GSM network
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GSM (Global System for Mobile communication) is a second generation cellular standard developed to provide voice and data services using digital modulation. It was developed in 1982 by the Groupe Special Mobile to replace incompatible analog cellular systems. GSM specifications include TDMA/FDMA access methods, GMSK modulation, and frequency bands of 900MHz and 1800MHz. The GSM system architecture consists of mobile stations, base station subsystem including BTS and BSC, network switching subsystem including MSC, HLR, VLR, and supplementary registers. GSM provides telecommunication services, bearer services like SMS, and supplementary services like call forwarding. Security is provided through authentication, encryption, and SIM cards. GSM has enabled international ro
GSM network
- 2. What is GSM ? Global System for Mobile (GSM) is a second generation cellular standard developed to cater voice services and data delivery using digital modulation
- 3. GSM: History Developed by Group Special Mobile (founded 1982) which was an initiative of CEPT ( Conference of European Post and Telecommunication ) Aim : to replace the incompatible analog system Presently the responsibility of GSM standardization resides with special mobile group under ETSI ( European telecommunication Standards Institute ) Full set of specifications phase-I became available in 1990 Under ETSI, GSM is named as “ Global System for Mobile communication “ Today many providers all over the world use GSM (more than 135 countries in Asia, Africa, Europe, Australia, America) More than 1300 million subscribers in world and 45 million subscriber in India.
- 4. Figures: March, 2005 37% 1% 4%43% 4% 3% 3% 3% (INDIA) 3% Arab World Asia Pacific Africa East Central Asia Europe Russia India North America South America GSM in World
- 6. GSM Services Tele-services Bearer or Data Services Supplementary services
- 7. Tele Services Telecommunication services that enable voice communication via mobile phones Offered services - Mobile telephony - Emergency calling
- 8. Bearer Services Include various data services for information transfer between GSM and other networks like PSTN, ISDN etc at rates from 300 to 9600 bps Short Message Service (SMS) up to 160 character alphanumeric data transmission to/from the mobile terminal Unified Messaging Services(UMS) Group 3 fax Voice mailbox Electronic mail
- 9. Supplementary Services Call related services : Call Waiting- Notification of an incoming call while on the handset Call Hold- Put a caller on hold to take another call Call Barring- All calls, outgoing calls, or incoming calls Call Forwarding- Calls can be sent to various numbers defined by the user Multi Party Call Conferencing - Link multiple calls together CLIP – Caller line identification presentation CLIR – Caller line identification restriction CUG – Closed user group
- 10. GSM System Architecture BSC BSC MSC MS MS MS BTS BTS BTS GMSC PSTN ISDN PDN EIR AUC HLR VLR
- 11. GSM System Architecture Mobile Station (MS) Mobile Equipment (ME) Subscriber Identity Module (SIM) Base Station Subsystem (BSS) Base Transceiver Station (BTS) Base Station Controller (BSC) Network Switching Subsystem(NSS) Mobile Switching Center (MSC) Home Location Register (HLR) Visitor Location Register (VLR) Authentication Center (AUC) Equipment Identity Register (EIR)
- 12. System Architecture Mobile Station (MS) The Mobile Station is made up of two entities :- 1. Mobile Equipment (ME) 2. Subscriber Identity Module (SIM)
- 13. System Architecture Mobile Station (MS) Mobile Equipment Portable,vehicle mounted, hand held device Uniquely identified by an IMEI (International Mobile Equipment Identity) Voice and data transmission Monitoring power and signal quality of surrounding cells for optimum handover Power level : 0.8W – 20 W 160 character long SMS.
- 14. System Architecture Mobile Station (MS) contd. Subscriber Identity Module (SIM) Smart card contains the International Mobile Subscriber Identity (IMSI) Allows user to send and receive calls and receive other subscribed services Encoded network identification details - Key Ki,Kc and A3,A5 and A8 algorithms Protected by a password or PIN Can be moved from phone to phone – contains key information to activate the phone
- 15. System Architecture Base Station Subsystem (BSS) Base Station Subsystem is composed of two parts that communicate across the standardized Abis interface allowing operation between components made by different suppliers 1. Base Transceiver Station (BTS) 2. Base Station Controller (BSC)
- 16. System Architecture Base Station Subsystem (BSS) Base Transceiver Station (BTS) :- Encodes, encrypts, multiplexes, modulates and feeds the RF signals to the antenna. Frequency hopping Communicates with Mobile station and BSC Consists of Transceivers (TRX) units
- 17. System Architecture Base Station Subsystem (BSS) Base Station Controller (BSC) Manages Radio resources for BTS Assigns Frequency and time slots for all MS’s in its area Handles call set up Transcoding and rate adaptation functionality Handover for each MS Radio Power control It communicates with MSC and BTS
- 18. System Architecture Network Switching Subsystem(NSS) Mobile Switching Center (MSC) Heart of the network Manages communication between GSM and other networks Call setup function and basic switching Call routing Billing information and collection Mobility management - Registration - Location Updating - Inter BSS and inter MSC call handoff MSC does gateway function while its customer roams to other network by using HLR/VLR.
