47936945 bss system description alcatel system

7/31/2019 47936945 BSS System Description Alcatel System

1/242

3BK 02974 AAAA TQZZA Ed. 07

Alcatel 900/1800BSS

System Description

Descriptive Document

System Guide


2/242

3BK 02974 AAAA TQZZA Ed. 072 / 240

Status Released

Change Note

Short Title System Description

All rights reserved. Passing on and copying of thisdocument, use and communication of its contentsnot permitted without written authorization from Alcatel.


3/242

Contents

3BK 02974 AAAA TQZZA Ed. 07 3 / 240

Contents

Preface 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 Introduction 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.1 Overview 18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.2 BSS Functions 19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.2.1 Call Set Up 19. . . . . . . . . . . . . . . . . . . . . . . . .1.2.2 Call Handling 20. . . . . . . . . . . . . . . . . . . . . . .1.2.3 Call Release 20. . . . . . . . . . . . . . . . . . . . . . . .1.2.4 Operations & Maintenance 21. . . . . . . . . . .

1.3 BSS Features 21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.3.1 Features Defined in the GSM

Recommendations 21. . . . . . . . . . . . . . . . . . .1.3.2 Alcatel BSS Features 23. . . . . . . . . . . . . . . . . .1.3.3 New Service Improvement Features 25. . . .

1.4 BSS Components 27. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.4.1 Base Station Controller 28. . . . . . . . . . . . . . .1.4.2 Base Transceiver Station 28. . . . . . . . . . . . . .1.4.3 Transmission Subsystem 29. . . . . . . . . . . . . .

1.5 External Components 31. . . . . . . . . . . . . . . . . . . . . . . . . .1.5.1 Network Subsystem 31. . . . . . . . . . . . . . . . . .1.5.2 Mobile Stations 32. . . . . . . . . . . . . . . . . . . . . .

1.5.3 Operations and MaintenanceCenterRadio 36. . . . . . . . . . . . . . . . . . . . . . . .

1.6 Network Management 37. . . . . . . . . . . . . . . . . . . . . . . . .1.6.1 Telecommunications Management

Network 37. . . . . . . . . . . . . . . . . . . . . . . . . . . .1.6.2 Q3 Interface 38. . . . . . . . . . . . . . . . . . . . . . . .

1.7 BSS Telecommunications Layers 39. . . . . . . . . . . . . . . . .1.7.1 Call Management 39. . . . . . . . . . . . . . . . . . .1.7.2 Mobility Management 40. . . . . . . . . . . . . . . .1.7.3 Radio Resource Management 40. . . . . . . . .1.7.4 The A Interface 41. . . . . . . . . . . . . . . . . . . . . .

1.7.5 The Abis Interface 42. . . . . . . . . . . . . . . . . . .1.7.6 The Air Interface 43. . . . . . . . . . . . . . . . . . . . .

2 Call Set Up 47. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.1 Overview 48. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.2 Mobile Originated Call 50. . . . . . . . . . . . . . . . . . . . . . . .2.2.1 Radio and Link Establishment 50. . . . . . . . .2.2.2 Authentication and Ciphering 55. . . . . . . . .2.2.3 Normal Assignment 55. . . . . . . . . . . . . . . . . .


4/242

Contents

3BK 02974 AAAA TQZZA Ed. 074 / 240

2.3 Mobile Terminated Call 61. . . . . . . . . . . . . . . . . . . . . . . .2.3.1 Radio and Link Establishment 61. . . . . . . . .2.3.2 Authentication and Ciphering 62. . . . . . . . .2.3.3 Normal Assignment 62. . . . . . . . . . . . . . . . . .

2.3.4 IMSI Attach-Detach 64. . . . . . . . . . . . . . . . .2.4 Paging 65. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.5 Congestion 69. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.5.1 Queueing 69. . . . . . . . . . . . . . . . . . . . . . . . . .2.5.2 Inqueue 69. . . . . . . . . . . . . . . . . . . . . . . . . . .

2.6 Classmark Handling 72. . . . . . . . . . . . . . . . . . . . . . . . . . .2.6.1 Classmark IE 72. . . . . . . . . . . . . . . . . . . . . . . .2.6.2 Classmark Updating 74. . . . . . . . . . . . . . . . .2.6.3 Location Updating with Classmark

Procedure 75. . . . . . . . . . . . . . . . . . . . . . . . . .

2.7 Authentication 77. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.8 Ciphering 79. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.8.1 Ciphering Keys 80. . . . . . . . . . . . . . . . . . . . . .2.8.2 Ciphering Procedure 81. . . . . . . . . . . . . . . . .

3 Call Handling 83. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.1 Overview 84. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.2 InCall Modification 85. . . . . . . . . . . . . . . . . . . . . . . . . . .3.2.1 InCall Modification Procedure 86. . . . . . . .3.2.2 Group 3 Fax Data Rate Change 87. . . . . . .3.2.3 Error Handling 88. . . . . . . . . . . . . . . . . . . . . .

3.3 Handover 89. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.3.1 Radio Measurements 90. . . . . . . . . . . . . . . . .3.3.2 Handover Detection 91. . . . . . . . . . . . . . . . . .3.3.3 Target Cell Evaluation 99. . . . . . . . . . . . . . . .3.3.4 Synchronous and Asynchronous Handover 100

3.4 Overload Control 107. . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.4.1 BTS Overload 107. . . . . . . . . . . . . . . . . . . . . . .3.4.2 BSC Overload 108. . . . . . . . . . . . . . . . . . . . . . .

4 Call Release 111. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.1 Overview 112. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.2 Call Release Procedures in Normal Service 114. . . . . . .

4.2.1 Normal Release 114. . . . . . . . . . . . . . . . . . . . .4.2.2 Calls Terminated Following a Channel

Change 119. . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.3 Call Release - Special Cases 120. . . . . . . . . . . . . . . . . . .4.3.1 Call Release Following Reset 120. . . . . . . . . .4.3.2 BSCInitiated Release 122. . . . . . . . . . . . . . . .4.3.3 BTSInitiated Call Release 124. . . . . . . . . . . . .


5/242

Contents

3BK 02974 AAAA TQZZA Ed. 07 5 / 240

4.3.4 MSInitiated Call Release 126. . . . . . . . . . . . .4.3.5 Remote TC Alarms 127. . . . . . . . . . . . . . . . . . .

5 Service Improvement Features 129. . . . . . . . . . . . . . . . . . . . . . .

5.1 Overview 130. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.2 Features Defined in the GSM Recommendations 131. . .5.2.1 Cellular Environment 131. . . . . . . . . . . . . . . . .5.2.2 RPC Uplink and Downlink 131. . . . . . . . . . . .5.2.3 Frequency Hopping 135. . . . . . . . . . . . . . . . . .5.2.4 Discontinuous Transmission 138. . . . . . . . . . .5.2.5 Discontinuous Reception 142. . . . . . . . . . . . . .5.2.6 Phase 2 Mobile Support in a Phase 1 Infrastruc

ture 142. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.2.7 Call Reestablishment by the MS 143. . . . . . .5.2.8 Short Message Service Cell Broadcast 144.

5.2.9 Enhanced FullRate 144. . . . . . . . . . . . . . . . . .5.3 Alcatel BSS Features 146. . . . . . . . . . . . . . . . . . . . . . . . . . .

5.3.1 Types of Cell Environments 146. . . . . . . . . . . .5.3.2 Antenna Diversity 147. . . . . . . . . . . . . . . . . . . .5.3.3 Multiple HumanMachine Interface 149. . . . .5.3.4 Night Time Concentration 151. . . . . . . . . . . .5.3.5 Secured X.25 Connection From BSC to

OMCR 153. . . . . . . . . . . . . . . . . . . . . . . . . . . .5.3.6 Usage State on Demand 155. . . . . . . . . . . . . .5.3.7 BSC Alerter 156. . . . . . . . . . . . . . . . . . . . . . . . .

5.4 New Service Improvement Features 158. . . . . . . . . . . . . .5.4.1 Power Control due to Radio Link Failure 1585.4.2 Q3 Multimanager 158. . . . . . . . . . . . . . . . . . .5.4.3 OMCR Connection to TSC through BSC 1585.4.4 Abis Signaling Links Static Multiplexing 159.5.4.5 Transcoder Pools 159. . . . . . . . . . . . . . . . . . . .5.4.6 Automatic PowerDown 160. . . . . . . . . . . . . . .5.4.7 Auto Identification 160. . . . . . . . . . . . . . . . . . .5.4.8 Automatic Paging Repetition 161. . . . . . . . . . .5.4.9 Access to PM Raw Counters via Binary

Files 162. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6 Handling User Traffic Across the BSS 163. . . . . . . . . . . . . . . . .

