Functions of GPRS Elements

8/6/2019 Functions of GPRS Elements

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Chapter 4 :Chapter 4 :Function of GPRS ElementsFunction of GPRS Elements

ObjectivesObjectives

!! Describe the locations for the CCUDescribe the locations for the CCU

!! Describe the four different types ofDescribe the four different types of

channel codec serviceschannel codec services!! Understand where the options are forUnderstand where the options are for

locating the PCUlocating the PCU

!! Discuss the role of the GGSN and SGSNDiscuss the role of the GGSN and SGSN

!! Understand the way that the HLR and VLRUnderstand the way that the HLR and VLR

interact in the GPRS network.interact in the GPRS network.


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ImpactImpact on theon the BaseBaseStationStation

SubsystemSubsystem(BSS)(BSS)!! NoNo majormajor changeschanges occuroccur inside the BSS.inside the BSS.

!! HoweverHowever,, twotwo functionsfunctions mustmust bebe insertedinsertedinside BSSinside BSS!! Channel CodecChannel CodecUnitUnit(CCU)(CCU)

!! LocatedLocated in thein the BaseBaseTransceiverTransceiverSystemSystem(BTS)(BTS)withoutwithout anyany hardwarehardware impactimpact..

!! PacketPacketControlControlUnitUnit(PCU)(PCU)!! CanCan bebe locatedlocated at theat the Network ServiceNetwork ServiceSubsystemSubsystem

(NSS) side(NSS) side oror at theat the BaseBaseStationStationControllerController(BSC)(BSC)

sideside oror itit cancan bebe locatedlocated in thein the PCUPCUSupportSupportNodeNode(PCUSN),(PCUSN), whichwhich residesresides betweenbetween the BSC an thethe BSC an theSGSN.SGSN.

Figure 4-1: Different places to locate the CCU and PCU


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TheThe PacketPacket ControlControl UnitUnit SupportSupport

NodeNode (PCUSN)(PCUSN)

!! PCUSN is a newPCUSN is a new functionalfunctional unitunit

!! PCUSN is aPCUSN is a standstand--alonealone nodenode in the BSSin the BSS!! MainMain functionfunction is tois to complementcomplement thethe BSCsBSCs (2G(2G

& 3G& 3G standardsstandards)) withwith the PCUthe PCU capabilitycapability..

!! TypicallyTypically connectedconnected to the BSCto the BSC withwithAAgprsgprsinterfaceinterface and to the SGSNand to the SGSN withwith GGbbinterfaceinterface

!! PCUSNPCUSN cancan bebe connectedconnected to a single BSCto a single BSC

oror multiplemultiple BSCsBSCs..

Channel Codec Unit (CCU)Channel Codec Unit (CCU)

!! CCU functions:CCU functions:!! The channelThe channel--coding functions (such ascoding functions (such as

forward error correction and interleaving onforward error correction and interleaving onthe air interface)the air interface)

!! Radio channel measurements (quality ofRadio channel measurements (quality ofreceive signal)receive signal)

!! Radio managementRadio management

!! CCU is located in the BTSCCU is located in the BTS

!! Can be softwareCan be software--only upgrades oronly upgrades orhardware and software upgrades,hardware and software upgrades,depending on the coding being performed.depending on the coding being performed.


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The initial releases of the CCUs support four differentcoding schemes:

CS-1: offers a data rate between 8 Kbps to 64 Kbps

CS-2: 12 Kbps to 96 KbpsCS-3: 14.4 Kbps to 96+ KbpsCS-4: 20 Kbps to 115+ Kbps

LAPD

OML: Operation and maintenance linksGSL: GPRS radio signaling linksRSL: Radio signaling links


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Function of the PCUSNFunction of the PCUSN

Serving GPRS Support NodeServing GPRS Support Node

(SGSN) Functions(SGSN) Functions


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!! Routing of packet data using the InternetRouting of packet data using the Internet

ProtocolProtocol

!! Mobility managementMobility management!! Session managementSession management

!! State control; mobile station stateState control; mobile station state

!! Data packet routing on the downlink,Data packet routing on the downlink,

including location trackingincluding location tracking

!!AuthenticationAuthentication

!! EncryptionEncryption!! CompressionCompression

The SGSN performs the followingfunctions:

Figure: The additional functions of the SGSN


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The additional functionsof the SGSN

!! Tracks the mobile station location byTracks the mobile station location by

routing areas or cell locationrouting areas or cell location

!! Keeps track of the connectedKeeps track of the connected GatewayGateway

GPRS Support NodeGPRS Support Node(GGSN) (IP, intranets,(GGSN) (IP, intranets,

the Internet, X.25)the Internet, X.25)

!! Maintains a log of the active Packet DataMaintains a log of the active Packet Data

Protocol(PDP) contextsProtocol(PDP) contexts

!! SGPRS attachSGPRS attach

Gateway GPRS Support NodeGateway GPRS Support Node

(GGSN)(GGSN)


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!! The GGSN serves as the interconnectThe GGSN serves as the interconnect

point between the SGSN and the externalpoint between the SGSN and the external

packet data network.packet data network.

