SYS01: GSM System Interfaces

**sran** · 2011-06-19, 11:09 PM

SYS01: GSM System Interfaces

Chapter 1
Introduction to GSM Interfaces .. i
Introduction to GSM Interfaces .. 1–1
Objectives .. 1–1
GSM System Entities .. 1–2
GSM Architecture .. 1–4
Signalling Links .. 1–6
Exercise .. 1–6
Terrestrial Interfaces ..1–8
Introduction ..1–8
Open Systems Interconnection (OSI) ..1–10
Introduction ..1–10
The Layer Concept ..1–10
Protocols ...1–12
Signalling Model ..1–14
GSM Specifications .. 1–16

Chapter 2
GSM Air Interface Review .. i
GSM Air Interface Review .. 2–1
Objectives .. 2–1
GSM Air Interface ..2–2
Bursts .. 2–2
Timing Advance and Power Control .. 2–4
Mapping Logical Channels onto the TDMA Frame Structure .2–6
Bursts .. 2–6
Multiframes and Timing ..2–8
The 26-frame Traffic Channel Multiframe .. 2–8
The 51-frame Control Channel Multiframe – BCCH/CCCH .2–10
GSM Control Channels ..2–12
BCCH Group .. 2–12
CCCH Group .. 2–12
DCCH Group .. 2–12
Multiframes and Timing ..2–14
The 51-frame Control Channel Multiframe – BCCH/CCCH .2–14
The 51-frame Dedicated Control Channel Multiframe – SDCCH and SACCH .2–16
The 51-frame Control Channel Multiframe – Combined Structure .2–18
Short Message Service Cell Broadcast (SMSCB) . 2–20
SMS Cell Broadcast .. 2–22
Multiple Background Messages .. 2–22

Chapter 3
GSM Air Interface Protocol ..i
GSM Air-interface Protocol .. 3–1
Objectives .. 3–1
MS – BTS Interface (Um or Air-interface) ..3–2
Air-interface – Layer 1 .. 3–4
Air-interface – Layer 1 (SACCH) ..3–10
Air-interface – Layer 2 .. 3–12
Modes of Operation .. 3–14
Unacknowledged Operation ..3–14
Acknowledged Operation .. 3–14
Data Link Connection Identifier (DLCI) .. 3–16
1. Service Access Point Identifier .. 3–16
2. Type of Control Channel .. 3–18
Air-interface – Layer 2 .. 3–20
Frame Format Peer-to-Peer Communication .3–20
Frame Delimitation ..3–24
Address Field ..3–24
SAPI – Service Access Point Identifier .. 3–26
LPD – Link Protocol Discriminator .. 3–26
Control Field Frame Formats .. 3–28
P/F – Poll/Final bit .. 3–28
S – Supervisory Function Bit(s) .. 3–30
U – Unnumbered Function Bit .. 3–32
Length Indicator .. 3–36
List of System Parameters (LAPDm) ..3–38
Air-interface – Layer 3 .. 3–40
Introduction ..3–40
Radio Resource Management Sub-layer .. 3–42
Mobility Management Sub-layer ..3–44
Connection Management Sub-layer .. 3–46
Layer 3 – Frame Structure .. 3–48
Protocol Discriminator/Skip Indicator ..3–50
Skip Indicator ..3–50
Transaction Identifier ..3–52
Message Type .. 3–54
Message Sequence Scenarios .. 3–56
Mobile Originating Call Establishment ..3–58
Mobile Terminating Call Establishment .. 3–60
Location Updating .. 3–62
Call Clearing .. 3–64
Message Flow Scenarios ..3–66
Exercise ... 3–68

Chapter 4
Common Bearer [2 Mbit/s Links] .. i
Common Bearer ..4–1
Objectives .. 4–1
Introduction ..4–2
Signalling Links – Common Channel Signalling .. 4–4
Transmission Code .. 4–6
High Density Bipolar 3 (HDB3) ..4–6
Time Division Multiplexing (TDM) ..4–8
Rx Buffer/Slip Loss ..4–10
Slip Loss Counters ..4–10
Frame Alignment Procedures .. 4–12
N Bit ..4–12
Synchronization ..4–14
Sync Loss Counters .. 4–14
Sync Timers ..4–14
GCLK Synchronization ..4–16
Remote Alarm ..4–22
Remote Loss Alarms ..4–22
Bit Error Rate (BER) .. 4–24
BER Timers ..4–24
BER Counters ..4–24
Cyclic Redundancy Checking (CRC) .. 4–26
Cyclic Redundancy Check ..4–26
Database Command .. 4–26
High Bit-Rate Digital Subscriber Line (HDSL) .. 4–28

