Chapter 1The GPRS Network

Contents:1.1GPRS and GSM1.GPRS and GSM 1.2Network elements and functionsThe GSM PLMNGPRS Network ArchitectureFunctions of GGSNFunctions of SGSNAdditional PS core entities Modifications for GPRS in the BSSGPRS MS 1.3Services and Network evolutionGPRS Network ServicesNetwork evolution into GERANGERAN reference architecture (Rel 5)

Chapter 1.1The GPRS Network

1.1GPRS and GSMGPRS and GSM

GPRS and GSMhigher flexibility on radio interface!higher efficiencyhigher throughputGSM Phase 2+High Speed Circuit Switched Data (HSCSD)channel bundlingnew coding schemes: up to 14.4 kbps/TSGeneral Packet Radio Service (GPRS)channel bundlingnew coding schemes: up to 21.4 kbps/TS+ capacity on demand+ multiplexing of subscribers on one phy. channelEnhancedData rates for GSM Evolution (EDGE)new modulation and coding schemesEnhancedCircuitSwitchedData (ECSD)up toup toup toup toEnhancedGeneralPacketRadioService (EGPRS)

Chapter 1.2The GPRS Network

1.2 Network elements and functionsThe GSM PLMNGPRS Network ArchitectureFunctions of GGSN Functions of SGSNAdditional PS core entities Modifications for GPRS in the BSSGPRS MS

The GSM PLMNMSC/VLRGMSCHLREIRAuCNSSBSSBSC PSTNTCBTS BTS MSAE(H)FDCAterAbisExtMain element in the NSS is the Mobile Switching Center (MSC) which contains the Visitor Location Register (VLR). The MSC represents the edge towards the BSS and on the other side the Gateway MSC (GMSC), the connection point to all external networks, like the Public Switched Telephone Network or ISDN. GSM is a circuit switched network, there are physical links to transport control information (signalling) and user data. The signalling links are SS7 based and circuits (voice channels) are switched through the MSC (or GMSC).HLRHome Location Register, a main database that contains data for each subscriber like IMSI, MSISDN, subscribed services, access rights etc. EIR Equipment Identity Register, if supported, may be integrated in the HLR. AuC Authentication Center, provides Authentication Triplets for every subscriber to perform authentication and ciphering (performed by MSC/VLR).SCPService Control Point, a database for Intelligent Network services.CSECAMEL Service Entity, a database for PLMN specific Intelligent Services, e.g. charging of roaming subscribers.SMSCShort Message Service Center, used for transfer of short messages. The GSM Public Land Mobile Networks (PLMN) consists out of a Network Switching Subsystem (NSS) and a Base Station System (BSS). CSESCPSMSCSS7

GPRS Network ArchitectureGGSNSGSNGnMSC/VLRGMSCHLREIRAuCGsGrGcGfGiNSSGERANBSS PSTN ISP IPvX backboneTCBSSBTS GbTCBTS BTS BTS BTS BTS MSAAbisE(H)FDCAterAbisExtHome SubscriberServer (HSS)Rel 5GPRS PS Core NetworkBSCPCUBSCPCU

Functions of GGSNGMSCGateway Mobile services Switching CentreGGSN Gateway GPRS Support Nodesignalling evaluation (SS7)switching (cs traffic)operational tasks incl. - collection of traffic statistics - alarms - generation of charging recordsinterrogation of HLRoften interfacing external networks, such as PSTN, ISDN

signalling evaluation (IP header)routing and tunneling of packet data (ps traffic)operational tasks incl. - collection of traffic statistics - alarms - generation of charging recordsinterrogation of HLRinterfaces external IP networksInterfaces internal IP network (IP BB)Allocates dynamic or static IP addresses to mobiles either by itself or with the help of a DHCP or a RADIUS serverGateway GPRS Support Node is an IP router that provides access to various PDP networks, e.g. the Internet

Functions of SGSN(V)MSC/VLRVisited MSC/ Visitor Location RegisterSGSN Serving GPRS Support Nodesignalling evaluation (SS7)switching (cs traffic)operational tasks incl. - collection of traffic statistics - alarms - generation of charging recordsMobility Management, incl. authentication, authorisation, location area updatesConnection Management, incl. call control, SMS, supplementary services Paging (CS)

signalling evaluation (IP header)routing (ps traffic)operational tasks incl. - collection of traffic statistics - alarms - generation of charging recordsGMM (GPRS Mobility Management), incl. authentication, authorisation, routing area updates SM (Session Management), incl. PDP (Packet Data Protocol) context management and SMS Paging (PS and CS as option)Protocol conversion between IP backbone and BSS protocols e.g. data compression for IP-Header and IP payload (V.42 bis, RFC 1144).

