WHAT IS MOBILITY ?• Access the Technology everywhere whether we are work or play, in the office, grounds or at home. To meet this demand the GSM (Global System for Mobile Communication) for mobile telephony was introduced in the mid- 1980s. A boom is underway, such that many GSM user find life without their phone practically inconceivable.
Broad Band 4GService type Narrow Band Wide Band 1G 2G 3G Multi media Wireless Internet Mobile IMT Digital system 2000 Voice IS 95 Analog IS 136 AMPS GSM ~ 24kbps ~64kbps ~2Mbps ~20Mbps 1980 1990 2000 2010 Years
Freq PN CodeFreq Freq Time Time TimeFDMA TDMA CDMA
FDMA ( FREQUENCY DIVISIONMULTIPLE ACCESS ) • In FDMA, the entire allocated cellular frequency spectrum is divided into a number of 30-kHz channels . • The power transmitted by a cell is only large enough to communicate with mobile stations located near the edge of the cell’s coverage area. • The radius of a cell might be one mile or less-referred to as a small cell
TDMA (TIME DIVISION MULTIPLEACCESS) • TDMA is a digital wireless air interface . • It divides each carrier frequency into a number of time slots, each of which constitutes an independent telephone circuit.
CDMA (CODE DIVISION MULTIPLEACCESS) • A digital multiple access technique specified by the Telecommunications Industry Association (TIA) as "IS-95." • One of the unique aspect of CDMA is that while there are certainly limits to the number of phone calls that can be handled by a carrier, this is not a fixed number . • Code division multiple access (CDMA) is a digital air interface standard, claiming eight to fifteen times the capacity of analog.
GSM IS A TDMA TECHNIQUE HISTORY OF GSM What ? •GSM: Global System for Mobile Communications •Formerly: Group Special Mobile When ? • 1982: GSM created to set standard. • 1988: Industrial development started. • 1991: First Systems Deployed.
Why ? •Higher digital voice quality.•Low cost alternatives to making calls such as SMS .•Ability to deploy equipment from different vendors. GSM Services • Tele-services • Bearer or Data Services • Supplementary services
Tele Services • Telecommunication services that enable voice communication via mobile phones • Offered services- Mobile telephony- Emergency calling
BEARER SERVICES• Short Message Service (SMS) o up to 160 character alphanumeric data transmission to/from the mobile terminal• Unified Messaging Services(UMS)• Group 3 fax• Voice mailbox• Include various data services for information transfer between GSM and other networks like PSTN, ISDN etc at rates from 300 to 9600 bps• Electronic mail
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
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 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) o 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) Major MSC 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
Visitor Location Registers (VLR) - Integrated with MSC 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 callsAuthentication Center (AUC) o mainly used for security o data storage location and functional part of the network o Ki is the primary elementEquipment 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 FREQUENCY ALLOCATION • GSM systems use radio frequencies between 890-915 MHz for receive and Downlink between 935-960 MHz for transmit. • RF carriers are spaced every 200 kHz, allowing a total of 124 carriers for use. Uplink • An RF carrier is a pair of radio frequencies, one used in each direction. • Transmit and receive frequencies are always separated by 45 MHz UPLINK FREQUENCIES DOWNLINK FREQUENCIES890 915 935 960 UPLINK AND DOWNLINK FREQUENCY SEPARATED BY 45MHZ
GSM SECURITY GSM Security MS NETWORK Random no Ki Ki Ki Ki A3 A8 A3 A8 SRES Kc Kc SRES Equal
EXPLANATION • 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