GSM Architecture 1

8/3/2019 GSM Architecture 1

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GSM Architecture


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rouprouppcialpcial

obileobile

GG

GSMGSM

SS

MM


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loballobalystem forystem for

obile Communicationsobile Communications

GGSS

MM

GSM ArchitectureGSM Architecture


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GSM - Public Land MobileGSM - Public Land MobileNetworkNetwork

INDIA has adopted GSM standard.INDIA has adopted GSM standard. Digital Cellular System based onDigital Cellular System based on

Narrowband ISDN.Narrowband ISDN. Operates at 900 MHz range.Operates at 900 MHz range. International Roaming facility.International Roaming facility.

Power class 0.8 to 20W.Power class 0.8 to 20W. Cell Radius upto 30 Kms.Cell Radius upto 30 Kms. Maximum mobility speed 250 Km/hr.Maximum mobility speed 250 Km/hr.


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Design Objectives of GSMDesign Objectives of GSM

Good speech quality.Good speech quality. Security and privacy.Security and privacy.

Low terminal and service cost.Low terminal and service cost.

Handheld terminals.Handheld terminals. International roaming.International roaming.

Range of new services & facilities.Range of new services & facilities. Digital radio.Digital radio. Spectral efficiency.Spectral efficiency.


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Communication PSTNCommunication PSTN

Telephone Exchanges

Subscriber

Line(2W)

Inter-Exchange

Junction

Subscriber

Line(2W)


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Communication - PLMNCommunication - PLMN

TelephoneExchange

Subscriber

Line(2W)

Inter-Exchange

Junction

Mobile SwitchingCentre (MSC)

BSC BTSMS


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Mobility IssuesMobility Issues

Demand on scarce Radio Resources.Demand on scarce Radio Resources. Authentication.Authentication. Security and Privacy.Security and Privacy. Providing service across networks.Providing service across networks. Maintain UNIQUE Service Profile.Maintain UNIQUE Service Profile. Keep track of users.Keep track of users. Maintain established communication.Maintain established communication. Power & Timing management of MS.Power & Timing management of MS. Roaming and Billing & AccountingRoaming and Billing & Accounting


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Wired Vs Wireless SANWired Vs Wireless SAN

Space Division MultiplexingSpace Division Multiplexing Available space much more than required and henceAvailable space much more than required and hencededicated access to each.dedicated access to each.

Teledensity of an area does not pose any problem.Teledensity of an area does not pose any problem. Static Network snapshots.Static Network snapshots.

WIREDWIRED

NETWORKNETWORK Lay as muchcable as needed

to meet the

demand.

TelephoneExchangeSubscriber

Line(2W)


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Wired Vs Wireless SANWired Vs Wireless SAN

Frequency/Time Division MultiplexingFrequency/Time Division Multiplexing Limited RF spectrum and hence RF channels assigned on demandLimited RF spectrum and hence RF channels assigned on demand Dynamically changing teledensity in each area.Dynamically changing teledensity in each area. Dynamic Network snapshots.Dynamic Network snapshots.

Mobile SwitchingCentre (MSC)

BSC BTS

MS

ONLY a windowof RF Spectrum

is available

RF Channels

WIRELESSWIRELESS

NETWORKNETWORK


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7 Cell Cluster Structure7 Cell Cluster Structure

F1

F7

F2

F3

F4

F5

F6

F1

F4

F5


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F1

F2F4

F5

F6

F7

F1

F2F4

F5

F6

F7

GSM - Cell layoutGSM - Cell layout

Farthest Separation

F3

F3


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GSM TerminologyGSM Terminology

Home networkHome network

Visited networkVisited network

Location AreaLocation Area RoamingRoaming

HandoverHandover POIPOI


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System ArchitectureSystem Architecture

Functional Architecture broadly divided intoFunctional Architecture broadly divided intosix parts:six parts:

Mobile Station.Mobile Station.Base Station Subsystem (BSS).Base Station Subsystem (BSS).

Network Switching SubsystemNetwork Switching Subsystem

(NSS).(NSS).Operation and MaintenanceOperation and MaintenanceSubsystem.Subsystem.

Enhanced Services SystemEnhanced Services System


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GSM Network OverviewGSM Network Overview

MEME

SIMSIMSIMSIM

BTS

BTS

BSC

BSC

MSC

HLR

EIR

VLR

AuCMobileStation Base Station Subsystem Network Subsystem

PSTNISDNPSPDNCSPDN

Um Abis

AOMC


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GSM Network ArchitectureGSM Network Architecture

MSS BTS BSCBSS VLR

AuCuC

MSCEIR

AuC

HLR

HLRLROMC

EIRIR

Bill ingCentreEnhancedServiceNodeSTN

OtherMSCsAir

Interface

VoiceVoice

SS7 CallProc

& Mtce

RS-232EIA

SS7Mtce

X.25

MAP MAP

MAP

ISUP

X.25

SS7ETSIBRAVoice Path

Signalling Path

XCD

R


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GSM Network ArchitectureGSM Network Architecture

MSS BTS BSCBSS VLR

AuCuC

MSCEIR

AuC

HLR

HLRLROMS

EIRIR

B&CCSnhancedServiceNodesSTN

OtherMSCsAir

Interface

Voice PathSignalling Path

XCDR


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GSM Reference ModelGSM Reference Model

A

MSMS BTS BSC

UmAbis

MSC HLR

EIR

VLR

AuC

VLROMC

MSC PSTN ISDN

E

FC

B D

G


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Mobile StationMobile Station

Mobile Station is really two distinctMobile Station is really two distinctentities.entities.

