operation and maintenance center

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Operation and maintenance Center (OMC)

The OMC provides the network operator with network operation andmaintenance services,

manages the subscriber information and implementsnetwork planning, to enhance the overall

working efficiency and servicequality of the system. There two type of operation and

maintenance centers:OMC-S and OMC-R. An OMC-S is mainly used for the maintenance work

atthe mobile switching subsystem (MSS) side; an OMC-R is mainly used for themaintenancework at the base station subsystem (BSS) side.

~ 46 ~Home location register (HLR)

The HLR provides subscriber information storage and management functionsfor the mobile

network, including mobile subscriber subscription andcancellation and service authorization and

cancellation. At the same time, it

helps in the implementation of subscribers call and service operations. A

CDMA can contain one or more HLRs based on the number of subscribers,equipment capacity

and network organization mode, with multi-HLR moderealized in the form of virtual HLRs. Thesubscriber information stored in theHLR includes the following two types in information:1.

Subscription information2. Subscriber-related information stored in the HLR\

Pakistan Telecommunication Company Limited (PTCL) is the largesttelecommunication company inPakistan. This company provides telephony services tothe nation and still holds the status of backbone for country's telecommunicationinfrastructure despite arrival of a dozen other telcos including telecom giants likeTelenor and China Mobile . The company consists of around 2000 telephone

exchanges across country providing largest fixed line network. GSM, CDMA,Broadband Internet, IPTV, wholesale data and backbone services are other majorresources of PTCL, making it a gigantic organization.

.

Mobile services switching center (MSC)

The MSC performs the telephonyswitching functions of the system. It controls calls to and from

other telephone anddata systems. It also performs such functions as toll ticketing, network

interfacing,common channel signaling, and others

BTS

The BTS handles the radio interface to the mobile station. The BTS isthe radio equipment

(transceivers and antennas) needed to service each cell inthe network. A group of BTSs are

controlled by a BSC.
http://en.wikipedia.org/wiki/Pakistanhttp://en.wikipedia.org/wiki/Pakistanhttp://en.wikipedia.org/wiki/Pakistanhttp://en.wikipedia.org/wiki/Pakistan


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The Switching System

The switching system (SS) is responsible for performing call processing andsubscriber-related

functions. The switching system includes the following functionalunits.

Home location registers (HLR)The HLR is a database used for storage andmanagement of subscriptions. The HLR is considered

the most important database, asit stores permanent data about subscribers, including a

subscriber's service profile

~ 51 ~location information, and activity status. When an individual buys a subscription fromone of the

PCS operators, he or she is registered in the HLR of that operator

.

Mobile services switching center (MSC)

The MSC performs the telephonyswitching functions of the system. It controls calls to and from

other telephone anddata systems. It also performs such functions as toll ticketing, network

interfacing,common channel signaling, and others.

Visitor location registers (VLR)

The VLR is a database that contains temporaryinformation about subscribers that is needed by

the MSC in order to service visitingsubscribers. The VLR is always integrated with the MSC.

When a mobile stationroams into a new MSC area, the VLR connected to that MSC will request

data aboutthe mobile station from the HLR. Later, if the mobile station makes a call, the

VLRwill have the information needed for call setup without having to interrogate the HLReach

time.

Authentication center (AUC)

A unit called the AUC provides authentication andencryption parameters that verify the user's

identity and ensure the confidentiality of each call. The AUC protects network operators from

different types of fraud found intoday's cellular world.

equipment identity register (EIR)

The EIR is a database that contains informationabout the identity of mobile equipment that

prevents calls from stolen, unauthorized,or defective mobile stations. The AUC and EIR are

implemented as stand-alone nodesor as a combined AUC/EIR node.

The Base Station System (BSS)

All radio-related functions are performed in the BSS, which consists of base stationcontrollers

(BSCs) and the base transceiver stations (BTSs).

BSC


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The BSC provides all the control functions and physical links betweenthe MSC and BTS. It is a

high-capacity switch that provides functions such ashandover, cell configuration data, and

control of radio frequency (RF) powerlevels in base transceiver stations. A number of BSCs are

served by an MSC

MAKING A TELEOHONE CALL

A telephone call starts when the caller lifts the handsets of the base. Once the dial tone is

heard, the caller uses a rotary or a push button dial mounted either on the handset or on the

base to enter a sequence of digits, the telephone number of called party. The switching

equipment from the exchange removes the dial tone from the line after the first digit is received

and after receiving the last digit, determines the called party is in the same exchange or a

different ones. If the called is in the same exchange, burst of ringing current is applied to the

called partys line. Each telephone contains a ringer that responds to specific electric

frequency. When the called party answers the telephone by pocking up the handset, steady start

to flow in the called partys line and is detected by the exchange. The exchange than stops

applying ringing and sets up the connection between the caller and the called party. If the

called party is in different exchange from the caller, the caller exchange set up the connection

over the telephone network to the called partys exchange. The called party then handles the

process of ringing, detecting an answer, and notifying the calling and billing machinery when

the call is completed. When conversation is over, one or both parties hang up by replacing their

handset on the base, stopping the flow of current. The exchange when initiates the process of

taking down the connection, including notifying billing equipment of the duration of the call if

appropriate

ABOUT A TELEPHONE EXCHANGE

All telephone subscribers are served by automatic exchanges, which perform the functions

the human operator. The number being dialed is stored and then passed to the exchanges

central computer, which in turns operates the switching to complete the call or routes it a

higher level switch for further processing. Todays automatic exchanges uses a pair of

computers, one running the program that provides services and the second monitoring the

operation of the first, ready to take over in a few seconds in the event of equipment failure.

operation and maintenance center

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