!!

TunnelingTunneling!! GPRS Tunneling ProtocolGPRS Tunneling Protocol(GTP)(GTP)

!! Like IP routingLike IP routing

Home Location Register (HLR)Home Location Register (HLR)


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Home Location Register (HLR)Home Location Register (HLR)

!! Is an existing GSM network elementIs an existing GSM network element

!! Responsible for keeping track of theResponsible for keeping track of themobiles location in the networkmobiles location in the network

!! For GPRS services:For GPRS services:

!! GPRS subscription dataGPRS subscription data

!! subscribed QoSsubscribed QoS

!! statically allocated PDP addressesstatically allocated PDP addresses

!!

roaming permissionsroaming permissions

The Visitor Location Register (VLR)The Visitor Location Register (VLR)

!! One with each MSCOne with each MSC

!! temporarytemporary

!! Contains additional informationContains additional information!! Stored authentication parametersStored authentication parameters

!! Location area identity (LAI)Location area identity (LAI)

!! Routing area identityRouting area identity

!! Mobile Station Roaming Number (MSRN)Mobile Station Roaming Number (MSRN)

!! TMSI or P_TMSITMSI or P_TMSI


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Other Network ElementsOther Network Elements

BG = Border Gateway (Security)

SS7/IP Gateway FunctionsSS7/IP Gateway Functions


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Domain Name System (DNS)Domain Name System (DNS)

Domain Name System (DNS)Domain Name System (DNS)

!!A GPRS network will likely be connected toA GPRS network will likely be connected to

the Internet (IPv4)the Internet (IPv4)

!! DHCP server is installedDHCP server is installed

!! The address resolution between IPThe address resolution between IP

address and GSM address is performed byaddress and GSM address is performed by

the GGSN, using the appropriate PDPthe GGSN, using the appropriate PDP

context.context.

!! Domain Name Server can be used to mapDomain Name Server can be used to map

between external IP addresses andbetween external IP addresses and

hostnamehostname


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Dynamic Host ConfigurationDynamic Host Configuration

Protocol (DHCP)Protocol (DHCP)

ChargingCharging

!! Examples:Examples:

!! allall--youyou--cancan--eateat -- modelmodel

!! DoCoMoDoCoMo model (0.0025 $ / packet)model (0.0025 $ / packet)

!! paypay--asas--youyou--gogo modelmodel

!! paypay--perper--minuteminute modelmodel

!! QoSQoS


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Charging Gateway FunctionCharging Gateway Function

!! Billing Record CollectorBilling Record Collector

!! Collects billing records from the GPRS nodesCollects billing records from the GPRS nodes

!! Flow Aggregation ProcessorFlow Aggregation Processor

!!Aggregates several billing records producedAggregates several billing records produced

during a PDP session into a single GPRSduring a PDP session into a single GPRS

accounting record. (accounting record. (Network AccountingNetwork AccountingRecordRecord, NAR), NAR)

!! Flow Data DistributorFlow Data Distributor

!! Provides access to the GPRS accountingProvides access to the GPRS accounting

records to the customer billing systemrecords to the customer billing system


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The Operation and MaintenanceThe Operation and Maintenance

Center (OMC)Center (OMC)

!!

Functions includeFunctions include!! Events and alarms on all switchingEvents and alarms on all switching

components and procedurescomponents and procedures

!! Fault managementFault management

!! Performance managementPerformance management

!! Security managementSecurity management

!! LocalLocal

The Network Management CenterThe Network Management Center

(NMC)(NMC)

!! Regional or nationalRegional or national

!! Functions includeFunctions include

!! Trunk route managementTrunk route management

!! HighHigh--level alarmslevel alarms

!! OMC assistanceOMC assistance


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Figure: Domain Management

PCUSN OAM ServerPCUSN OAM Server


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OMCOMC--D ArchitectureD Architecture

!!

OMCOMC--D device support providesD device support provides!! fault managementfault management

!! configuration managementconfiguration management

!! performance managementperformance management

!! security managementsecurity management

!! for the following devices (next slidefor the following devices (next slide-->)>)

SMR = Service Management ReporterMDP = Management Data Provider

Functions of GPRS Elements

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