Mobile equipment or Mobileterminal.

SIM Card.

Mobile equipment, which is the actualMobile equipment, which is the actualHardware, is almost anonymous.Hardware, is almost anonymous.

SIM card, implemented as a smart cardSIM card, implemented as a smart cardholds the subscriber information.holds the subscriber information.


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Mobile TerminalMobile Terminal

Different terminals distinguishedDifferent terminals distinguishedprincipally by their power andprincipally by their power andapplication.application.

Fixed terminals 20WPortable terminals for cars 8WHandheld terminals 2W

Sophisticated terminals 0.8W Every terminal has an InternationalEvery terminal has an International

Mobile Equipment Identity (IMEI).Mobile Equipment Identity (IMEI).


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The SIMThe SIM

SIM provides Personal Mobility.SIM provides Personal Mobility. Holds a unique identifier calledHolds a unique identifier called

International Mobile Subscriber IdentityInternational Mobile Subscriber Identity

(IMSI), Service profile, Secret key for(IMSI), Service profile, Secret key forauthentication, etc.authentication, etc.

Provides user access to all subscribedProvides user access to all subscribed

services. SIM makes the terminalservices. SIM makes the terminaloperational.operational.

Can be password protected by a 4 to 8 digitCan be password protected by a 4 to 8 digitPersonal Identification Number.Personal Identification Number.


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The SIMThe SIM

SIM is classified on the basis of:SIM is classified on the basis of:Operating voltage.

RAM capacity. Operating Voltages:Operating Voltages:

3V and 5V.

RAM Capacity:RAM Capacity:8K, 16K, 32K and 64K


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BSS ConnectivityBSS Connectivity

BSC

BTS

BTS

BTS

To

MSCXCDR


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Base Station SubsystemBase Station Subsystem

BSS connects the MS and the NSS.BSS connects the MS and the NSS.

Composed of three parts:Composed of three parts:

The Base Transceiver Station (BTS)also called Base Station (BS)Transcoder and. Base Station Controller (BSC).

BSS provides the radio interface functions.BSS provides the radio interface functions.

Completely digital.Completely digital.

Base Transceiver StationBase Transceiver Station


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Base Transceiver StationBase Transceiver Station(BTS)(BTS)

BTS houses the radio transceivers thatBTS houses the radio transceivers thatdefine a cell.define a cell.

Handles the radio-link protocols withHandles the radio-link protocols withthe Mobile Stationthe Mobile Station

Each BTS can support a number ofEach BTS can support a number oftransceivers depending on the densitytransceivers depending on the densityof subscribers in the cell.of subscribers in the cell.

Needs to be rugged, reliable, portable.Needs to be rugged, reliable, portable.


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Base Station ControllerBase Station Controller

BSC manages the radio resourcesBSC manages the radio resourcesfor one or a group of BTSs.for one or a group of BTSs.

Handles radio-channel setup,Handles radio-channel setup,frequency hopping, handovers,frequency hopping, handovers,and control of the RF power levels.and control of the RF power levels.

Establishes connection betweenEstablishes connection betweenthe mobile station and the MSC.the mobile station and the MSC.


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Network & SwitchingNetwork & Switching


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Network & SwitchingNetwork & SwitchingSubsystemSubsystem

Manages the communication betweenManages the communication betweenthe mobile users and other users.the mobile users and other users.

Provides all the functionality needed toProvides all the functionality needed tohandle a mobile subscriber such as:handle a mobile subscriber such as:Registration.Authentication and security.

Location updating.Handovers andRouting to roaming subscribers.



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Central component is the MSCCentral component is the MSC(Mobile Services Switching Centre).(Mobile Services Switching Centre).

It performs the switching functionsIt performs the switching functionsof the network.of the network.

Gateway Mobile Services SwitchingGateway Mobile Services SwitchingCentre interfaces between theCentre interfaces between themobile network and PSTN.mobile network and PSTN.



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Services provided in conjunctionServices provided in conjunctionwith four intelligent databases.with four intelligent databases.

