Maulana Azad National Institute of Technology,Bhopal Department of Computer Science & Engineering GSM Guided By: Mrs. NAMITA TIWARI Presented By: Priyanka Chhabra Priyanka Chhabra

GSM – GLOBAL SYSTEM FOR MOBILE COMMUNICATION

HISTORY GSM criteria – –Good subjective speech quality –Low terminal and service cost –Support for international roaming –Ability to support handheld terminals –Support for range of new services and facilities –Enhanced Features –ISDN compatibility –Enhance privacy –Security against fraud

HISTORY contd. Phase I of GSM specifications was published in 1990 International demand was so great that the system name was changed from Groupe Special Mobile to Global Systems for Mobile Communications (still GSM) Commercial service started in mid first paying customers were signed up for service By 1993 there were 36 GSM networks in 22 countries Early 1994 there were 1.3 million subscribers worldwide By 1996 there were more than 25 million subscribers worldwide By October 1997 it had grown to more than 55 million subscribers worldwide

Building Blocks AMPS – Advanced Mobile Phone System TACS – Total Access Communication System NMT – Nordic Mobile Telephone System

Building Blocks contd. AMPS – Advanced Mobile Phone System analog technology used in North and South America and approximately 35 other countries operates in the 800 MHz band using FDMA technology

Building Blocks contd. TACS – Total Access Communication System variant of AMPS deployed in a number of countries primarily in the UK

Building Blocks contd. NMT – Nordic Mobile Telephone System analog technology deployed in the Benelux countries and Russia operates in the 450 and 900 MHz band first technology to offer international roaming – only within the Nordic countries

The GSM Bands

 Teleservices (TS)  Bearer services (BS)  Supplementary Services (SS) The GSM Services

Tele Services Telecommunication services that enable voice communication via mobile phones Offered services - Telephony - Emergency calling – Voice messaging

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 Group 3 fax Voice mailbox Electronic mail

Call forwarding. Barring of Outgoing Calls. Barring of Incoming Calls. Advice of Charge (AoC). Call Hold.. Call Waiting. Multiparty service. Calling Line Identification presentation/restriction.. Closed User Groups (CUGs). Explicit Call Transfer (ECT). Supplementary Services

GSM Architecture

The Four blocks Mobile Station Subsystem (MSS) – Mobile Termination (MT) and SIM card (SIM) Base Station Subsystem (BSS) – BSC and BTS Network and Switching Subsystem (NSS) – MSC, HLR, VLR, EIR and AuC Operation and Support Subsystem (OSS) – OMC and NMC

System Architecture Mobile Station (MS) The Mobile Station is made up of two entities: 1.Mobile Equipment (ME) 2.Subscriber Identity Module (SIM)

System Architecture Mobile Station (MS) contd. Mobile Equipment Produced by many different manufacturers Must obtain approval from the standardization body Uniquely identified by an IMEI (International Mobile Equipment Identity)

System Architecture Mobile Station (MS) contd. Subscriber Identity Module (SIM) Smart card containing the International Mobile Subscriber Identity (IMSI) Allows user to send and receive calls and receive other subscribed services Encoded network identification details Protected by a password or PIN Can be moved from phone to phone – contains key information to activate the phone

20 SIM Anatomy

Base Station Subsystem Consists of Base Transceiver Station (BTS) – radio equipments responsible for radio coverage Base Station Controller Controls a few BTS Manages Resources for BTS Handles call set up Location update Handover for each MS Manage radio resource management, signaling transmission, power control, handover control, frequency hopping control etc. Transcoder/Rate Adapter Unit (optional) – A device placed between GSM elements (BTS, BSC and MSC) to conserve bandwidth resources. – Combines four 13 kbps speech channels to one 64 kbps data stream. Thirty 64 kbps channels can then be multiplexed to a E1 channel. Located at BTS, BSC (more often) or MSC.

Perform functions such as call setup, paging, resource allocation, location registration, encryption, interfacing with other networks, handoff control, billing, synchronization, echo canceling and interface with external networks. Consist of 4 elements – MSC, HLR, VLR, AuC and EIR – MSC is the processor, the others are database units. Network and Switching Subsystem (NSS)

Mobile Switching Center (MSC) Switch speech and data connections between: Base Station Controllers Mobile Switching Centers GSM-networks Other external networks Heart of the network Three main jobs: 1) connects calls from sender to receiver 2) collects details of the calls made and received 3) supervises operation of the rest of the network components

Home Location Register (HLR) HLR contains a list of subscribers belonging to one or more MSC areas. Permanent subscriber data including IMSI, MSISDN, roaming restriction, permitted supplementary services and authentication key. Temporary subscriber data consist of MSRN, data related to encryption, VLR address, MSC address and roaming restriction. HLR is usually centralized within a network. Visitor Location Register (VLR) Similar to HLR but for visitors When a roamer appears, his HLR data is transferred to the local VLR. VLR is usually co-located with MSC.

Authentication Center (AuC) Performs authentication function for each subscriber within the system. A key Ki kept in SIM and AuC. This key is never transmitted over air. Authenticate by using a random challenge. Vulnerability is present when encrypted authentication keys must be transmitted from HLR to VLR. Equipment Identity Register (EIR) Records the IMEI of all subscribers in three lists. White list ---- clean equipment Black list ---- stolen equipment Gray list ---- equipment with minor problems

OSS consists of two entities not fully specified in GSM. They are – Operation and Maintenance Center (OMC) – Network Management Center (NMC) Performs alarm handling, fault management, performance management, configuration management, traffic data acquisition, activate and deactivate functions, and long term planning. Normally centralized in a network. Implementation of these functions are operator specific. Operation and Support Subsystem (OSS)

A-Interface ---- between BSC and MSC, E1 link. Abis-Interface ---- between BTS and BSC using LADP (Link Access Data Protocol) protocol. B-Interface ---- between MSC and VLR C-Interface ---- between MSC and HLR D-Interface ---- between HLR and VLR E-Interface ---- between MSCs F-Interface ---- between MSC and EIR Um-Interface ---- between MSS and BSS. Open Interfaces

Call Routing Call Originating from MS Call termination to MS

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. 5MSC routes the call to GMSC 6GMSC 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

Incoming Call 1. Calling a GSM subscribers 2. Forwarding call to GSMC 3. Signal Setup to HLR Request MSRN from VLR 6. Forward responsible MSC to GMSC 7. Forward Call to current MSC Get current status of MS Paging of MS MS answers Security checks Set up connection

Handovers Between 1 and 2 – Inter BTS / Intra BSC Between 1 and 3 – Inter BSC/ Intra MSC Between 1 and 4 – Inter MSC

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(Authentication) algorithm for authentication - A5(Ciphering) algorithm for encryption - A8(Ciphering Key Generation) algorithm for key generation

Call Management (CM) and Mobility Management (MM) CM consists of setup, emergency setup, call proceeding, progress, call confirm, alerting, connect, user information, disconnect, release, status, congestion control, etc all together 18 messages. MM consists of authentication request, authentication response, identify request, location update request, etc

GSM Mobile Services A prepaid mobile phone (also commonly referred to as pay-as-you-go or prepaid wireless) is a mobile phone for which service is purchased in advance of use. Advantages –Lower cost for low usage –Easier to control spending –Available to those who do not have an address Limitations –Every time pay before –No balance means cant make any call

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

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: Kbps  EDGE (Enhanced data rate for GSM Evolution)  Data rate: Kbps (max)  3 Generation  WCDMA(Wide band CDMA)  Data rate : – 2.0 Mbps

Future -- UMTS (Universal Mobile Telephone System Reasons for innovations -new service requirements -availability of new radio bands