Additional PS core entitiesGGSNSGSN IPvX backboneGPRS PS Core NetworkCGBilling CentreBGLIGLEADNSCharging Gateway:GPRS charging data records (CDR) are generated by SGSNs and GGSNs, and sent to the CG via interface Ga.The Charging Gateway collects all this data togetherprocesses it passes it to the Billing SystemBorder Gateways: BGs are to interconnect operators' GPRS backbone networks via a secure connection to support roamingLawful Interception Gateway:Lawful interception is an action based on the law, which is performed by the GPRS network It provides information for a Law Enforcement Agency (LEA) about some pre-defined target subscriberInformation could include data sent and received by the interception targetlocation informationsubscriber informationetc. Domain Name Server:used to convert IP names into IP addresses or vice versa.DNSBGLIGCG

Modifications for GPRS in the BSS SGSN site

BSC site

BTS

CCUCCUPCUAbisChannel Codec Unit:BTS SW upgrade for new Coding Scheme (CS 1-4 or CS 1+2). GbAterCCU

The PCU (Packet Control Unit):Performs radio specific functions (Radio Resource Management) Manages sub-multiplexing of multiple MS on one physical channel Decides which radio resources are dynamically allocated to packet switched or circuit switched use Is responsible for packet segmentation and re-assembly Guarantees reliable link to MS Terminates Gb interface In most vendors implementation the PCU is a part of the BSC, in principle it could be as well a standalone module or integrated in the BTS.

PCU

GPRS MSSimultaneous CS and PS attach activation monitorno simultaneous trafficsimultaneous attach activation monitor invocation trafficof GSM and GPRSpure GPRS oralternative use of GSM and GPRS onlyclassBclassCclassAA class A MS may be attached to the CS and PS core simultaneously. While the MS is in packet transfer mode and there is an incoming call the MS can continue its packet session while making the call and enters the Dual Transfer Mode (DTM). DTM requires additionally support by networks (BSS).

A class B MS may be attached to the CS and PS core simultaneously. While the MS is in packet transfer mode and there is an incoming call the MS can take the call, the packet transfer has to be suspended and resumed after the call is finished.

A class C MS may be attached to the CS or PS core. While the MS is in packet transfer mode there can be no incoming call. Usually these MSs are PCMCIA cards.

Chapter 1.3The GPRS Network

1.3 Services and Network evolutionGPRS Network ServicesNetwork evolutions into GERANGERAN Reference architecture (Rel 5)

GPRS Network ServicesRouterRouterApplicationServerMSBSSNSSGGSNGGSNSGSNPCUuser's point of viewThe objective of this training are the (E)GPRS signalling protocols, and to show, how a user data packet is transmitted through the GPRS network. The user data transmission can be seen from two points of view:end user's point of view: The subscriber wants to exchange user data packets between the mobile terminal (MT) attached to his MS (or internal) and an application server, located in a PDN.

operator's point of view: The operator is especially responsible to transmit the user data from one access point of the PLMN to another. The access points to and from the PLMN are the MS and the GGSN.

The operator is required to offer a certain Quality of Service (QoS) in order to enable new services. Services are categorized into (Rel 99)Interactive classBackground classStreaming classConversational class

Network evolutions into GERAN2G NetworkGERAN (GSM/EDGE Radio Access Network)GSMHSCSDGPRSECSDEGPRSclassicTDMA/136TDMA/136 +TDMA/136HS OutdoorTDMA/136HSindoorEGPRScompactSupport of Interactive and Background PS Services (Rel 99)Support of streaming (Rel 4) and conversational PS Services (Rel 5)In order to deliver the required QoS for a certain service the existing networks are enhanced. ETSI standardized the GSM radio interface and defined GSM, GPRS, EDGE access to PS Core Network (Rel 97, 98 ,99). Due to aspects of harmonization and interworking with 3G the specifications has been moved to 3GPP. Rel 99 has been adopted by 3GPP. Since then the GSM access network is referred to as GERAN. The evolution of GERAN is done in Rel 4, 5, 6,... (along with the evolution of CN entities).Currently Rel 4, 5 and 6 features are adopted in order to fullfil the requirements for new services

GERAN Reference architecture (Rel 5)A MS may operate in Gb mode (class A, B or C MS) or Iu mode. For Iu mode the MS may operate CS/PS mode: correspondends to Class A in A/Gb modePS mode: MS can only operate packet switched servicesCS mode: MS can only operate circuit switched servicesGSM/UMTSCore NetworkGERANGbAIuCSMSUmIur-gBSCBTSBTSBSSBSSMSIur-gUTRANRNCIuPSTo 3G CN (Iu mode) To 2G CN (A/Gb mode) required for Rel 4 or older MSsEnhancedcompared to Rel 99 (Support of Realtime Packet services)-Interactive,-Background,-Streaming PS Services-Interactive,-Background,-Streaming-Conversational PS ServicesIur-g (cancelled)-Interface carries only control signalling-no user data-improved interworking GERAN-UTRAN-Radio specific procedures handled completely inside RANIuCSIuPSTo 3G CN

Kap. X KapitelberschriftKursnummer / Kurstitel / VersionKap. X KapitelberschriftKursnummer / Kurstitel / VersionKap. X KapitelberschriftKursnummer / Kurstitel / VersionKap. X KapitelberschriftKursnummer / Kurstitel / VersionKap. X KapitelberschriftKursnummer / Kurstitel / VersionKap. X KapitelberschriftKursnummer / Kurstitel / VersionKap. X KapitelberschriftKursnummer / Kurstitel / VersionKap. X KapitelberschriftKursnummer / Kurstitel / VersionKap. X KapitelberschriftKursnummer / Kurstitel / VersionKap. X KapitelberschriftKursnummer / Kurstitel / VersionKap. X KapitelberschriftKursnummer / Kurstitel / VersionKap. X KapitelberschriftKursnummer / Kurstitel / VersionKap. X KapitelberschriftKursnummer / Kurstitel / VersionKap. X KapitelberschriftKursnummer / Kurstitel / VersionKap. X KapitelberschriftKursnummer / Kurstitel / Version