- 19. System Architecture Network Switching Subsystem Home Location Registers (HLR) - permanent database about mobile subscribers in a large service area(generally one per GSM network operator) - database contains IMSI, MSISDN, prepaid/postpaid, roaming restrictions, supplementary services. Visitor Location Registers (VLR) - Temporary database which updates whenever new MS enters its area, by HLR database - Controls those mobiles roaming in its area - Reduces number of queries to HLR - Database contains IMSI, TMSI, MSISDN, MSRN, Location Area, authentication key
- 20. System Architecture Network Switching Subsystem Authentication Center (AUC) - Protects against intruders in air interface - Maintains authentication keys and algorithms and provides security triplets ( RAND, SRES, Kc) - Generally associated with HLR Equipment Identity Register (EIR) - Database that is used to track handsets using the IMEI (International Mobile Equipment Identity) - Made up of three sub-classes: The White List, The Black List and the Gray List - Only one EIR per PLMN
- 21. GSM Specifications-1 RF Spectrum GSM 900 - Mobile to BTS (uplink) :- 890-915 MHz - BTS to Mobile(downlink) :- 935-960 MHz - Bandwidth :- 2* 25 MHz GSM 1800 - Mobile to BTS (uplink) :- 1710-1785 MHz - BTS to Mobile(downlink) :- 1805-1880 MHz - Bandwidth :- 2* 75 MHz
- 22. GSM Specification-2 Carrier Separation :- 200 KHz Duplex Distance :- 45 MHz No. of RF carriers :- 124 Access Method :- TDMA/FDMA Modulation Method :- GMSK Modulation data rate :- 270.833 Kbps
- 23. Speech decoding Channel decoding De-interleaving Burst Formatting De-ciphering DemodulationModulation Ciphering Burst Formatting Interleaving Channel Coding Speech coding Radio Interface Speech Speech 13 Kbps 22.8 Kbps 22.8 Kbps 33.6 Kbps 33.6 Kbps 270.83 Kbps GSM Operation
- 24. Call Routing Call Originating from MS Call termination to MS
- 25. Outgoing Call 1. MS sends dialled number to BSS 2. BSS sends dialled number to MSC 3,4 MSC checks VLR if MS is allowed the requested service. If so, MSC asks BSS to allocate resources for call. 5 MSC routes the call to GMSC 6 GMSC routes the call to local exchange of called user 7, 8, 9,10 Answer back(ring back) tone is routed from called user to MS via GMSC, MSC, BSS
- 26. Incoming Call 1. Calling a GSM subscribers 2. Forwarding call to GSMC 3. Signal Setup to HLR 4,5. Request MSRN from VLR 6. Forward responsible MSC to GMSC 7. Forward Call to current MSC 8,9. Get current status of MS 10,11. Paging of MS 1 2,13. MS answers 14,15. Security checks 16,17. Set up connection
- 27. 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
- 28. Characteristics of GSM Standard Fully digital system using 900,1800 MHz frequency band. TDMA over radio carriers(200 KHz carrier spacing. 8 full rate or 16 half rate TDMA channels per carrier. 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).
- 29. 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). Encryption capability for information security and privacy. Compatibility with ISDN, leading to wider range of services
- 30. GSM Applications Mobile telephony GSM-R Telemetry System - Fleet management - Automatic meter reading - Toll Collection - Remote control and fault reporting of DG sets Value Added Services
- 31. Future Of GSM 2nd Generation GSM -9.6 Kbps (data rate) 2.5 Generation ( Future of GSM) HSCSD (High Speed ckt 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) 3 Generation WCDMA(Wide band CDMA) Data rate :- 0.348 – 2.0 Mbps
- 32. Thanks !