Home Location Register (HLR)Home Location Register (HLR) Visitor Location Register (VLR)Visitor Location Register (VLR)

Authentication Centre (AuC)Authentication Centre (AuC) Equipment Identity Register (EIR)Equipment Identity Register (EIR)


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Home Location RegisterHome Location Register

Contains all administrativeContains all administrativeinformation of each subscriberinformation of each subscriber

registered in an GSM network.registered in an GSM network. Logically there is one HLR perLogically there is one HLR perGSM/PLMN network.GSM/PLMN network.

Can be implemented as distributedCan be implemented as distributeddatabase also.database also.


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Home Location RegisterHome Location Register

International Mobile Subscriber IdentityInternational Mobile Subscriber Identity(IMSI). Also in SIM of MS as(IMSI). Also in SIM of MS asIMSI/TMSI.IMSI/TMSI.

Mobile Subscriber ISDN NumberMobile Subscriber ISDN Number(MSISDN).(MSISDN).

Permanent copy of subscriber data.Permanent copy of subscriber data.

Mobile Station Roaming NumberMobile Station Roaming Number(MSRN), typically the CCS#7 SP code of(MSRN), typically the CCS#7 SP code ofthe visited MSC/VLR.the visited MSC/VLR.


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Visitor Location RegisterVisitor Location Register

For managing originating andFor managing originating andterminating calls under its coverageterminating calls under its coverage

area, each MSC need subscriber dataarea, each MSC need subscriber dataheld in HLR.held in HLR.

To avoid high signalling load betweenTo avoid high signalling load between

MSCs and HLR, subscriber data areMSCs and HLR, subscriber data aredownloaded at registration and held indownloaded at registration and held ina local database called VLR.a local database called VLR.


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VLR Contains selected administrativeVLR Contains selected administrativeinformation from HLR needed forinformation from HLR needed for

call control and provision ofcall control and provision ofsubscribed services for each mobilesubscribed services for each mobile

located in the geographical arealocated in the geographical areacontrolled by the MSC.controlled by the MSC.


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In the canonical architecture, each VLRIn the canonical architecture, each VLRcorresponds to one MSC, even though acorresponds to one MSC, even though a

VLR can hold data for one or severalVLR can hold data for one or several

MSCs of the same PLMN.MSCs of the same PLMN. Holds IMSI, MSRN, HLR copy (Sub data).Holds IMSI, MSRN, HLR copy (Sub data).

Temporary Mobile Subscriber IdentityTemporary Mobile Subscriber Identity

(TMSI).(TMSI). Location Area Code (LAC) of MS.Location Area Code (LAC) of MS.


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Authentication CentreAuthentication Centre

A protected database used for securityA protected database used for securitypurposes.purposes.

Replicates the copy of the secret keyReplicates the copy of the secret key

(Authentication Key (Authentication Key KiKi) stored in each) stored in eachsubscribers SIM card.subscribers SIM card.

Provides all the parameters needed forProvides all the parameters needed for

authentication and encryption overauthentication and encryption overradio channels.radio channels.

Considered to be part of HLR.Considered to be part of HLR.


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Equipment Identity RegisterEquipment Identity Register

A database that contains a list of all validA database that contains a list of all validmobile equipment in the network.mobile equipment in the network.

Generates Valid, Suspect & FraudulentGenerates Valid, Suspect & Fraudulentlists of Mobile Equipment through the uselists of Mobile Equipment through the useof International Mobile Equipmentof International Mobile EquipmentIdentity (IMEI).Identity (IMEI).

Forbid calls fromForbid calls from unauthorisedunauthorised terminalsterminals(non-standard terminals)(non-standard terminals)


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Operation & SupportOperation & Support


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Operation & SupportOperation & SupportSubsystemSubsystem

OMS comprises of :OMS comprises of : Operation and Maintenance

Centre (OMC) for Radio OMC-R. OMC for Switch OMC-S

Configures, controls and monitorsConfigures, controls and monitors

the GSM system.the GSM system. Controls the traffic load in BSSs.Controls the traffic load in BSSs.


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OMCOMC

The maintenance control point for allThe maintenance control point for allnetwork elements in a GSM system.network elements in a GSM system.

Office Data Management.Office Data Management.

Operation and Administration.Operation and Administration.

Data and Software storage for networkData and Software storage for network

elements.elements.

Traffic reporting and analysis.Traffic reporting and analysis.

Must comply with TMN architecture.Must comply with TMN architecture.


