GSMGlobal System for Mobile Communications

Contents

GSM PrinciplesCellular TechnologyGSM NetworkCall ProcessingHandoffsGPRSEDGE

Any time AnywhereMobility & Roaming High capacity & subs. densityEfficient use of radio spectrumSeamless Network ArchitectureLow costFlexibilityInnovative ServicesStandard InterfacesMOBILE COMMUNICATION OBJECTIVES

Public Land Mobile NetworkINDIA has adopted GSM standard for PLMN.Digital Cellular System.Operates at 900 MHz.International Roaming facility.Power class 0.8 to 20W.Cell Radius upto 35 Kms.Maximum mobility speed 250 Km/hr.

Allocated GSM Frequency BandsGSM900 :up: 890~915MHz down: 935~960MHzduplex interval: 45MHzbandwidth: 25MHzfrequency interval: 200KHzGSM1800 :up: 1710-1785MHz down: 1805-1880MHzduplex interval: 95MHz working bandwidth: 75MHzfrequency interval: 200KHzEGSM900 :up: 880~890MHz down: 925~935MHzduplex interval: 45MHzbandwidth: 10MHzfrequency interval: 200KHzGSM1900MHz:up:1850~1910MHzdown:1930~1990MHzduplex interval: 80MHz working bandwidth: 60MHzfrequency interval: 200KHz

GSM PRINCIPLES BANDWIDTH MANAGEMENT TECHNIQUESFDMA TDMA Cellular Technology & Frequency Re-use Scheme

FDMAFrequency Division Multiple Access SchemeUplink Frequency Band = (890 915) MHzDownlink Frequency Band = (935 960) MHzAbsolute Radio Freq Carrier Number (ARFCN)Bandwidth = 915 890 or 960 935 = 25 MHz

GSMFDMA

TDMATime Division Multiple Access SchemeOne Radio Frequency = Eight Time SlotsOne TDMA Frame = Eight Time SlotsOne Time Slot = One Physical ChannelOne Time Slot Duration = 0.577 msec

GSMTDMA45 MHzFrequencyF2F1(Cell transmit)F2F1(Cell Rx)AmplitudeTypical TDMA/ FDMA frame structure

CELLULAR TECHNOLOGY

Cellular TechnologyCell Site

Cluster

CELLULAR MOBILE CONCEPTS

WHAT IS A CELL ? A base station (transmitter) having a number of RF channels is called a cell Each cell covers a a limited number of mobile subscribers within the cell boundaries ( Coverage area) Typical Cell Radius Aprrox = 30 Km (Start up), 1 Km (Mature)

Types of Cells

OMNI CELLSSECTOR CELLS - Two Sector Cells - Three Sector Cells

Fundamental problemsRadio range, or coverageno. of channels, or voice circuitsFull, seamless service coverageLarge no. of subscribers in the range of millions

Frequency Re-use Scheme

Frequency Re-use Scheme

CLUSTER

A CLUSTER OF CELLS

4567231

CELLULAR MOBILE CONCEPTS

CELLULAR MOBILE CONCEPTS

CO-CHL INTERFERENCE :Interference caused by another cell/mobile using the same frequency DRCo Chl Interference is a Function of Qthe re-use ratio:

Q =D / R Lower Q Increased Co-Chl Interference Higher Q Reduced Co-Chl Interference

CLASSIFICATION OF CELLSMICRO CELLMACRO CELLUMBRELLA CELL

GSM subsystemsNetwork Subsystem includes the equipments and functions related to end-to-end call.

Radio Subsystem includes the equipments and functions related to the management of the connections on the radio path.

3. Operations and Maintenance subsystem includes the operation and maintenance of GSM equipment for the radio and network interface.

Network Architecture

HLRPSTNISDNDataNetworks(Air interfaceOSSBSC1 MSC=16 BSC1 BSC=1024 TRUA InterfaceA-bis interfaceBSC:BASE STATION CONTROLLER, BTS: BASE TRANSRECEIVER STATION, OSS: OPERATION AND SUPPORT SUBSYSTEM.ss

GSM Network StructureGSM Service Area: Total area served by the combination of all member countries where a mobile can be served.PLMN Service Area:It is one N/W area. MSC Service Area:There can many MSC/VLR in one PLMN area.It is one Mobile Exch. Area.Location Area: A LA is a part of the MSC/VLR service area in which a MS may move freely without updating location information to the MSC/VLR exchange that control the LA. Cells