Chapter 5
BTS – BSC Interface (A-bis) ..i
BTS – BSC Interface ..5–1
Objectives .. 5–1
BSC – BTS Interface (A-bis) .. 5–2
Introduction ..5–2
GSM Specifications .. 5–4
Signalling Model ..5–6
A-bis Limitations ..5–8
Introduction ..5–8
Link Capacity .. 5–8
Processors .. 5–8
Redundancy ..5–8
Summary ..5–8
******** Defined A-bis Interface (Mobis) .. 5–10
Introduction ..5–10
******** A-bis ..5–10
Functional Division between BSC and BTS . 5–12
MTP L3/SCCP Preselector .. 5–12
Connectionless Manager .. 5–12
SCCP State Machine (SSM) ..5–12
Switch Manager .. 5–12
Cell Resource Manager ..5–12
Radio Resource State Machine (RRSM) ..5–12
Radio Channel Interface .. 5–14
********/GSM A-bis Comparison ..5–16
GSM A-bis .. 5–16
******** A-bis ..5–16
Interface Structure ..5–18
MSI Defaults .. 5–20
Signalling Links Logical Channels .. 5–22
Radio Signalling Link (RSL) .. 5–22
Transparent Messages .. 5–22
Layer 2 Management Link (L2ML) .. 5–22
Layer 2 – Link Access Procedure LAPD .. 5–24
Introduction ..5–24
Frame Structure ..5–26
Definition of Fields ..5–26
Address Field .. 5–28
Service Access Point Identifier (SAPI) .. 5–28
Terminal Endpoint Identifier (TEI) ..5–28
TEI Allocation ..5–30
Control Field .. 5–32
Unnumbered Frames ..5–34
Set Asynchronous Balanced Mode Extended (SABME) Command . 5–34
Disconnect (DISC) Command .. 5–34
Unnumbered Information (UI) Command .. 5–34
Unnumbered Acknowledgment (UA) Response .5–34
Alignment Procedures .. 5–36
Layer 2 timers ..5–36
Timer T203 .. 5–36
Supervisory Control .. 5–38
Layer 2 – Link Access Procedure LAPD .. 5–40
Frame Check Sequence (FCS) Field .. 5–40
Layer 3 Model ..5–42
Complete Layer 2/Layer 3 Message Example (A-bis Defined) . 5–44
Encryption Command ..5–44
Message Discriminator .. 5–46
Message Type .. 5–48
Message Sequence Scenarios .. 5–50
Global Reset .. 5–52
Mobile Originated Connection Establishment .. 5–54
Message Sequence Scenarios .. 5–56
Traffic Assignment Procedures ..5–56
Traffic Assignment Procedures .. 5–58
Request Queued – T11 Expiry ..5–58
Message Sequence Scenarios .. 5–60
Successful Intra-BTS Handover .. 5–60
Successful Inter-BSC Handover ..5–62
Appendix A .. 5–i
BSC to BTS Interface Message Types .. 5–ii
Part A – Message Types as Defined and Implemented by ******** .5–ii
BSC to BTS Messages ..5–ii
BTS to BSC Messages as Defined and Implemented by ******** . 5–iv
Part B ... 5–vii
Message Elements .. 5–vii
1) Message Elements defined by GSM 08.08 . 5–vii
2) Message Elements defined by GSM 08.58 . 5–ix
3) Message Elements defined by GSM 04.08 . 5–x
4) Message Elements defined by GSM 04.08 . 5–xi
5) Message Elements defined by ******** .5–xii
Appendix B .. 5–i
BSC to BTS Interface (A-bis) .. 5–ii
Exercise .. 5–ii