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Unified Messaging Services (UMS)Unified Messaging Services (UMS)Voice Mail (VM)FAX Mail (FM)E-Mail (EM)Short Message Service (SMS)

Wireless Application Protocol (WAP)Wireless Application Protocol (WAP) Intelligent Network (IN)Intelligent Network (IN)

Billing & Customer CareBilling & Customer Care


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Billing & Customer CareBilling & Customer CareSystemSystem

Mediation DeviceMediation Device Interconnect Billing SubsystemInterconnect Billing Subsystem

Billing SubsystemBilling SubsystemRating Module

Billing ModuleRoaming settlement subsystemCustomer Service ModuleOrder Management ModuleSmart Card Handling Module

Service Provisioning SubsystemService Provisioning Subsystem Networking SubsystemNetworking Subsystem

Printing SubsystemPrinting Subsystem


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GSM FunctionsGSM Functions

GSM functions are broadly classified intoGSM functions are broadly classified into5 main functional Blocks:5 main functional Blocks:

TransmissionTransmission

Radio Resources Management (RR)Radio Resources Management (RR)

Mobility Management (MM)Mobility Management (MM)

Communication Management (CM)Communication Management (CM) Operation, Administration andOperation, Administration andMaintenance (OAM)Maintenance (OAM)


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Spectral Allocation in GSMSpectral Allocation in GSM

DOWNLINK

935-960 MHz

UPLINK

890-915 MHz

n erconnec on on erconnec on o


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n erconnec on on erconnec on oFunctionsFunctions

PHY

LAPDm

RR

MM

CM

PHY

LAPDm

RR

PHY

LAPDm

BTSM

MTP

SCCP

BSSAP

MM

CM

PHY

LAPDm

BTSM

MTP

SCCP

BSSAP

Um AAbisMSMSMSMS BTSBTSBTSBTS BSCBSCBSCBSC MSCMSCMSCMSC


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A combination of FDMA and TDMA isA combination of FDMA and TDMA isused.used.

25MHz band divided into 125 carrier25MHz band divided into 125 carrierfrequencies spaced 200KHz apart.frequencies spaced 200KHz apart.

One or more carrier assigned to eachOne or more carrier assigned to each

base station.base station. Each carrier band divided using TDMA.Each carrier band divided using TDMA.


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Organisation of physical channels intoOrganisation of physical channels intotraffic and control channels.traffic and control channels.

Speech coding (RPE-LPC) 13KbpsSpeech coding (RPE-LPC) 13Kbps

Channel coding and modulationChannel coding and modulation

Organisation of hierarchical multiframeOrganisation of hierarchical multiframestructures.structures.

Burst structure and assembly.Burst structure and assembly.

MultipathMultipath equalisationequalisation..


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FDMA/TDMA SchemeFDMA/TDMA Scheme

BP1 BP2 BP3 BP4 BP5 BP6 BP7 BP8 BP1 BP2t

890.0

890.2

890.4

890.6

890.8

891.0

891.2

915

f

GUARD BAND

SLOTSLOT


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Logical Channel ArchitectureLogical Channel Architecture

PHYSICALCHAN

NELS

Control channels

(CCH)

Traffic channels(TCH)

Paging

Access

User Speech/Data

Associated controland Supervision


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Logical Channel ArchitectureLogical Channel Architecture

PHYSI

CALCHA

NNELS

PHYSI

CALCHANNELS



User Speech/DataUser Speech/Data



Broadcastchannels (BCH)

Broadcastchannels (BCH)

Synchronisation (DL)Synchronisation (DL)

Frequency Correction (DL)Frequency Correction (DL)

Broadcast Control(DL)Broadcast Control(DL)

Common Controlchannels (CCH)

Common Controlchannels (CCH)

Paging (DL)Paging (DL)

Access and Grant (BW)Access and Grant (BW)

Speech - Radio Waves -Speech - Radio Waves -


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Speech Radio Waves Speech Radio Waves SpeechSpeech

Speech Coding

Channel Coding

Interleaving

Burst Assembling

Ciphering

Modulation

Speech decoding

Channel decoding

De-interleaving

Burst disassembling

De-ciphering

De-modulation


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Speech CodingSpeech Coding

Analog to Digital conversion.Analog to Digital conversion.

RPE-LPC with long term predictor loopRPE-LPC with long term predictor loop

based on the assumption that based on the assumption thatsamples does not change very quickly.samples does not change very quickly.

Speech divided into 20mSec samples,Speech divided into 20mSec samples,

each of which is encoded as 260 bits.each of which is encoded as 260 bits. The total bit rate is 13Kbps.The total bit rate is 13Kbps.


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Speech CodingSpeech Coding

13Kbps coding is called the Full-Rate13Kbps coding is called the Full-Ratespeech coding.speech coding.

Enhanced Full-Rate (EFR) speechEnhanced Full-Rate (EFR) speech

coding algorithms implemented incoding algorithms implemented inGSM1900 provide improved speechGSM1900 provide improved speechquality at 13Kbps.quality at 13Kbps.

Half Rate codecs are available and canHalf Rate codecs are available and candouble RF channel capacity.double RF channel capacity.


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Channel CodingChannel Coding

260 bits classified as260 bits classified asClass Ia 50 bits Most sensitiveClass Ib 132 bits Moderatelysensitive to bit errors.

Class II 78 bits Least sensitive

to bit errors Coding adapted to needs.Coding adapted to needs.