6.1 Overview 164. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.2 Speech 165. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.3 Data 168. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6.3.1 Transparent Mode 169. . . . . . . . . . . . . . . . . . .6.3.2 NonTransparent Mode 170. . . . . . . . . . . . . . .

7 Cell Environments 171. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.1 Overview 172. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


6/242

Contents

3BK 02974 AAAA TQZZA Ed. 076 / 240

7.2 Concentric Cell 174. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.3 Sectored Site 175. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.4 Extended Cell 176. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.5 Umbrella Cell 178. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7.5.1 Mini Cell 178. . . . . . . . . . . . . . . . . . . . . . . . . . .7.5.2 Microcell 179. . . . . . . . . . . . . . . . . . . . . . . . . . .

8 Operations & Maintenance 183. . . . . . . . . . . . . . . . . . . . . . . . . .

8.1 Overview 184. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8.1.1 BSC O&M Functions 184. . . . . . . . . . . . . . . . .8.1.2 BTS O&M (G1 and G2 BTSs) 186. . . . . . . . . .8.1.3 BTS A9100 O&M 187. . . . . . . . . . . . . . . . . . . .8.1.4 BTS O&M Functions (All Generations) 188. .8.1.5 TSC O&M Functions 188. . . . . . . . . . . . . . . . .8.1.6 OMCR in O&M Functions 190. . . . . . . . . . . .

8.2 O&M Communication Mechanism 191. . . . . . . . . . . . . . .8.2.1 O&M Command Flows 191. . . . . . . . . . . . . . .8.2.2 Spontaneous Messages 193. . . . . . . . . . . . . . .

8.3 Alarms 194. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8.3.1 Alarm Generation 194. . . . . . . . . . . . . . . . . . .8.3.2 BSC Alarms 195. . . . . . . . . . . . . . . . . . . . . . . . .8.3.3 BTS Alarms 199. . . . . . . . . . . . . . . . . . . . . . . . .8.3.4 TSC Alarms 200. . . . . . . . . . . . . . . . . . . . . . . . .

8.4 Status Changes 201. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8.4.1 Phases of Board Operations 201. . . . . . . . . . .8.4.2 State Change Operations 202. . . . . . . . . . . . .8.4.3 States In Traffic 203. . . . . . . . . . . . . . . . . . . . . .8.4.4 States Not In Traffic 204. . . . . . . . . . . . . . . . . .8.4.5 BSS SBL Operator Commands 205. . . . . . . . .8.4.6 Recovery Example: CU Failures with

BCCH 207. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8.4.7 Reset Example: TSC RESET 209. . . . . . . . . . . .

8.5 Tracing 211. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8.5.1 Call Tracing 211. . . . . . . . . . . . . . . . . . . . . . . . .8.5.2 IMSI Tracing 212. . . . . . . . . . . . . . . . . . . . . . . .

8.6 Measurement Jobs 213. . . . . . . . . . . . . . . . . . . . . . . . . . . .8.6.1 OMCR Measurement Job Classes 213. . . . .8.6.2 Measurement Results 214. . . . . . . . . . . . . . . . .8.6.3 Counters 214. . . . . . . . . . . . . . . . . . . . . . . . . . .8.6.4 Data Collection on the BSC 216. . . . . . . . . . .8.6.5 Counter Examples 218. . . . . . . . . . . . . . . . . . .

8.7 Audits 220. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8.8 Modifying Telecom Parameters 222. . . . . . . . . . . . . . . . . .

Abbreviations 223. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


7/242

Contents

3BK 02974 AAAA TQZZA Ed. 07 7 / 240

Appendix A Air Interface Channels 229. . . . . . . . . . . . . .

Index 231. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


8/242

Contents

3BK 02974 AAAA TQZZA Ed. 078 / 240

Figures

Figure 1 BSS in the PLMN 18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 2 Base Station Subsystem Components 27. . . . . . . . . . . . . . . . . . .

Figure 3 Transmission Subsystem Components 30. . . . . . . . . . . . . . . . . . .Figure 4 Logical Position of External Components Associated with BSS 31Figure 5 Location Update 35. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 6 TMN System Hierarchy 37. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 7 General Telecommunication Layers within GSM 39. . . . . . . . . .Figure 8 BSS Application, Transmission Layers and Interfaces 40. . . . . .Figure 9 Time Slot 4 of a TDMA Frame Supporting AGCHs 44. . . . . . . .Figure 10 Radio and Link Establishment for Mobile Originated Call 51. .Figure 11 SDCCH Channel Activation 52. . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 12 Immediate Assignment 53. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 13 Connection for Mobile Originated Call 54. . . . . . . . . . . . . . . . .

Figure 14 Normal Assignment for Mobile Originated Call 56. . . . . . . . . .Figure 15 TCH Channel Activation 58. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 16 TCH Channel Assignment 59. . . . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 17 Call Connection for Mobile Originated Call 60. . . . . . . . . . . . .Figure 18 Radio and Link Establishment for Mobile Terminated Call 62. .Figure 19 Normal Assignment for Mobile Terminated Call 63. . . . . . . . . .Figure 20 CCCH with Three Blocks Reserved for AGCH 65. . . . . . . . . . . .Figure 21 Four TDMA Frame Cycles Providing 24 Paging Subchannels 66Figure 22 Paging Message Sequence 68. . . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 23 Location Update with Classmark Update 75. . . . . . . . . . . . . . . .Figure 24 Location Update with MS Sending LAI of Previous VLR 77. . . . .Figure 25 Ciphering Procedure 82. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 26 Quality and Level Handover 93. . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 27 Better Zone Handover 95. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 28 Better Cell Handover (Power Budget) 96. . . . . . . . . . . . . . . . . . . .Figure 29 Distance Handover 97. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 30 Umbrella Cell Load in Mobile Velocity Dependent Handover 98Figure 31 Synchronous Internal Handover 103. . . . . . . . . . . . . . . . . . . . . . . .Figure 32 Asynchronous External Handover 106. . . . . . . . . . . . . . . . . . . . . . .Figure 33 MS Disconnecting a Call 114. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 34 Normal Call Release 115. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 35 Initiation of Normal Release by MSC 116. . . . . . . . . . . . . . . . . . . .Figure 36 BSC/BTS/MS interactions in Normal Call Release 117. . . . . . . . .Figure 37 Normal Release Final Steps 118. . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 38 Call Release Following a Channel Change 119. . . . . . . . . . . . . .Figure 39 Call Release Following Reset 121. . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 40 BSCinitiated Call Release toward the MSC 122. . . . . . . . . . . . . .Figure 41 BTSinitiated Call Release following LAPD failure 125. . . . . . . . .Figure 42 Call Release due to MS initiated Radio Link Failure 126. . . . . . .Figure 43 Call Release due to Communication Failure detected by TC 127Figure 44 Power Control Flow of Measurement and Decision Action 134. .


9/242

Contents

3BK 02974 AAAA TQZZA Ed. 07 9 / 240

Figure 45 Power Output Balancing Based on Received Quality and SignalLevels 134. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 46 Frequency Hopping within an FHS 137. . . . . . . . . . . . . . . . . . . . . .Figure 47 Different Forms of Discontinuous Transmission 141. . . . . . . . . . .

Figure 48 Short Message Service Cell Broadcast 144. . . . . . . . . . . . . . . . .Figure 49 Antenna Diversity on G1 and G2 BTSs 147. . . . . . . . . . . . . . . . . .Figure 50 Antenna Diversity on the BTS A9100 (1 Sector, 3X4 Transceiver

Configuration) 148. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 51 Multiple HMI Access to OMCRs 149. . . . . . . . . . . . . . . . . . . . . . .Figure 52 Night Time Concentration 151. . . . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 53 X.25 Without Redundancy 153. . . . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 54 X.25 With Redundancy 154. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 55 Encoded Speech Transmission Across the BSS 165. . . . . . . . . . . .Figure 56 Multiplexed Ater Interface 166. . . . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 57 Data Transmission Across the BSS 168. . . . . . . . . . . . . . . . . . . . . .

