GSM NetworksGSM Networks

Slide 5

GSM Network OverviewGSM Network Overview

BSCBTS

BTS

Mobile

Station

Access Network:Base Station Subsystem

HLR VLR EIR AuC

MSC PSTN

Um Abis A

Core Network:GSM CS network

SS7

Slide 29

GSM Network ProtocolsGSM Network Protocols

Slide 30

GSM Signaling ProtocolsGSM Signaling Protocols

Layer 1 (physical layer) Uses many channel structures

Layer 2 (data link layer)Across Um interface uses LAPDm (a slight modification of LAPD protocol used in ISDN)Across Abis uses LAPDAcross A interface, uses MTP and SCCP of SS7 SAPI=0 Identifies radio signaling procedures

Layer 3 is sub-divided into 3 sub-layers

Slide 31

Layer 3 Signaling ProtocolsLayer 3 Signaling Protocols

RR: Radio Resources ManagementEstablishment, maintenance, and termination of radio channels that allow point-to-point dialogue between network and mobile stations; including cell selection and handover procedures MM: Mobility ManagementManages location updating, registration, security and authentication proceduresCM: Connection ManagementHandles general call control, similar to CCITT Recommendation Q.931, and provides supplementary services & Short Message Services (SMS)

Slide 32

HandoverHandover

Four types of handovers: Channels (time slots) in same cell Between cells within same BSC Between BSCs, within same MSC Between MSCs

PSTN

BTS

BTS

BTS

BTS

BTS

BTS

BTS

BSC BSC

MSC

BTS

BTS

BTS

BTS

BTS

BTS

BTS

BSC BSC

MSC

Slide 33

MAP (Mobile Application Part)MAP (Mobile Application Part)

SS7 top layer protocolResponsible for signaling between different entities in network, such as between HLR and VLR MAP specification is complexSeveral variants for the big manufacturers (Ericsson, Motorola …)

Slide 35

SummarySummary

GSM is the dominant cellular technology todayGSM offers high quality voice with advanced servicesGSM is the stepping-stone to 3G networks