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Channel CodingChannel Coding

Block Convolutional CodesBlock Convolutional Codes Used for basic error correction. Allows classical

decoding methods. Able to use soft informationprovided by modulation

Fire CodesFire Codes Used for error detection/correction for signalling.

Decoder can detect/correct errors in bursts.

Simple CodesSimple Codes Used for error detection, for signalling and for

highly significant bits in the speech frames.


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Frequency HoppingFrequency Hopping

t890.0890.2

890.4

890.6

890.8

891.0

891.2

915f

GUARD BAND

BP1 BP2 BP3 BP4 BP5BP6 BP7 BP8BP1 BP2 BP3 BP4 BP5BP6 BP7 BP8 BP1 BP2 BP3 BP4 BP5BP6 BP7 BP8


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MS is frequency agile for transmitMS is frequency agile for transmitand receive bursts.and receive bursts.

Slow frequency hopping to:Slow frequency hopping to:Randomise the co-channelinterference effect.

Alleviate multipath fading. FH algorithm broadcast on BCCH.FH algorithm broadcast on BCCH.


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InterleavingInterleaving

Convolutional codes work better whenConvolutional codes work better whenerrors are evenly spread.errors are evenly spread.

Modulation and transmission are suchModulation and transmission are suchthat errors after demodulation tend tothat errors after demodulation tend tocome in bursts.come in bursts.

Interleaving avoids both proximity inInterleaving avoids both proximity inthe burst as well as in coding the data.the burst as well as in coding the data.


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InterleavingInterleaving

A code word (456 bits) on 4 burstsA code word (456 bits) on 4 bursts Block rectangular interleaver. Block rectangular interleaver.

A code word on 8 half bursts A code word on 8 half bursts Block diagonal interleaver.Block diagonal interleaver.

A complex interleaving used forA complex interleaving used for

high rate data (TCH/F9.6 andhigh rate data (TCH/F9.6 andTCH/H4.8)TCH/H4.8)


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Burst AssemblyBurst Assembly

0 2047

Hyperframe = 2048 Superframes

3 Hours 28 Minutes 53 Seconds and 760 milliseconds

500

250

Superframe = 26 51 multiframes

6.12 Seconds

51 MultiframeApprox 235 mS

26 Multiframe120 mS

2524210 50494810

76543210

TDMA frame4.615 mS

OrganisationOrganisation of Speech &of Speech &


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OrganisationOrganisation of Speech &of Speech &DataData

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

BP 7BP 6BP 5BP 4BP 3BP 2BP 1BP 0

8.253571261573

Frames 0-11 : TCH Frames 12 : SACCH Frames 13-24 : TCH Frames 25 : Unused

26 frame multiframeDuration: 120 ms

TDMA frameDuration: 60/13 ms

=4.615 ms

TrainingTrainingsequencesequence

StealingStealingbitbit

StealingStealingbitbit

Data bitsData bits Data bitsData bitsTailTailbitsbits

TailTailbitsbits

GuardGuardbitsbits

Normal burstNormal burstDuration 15/26 msDuration 15/26 ms


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CipheringCiphering

Used to protect signalling and userUsed to protect signalling and userdata.data.

Ciphering Key (Kc) computed usingCiphering Key (Kc) computed using

algorithm A8 + Ki + RAND.algorithm A8 + Ki + RAND. Kc + Algorithm A5 + burst numberKc + Algorithm A5 + burst number

114 bits sequence.114 bits sequence.

114 bits sequence is XORed with two114 bits sequence is XORed with two54 bit blocks of data included in the54 bit blocks of data included in thenormal burst.normal burst.

Modulation andModulation and


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Modulation andModulation andDemodulationDemodulation

Gaussion-filtered Minimum ShiftGaussion-filtered Minimum ShiftKeying (GMSK).Keying (GMSK).

Modulation rate is 270 5/6 KbaudsModulation rate is 270 5/6 Kbaudsfor 270 5/6 Kbits.for 270 5/6 Kbits.

Minimised side lobes by limitingMinimised side lobes by limitingspurious emissions.spurious emissions.

Modulation andModulation and


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Modulation andModulation andDemodulationDemodulation

Constant envelopeConstant envelopeSpectrum compactness andDemodulation performance

DemodulationDemodulationEqualisation

Correct quality of reception withmultipath spread upto 20Sec.


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GMSK ModulatorGMSK Modulator

IntegrationGaussian

Filter

COS

SIN

+

Cost

Sint

Cos(t+f)f

GAUSSUAN MINIMUM SHIFTKEYING

Radio ResourcesRadio Resources


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ad o esou cesad o esou cesManagementManagement

Channel AssignmentChannel Assignment HandoverHandover


Power-level controlPower-level control

Discontinuous TransmissionDiscontinuous Transmission

Discontinuous ReceptionDiscontinuous Reception Timing AdvanceTiming Advance


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HandoverHandover

Intra-cell handoverIntra-cell handover Intra-BSC handoverIntra-BSC handover

Inter-BSC/intra-MSC handoverInter-BSC/intra-MSC handover Inter-MSC handoverInter-MSC handover

Minimum acceptable performanceMinimum acceptable performance Power budget algorithmPower budget algorithm

Discontinuous TransmissionDiscontinuous Transmission


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Discontinuous TransmissionDiscontinuous Transmission(DTX)(DTX)

Speech activity only 40% of time.Speech activity only 40% of time. Needs Voice activity detection.Needs Voice activity detection. Determination of voice thresholdDetermination of voice threshold

vis--vis noise.vis--vis noise. Annoying clicks/inefficient DTX.Annoying clicks/inefficient DTX.