Figure 58 Example: Cell Configurations 173. . . . . . . . . . . . . . . . . . . . . . . . . .Figure 59 Sectored site configuration 175. . . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 60 Example of Extended Cell Topology 177. . . . . . . . . . . . . . . . . . . . .Figure 61 Umbrella Cell with Mini Cells 178. . . . . . . . . . . . . . . . . . . . . . . . . .Figure 62 Example: Handovers due to Threshold Triggering 180. . . . . . . . .Figure 63 BSC O&M Components 185. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 64 O&M Components and Data Flow in the G1 and G2 BTS 186.Figure 65 O&M Components and Data Flow in the BTS A9100 187. . . . . .Figure 66 Transmission System O&M Components 189. . . . . . . . . . . . . . . . .Figure 67 Example: Message Flow Using CMISE 191. . . . . . . . . . . . . . . . . .Figure 68 Example: BSC Command Flow 192. . . . . . . . . . . . . . . . . . . . . . . .Figure 69 RSL Correlation on the Abis Interface 196. . . . . . . . . . . . . . . . . . .Figure 70 Example: Alarm Report 198. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 71 States and Phases of Board Operation 202. . . . . . . . . . . . . . . . . .Figure 72 Relationship Between SBL States 204. . . . . . . . . . . . . . . . . . . . . . . .Figure 73 Example: Loss of CU Holding BCCH. 209. . . . . . . . . . . . . . . . . . .Figure 74 TSC Reset 210. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 75 Counter Object Tree 216. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Figure 76 Data Collectors within the BSC 217. . . . . . . . . . . . . . . . . . . . . . . . .Figure 77 Example: Counter Object Tree 219. . . . . . . . . . . . . . . . . . . . . . . . .Figure 78 Channels and Their Direction of Flow 230. . . . . . . . . . . . . . . . . . .


10/242

Contents

3BK 02974 AAAA TQZZA Ed. 0710 / 240

Tables

Table 1 System Information Messages 46. . . . . . . . . . . . . . . . . . . . . . . . . .Table 2 Types of Calls 48. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 3 Call Set Up Phases 49. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 4 Cell List Identifier and Paging Performed 67. . . . . . . . . . . . . . . .Table 5 Paging Request Message and MS Identification 67. . . . . . . . . . .Table 6 Classmark Handling 72. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 7 Classmark Configuration 74. . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 8 MS Ciphering Capabilities 79. . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 9 Radio Link Measurements 133. . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 10 MS Maximum and Minimum Power Ranges 135. . . . . . . . . . . . . .Table 11 Downlink DTX Status in Channel_activation 139. . . . . . . . . . . . . .Table 12 Operator DTX Options 140. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 13 BSC Alerter Types 157. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 14 Data Rate Conversions Across the Air Interface 169. . . . . . . . . . .Table 15 O&M Functions 185. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 16 Functional Unit States 201. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 17 SBL O&M Operator Commands 206. . . . . . . . . . . . . . . . . . . . . . .Table 18 Measurement Job Classes 213. . . . . . . . . . . . . . . . . . . . . . . . . . . . .Table 19 Audit Types 220. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


11/242

Purpose

Audience

Preface

11 / 2403BK 02974 AAAA TQZZA Ed. 07

Preface

This document provides detailed descriptions of the functions andfeatures of the Alcatel 900/1800 Base Station Subsystem (BSS).Some functions and features may not be available on the systeminstalled at your location.

The technical information in this document covers:

" Mobile Communications Support

These areas describe how the BSS handles communicationsbetween a Mobile Station (MS) and the NetworkSubsystem (NSS). It follows a call through the Alcatel BSS, and

describes how each element in the system functionsindividually and with other elements. This shows how the BSSand its units react as a system.

" Operations and Maintenance

These areas describe the Operations and Maintenance (O&M)functions within the system. It describes both local anddistributed O&M functions in a BSS.

This manual is for people requiring an indepth understanding ofthe functions of the Alcatel BSS:

" Network decision makers who require an understanding ofthe underlying functions of the system, including:

D Network plannersD Technical design staffD Trainers.


12/242


13/242

Conventions

Chapter Description

Preface

13 / 2403BK 02974 AAAA TQZZA Ed. 07

This section describes the type fonts and character styles used inthe document to indicate different types of messages.

Convention Type Meaning

message_types Messages are shown in lower case bolditalic type.

PARAMETER_TYPES Parameters which are part of a message orprotocol are shown in upper case italiccharacters.

COMMANDS Commands are shown in upper casecharacters.

{} These brackets indicate a message pairconsisting of a message followed by an

acknowledgement for that message.

This section provides a brief description of the contents of eachchapter.

Chapter 1 Introduction, provides a brief overview of theAlcatel BSS, its functions and features. Itdescribes:

G The internal and external components and

interfacesG An MS and its interaction, in idle mode,

with the BSS

G The distribution of telecommunicationssoftware in the BSS.

Chapter 2 Call Set Up, provides an overview of how a callis set up between the NSS and the MS. It detailsthe various kinds of calls that can be set up. Thetype of teleservice and bearer service requiredare also explained.

The chapter further describes the following partsof the call procedure:

G Mobile Originated CallG Mobile Terminated CallG PagingG CongestionG Classmark HandlingG AuthenticationG Ciphering.


14/242

Preface

14 / 240 3BK 02974 AAAA TQZZA Ed. 07

Chapter 3 Call Handling, provides an overview of CallHandling and explains the supervision of a callin progress. It describes:

G Incall modification, i.e. the process ofchanging from and to data and speech,and the implications for the system.

G Handover procedures, the underlyingreasons for handover, and themeasurements used to detect the need forhandover.

G Overload conditions.

Chapter 4 Call Release, provides an overview of CallRelease and describes the procedures which

ensure resource allocation to a call. Itspecifically describes Call Release procedures innormal service plus the following special cases:

G Following ResetG BSC initiatedG BTS initiatedG MS initiated.

This chapter also describes Remote TC Alarms,and the processes used to break a connectionand disconnect the resources, depending on the

nature of radio transmission.

Chapter 5 Service Improvement Features, provides anoverview of the BSS Service ImprovementFeatures. It describes how these featuresimprove the quality of service between the MSand BSS, maximize the BSS and MS resources orincreases operator efficiency. The serviceimprovement features in the Alcatel BSS areclassed as follows:

G Features defined in the GSM recommendations

G Alcatel BSS Features.

In addition, service improvement features whichare new with the current BSS are described in aseparate section.


15/242

Preface

15 / 2403BK 02974 AAAA TQZZA Ed. 07

Chapter 6 Handling User Traffic Across the BSS, describesthe flow of speech and data traffic across theBSS. It describes:

G How speech is encoded and rate adaptedthroughout the BSS

G What types of data can be transferredacross the BSS

G Where data error correction is performed

G How the data rate is adapted.

Chapter 7 Cell Environments, describes the cellenvironments available in the Alcatel 900/1800BSS. The following cell environments aredescribed:

G Single CellG Concentric CellG Sectored SiteG Extended CellG Umbrella CellG Mini CellG Microcell.

Chapter 8 Operations and Maintenance, provides anoverview and explains O&M functions in the

context of an operational network. It describes:G O&M Communication Mechanism

G Alarms

G Status Changes

G Call and International Mobile SubscriberIdentity (IMSI) Tracing

G Measurement Jobs

G Audits

G

Modifying Telecom Parameters.Abbreviations Abbreviations are defined at their first use, and

listed after the last chapter.


16/242

Preface

16 / 240 3BK 02974 AAAA TQZZA Ed. 07

Appendix A Air Interface Channels, provides an overview ofthe different channels used in the Air Interface:

G Traffic channelsG Broadcast channelsG Common Control channelsG Dedicated channelsG Associated channels.

Index An Index is included at the end of thedocument.


17/242

1 Introduction

17 / 2403BK 02974 AAAA TQZZA Ed. 07

1 Introduction

This chapter gives a brief overview of the Alcatel BSS, its functionsand features. It describes:

G The internal and external components and interfacesG An MS and its interaction, in idle mode, with the BSSG The distribution of telecommunications software in the BSS.


18/242

EVOLIUMRadio

Solutions

1 Introduction

18 / 240 3BK 02974 AAAA TQZZA Ed. 07

1.1 Overview

The BSS provides radio coverage for GSM subscribers in a definedarea. Its principal role is to provide and support signaling and

traffic channels between MSs and the NSS.Figure 1 shows the BSS within the Public Land MobileNetwork (PLMN).

BTS

Base Station SubsystemMobileStations

NetworkSubsystem

FixedNetwork

PLMN

BSC

OMCR

MSC PSTN

NMC

PSTN = Public Switched Telephone NetworkOMCR = Operations & Maintenance

Center RadioNMC = Network Management CenterTSS = Transmission Subsystem

TSS TSS

Figure 1 BSS in the PLMN

To respond to the swiftly evolving needs in BSSs, Alcatel offers theEVOLIUM Radio Solutions.

The Alcatel EVOLIUMRadio Solutions includes the following BSSequipment described in this document:

" G2 Base Station Controller (BSC)" G2 Transcoder (TC)" BTS A9100 Base Transceiver Station" Micro Base Transceiver Station (MicroBTS) M1M and M2M.