Chapter 6
BSC–MSC Interface (A-interface) .. i
BSC–MSC Interface ..6–1
Objectives .. 6–1
Introduction ..6–2
A-interface Capabilities ..6–2
A-interface specification objectives ..6–2
A-interface Characteristics .. 6–2
GSM Specification ..6–4
08.0x ..6–4
A-Interface Functions .. 6–6
Signalling System No7 (C7) ..6–8
Introduction ..6–8
Messages Transfer Part (MTP) .. 6–10
Level 2 Header Part .. 6–14
LSSU Status Field Format ..6–16
Alignment Procedure ..6–18
Alignment Status Indications ..6–18
Message Signal Unit (MSU) ..6–22
Service Information Octet (SIO) .. 6–24
Signalling Information Field (SIF) ..6–26
Routing Label .. 6–26
Signalling Connection Control Part (SCCP) .. 6–28
Introduction ..6–28
Protocol Classes ..6–28
SCCP Message Format ..6–30
Establishment Procedure .. 6–32
SCCP Message Parameters ..6–34
SCCP Message Example ..6–36
Called/Calling Party Address Parameter ..6–38
Radio Subsystem Application Part (BSSAP) ..6–40
BSSAP Message Structure ..6–42
BSSAP Message Header ..6–44
DTAP Header Structure ..6–44
BSSMAP Header Structure .. 6–46
BSSAP Message Structure ..6–48
Complete Message Format .. 6–48
BSS Management Application Part (BSSMAP) ..6–50
Procedures .. 6–50
Normal Mobile Station (MS) to PSTN Call Set. 6–52
A-Interface Messages .. 6–54
Normal PSTN to MS Call ..6–56
A-Interface Messages .. 6–58
Call from PSTN to MS .. 6–58
Procedures – Global ..6–60
Blocking .. 6–60
Group Circuit Procedures ..6–62
Unblocking .. 6–64
Resource Indication .. 6–66
Resource Indication Procedure ..6–66
Global Reset Procedure ..6–68
Reset at the MSC .. 6–68
Reset at the BSS .. 6–70
Procedures – Global ..6–72
Reset Circuit at the MSC .. 6–72
Reset Circuit at the BSS .. 6–72
Paging .. 6–74
Handover Candidate Enquiry .. 6–76
Flow Control ..6–76
Procedures – Dedicated .. 6–78
Assignment ..6–78
External Handover ..6–80
Handover Required Indication .. 6–80
Handover Resource Allocation ..6–80
Handover Execution .. 6–82
Release ..6–84
Classmark Update ..6–86
Cipher Mode Control ..6–88
Initial MS Message ..6–90
Queueing Indication .. 6–92
Timers ...6–94
MTP Level 2 Timers .. 6–94
MTP Level 3 Timers .. 6–94
BSSMAP Timers ..6–95
Appendix A .. 6–i
Appendix A – MSC to BSC Interface (A-interface) . 6–ii
Exercise .. 6–ii
Appendix B .. 6–i
Appendix B – MSC–BSS Message Types ..6–ii
DTAP Messages ..6–ii
BSSMAP ..6–iii
MSC–BSS Message Types ..6–iv
BSSMAP ..6–iv
BSSMAP Messages .. 6–iv
BSSMAP Messages .. 6–v

Chapter 7
BSS–OMCR Interface (OML) .. i
BSS–OMCR Interface .. 7–1
Objectives .. 7–1
BSS–OMCR Interface (OML) .. 7–2
Introduction ..7–2
******** Application Layer .. 7–4
File Transfer ..7–4
Event/Alarm Reporting .. 7–4
Remote Login ..7–4
OMC–BSS Interconnection ..7–6
OML ...7–8
X.25 Layers ..7–10
Introduction ..7–10
Physical Link Layer 1 ..7–12
Data Link Layer 2 .. 7–14
Overview ..7–14
Address Field .. 7–16
Frame Types – Control field encoding ..7–18
X.25 Packet Level Protocol (PLP) .. 7–20
Packet Header .. 7–22
Logical Channel Numbers (LCN) ..7–24
Packet Type Identifier (PTI) ..7–26
Control Packet Types .. 7–28
Additional Fields ..7–30
OMC to BSS Communication DTE Addresses ..7–32
Virtual Call Setup Procedure .. 7–34

Chapter 8
SMS Cell Broadcast Link ..i
SMS Cell Broadcast Link ..8–1
Objectives .. 8–1
Short Message Service Cell Broadcast ..8–2
Cell Broadcast Link (CBL) ..8–4
CBC, Cell Broadcast Responsibilities ..8–6
BSS, Cell Broadcast Responsibilities ..8–8
Mobiles Cell Broadcast Responsibilities ..8–10
SMS CB Database Commands .. 8–12
Command Line .. 8–12
Functional Description .. 8–12
CBL Message Flow Scenarios ..8–14
CBL Protocol .. 8–16
Multiple SVC Connections ..8–16
Cell Broadcast Messages from BSC to BTS ..8–18
SMS CB Message Structure (Air-Interface) .. 8–20
DRX Scheduling Message Coding .. 8–22
New SMS CB Message Bitmap .. 8–24
New SMS CB Message Description .. 8–24
Other Message Descriptions ..8–24
Message Description Encoding .. 8–26
First Transmission of an SMS CB within the Schedule Period . 8–26
Retransmission Indication ..8–26
Free Message Slot, Optional Reading ..8–28
Free Message Slot, Reading Advised (not yet implemented by ********) . 8–28
Reserved Codepoints ..8–28
Appendix A
The 24-Channel System .. 8–i
The 24-Channel (T1) System .. 8–ii
24-Channel (T1) System .. 8–iv
Channel - associated signalling .. 8–iv
Common - channel signalling .. 8–iv
Comparison of T1 and E1 Systems ..8–iv
Glossary of Terms ..Glos–1