Generation of Comfort Noise atGeneration of Comfort Noise atreceiver to avoid the feeling of thereceiver to avoid the feeling of theset being dead.set being dead.

Di i R i


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Discontinuous ReceptionDiscontinuous Reception

Used to conserve mobile stationsUsed to conserve mobile stationspowerpower

Paging channel divided into sub-Paging channel divided into sub-channelschannels

Assign specific sub-channel to eachAssign specific sub-channel to eachmobile station.mobile station.

Listen to the sub-channelListen to the sub-channel Sleep until next sub-channel slot.Sleep until next sub-channel slot.


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Timing AdvanceTiming Advance

BP1BP2

BP0

BP6BP7

BP7

BP0

BP2

i i d


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Timing AdvanceTiming Advance

Mobiles at different distances from theMobiles at different distances from thebase station cause different delay forbase station cause different delay forsignal arrival at BS.signal arrival at BS.

Timing advance is to synchronise theTiming advance is to synchronise thearrival of signal at BS.arrival of signal at BS.

BS measures the time delay and adviseBS measures the time delay and advise

MS to advance the transmission of itsMS to advance the transmission of itsbursts appropriately.bursts appropriately.

C l


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Power ControlPower Control

BS while performing measurement ofBS while performing measurement oftiming also performs the measurementtiming also performs the measurement

of the power level of each MS.of the power level of each MS. Power control commands are send toPower control commands are send tomobiles to adjust the transmit powermobiles to adjust the transmit power

level of each mobile station so as tolevel of each mobile station so as toensure that BS receives all the burstsensure that BS receives all the burstsalmost at the same power.almost at the same power.

M bili M (MM)


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MM layer is built on top of the RR layer.MM layer is built on top of the RR layer. Handles all functions arising out of theHandles all functions arising out of the

mobility of the subscriber.mobility of the subscriber.

Handles authentication & security.Handles authentication & security. Concerned with the procedures to knowConcerned with the procedures to know

the current location of the powered-onthe current location of the powered-onmobile.mobile.

k iN k A i GSM


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PUBLIC LAND MOBILE NETWORK (PLMN) AREA

Network Areas in GSMNetwork Areas in GSM

MSC Area

Location Area

Location Area

Location Area

MSC Area

Cell

Location Area

Location Area

Location Area

Cell

bili ( )M bilit M t (MM)


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Hierarchical area for pagingHierarchical area for paging Page every cell Vs location updatePage every cell Vs location update

Reliability through periodic locationReliability through periodic locationupdating procedure.updating procedure.

Trade off between signalling loadTrade off between signalling load

and speed of recovery.and speed of recovery. IMSI attach and detach procedureIMSI attach and detach procedure

A h i i d S iA th ti ti d S it


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Authentication and SecurityAuthentication and Security

Is the user the one he claims to beIs the user the one he claims to beAuthentication involves:Authentication involves:

SIM in the mobile.Authentication Centre.

Secret Key stored in SIM & AuCSecret Key stored in SIM & AuC

Generation of Signed Response byGeneration of Signed Response byboth and verification.both and verification.

Di N b All iDi t N b All ti


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Directory Number AllocationDirectory Number Allocation

PSTNPSTNLOCALLOCAL

EXCHANGEEXCHANGE

MSC

MSCMSC

MSISDN

MSRNMSRN

Used to referhome subscribers

Used to referUsed to referroamingroamingsubscriberssubscribers

Home Location RegisterHome Location Register(HLR)(HLR)


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gg(HLR)(HLR)

MSISDN IMSI MSRN Subscriber Data

xx

xx

xx

IMSI

MSISDN

Visitor Location RegisterVisitor Location Register(VLR)(VLR)


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gg(VLR)(VLR)

MSISDN IMSI MSRN LAC TMSI Subscriber Data

xx

xx

MSRN

xx

xx

IMSI

TMSI

S t S itS t S it


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System SecuritySystem Security

Equipment identity confidentiality.Equipment identity confidentiality. Data confidentialityData confidentiality

User identity confidentiality.User identity confidentiality.