19/242

Mobility ManagementCalls

Supplementary ServiceCalls

User Traffic Calls

1 Introduction

19 / 2403BK 02974 AAAA TQZZA Ed. 07

1.2 BSS Functions

Functions are defined by the International TelecommunicationsUnion (ITU) and European Telecommunication Standards

Institute (ETSI) recommendations.This section describes the BSS functions with a systemwide view;that is, how the BSS functions work together within the system. Thefunctional units are indicated where applicable, but are notdescribed. For more information, refer to the specific unitdescription manuals, such as the BTS Functional Description.

The BSS provides signaling and traffic channels between the MSand the NSS. To ensure a high level of service to the subscribers,the BSS offers the following functions:

" Call Set Up" Call Handling" Call Release" Operations & Maintenance.

1.2.1 Call Set Up

The Call Setup function is used for speech and data calls. Thethree basic types of call are:

" Mobility Management" Supplementary service" User traffic.

Mobility Management calls, such as location update, are used bythe system to gather Mobile Station information. The exchangesare protocol messages only. Therefore, only a signaling channel isused.

Supplementary service calls, such as Short Message Service (SMS)allows the Mobile Station to send and receive messages to andfrom the BTS. These calls pass small amounts of information.Therefore, only a signaling channel is used.

User traffic calls, such as speech or data calls to a correspondent,can pass large amounts of information. Therefore, they requiregreater bandwidth than a signaling channel. These calls use trafficchannels.


20/242

1 Introduction

20 / 240 3BK 02974 AAAA TQZZA Ed. 07

Call set up processes include:

" Radio and Link Establishment to assign a signaling channelbetween the MS and the NSS

"

Classmark handling to manage different MS power andciphering capabilities

" Ciphering to ensure data security on the Air Interface

" The normal assignment process to assign a traffic channelbetween the MS and the NSS.

Refer to Chapter 2 for more information on call set up.

1.2.2 Call Handling

The call handling function is used when a call moves to another

cell, or moves to and from data and speech. Call handlinginvolves:

" Incall channel modification during a call

" Handover to change channels when an MS moves from onecell to another

" Handover when the quality of the current channel dropsbelow an acceptable level

" Ciphering to ensure data security on the Air Interface

" Overload control to manage the call load on the system.Refer to Chapter 3 for more information on call handling.

1.2.3 Call Release

The call release function ensures that resources allocated to a callare free for reuse when they are no longer required by the currentcall.

Specifically the Call Release function includes:

" Call Release in normal service:D Calls terminated by call managementD Calls terminated following a channel change.

" Special Cases:D Call release following a resetD BSC initiated releaseD BTS initiated releaseD MS initiated release.

Refer to Chapter 4 for more information on call release.


21/242

Cellular Environment

1 Introduction

21 / 2403BK 02974 AAAA TQZZA Ed. 07

1.2.4 Operations & Maintenance

O&M provides the operator interface for the management andcontrol of the BSS, and its interconnection to the NSS. O&M is

divided into three principal areas:" Configuration Management" Fault Management" Performance Management.

Refer to Chapter 8 for more information concerning O&M.

1.3 BSS Features

There are two categories of Features in the Alcatel BSS:

" Features defined in the ITU and ETSI GSM recommendations" Alcatel BSS Service Features.

Note Some of these features may not be available on your system.

1.3.1 Features Defined in the GSM Recommendations

The Alcatel BSS supports the following features, defined in the ITUand ETSI GSM recommendations:

" Cellular environment" Radio Power Control (RPC) uplink and downlink" Frequency Hopping (FH)" Discontinuous Transmission/Voice Activity Detection (DTX/VAD)" Discontinuous Reception (mechanism) (DRX)" Call reestablishment by the MS" Short Message Service Cell Broadcast (SMSCB)" Enhanced FullRate (EFR).

The standard developed by the Groupe Speciale Mobile specifiesa digital cellular network, as described in the System Introduction

document.

For details on cell environments offered in the Alcatel BSS, refer toChapter 7.


22/242

RPC Uplink andDownlink

Frequency Hopping

DiscontinuousTransmission/Voice

Activity Detection

DiscontinuousReception

Call Reestablishmentby MS

Short Message Service Cell Broadcast

1 Introduction

22 / 240 3BK 02974 AAAA TQZZA Ed. 07

This feature ensures the dynamic balance between the quality ofthe radio link in the uplink and downlink directions. It protectsagainst interference with other cells and contributes to powerconservation. The balance is maintained by controlling the power

output level to balance the reception power level and receptionquality.

FH is implemented within the system to reduce the limiting factorthat frequency reuse can introduce. This feature improves thecapability of coping with adjacent channel interference andimproves security. FH provides Frequency Diversity and InterfaceDiversity. Two types of Frequency Hopping are available:

" Baseband Frequency Hopping" Synthesized Frequency Hopping

DTX/VAD is used to decrease the average interference levelgenerated by the network in both the uplink and downlinkdirections. This feature, in association with frequency hopping,significantly improves spectrum efficiency without jeopardizing thequality of the telephony service.

DRX is used to conserve battery power. It allows the MS to switchoff its receiver and data processing while in the idle mode. Thereceiver and data processing of the MS is only switched on for ashort time when the MS expects a message from the BTS. Instead

of the MS listening continually on the Paging Channel (PCH)subchannel Common Control Channel (CCCH) for a pagingmessage, it only listens to that part of the PCH which correspondsto its paging group. Power conservation is achieved byimplementing an off/on ratio of 98 to 2.

Call Reestablishment by the MS allows an MS to resume aconnection in progress after a radio link failure. This is possibleonly if there remains at least one active call control connectionbetween the MS and MSC.

" Complete redundancy" OMCR side redundancy" BSC side redundancy.

SMSCB allows messages to be broadcast to the MSs. This servicecan be used for a number of reasons, e.g. to transmit taxationinformation, road traffic information, etc. An SMSCB messagecan be transmitted to all the cells connected to the BSC, or toselected cells only, as required.


23/242

Enhanced FullRate

Types of Cell

Environments

Antenna Diversity

Antenna PreAmplifierEquipment

1 Introduction

23 / 2403BK 02974 AAAA TQZZA Ed. 07

EFR allows the use of codecs with an improved speech encodingalgorithm, which provides enhanced speech quality on fullratechannels.

1.3.2 Alcatel BSS Features

This section provides an outline of features provided in the AlcatelBSS. These features are designed to:

" Improve the quality of service between the MS and BSS" Maximize resources" Increase operator efficiency.

Features supported include:

" Types of cell environments

" Antenna diversity" Antenna preamplifier" Improved Multipath Delay Equalization" Minimum Frequency spacing" Multiple Human Machine Interface (HMI) access to OMCRs" Night Time Concentration (NTC)" Secured X.25 connection from BSC to OMCR" Usage state on demand" BSC alerter.

Several types of cell environments are available in the Alcatel BSS.

This availability means that cells can be configured to meet therequirements of geography and the strategies of the NetworkOperator.

Refer to Chapter 7 for more information concerning CellEnvironments.

Antenna Diversity is used to improve the performance of the radiopath in the uplink direction in large cell configurations. Protectionagainst multipath fading is achieved by duplicating the receiveantenna and receive path up to the Frame Unit (FU) of the BTS (orthe Transceiver Equipment (TRE) for a BTS A9100). The FU (or TRE)uses the data burst which has the fewest errors. This increases thelowpower MS range, therefore allowing larger cells.

Antenna preamplifier equipment is used to improve the sensitivityof the BTS, which results in better coverage. The use of thisequipment allows the adaptive power control to reduce the outputpower of the MSs. This results in a reduced overall interferencelevel in the network.


24/242


25/242

Power Control due toRadio Link Failure

Q3 Multimanager

OMCNSS Session from

OMCR Terminal

OMCR Connection toTSC through BSC

Abis Signaling LinksStatic Multiplexing

1 Introduction

25 / 2403BK 02974 AAAA TQZZA Ed. 07

1.3.3 New Service Improvement Features

Alcatel has introduced the following new service improvementfeatures with the current BSS:

" Power control due to radio link failure" Q3 Multimanager" OMCNSS Session from OMCR Terminal" OMCR connection to TSC through BSC" Abis signaling links static multiplexing" Transcoder pools" Automatic powerdown" Auto Identification" Automatic paging repetition." Access to PM raw counters via binary files.

This feature provides an automatic attempt to recover the AirInterface after an interruption of the SACCH.

For more information, see Section 4.3.4.

The Q3 Multimanager feature permits the OMCR tocommunicate over the Q3 Interface with multiple NetworkManagement Centers (NMCs). Refer to Section 1.6.2 for moreinformation.

In this feature, a remote terminal interface allows access to

OMCNSS functions from the OMCR terminal. This means thatfrom the same terminal, an operator can open two simultaneouswindows, one connected to the OMCR and the other to theOMCNSS. Each window provides commands and messagesspecific to the OMCR with which it is associated.