GSMPLMN Service Area

MSCMSCMSCMSCVLRVLRVLRIIIIVIIII

GSMMSC Service AreaMSCVLRLA1LA2LA3LA6LA4LA5

GSMCells

MSCVLRLA1LA2LA3LA6LA4LA5C1C2C3C6C5C4C=CELL

GSMRelation between areas in GSMLocation AreaCellArea served by a BTSLocation AreaMSC Service AreaPLMN Service AreaGSM Service Area

Call Processing

Mobile To Land Call Set-up ScenarioPhases of Mobile To Land Call SETUP PHASE ( Mobile Originated Call- MO Call ) RINGING PHASE CONVERSATION PHASE RELEASE PHASE

- REQUEST FOR SERVICE ( CHANNEL ) BY MS- CM SERVICE REQUEST - AUTHENTICATION- CIPHERING- SETUP MESSAGE- EQUIPMENT VALIDATION ( EIR CHECK )- VALIDATION AT VLR- ASSIGNMENTMobile To Land Call Set-up Scenario SETUP PHASE

Mobile To Land Call Set-up ScenarioMSC/VLRCall Setup messageIs the requested basic service provisioned for the subscriber ?YesNoRelease Complete message to MSPreliminary Digit AnalysisIs the number of digits less than the minimum expected?YesRelease Complete message to MSNo1. Check of ODB( BAOC/BOIC/ BOIC Ex HC )2. Subscriber call barring checks ( BAOC/BOIC etc. )ASSIGNM ENT

Land To Mobile Call Set-up ScenarioPhases of Land To Mobile Call Routing Analysis Paging Authentication Call-Setup Ciphering Call Release( Mobile Terminating - MT Call )

Mobile To Mobile Call Set-up ScenarioPhases of Mobile To Mobile Call Request for service. Authentication Call-Setup Ciphering Call Release Routing Analysis Paging Authentication Ciphering Call-SetupMobile Originating Mobile Terminating Call-Release

HandoverHard Handover Break before makeSoft Handover make before breakSofter Handover

Evolution from GSM to 3GThe GSM Growth PhasesGSM2GHSCSDGPRS2.5GEDGE3G

GSM EvolutionGPRS200 KHz carrier115 Kbps peak data ratesEDGE200 KHz carrierData rates up to 384 Kbps8-PSK modulationHigher symbol rateUMTS5 MHz carrier2 Mbps peak data ratesNew IMT-2000 2 GHz spectrumGSM200 KHz carrier8 full-rate time slots16 half-rate time slotsGSMGPRSEDGEUMTS3G

2.5G

2G

HSCSDHSCSDCircuit-switched data64 Kbps peak data rates

MAIN ADVANTAGES FOR OPERATORS More Revenue : By providing more than a mobile connection. Also operator can charge on the basis of type and amount of content accessed. Huge Potential Market for Data Sevices : Mobile Phone and Internet, both are fastest growing technologies and GPRS is the merger of two. Fast Roll-out and Continuous Network Expansion :GPRS is an integral part of GSM. GPRS uses excess voice capacity for data : GPRS Packets are transmitted in short, free periods between busy hour calls.

GPRS GSM1. SUPPORTS BOTH CKT.Only circuit switched. SWITCHED as well as packet switched service.

2. MS Utilizes AutomaticNo re-transmission is retransmission (ARQ) at provided. data link layer to re-transmit error frames.

3. Multiple time slots can be Single time slot per user. allotted to a single user

4. One time slot can be allottedSingle time slot per user. to several users.

5. Charging/ billing more complexSimple time-based billing. (Volume based, Q.O.S. based)GPRS Vs GSM

* Communications- E-mail, fax, intranet/ internet access.

* Value added services - Information services, games, e-commerce.

* Location-based applications - Navigation, traffic conditions, airline/rail schedule, location finder.

* Vertical applications - Freight delivery, fleet management, sales-force automation

* Location sensitive A user nearing a cinema hall or Advertising - a restaurant receives flashes of advertisement

TYPICAL GPRS SERVICES

GPRS Network

EDGE Enhanced Data rates for GSM EvolutionGPRS = General Packet Radio System EGPRS = GPRS + EDGE modulation

What EDGE would mean to subscribers Streaming Applications Very high speed downloads Corporate Intranet connections Quicker MMS Video Phone Vertical corporate applications Video Conference, Remote presentations

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