A th ti ti d S itA th ti ti d S it


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Authentication and SecurityAuthentication and Security

Computation of Ciphering keyComputation of Ciphering key Kc + FDMA FN + A5 generate 114 bitsKc + FDMA FN + A5 generate 114 bits

sequencesequence

XORed with burst data bitsXORed with burst data bits Interleaving, encoding enable furtherInterleaving, encoding enable further

securitysecurity

Use of IMEI white, grey & black listedUse of IMEI white, grey & black listedmobile terminalsmobile terminals

CommunicationCommunicationM tM t


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ManagementManagement

Responsible forResponsible forCall Control (CC)Supplementary Services ManagementShort Message Service Management

Call control as per ISDN specificationCall control as per ISDN specificationrecommended in Q.931recommended in Q.931

Mobility & Roaming incorporatedMobility & Roaming incorporated

CC manage call setup, service mgt & callCC manage call setup, service mgt & callreleaserelease

C ll R tiC ll R ti


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Call RoutingCall Routing

Mobile Subscriber ISDN numberMobile Subscriber ISDN numberdefined by E.164 Numbering Plan.defined by E.164 Numbering Plan.

Call Routing involve:Call Routing involve:MSISDNMSRN

IMSITMSI

N b i PlN mbering Plan


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Numbering PlanNumbering Plan

MOBILEMOBILE

COUNTRYCOUNTRY

CODECODE

MOBILEMOBILE

NETWORKNETWORK

CODECODE

MOBILE SUBSCRIBERMOBILE SUBSCRIBER

IDENTIFICATION NUMBERIDENTIFICATION NUMBER

3 2 Maximum 10 digits

TMSIMSI

COUNTRYCOUNTRY

CODECODE

NATIONALNATIONAL

DESTINATIONDESTINATION

CODECODE

SUBSCRIBER NUMBERSUBSCRIBER NUMBER

1-3 1-3 Maximum 10 digits

MSISDN/MSRNSISDN/MSRN98 XYZ - ABCDE

N b i PlNumbering Plan


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MCCMCC MNCMNCLACLAC

1-3 1-3 Flexible length

GCICI

CELLCELL

INDENTITYINDENTITY

TMSITMSIMOBILEMOBILE

COUNTRYCOUNTRY

CODECODE

MOBILEMOBILE

NETWORKNETWORK

CODECODE

LOCATIONLOCATION

AREA CODEAREA CODE

3 2 4 Hex

TMSI with in a LAMSI with in a LA

4 Hex

4 Hex

N b i PlNumbering Plan


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SPARE (SP)SPARE (SP)TYPETYPE

APPROVALAPPROVAL

CODE (TAC)CODE (TAC)

FINALFINAL

ASSEMBLYASSEMBLY

CODE(FAC)CODE(FAC)

SERIALSERIAL

NUMBERNUMBER

(SNR)(SNR)

6 2 6

IMEIMEI

1

PLMN Colour CodePLMN Colour Code

NCCNCC

3Bits

BSICSIC

BS Colour CodeBS Colour Code

BCCBCC

3Bits

Ser ices Pro ided b GSMServices Provided by GSM


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Services Provided by GSMServices Provided by GSM

Design objective is to haveDesign objective is to haveinteroperability with ISDN.interoperability with ISDN.

Services provided are a subset ofServices provided are a subset ofISDN services.ISDN services.

Support for various data servicesSupport for various data servicesupto 9600 bps.upto 9600 bps.

GSM ServicesGSM Services


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Teleservices

SupplementaryServices

Bearer Services

TELECOMMUNICATION SERVICES

GSM ServicesGSM Services

Classification of GSMClassification of GSMServicesServices


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ServicesServices

E1 introduced at the start of the service.E1 introduced at the start of the service.

E2 introduced at the end of 1991.E2 introduced at the end of 1991. Eh introduced on availability of half-rateEh introduced on availability of half-rate

channels.channels.

A services that are optional.A services that are optional.

Teleservices in GSMTeleservices in GSM


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Teleservices in GSMTeleservices in GSM

Telephony (E1 & Eh).Telephony (E1 & Eh). Facsimile Group 3 (E1).Facsimile Group 3 (E1).

Emergency Calls (E1 & Eh).Emergency Calls (E1 & Eh).

Teletex.Teletex.

Short Message Services (E1,E2 & A).Short Message Services (E1,E2 & A).

Fax mail.Fax mail.Voice mail.Voice mail.