This feature allows the OMCR operator to remotely configurecertain TSC supervision devices using the existing OMCR - BSCX.25 link. This permits a new transmission scheme correspondingto a new Abis configuration to be set up before onsitemodifications are made, with corresponding time gain. Testing

can be carried out immediately after the onsite operation.

This feature increases the maximum number of TRXs connected tothe same link from 9 to 12. This feature is used with the G2 BTSand Evolium BSSs.


26/242

Transcoder Pools

Automatic PowerDown

Auto Identification

Automatic PagingRepetition

Access to PM RawCounters via Binary

Files

1 Introduction

26 / 240 3BK 02974 AAAA TQZZA Ed. 07

The demands of GSM subscribers for new services is constantlyevolving. At the same time, GSM operators need to protect theirinvestment in capital equipment. The Transcoder Pools featureserves both needs. It permits the grouping of Transcoders having

the same capacities into pools on the A Interface, as defined in theGSM phase 2 recommendations. This permits efficient use ofexisting infrastructure, without having to replace or redeploy olderTCs when a new feature is added.

This feature is for batteryequipped, BTS A9100s, most usuallyinstalled outdoors. It allows the BTS A9100 to continue operatingin degraded mode in the event of a main power supply failure,and effects an orderly shutdown of TRE units, keeping the cell alivefor up to one hour.

Auto Identification gives the BTS A9100 the capacity to recognizeits own hardware configuration, and to provide this information tothe BTS Terminal.

If an idle MS performs a cell reselection at the same time that it ispaged, or if a paging message is lost on the Air Interface, the MSmay not receive a paging message. Automatic Paging Repetitionensures that paging messages are not lost by automaticallyrepeating an unanswered page on the PCH.

For more information about paging, refer to Chapter 2.

This feature provides a facility to export PerformanceManagement (PM) raw counters to an external PM processingsystem.


27/242

1 Introduction

27 / 2403BK 02974 AAAA TQZZA Ed. 07

1.4 BSS Components

There are three main units in the BSS:

" The BTS, which provides the radio transmission and receptionfunctions for a cell.

" The BSC, which acts as the controller of the BSS. The BSCprovides control of the BTSs and their resources, and performsswitching functions within the BSS.

" The Transmission Subsystem (TSS), which links the BTS and theBSC. The TSS also provides the physical layer, and support ofthe data link layer, for the internal interfaces.

The BSS shown in Figure 2 is supervised by the OMCR. In a largenetwork, one or more highlevel supervisors, a Network

Management Center, can exist to centralize network managementactivities. The NMC has the authority to send directives to theOMCR.

For more information about the NMC, refer to NMC and OMCRInterworking, and to documentation supplied with the NMC.

BTS


NetworkSubsystem

BSC

OMCR

MSC

NMC

TSS TSSTo/fromPSTN

Figure 2 Base Station Subsystem Components


28/242

1 Introduction

28 / 240 3BK 02974 AAAA TQZZA Ed. 07

1.4.1 Base Station Controller

The BSC provides control of the BTSs and manages radioresources and radio parameters. From a transmission point of

view, the BSC also performs a concentration function if more radioTraffic Channel (TCH) than terrestrial channels are connected tothe MSC. A single BSC can control a large number of BTSs. Theexact number is a function of the BSC equipment and theconfigurations used.

The BSC provides:

" Resource management

" Database management

" Radio measurement processing

" Channel management

" Operations and maintenance functions within the BSS

" Communication with the OMCR

" Switching between the Air Interface channels (and theirassociated Abis channels), and the A Interface channels.Further information concerning these interfaces can be foundin Sections 1.7.4, 1.7.5 and 1.7.6.

For a more detailed description of the BSC, refer to the G1 BSCFunctional Description and G2 BSC Functional Description

documents.

1.4.2 Base Transceiver Station

The BTS provides radio transmission, control and basebandfunctions for a cell. The BTS also supports the Air Interface with theMSs.

The BTS performs the following functions under the control of theBSC:

" Transmit and receive functions" Antenna diversity" Frequency hopping" Radio channel measurements" Radio frequency testing.

For a more detailed description of the BTS, refer to the BTSFunctional Description or BTS A9100 Functional Descriptiondocuments.


29/242

1 Introduction

29 / 2403BK 02974 AAAA TQZZA Ed. 07

1.4.3 Transmission Subsystem

The main function of the TSS is to provide efficient use of theterrestrial links between the equipment of the BSS. The

components of the TSS are shown in Figure 3.Each TSS component provides a specific set of functions:

" The Base Station Interface Equipment (BIE) performs signalingand submultiplexing on the Abis Interface

" The Submultiplexer (SM) performs submultiplexing on the AterInterface

" The Transcoder (TC) provides O&M control of theTransmission System. It also provides:

D Conversion between Alaw and Radio Test

EquipmentLong Term Prediction (RTELTP) encoded traffic(speech)

D Conversion between Alaw and Algebraic Code ExcitedLinear Prediction (ACELP) encoded traffic (speech)

D Rate adaptation (data).

The TC is normally located next to the MSC. If submultiplexingis required on the MSC to BSC link, an SM is located at eachend of the link.

" The Transcoder Submultiplexer Controller (TSC) collects and

processes transmission data. It also provides an operatorinterface to control the equipment of the TSS.


30/242

1 Introduction

30 / 240 3BK 02974 AAAA TQZZA Ed. 07

OMCR

BTS BSC

MSC

BIE = Base Station Interface EquipmentSM = Submultiplexer

BSC

TC

TCBTS

BTSTSC

BIE

BIE BIE

BIE SM SM

TSC = Transcoder Submultiplexer ControllerTC = Transcoder

TSC

Figure 3 Transmission Subsystem Components


31/242

1 Introduction

31 / 2403BK 02974 AAAA TQZZA Ed. 07

1.5 External Components

The BSS communicates with three external components, they are:

" The NSS on the A Interface" The MS on the Air Interface" The OMCR on the BSS/OMCR Interface.

Figure 4 shows the logical position of the the ExternalComponents.

BTS


NetworkSubsystem

BSC

FixedNetwork

PSTN

PLMN

OMCR

TSS TSS MSCHLRVLRAuCEIR

HLR = Home Location RegisterVLR = Visitor Location Register

AuC = Authentication CenterEIR = Equipment Identity Register

Figure 4 Logical Position of External Components Associated with BSS

1.5.1 Network Subsystem

Managing communication within the PLMN and external networksis the primary role of the NSS. The NSS manages the subscriberadministration databases, it contains the following components:

" MSC" Home Location Register (HLR)" Visitor Location Register (VLR)" Authentication Center (AuC)" Equipment Identity Register (EIR).


32/242

MSC

Home LocationRegister

Visitor LocationRegister

Authentication Center

Equipment IdentityRegister

1 Introduction

32 / 240 3BK 02974 AAAA TQZZA Ed. 07

Performs and coordinates the outgoing and incoming Call Set Upfunction. The MSC is a large capacity switch used for passingmobile traffic to mobile subscribers, or to subscribers of externalnetworks. This part of the NSS Interfaces with the BSS.

The HLR is the central database within a given network for mobilesubscriber specific data. It contains static data such as accessauthorization, information about subscribers and supplementaryservices. It also controls the dynamic data about the cell in whichthe MS is located.

The VLR temporarily stores information about MSs entering itscoverage area. Linked to one or more MSCs, the VLR transmitsdata to a new VLR when an MS changes areas.

The AuC manages the security data used for subscriberauthentication.

The EIR contains the lists of mobile station equipment identities.

1.5.2 Mobile Stations

MSs provide radio and processing functions which allowsubscribers to access the mobile network via the Air Interface.

Subscriber related information is stored on a specific device calleda Subscriber Identity Module (SIM).

The SIM is a removable smartcard that conforms tointernationally recognized standards specified by the InternationalStandards Organization (ISO). It contains the International MobileSubscriber Identity (IMSI). This is used by the Network Operator toidentify the subscriber in the network and to provide security andprotection against misuse.

Each MS has its own International Mobile Station EquipmentIdentity (IMEI). The IMEI is used by the Network Operator to

prevent stolen, or nontype approved MSs from accessing thenetwork.

There are three types of MS in GSM:

" Phase 1" Phase 1 extended" Phase 2.

MSs have different capabilities according to the the class of MSand the purpose for which the MS was designed. Thesedifferences include power output and ciphering.


33/242

MS Idle Mode

MS Cell Selection and

Reselection

1 Introduction

33 / 2403BK 02974 AAAA TQZZA Ed. 07

Only phase 2 MSs can turn off ciphering, or change the cipheringmode, during a channel change procedure such as a handover.The ciphering capability of an MS is signalled to the BSS in the MSClassmark.

