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CONTENTS
GSM PROTOCOLS
RADIO INTERFACE PROTOCOL
ABIS INTERFACE PROTOCOL
ATER INTERFACE PROTOCOL A-INTERFACE PROTOCOL
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PROTOCOL
Protocol is defined as:
Set of Rules which make communication
possible between two devices.
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GSM PROTOCOLS
GSM Protocols Include: LAPDm on Air Interface between MS and Base Station
LAPD on Abis Interface between Base Station and BSC
LAPD on Ater Interface between BSC and TCU.
SS7 on A-interface between TCU and MSC
The Radio Resource [RR] procedure handles Setup, Re-establishment,Handover, TCH mode modify and release of calls.
The Mobility Management [MM] procedures provide Registration,Location and Authentication of MS.
The Connection Management [CM] procedures provide SupplementaryServices [SS], Call Control [CC], Short Message Service [SMS].
To establish a connection with MS, CM must require MM, which in turnrequires RR to open the radio connection.
RR includes LAPDm and LAPD protocols on Air, Abis & Ater interface.
MM and CM messages are transparent to BSS and include SS7 protocol onA-Interface.
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PROTOCOL MODEL
NSS
BSCBTS
MS
MM
BSSAP
SCCP
MTP3
MTP2
TCA
P
M
AP
PCM
CM
MM
MTP3
MTP2
SCCP
PCM E1/T1PCM
SCCP
MTP3
MTP2
D
TA
P
R
R
O & M
R SM
LA
PD
RSM
O & M
RADIORADIO
RR
I
SUP
/
TU
P
CM
Um
Interface
Abis
Interface A-Interface
BSSAP
MTP1
RR
BS
SM
AP
LA
PD
LA
PD
m
LA
PD
m
RR D
T
A
P
BS
SMA
P
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RADIO INTERFACE
Radio Interface is between MS and Base Station. Radio Interface has
features:
Totally Normalized Full Inter-operability between Mobile Stations and infrastructure from different
manufacturers
Radio Interface is organized in three levels:
Level-1 Physical Support TDMA and FDMA
Logical Channels Multiplexing
Level-2 LAPDm Protocol
No Flag
No error retransmission mechanism due to real time constraints
Level-3 Radio Interface Layer [RIL] Protocol involves three sub-layers
Radio Resource Management [RR]: Paging, Power Control, Ciphering, Handovers
Mobility Management [MM]: Security, IMSI Attach / Detach, Location
Connection Management [CM]: Call Control, SMS, DTMF
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RADIO INTERFACE
Connection ManagementConnection Management
Mobility ManagementMobility Management
Radio Resource ManagementRadio Resource Management
Multiplexing
RACH BCCHPCH
AGCH SDCCH FACCH SACCH
TC0 TC11 SACCH TC13 TC24 IDLE
Level 3
Level 2 = LAPDmLogical Channels
Level 1
Physical Channels
Protocols Involved
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ABIS INTERFACE
Abis Interface is between BTS and BSC.
PCM digital links at 2.048Mbps [E1] or 1.544Mbps [T1], carrying 32 or
24 timeslots at 64kbps are used for physical interconnection betweenBTS and BSC.
Abis Interface has following features: Partly Normalized
No Inter-Operability
Radio Interface is organized in three levels: Level-1 PCM Transmission [E1 or T1]
Speech coded at 16kbps and sub multiplexed in 64kbps timeslots
Data which rate is adapted and synchronized
Level-2 LAPD Protocol RSL = Radio Signaling Link
OML = Operation and Maintenance Link
Level-3 Application Protocols
RSM = Radio Subsystem Management
O&M = Operation and Maintenance Procedures
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ABIS INTERFACE
RSMO&M
RSL OML
RSM O&M O&M
Level 1 layer
RSL OML
TRXBCF
Level 3
layer
LAPD
Level 2
layer
BTS side BSC side
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ABIS INTERFACE
Speech 1 TS = 4 channels
LAPD Radio O&M
P
CM
PC
MData300, 1200, 1200/75, 2400,
4800, 9600, 14400 bit/s
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ATER INTERFACE
Ater Interface is between BSC and TCU.
Ater Interface carried 120 communications using E1 and 92
communications using T1. PCM digital links at 2.048Mbps [E1] or 1.544Mbps [T1], carrying 32 or
24 timeslots at 64kbps are used for physical interconnection between
BSC and TCU carrying:
Reserved Signaling Channels for CCS7
Speech and Data Channels [16kbps]
BSC-TCU signaling Link LAPD
O&M data to OMCR [X.25] via MSC
Signaling messages are carried on specific timeslots [TS]: LAPD signaling TS between the BSC and TCU
SS7 TS between the BSC and the MSC
X.25 TS2 reserved for specific configurations
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ATER INTERFACE
Ater interface A interface
LAPD TS 1
SS7 TS
X.25 TS 2 *
SS7 TS
X.25 TS 2 *
BSC
PCM link PCM link
O&M
Speech TS Speech TSTranscoding
Data TS Data TSRate
Adaptation
TCU
MSC
OMC
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ATER INTERFACE
LAPD
SS7
Speech 1 TS = 4 channels
Data 300, 1200, 1200/75, 2400,4800, 9600, 14400 bit/s
O&M
X.25
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A-INTERFACE
A- Interface is between MSC and BSS and has following features:
Totally normalized to allow multi vendor equipment
Full Inter operability in most cases and after testing SS7 is the signaling used on A-Interface, SS7 signaling has two parts:
Message Transfer Part [MTP]
SignalingConnection Control Part [SCCP]
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A-INTERFACE
Speech/Data 1 TS = 1 channel
SS7
BSS NSS
X.25
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THANK YOU!