INTRODUCTION Global System for Mobile (GSM) is a second generation cellular standard developed to cater voice services and data delivery using digital modulation. Aim Of GSM is to replace the incompatible analog system . Today many providers all over the world use GSM (more than 135 countries in Asia, Africa, Europe, Australia, America)
ARCHITECTURE Mobile Station Mobile Equipment (ME) Subscriber Identity Module (SIM) Base Station Subsystem (BSS): Base Transceiver Station Base Station Controller Network Subsystem: Mobile Switching Center (MSC) Home Location Register (HLR) Visitor Location Register (VLR) Authentication Center (AUC) Equipment Identity Register (EIR)
MOBILE STATION (MS)• The Mobile Station is made up of two entities: Mobile Equipment (ME) o The Mobile Equipment is the hardware used by the subscriber to access the network . o Uniquely identified by an IMEI (International Mobile Equipment Identity) Subscriber Identity Module (SIM) o Smart card containing the International Mobile Subscriber Identity (IMSI) o Allows user to send and receive calls and receive other subscribed services o Protected by a password or PIN
BASE STATION SUBSYSTEM Base Station Subsystem is composed of two parts : 1) Base Transceiver Station (BTS) 2) Base Station Controller (BSC) • Base Transceiver Station (BTS) Houses the radio transceivers that define a cell Handles radio-link protocols with the Mobile Station
Base Station Controller (BSC) Manages Resources for BTS , Handles call set up, Location update, Handover for each MS.
NETWORK SUBSYSTEM Mobile Services Switching Center (MSC) MSC performs following functions : Switching and call routing Charging Service provisioning Communication with HLR Communication with the VLR Communication with other MSCs Control of connected BSCs Direct access to Internet services Home Location Registers (HLR) : Contains administrative information of each subscriber Most important database
NETWORK SUBSYSTEM Visitor Location Registers (VLR) o tracks which customers have the phone on and ready to receive a call o periodically updates the database on which phones are turned on and ready to receive calls Authentication Center (AUC) o mainly used for security o data storage location and functional part of the network Equipment Identity Register (EIR) - Database that is used to track handsets using the IMEI ,Made up of three sub-classes: The White List, The Black List and the Gray List o Optional database
GSM SPECIFICATIONS• GSM systems use radio frequencies between 890-915 MHz for receive and between 935-960 MHz for transmit.• RF carriers are spaced every 200 kHz, allowing a total of 124 carriers for use.• An RF carrier is a pair of radio frequencies, one used in each direction.• Transmit and receive frequencies are always separated by 45 MHz .
SECURITY IN GSM On air interface, GSM uses encryption and TMSI instead of IMSI. SIM is provided 4-8 digit PIN to validate the ownership of SIM 3 algorithms are specified : - A3 algorithm for authentication - A5 algorithm for encryption - A8 algorithm for key generation
CHARACTERISTICS OF GSM STANDARD Fully digital system using 900,1800 MHz frequency band. TDMA over radio carriers(200 KHz carrier spacing. User/terminal authentication for fraud control. Encryption of speech and data transmission over the radio path. Full international roaming capability. Low speed data services (up to 9.6 Kb/s). Compatibility with ISDN. Support of Short Message Service (SMS).
ADVANTAGES OF GSM OVER ANALOG SYSTEM Capacity increases Reduced RF transmission power and longer battery life. International roaming capability. Better security against fraud (through terminal validation and user authentication.
GSM APPLICATIONS Telemetry System- Fleet management- Automatic meter reading- Toll Collection Value Added Services
FUTURE OF GSMo 2nd Generation GSM -9.6 Kbps (data rate)o 2.5 Generation ( Future of GSM) HSCSD (High Speed circuit Switched data) Data rate : 76.8 Kbps (9.6 x 8 kbps) GPRS (General Packet Radio service) Data rate: 14.4 - 115.2 Kbps EDGE (Enhanced data rate for GSM Evolution) Data rate: 547.2 Kbps (max)o 3 Generation WCDMA(Wide band CDMA) Data rate : 0.348 – 2.0 Mbps