Ciphering is used to protect information transmitted on the AirInterface. This is performed between the BTS and the MS (i.e. AirInterface). Transmission ciphering does not depend on the type ofdata to be transmitted (i.e. speech, user data, signaling), but tonormal transmission bursts. See Section 2.8 for further informationconcerning MS ciphering capabilities.

An MS is in idle mode when it is switched on, but notcommunicating with the network on a Standalone DedicatedControl Channel (SDCCH) or a TCH. The BSS supports three idlemode functions:

" Cell selection and cell reselection" Location updating" Overload control.

An MS monitors the broadcast messages from the BTS. Thisincludes monitoring the Frequency Correction Channel (FCCH)and Synchronization Channel (SCH).

The MS chooses the best cell on which to camp. If this cell is in alocation area other than that stored in the MS memory, then theMS initiates a location update procedure. For an MS to camp on a

cell, it has to synchronize with the cell.

The BTS broadcasts an FCCH and a SCH at a defined time in theBroadcast Control Channel (BCCH) cycle. These channels areused as reference points for the MS to synchronize with the BCCH.Once synchronized, the MS continues to monitor these channels tostay synchronized.

This type of synchronization, along with cell configuration andchannel frequency information, enables the MS to calculate wherechannels occur in the multiframe sequences.

Timing advance information is sent to the MS when an SDCCH isassigned. The MS uses the channel configuration information tocalculate which part of the CCCH contains its paging message,and therefore which Time Slot to monitor for paging messages.When the MS is camped on a cell, it continues to monitor theBCCH transmissions from neighboring cells. The BCCHfrequencies of the neighboring cells are transmitted on the BCCHof the home cell (sys_info 2). It can decide to camp on a new cellif it receives a better signal from an adjacent cell.


34/242

Location Updating

1 Introduction

34 / 240 3BK 02974 AAAA TQZZA Ed. 07

Reasons for moving to a new cell include:

" A problem in the existing cell" The MS moving.

If the MS moves to a new cell which is in the same locationarea as the one currently in its memory, it does not initiate alocation update. It recalculates its paging group and monitorsthe new paging channel. Paging messages are broadcastfrom all cells in a particular location area.

The location update procedure is always initiated by the MS.Location update is performed after the call has finished (cellreselection). Reasons for location updates include:

" A periodic update" A handover to a cell in a new location area.

The MS camps on a cell with a different location area code to theone in the MS memory. Periodic location update is performed bythe MS after a lack of signaling activity for a specific time. If thetimer expires, the MS initiates a location update, even if it has notchanged Location Area (LA).

The duration of the MS timer is defined by the network and sent tothe MS as system information messages on the BCCH. The timecan be between six minutes and 25 hours. When an MS is handedover to a cell in a new location area, there is no automaticlocation update in the network.

A new Location Area Identity (LAI) in the BCCH (sys_info 3 andsys_info 4) is detected by the MS when the current call hasfinished, and initiates the location update procedure. This savesthe system performing several location updates if the MS ishanded over several times during a call. The MS initiates thelocation update procedure by sending a channel_requestmessage indicating that the call is for a location update. The BSSassigns a dedicated signaling channel and establishes a signalingpath between the MS and MSC. See Section 2.2 for moreinformation.

When a signaling path is established, the MS sends the LAI of theold cell on which it was camped to the MSC. The new VLRinterrogates the old VLR for authentication and subscriberinformation. For further information see Sections 2.6.3 and 2.7.

The LAI is made up of:

" Mobile Country Code (MCC)" Mobile Network Code (MNC)" Location Area Code (LAC).


35/242

Overload Control

1 Introduction

35 / 2403BK 02974 AAAA TQZZA Ed. 07

The BSS adds the cell identity of the MS current location to themessage sent to the MSC. This information is sent in an MobilityManagement (MM) sublayer message and is transparent to theBSS. The NSS stores this information in either its HLR or its VLR.

Following a location update procedure, the VLR can assign a newTemporary Mobile Subscriber Identity (TMSI) to the MS. SeeSection 2.7 for more information about the TMSI. Figure 5 showsan MS as it moves to a new location area.

MSCBSCBTS

MSC

BSCBTS

Protocol Messages

VLR

VLR

MS moving and connectingin a new location area

MS

MS

Figure 5 Location Update

To protect the system against overload, the system can bar accessto MSs, by changing the Random Access Channel (RACH) controlinformation in the system information messages described inTable 1. For further information, see Section 3.4.


36/242

1 Introduction

36 / 240 3BK 02974 AAAA TQZZA Ed. 07

1.5.3 Operations and Maintenance CenterRadio

The OMCR supervises one or more BSSs. It performs thefollowing functions:

" Manages the BSS software versions" Acts as the central repository for configurations" Manages fault and performance measurement reports" Handles supervision of alarms and events.

The reported data is available to the operator from the OMCR'scentral database. The OMCR only performs O&M activities. Itdoes not perform user traffic processing or call establishment andcontrol activities. Refer to the Operations & Maintenance Principlesfor more information.

Operator actions via the terminal interface trigger commands

throughout the BSS. The OMCR provides objectorientedmanagement information, and supports a Manager/Agentscheme to perform and control management activities. Theterminal interface supports different user profiles with differentaccess rights.

For further information about Manager/Agent communications,see the NMC and OMCR Interworking document.


37/242

1 Introduction

37 / 2403BK 02974 AAAA TQZZA Ed. 07

1.6 Network Management

Normally the OMCR provides all the network management andcontrol functions required by the BSS. However, the management

and control functions are proprietary to the system supplier. Inkeeping with ITU and ETSI recommendations, the NetworkManagement function is supported. Network Management iscompatible with all equipment, even that of differentmanufacturers. Network Management is controlled from one orseveral NMCs.

1.6.1 Telecommunications Management Network

The ability to transfer management information across theTelecommunications Management Network (TMN) environment isdefined by a protocol suite, the Q Interfaces. Figure 6 shows thehierarchical structure of the TMN. It graphically defines therespective management responsibilities in the three main levels ofthe Management Information Tree (MIT).

NMC

OMCR

BSC

BTS

BTS

BTS

Q3

BSS

OSS

OSS = Operation Support System

NMC Operator(Resource Management)

OMCR Operator(Resource and Equipment

Management)

Security Block (SBL)Management

Network Management

&Network Element

Management

Mediation Function

Network Element

Figure 6 TMN System Hierarchy


38/242

Q3 Multimanager

1 Introduction

38 / 240 3BK 02974 AAAA TQZZA Ed. 07

1.6.2 Q3 Interface

Communication between the NMC and the OMCR takes placeacross the Q3 Interface (see Figure 6). The Q3 protocols can be

divided into the following main areas:" Association connection and disconnection mechanisms" Message format and structure" Command types.

The Q3 Multimanager feature allows the OMCR to communicateover the Q3 Interface with multiple NMCs, permitting the networkoperator to concentrate specific functions on each of severalNMCs. For example, in a large network, one NMC might bededicated exclusively to Performance Management, and anotherto Fault Management, etc.

For further information on Network Management and the Q3Interface see the NMC and OMCR Interworking document.


39/242

1 Introduction

39 / 2403BK 02974 AAAA TQZZA Ed. 07

1.7 BSS Telecommunications Layers

The telecommunications functions of a GSM network are split intolayers. These layers are split into two basic categories:

" The Application layer is split into sublayers, to control:

D Call Management (CM)D Mobility Management (MM)D Radio Resource Management (RRM).

" The transmission layers which provide transmission betweenthe various components.

Note These transmission layers relate to the OSI layers, that is, thePhysical Layer (i.e. Layer 1) and the Data Layer (i.e. Layer 2). Theprotocols used for these layers are standard.

Figure 7 shows the general distribution of the telecommunicationfunctions within a GSM network.

MS BTS BSC NSS

CM

MM

RRM

TRANSMISSION

GSMApplicationLayers

Figure 7 General Telecommunication Layers within GSM

1.7.1 Call Management

The Call Management sublayer performs Call Control (CACO) to

establish, maintain and release calls. SMS within CallManagement allows the MS to send and receive messages of upto 160 characters. The Supplementary Service (SS) functions arealso provided to the MSs as part of Call Management.


40/242

1 Introduction

40 / 240 3BK 02974 AAAA TQZZA Ed. 07

1.7.2 Mobility Management

The MM sublayer is used by the NSS to manage the subscriberdatabase, including information on subscriber location and

authentication. It is also used by the MSs to send location updateswhen they move to new location areas.

1.7.3 Radio Resource Management

The RRM sublayer establishes, maintains and releases stableconnections between the MS and MSC for the duration of a call.This includes functions such as managing the limited radioresources, to ensure high service availability. It also performshandovers when an MS moves during a call, or the channelquality falls below an acceptable level. RRM functions occur mainly

between the MS and the BSC.

