Noise CDMA Code Division Multiple Access TRX Transceiver HPA High Power Amplifier PWS Power Subsystem LAN Local Area Network AAA Authorizing, Authentication, Accounting


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