Bearer Services in GSMBearer Services in GSM


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Bearer Services in GSMBearer Services in GSM

300 to 9600 bps (E1)300 to 9600 bps (E1)Asynchronous and synchronous dataAsynchronous and synchronous dataAlternate speech and dataAlternate speech and data

Asynchronous PAD accessAsynchronous PAD access

2400-9600 bps (E2)2400-9600 bps (E2)

Synchronous dedicated packet dataSynchronous dedicated packet dataaccessaccess

Supplementary Services (E1)Supplementary Services (E1)


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Call Forwarding Busy (CFB)Call Forwarding Busy (CFB) Call Forwarding Unreachable (CFNRc)Call Forwarding Unreachable (CFNRc)

Call Forwarding No reply (CFNRy)Call Forwarding No reply (CFNRy)

Call Forwarding Unconditional (CFU)Call Forwarding Unconditional (CFU) Barring of All Outgoing Calls (BAOC)Barring of All Outgoing Calls (BAOC)

Barring of Outgoing International Calls (BOIC)Barring of Outgoing International Calls (BOIC)

BOIC except those directed towards HomeBOIC except those directed towards HomePLMN Country (BOIC-exHC)PLMN Country (BOIC-exHC)

Barring of All Incoming Calls (BAIC)Barring of All Incoming Calls (BAIC)



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Call Hold (CH)Call Hold (CH)

Call Waiting (CW)Call Waiting (CW)

Advice of Charge (AoC)Advice of Charge (AoC)

Multi-party serviceMulti-party service

Supplementary Services (A)Supplementary Services (A)


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Supplementary Services (A)Supplementary Services (A)

Barring of Incoming Calls while roamingBarring of Incoming Calls while roaming

Closed User Group (CUG)Closed User Group (CUG)

Calling Line Identification Presentation (CLIP)Calling Line Identification Presentation (CLIP) Calling Line Identification Restriction (CLIR)Calling Line Identification Restriction (CLIR)

Connected Line Identification Presentation (COLP)Connected Line Identification Presentation (COLP)

Connected Line Identification Restriction (COLR)Connected Line Identification Restriction (COLR) Operator Determined BarringOperator Determined Barring

Fixed to Mobile Call RoutingFixed to Mobile Call Routing


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Fixed to Mobile Call RoutingFixed to Mobile Call Routing

MSISDN

IMSI/TMSI

MSRN IMSI/TMSI

MSISDN MSRN

MSISDN IMSI/TMSI

VLR

PSTPST

NNMSCMSC

HLR

BSS

BSS


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Call Management Call Management Request forRequest forServiceService


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ServiceService

UmBA

MSMSMSMS BSSBSSBSSBSS MSCMSCMSCMSC VLRVLRVLRVLR

Channel Request

Dedicated Sig.Chl.

assignment

Service Request

Service Request

Service Request

1

2

3

4

5

Call Management Call Management AuthenticationAuthentication


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AuthenticationAuthentication

DBMSMSMSMS MSCMSCMSCMSC VLRVLRVLRVLR HLRHLRHLRHLR

6

7

8

9

12

AuCAuCAuCAuC

Get Authparameters Get Auth

parameters

AuthparametersGet Auth

parametersAuthenticateMobile Stn

AuthenticateMobile Stn

10

11

AuthenticationResponse

13Authentication

Response

Call Management CipheringCall Management Ciphering


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Call Management CipheringCall Management Ciphering

UmBA


Cipher modeComplete

Cipher modeCommand

Cipher Command

Set Ciphering14

15

16

17

18

Cipher mode

Complete

Call Management EqtCall Management EqtValidationValidation


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ValidationValidation

FMSMSMSMS MSCMSCMSCMSC EIREIREIREIR

IMEI Check Results

IMEI Request19

20

21

22

Check IMEI

IMEI Response

PSTN Call Setup withPSTN Call Setup withMobileMobile


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MobileMobile

Call setupRequest

TCH Assign

Call Proceeding

Access Sub data

Select bestaccess CCH

UmBA


Sub data

Validate

Assign TK & Radio

Tune to TCH

TCH ConfirmTK & Radio

Confirm

a e up w anu wNWNW


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NWNW

Connect

Alert Mobile

Outpulse digits

UmBA

MSMSMSMS BSSBSSBSSBSS MSCMSCMSCMSC PSTNPSTNPSTNPSTN

Answer

Select OG Trunk

Connect ACK

Connect path

Incoming Call to MobileIncoming Call to MobileStationStation


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StationStation

Incoming Call

UmBA

MSMSMSMS BSSBSSBSSBSS MSCMSCMSCMSC PSTNPSTNPSTNPSTN

Ring BackValidate

Listening onPCCH

Page in LAPage

Tune to best ACCH

Page Response Page Response

ValidateSet UpTCH Assign

TCH ConfirmAlert

MS Ring Answer Remove RBT

Connect Path

Cellular Call SetupCellular Call Setup


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Mobile Originated Call.Mobile Originated Call.Key in the correct number to be dialled in

the cellular phone before connecting to

the network.Press the send button to originate the

call.Base station identifies the celfone and

passes the information to the MSC.MSC sets up the call.When the called party answers, voice

connection is completed.



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Mobile Terminated Call.Mobile Terminated Call. Call arrives at the home MSC. MSC converts received digits to Mobile

identification number. Broadcast a paging message over the locationarea.

Celfone recognises the page and responds. MSC selects an idle voice channel. Celfone switches to the assigned voice chl. Celfone alerted and RBT connected to caller. When Celfone answers, connection

established.


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Documents

GSM Architecture 1