Figure 8 shows the application layers, transmission layers andInterfaces of the BSS.

MS BTS BSC MSC

MM

RRM

GSMApplicationLayers

Layer 2

Air Interface Abis Interface A Interface

Layer1 Layer1L1L1L1L1

TC08.60

CM

LAPDM LAPD LAPDSCCP

SS7

SCCP

SS7

LAPDM

BSSAP BSSAP BSSAP

BSSAP = BSS Application PartLAPD = Link Access Procedure on the D ChannelLAPDM = Link Access Protocol on the D Mobile ChannelSCCP = signaling Connection Control PartSS7 = ITU signaling System No. 7

Figure 8 BSS Application, Transmission Layers and Interfaces


41/242

Physical Layer 1

Data Link Layer 2

Application SublayerRRM

1 Introduction

41 / 2403BK 02974 AAAA TQZZA Ed. 07

1.7.4 The A Interface

The A Interface is used for communication between the BSC andthe MSC. The connection between the BSC and MSC can be via

one of the following:" Terrestrial lines" Satellite link.

The A Interface comprises the:

" Physical layer 1

" Data Link layer 2" RRM sublayer 3 of the application layer

The physical layer provides a physical connection to transport thesignals. It supports a 2 Mbit/s link divided into 32 x 64 kbit/schannels by Time Division Multiplex (TDM). The actual physicallink used depends on Network Operator implementation.

Layer 2 provides the frame handling functions for the interface. Itis also used to pass signaling messages using the ITU signalingSystem No. 7 (SS7) protocol. This comprises:

" Message Transfer Part (MTP), which provides the mechanismfor reliable transfer of the signaling messages.

" signaling Connection Control Part (SCCP), which provides the

mechanism to identify transactions relating to a specificcommunication.

To transfer layer 3 messages relating to a transaction, the SCCPuses the BSS Application Part (BSSAP). This is divided into twoparts:

" Direct Transfer Application Part (DTAP), which transfersmessages directly between the MSC and the MS. Thesemessages are not interpreted by the BSS. The BSS must readand recognize the initial message as a DTAP message.

" BSS Management Application Part (BSSMAP) to supportprocedures between the MSC and the BSC, such as resourcemanagement and handover control.

On the A Interface, the process is terminated at the BSC.Messages for the BSS, passed by the BSSMAP, are interpretedby the BSC layer 3.


42/242

Ater Interface

Physical Layer 1

Data Link Layer 2

Application SublayerBTS

1 Introduction

42 / 240 3BK 02974 AAAA TQZZA Ed. 07

The part of the A Interface between the TC and BSC is known asthe Ater Interface. If SMs are placed between the TC and BSCthere is also an Atermux Interface. The Atermux Interface is theresult of multiplexing three Ater Interfaces. Transcoding is a layer 1

process, therefore the difference between the two interfaces is atthe physical level.

1.7.5 The Abis Interface

The Abis Interface is used for communication between the BSCand the BTS.

The Abis Interface comprises:

" Physical layer 1

" Data Link layer 2" BTS management sublayer 3 of the application layer

The physical layer provides a physical connection to transport thesignals. It supports a 2 Mbit/s link divided into 32 x 64 kbit/schannels by TDM.

The physical link used depends on the Network Operatorimplementing the interface.

The data link layer provides frame handling and signalingfunctions using the Link Access Procedure on the D Channel

(LAPD).

This layer supports three types of signaling links:

" The Radio signaling Link (RSL) for signaling to the MS(including SMS)

" The Operations and Maintenance Link (OML) for O&Minformation

" The Layer 2 Management Link (L2ML) for the layer 2management functions such as frame checking and errorcorrection.

The BTS management layer is used for layer 3 messages betweenthe BSC and the BTS. Some of these messages are transparent tothe BTS. These are passed directly to the MS using the BTS RRmanagement sublayer 3 on the Air Interface. Nontransparentmessages include messages for radio link layer control andchannel management.


43/242

Physical Layer 1

Data Link Layer 2

Application SublayerRRM

Air Interface Channels

1 Introduction

43 / 2403BK 02974 AAAA TQZZA Ed. 07

1.7.6 The Air Interface

The Air Interface is the radio interface between the BTS and theMS.

The Air Interface comprises:

" Physical layer 1

" Data Link layer 2" RRM sublayer 3 of the application layer

'

The physical layer is a radio link where channels are divided bytime and frequency.

The data link layer provides frame handling and signalingfunctions, using a modified version of the Link Access Protocol on

the Dm Channel (LAPDm).

On the Air Interface, most of the layer 3 messages are transparentto the BTS. The BTS uses layer 3 to extract certain information fromsome messages before passing on the equivalent message.

For example, when the BTS receives an encryption_commandmessage from the BSC, it reads the Ki value and the algorithm tobe used, before passing on the cipher_mode_commandmessage. This procedure is explained in detail in Section 2.8.

The Air Interface is divided by frequency and time, using

FrequencyDivision Multiplex Access (FDMA) and Time DivisionMultiple Access (TDMA). This provides frames of eight Time Slotsfor each frequency supported by the cell. The channels of the cellare then assigned to specific Time Slots within the TDMA frames.

However, not all channels require the full capacity of a Time Slotat each occurrence of a frame. Channels are configured to shareTime Slots by only using certain occurrences of the frame. Thecycle of frame occurrences is known as a multiframe. A multiframecan be 26 or 51 occurrences of a frame, depending on thechannels configured within it. Within a multiframe, the same

physical channel can support more than one logical channel.


44/242

Traffic Channels

Control Channels

1 Introduction

44 / 240 3BK 02974 AAAA TQZZA Ed. 07

Figure 9 shows Time Slot four of a TDMA frame supporting AccessGrant Channels (AGCHs).

A

GCH

A

GCH

A

GCH

A

GCH

A

GCH

Frame 1 Frame 2 Frame 3 Frame 4 Frame 5

Figure 9 Time Slot 4 of a TDMA Frame Supporting AGCHs

Channels can be divided into traffic channels and controlchannels.

A TCH can be used for speech or data. The Alcatel BSS supports

the following types of traffic channels:" Speech:

D A Full Rate Speech TCH (TCH/FS)D An Enhanced Full Rate Speech TCHD A Half Rate Speech TCH (TCH/HS).

" Data:

D A Full Rate Data TCH (9.6 Kbit/s) (TCH/F9.6)D A Full Rate Data TCH (4.8 Kbit/s) (TCH/F4.8)D A Half Rate Data TCH (4.8 Kbit/s) (TCH/H4.8)

D A Full Rate Data TCH (


45/242

1 Introduction

45 / 2403BK 02974 AAAA TQZZA Ed. 07

" The Dedicated Control Channel (DCCH) and AssociatedControl Channel (ACCH) pass signaling information for aspecific MS transaction. Two channels use the DCCH TimeSlot:

D SDCCHD Cell Broadcast Channel (CBCH).

Two channels use the ACCH Time Slot:

D Fast Associated Control Channel (FACCH) which can alsosteal TCH Time Slots

D Slow Associated Control Channel (SACCH).

An ACCH channel is always associated with a TCH.

For a complete description of the Air Interface channels, seeAppendix A.


46/242

System InformationMessages

1 Introduction

46 / 240 3BK 02974 AAAA TQZZA Ed. 07

System information messages transmit information about the cellto the MS. There are six system information messages. Four aresent on the BCCH as a general broadcast to any MSs in the cells,and two sent on the SACCH to MSs in communication with the

BSS. Table 1 shows the system information messages, the channelon which they are transmitted and the type of information in each.

Table 1 System Information Messages

Message Channel Information

Sys_info 1 BCCH Cell channel description

RACH control information.

Sys_info 2 BCCH Neighbor cell BCCH frequency list


Sys_info 3 BCCH Cell Identity (CI)

Location Area Identity

Control channel description

Cell options:

G Power central information

G Discontinuous Transmission

(mechanism) (DTX) information

G Radio link timeout.

Cell selection parameters:

G Max transmit power allowed in cell

G Min receive level to access cell.


Sys_info 4 BCCH LAI

Cell selection parameters:

G Maximum transmit power allowed in cell

G Minimum receive level to access cell.

RACH control informationCBCH channel description.

Sys_info 5 SACCH Neighbor cell BCCH frequency list.

Sys_info 6 SACCH LAI

Cell options:

G Power control information

G DTX information

G Radio link timeout.


47/242

2 Call Set Up

47 / 2403BK 02974 AAAA TQZZA Ed. 07

2 Call Set Up

This chapter provides an overview of how a call is set up betweenthe NSS and the MS. It describes the various kinds of calls that canbe set up. The type of teleservice and bearer service required arealso described.

