GSM : GLOBAL SYSTEM FOR MOBILE COMMUNICATION

  GSM

         It is a set of recommendations and specification for a digital cellular telephone network.

         A GSM Network comprises of many function units.

• MOBILE STATION:- The Mobile station consists of physical equipment such as SIM card, Display and digital signal processor, Radio transceiver.It provides.

              1. Teleservices

              2. Data bearer services

              3. Air interface to the user

              4. The features' supplementary services

The MS also provides receptor for SMS messages, enabling the user to toggle between voice and user data.The mobile system facilitates access to voice messaging system. The MS also provides access to the various data service available in a GSM network.

* GSM system provides a greater subscriber capacity than analogue system, 

* GSM system allows 25KHz per user

SIM

 SIM(SUBSCRIBER IDENTIFICATION MODULE) :- By making a distinction between the subscriber identity and the mobile equipment identity, a GSM PLMN can route calls and perform billing based on the identity of the subscriber rather than the mobile equipment being used. This can be done using a removable Subscriber Information Module (SIM). A ”smart card” is one possible implementation of a SIM module

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MSISDN:-MSISDN means "mobile subscriber integrated services digital network". It is the telephone no of the MS. This is the no a calling party dials to reach the subscriber.It is used by the land network to route calls towards the MSC.

              MSISDN= CC+NDC+SN

CC-Country code (e.g for india , country code is 91)

NDC-National destination code

SN-Subscriber number

IMSI:- IMSI means "International mobile subscriber identity". It is a no that network identify unique to a SIM.It is the primary identity of the permenantly assigned to that subscriber.

               IMSI=MCC+MNC+MSIN

MCC-Mobile country code  (e.g for india, mobile country code is 404)

MNC-Mobile network code (it is a two digital code)

MSIN-Mobile subscriber identity number ( it is a ten digital code)

IMEI:- IMEI means "International mobile equipment identity".It is serial number unique to each mobile.This no  is permanently stored in the mobile equipment.IMEI can be used to identify MS, that are reported stolen or operating incorrectly.

           IMEI=TAC+FAC+SNR+SP

TAC-Type approval code (it is six digit code)

FAC-Final assembly code(it is two digit code)

SNR- Serial no( it is six digit code)

SP-   Spare( it is single digit code)

TMSI:-The GSM system can also assign a Temporary Mobile Subscriber Identity (TMSI). After the subscriber’s IMSI has been initialized on the system, the TMSI can be used for sending backward and forward across the network to identify the subscriber. The system automatically changes the TMSI at regular intervals, thus protecting the subscriber from being identified by someone attempting to monitor the radio channels. The TMSI is a local number and is always transmitted with the Local numbers and is always transmitted with the Location Area Identification (LAI) to avoid ambiguities.

EIR:- EIR means" Equipment identity register". A listing of the allowed IMEI is maintained by the PLMN’s in the Equipment Identity Register (EIR) to validate the mobile equipment.