signalling protocol
TRANSCRIPT
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Model of GSM
Rasha Morsi
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Presentation outline:
AcronymsExample of communication over 3 layers GSM as an OSI related modelFunctional Layers of GSMMore Protocols!Protocol overviewNext presentationReferences
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Acronyms
MS : Mobile Station BTS : Base Transceiver Station BSC : Base Station Controller MSC : Mobile-services Switching Center. VLR : Visitor Location Register HLR : Home Location Register AUC : Authentication center EIR : Equipment Identity Register GMSC: Gateway MSC
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Example of communication over 3 layers [1]:
Layer 3
Layer 2
Layer 1
Brazil Germany
CookCook
CaptainCaptain
Radio Operator
RadioOperator
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RIL3 - CC
RIL3 - MM
CCM
MMRR
APPL LI AC YA ET RION
MS BTSAir (Um)Interface
A-bisInterface
BSC
MAP/EMAP/G
MAP/D
AnchorMSC/VLR
RelayMSC/VLR
DATPRIL3 - RR RSM BSSMAP
Distribution Protocol TCAPComponent Sublayer
Transaction Sublayer
A B C,D HLR/AuCGMSCSMS gateway
MAP/C
PresentationLayer *Session Layer *TransportLayer *
NetworkLayer
PhysicalData Link LAP-D
Radio
LAP-D
64kbps ch
SCCP
MTP3
MTP2
MTP1
SCCP
MTP3
MTP2
MTP1
SCCP
MTP3
MTP2
MTP1
SCCP
MTP3
MTP2
MTP1
PSTM/ISDN
MTP3
MTP2
MTP1
TUP,ISUP
OSI
LAYERS
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Functional Layers of GSM:
Three layers : Physical Data Link Layer 3
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Physical Layer:
lowest layer of radio interfaceprovides functions to transfer bit streams over
the physical radio links
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Data Link Layer:
provides a reliable dedicated signaling link between the MS and BS
Layer 2 protocol is based on an adaptation of ISDN link access procedure (LAP-Dm)
standard LAP-D used between BTS and BSCMessage Transfer Part (MTP) of SS7 is used between
BSC - MSC to provide a reliable data link service.Same Protocol ( MTP1) is kept between MSCs, MSC-
HLR/AUC,AUC-GMSC and GMSC-PSTN.
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RIL3 - CC
RIL3 - MM
CCM
MMRR
APPL LI AC YA ET RION
MS BTSAir (Um)Interface
A-bisInterface
BSC
MAP/EMAP/G
MAP/D
AnchorMSC/VLR
RelayMSC/VLR
DATPRIL3 - RR RSM BSSMAP
Distribution Protocol TCAPComponent Sublayer
Transaction Sublayer
A B HLR/AuCC,D
GMSCSMS gateway
MAP/C
PresentationLayer *Session Layer *TransportLayer *
NetworkLayer
PhysicalData Link LAP-D
Radio
LAP-D
64kbps ch
SCCP
MTP3
MTP2
MTP1
SCCP
MTP3
MTP2
MTP1
SCCP
MTP3
MTP2
MTP1
SCCP
MTP3
MTP2
MTP1
PSTN/ISDN
MTP3
MTP2
MTP1
TUP,ISUP
OSI
LAYERS
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Layer 3 :Radio Resource Management (RR), Mobility Management
(MM), Call Control Management (CCM or CM).Overall objectives:
establishment, operation, and release of a dedicated radio channel connection (RR).
Location update, authentication, and Temporary Mobile Subscriber Identity (TMSI) reallocation (MM)
establishment, maintenance, and termination of a circuit-switched call (CCM)
Supplementary Service (SS) support Short Message Service (SMS) support
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Radio Resource Management (RR): RR protocol provides control functions for the
operation of common and dedicated channels. RIL3 RR :
protocols establishes and releases radio connections between MS-various BSCs for the duration of the call.
Provides system information broadcastinginter- and intracell change of channels
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Radio Subsystem Management (RSM) protocol provides functions between the BTS-BSC.
Direct Transfer Application Part (DATP) protocols provide RR messages between the MS-MSC.
The BSS Management Application Part (BSSMAP) protocols provide RR messages between the BSC-MSC
The distinction between DTAP and BSSMAP is provided by a small “distribution” protocol below them.
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Mobility Management (MM): defines dialog between MS and the network. Deals with MS location, security functions
(authentication and ciphering key management)
provides connection management services to the Call Control Layer.
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Call Control Management Layer (CM): CM protocol controls end-to-end call
establishment ( both mobile originating and terminating)and all functions relating to call management.
Includes independent entities : SMS, SS protocols
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More Protocols!
In addition, there are other protocols: MTP3 and Signaling Connection Control Part
(SCCP) used above layer 2 between BSCs - MSCs and MSCs - different databases.
Transaction Capabilities Application Part (TCAP) protocol : sits above SSCP supports transactions between 2 nodes of networkmanages transaction on an end-to-end basis
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Mobile Application Part (MAP) protocol :between MSC, VLR, HLR, and AUC in form of query
and response messages.Protocols designated as MAP/B through MAP/H
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Protocol Overview:
LAP-D: LAPDm used on the air interface(MS - BTS) LAPD used on A-bis interface(BTS - BSC)
MTP: is the basic layer information exchange MTP1, MTP2 provide the means of protected
message exchange between adjacent nodes of a signaling network
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LAPDm Frame Structure
CRC CRC
Address fieldAddress field
Control field Control field
Length indicator field
Fill BitsInformation field
Octet no.
1
2
3
10.12
.
.
.
Bit no. 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1 Octet no.
1
2
3
4
.
.
.
101112
Format type A Format type B
[2]
Network Tx: 00101011Mobile Tx : 11111111 or 00101011
( 8-, 16-, 24-)
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LAPD frame structure:Octet no.
Fill Bits
Length indicator field 1
2.....
i
Bit no. 8 7 6 5 4 3 2 1
Length indicator field
Information field
Fill Bits
Octet no.
1
2..i
i +1...k
A-bis format type B-bis format type
[2]
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Next Presentation :
Detailed Layer 3 Protocols in relation to mobility management
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References :
GSM System Engineering , Asha Mehrotra, Artech House Publishers, 1997An Introduction to GSM , Redl, Weber, and
Oliphant, Artech House Publishers, 1995