This chapter also describes the following parts of the Call Set Upprocedure:

G Mobile Originated CallG Mobile Terminated CallG Paging

G CongestionG Classmark HandingG AuthenticationG Ciphering.


48/242

Call Types

2 Call Set Up

48 / 240 3BK 02974 AAAA TQZZA Ed. 07

2.1 Overview

Call set up is required to establish communication between an MSand the NSS. The NSS is responsible for establishing the

connection with the correspondent. Different types of calls requiredifferent teleservices. These teleservices are defined in the GSMspecifications. The type of teleservice and bearer service to beused is negotiated before the normal assignment procedure; seeSection 2.2.3 for more information.

Table 2 shows the three basic types of call:

Table 2 Types of Calls

Type of Call Description

Mobility Management Calls These calls, e.g. location update, are used by the system to gatherMS information. The exchanges are protocol messages only; therefore, only a signalling channel is used. Figure 5 illustrates the location update procedure.

Service Calls These calls, e.g. SMS and SS calls, pass small amounts of information. Therefore, only a signalling channel is used.

User Traffic Calls These calls, e.g. speech or data calls to a correspondent, can passlarge amounts of information. Therefore they require greater bandwidth than a signalling channel. These calls use traffic channels.

The channels used for calls are the SDCCH for signalling and theTCH for user traffic (see Section 1.7.6 for more information).These channels are associated with FACCH/SACCH. An SDCCH isalways assigned for call set up, even if a TCH is later required forthe call.

The role of the BSS in call set up is to assign the correct channelfor the call, and to provide and manage a communications pathbetween the MS and the MSC.


49/242

Call Set Up Phases

2 Call Set Up

49 / 2403BK 02974 AAAA TQZZA Ed. 07

Table 4 shows the phases involved in call set up:

Table 3 Call Set Up Phases

Phase Composition

Radio and LinkEstablishment

Paging (for mobile terminated calls only)

If ATTACH_DETACH_ALLOWED is activated, the MSIMSI_detach message can eliminate the need forpaging. See Section 2.3.4.

Immediate assignment procedure to assign anSDCCH

A interface connection, to assign a SCCP signallingchannel between the BSC and MSC

Assignment of a switching path through the BSC.

Authentication andCiphering

Classmark handling

Authentication

Ciphering.

Normal assignment Teleservice/bearer service negotiation

Channel allocation

Physical context procedure

Assigning a TCH, if required

Connecting the call.

The phases are described in Sections 2.2 and 2.3.


50/242

Channel Request

2 Call Set Up

50 / 240 3BK 02974 AAAA TQZZA Ed. 07

2.2 Mobile Originated Call

A call initiated by an MS can either be a subscriber call, wherespeech and/or data is passed across the network, or a location

update call from an MS in idle mode. Location update informationis passed on the signalling connection. Therefore, the initial callset up procedure is similar to a subscriber call. The locationupdate does not require allocation of a TCH.

2.2.1 Radio and Link Establishment

The radio and link establishment procedure establishes signallinglinks between:

" The BSS and the MS via the SDCCH channel

" The BSS and the MSC via the SCCP link.These links pass the information for call negotiation, and set up aTCH, if required.

Figure 10 shows radio and link establishment for a mobileoriginated call.

The MS initiates a call by sending a channel_request message,with a Random Access Information Value (REF). The REF includesan establishment cause and a Random Number (used forauthentication) (RAND). It is transmitted on the RACH channel.

The RACH channel is associated with the CCCH channel which theMS is monitoring while in idle mode. The establishment cause fieldof the REF specifies:

" An emergency call" Call reestablishment" Response to paging" MS originating speech call" MS originating data call" Location update" Service call (SMS etc.).

The MS notes the random number and frame number associatedwith each channel_request message. These are used by the MSto recognize the response sent from the BSS. This response is senton the AGCH, which can be monitored by many MSs. The MSdecodes all messages sent on this AGCH, and only accepts amessage with a random number and frame number matching oneof the last three requests sent.


51/242

2 Call Set Up

51 / 2403BK 02974 AAAA TQZZA Ed. 07

MS BTS BSC MSC

SDCCHAllocation

Switch toSDCCH

REF = Random access information valueRFN = Reduced frame numberTA = Timing Advancecm = ClassmarkID = Mobile Identity power = MS power, BTS powerSDCCH = Description of the allocated SDCCH channelService Request = Initial layer 3 message including the MS identity and classmarkUA = Unnumbered Acknowledgement

REF storedin MSmemory

Service Request mustmatch original sent

by MS in the SABM

MS comparesmessage withREF in memory

Figure 10 Radio and Link Establishment for Mobile Originated Call

The MS continues to transmit channel_request messages until itreceives a response. If no response is received before the MS hastransmitted a predefined number of retries, the MS:

" Displays a network error message for all calls except locationupdates

" Performs automatic reselection for location update calls. Thismeans that the MS attempts random access on a different cell.


52/242

SDCCH Channel

Activation

2 Call Set Up

52 / 240 3BK 02974 AAAA TQZZA Ed. 07

On receipt of the channel_request message from the MS, the BTSsends a channel_required message to the BSC. This messagecontains the random number sent by the MS, and the timingadvance measured by the BTS.

The BSC checks the channel_required message to ensure it canaccept the request. It allocates an SDCCH channel if one isavailable. The resource management software of the BSCallocates the SDCCH on the basis of which TCH has the mostavailable SDCCHs. This ensures the load is spread between theTCHs.

The BSC then sends a channel_activation message to the BTS. Italso sets a timer to wait for an acknowledgment from the BTS,indicating that it is ready to activate the channel. Thechannel_activation message contains:

" A description of the SDCCH to be used

" The timing advance

" MS and BTS power commands. The MS and BTS power areset to the maximum allowed in the cell.

The BTS initiates the physical layer resources for the channel andsets the LAPDm contention resolution ready for the first MSmessage on the SDCCH. It then sends achannel_activation_acknowledgementmessage to the BSC.The BSC stops its guard timer.

Note Contention resolution prevents two MSs connecting to the sameSDCCH.

Figure 11 shows the Channel Activation procedure.

MS BTS BSC MSC

SDCCHAllocation

TA = Timing Advancepower = MS power, BTS powerSDCCH = Description of the allocated SDCCH channel

Figure 11 SDCCH Channel Activation


53/242

Immediate Assignment

Set AsynchronousBalanced Mode

Contention Resolution

2 Call Set Up

53 / 2403BK 02974 AAAA TQZZA Ed. 07

The BSC builds and sends an immediate_assign_commandmessage reiterating the information given in thechannel_activation message. This message also includes therandom number and frame number of the original MS request to

which the BSC is replying. It also instructs the BTS to inform the MSof the SDCCH channel assignment. The BSC starts a guard timerfor the MS to respond.

Figure 12 shows the Immediate Assignment procedure.

MS BTS BSC MSC

Switch toSDCCH

REF = Random access information valueRFN = Reduced frame numberTA = Timing AdvanceSDCCH = Description of the allocated SDCCH channel

Figure 12 Immediate Assignment

The BTS sends the immediate_assignment message to the MS onthe AGCH.

The MS checks the random number and frame number in theimmediate_assignment message. If it matches those from one ofits last three channel_request messages, the MS switches to theindicated SDCCH and sets its timing advance to the valueindicated in the immediate_assignment message.

The first layer 2 frame sent on the SDCCH is a standard LAPDmtype frame, known as the Set Asynchronous BalancedMode (SABM). This is equivalent to the Set Asynchronous BalancedMode Extended (SABME) frame in the Link Access Procedure on

the D Channel (LAPD). On the Air interface, it establishes theLAPDm connection with the BTS. This frame can also contain layer3 messages.

The MS starts its LAPDm connection and sends a layer 3 messagein its first frame. The BTS uses this message for contentionresolution. The BTS sends an acknowledgement to the MScontaining the same layer 3 message. Therefore, only the MS thatsent the message can accept the acknowledgement from the BTSand consider itself connected.


54/242

Establish Indication

SCCP Connection

2 Call Set Up

54 / 240 3BK 02974 AAAA TQZZA Ed. 07

Figure 13 shows the establishment of the connection for a mobileoriginated call.

MS BTS BSC MSC

cm = Classmark

Service Request = Initial layer 3 message including the MS identify and classmarkUA = Unnumbered Acknowledgement

Figure 13 Connection for Mobile Originated Call

For an MS originated call, the layer 3 message from the MScontains:

" An Information Element (IE) indicating:

D CM service request (speech/data, SMS, emergency call)

D Location updating request (location updating procedure)

D CM reestablishment request ( after a failure)

D IMSI detach indication (MS power off - see section 2.3.4for more information).

" The MS identity (see Section 2.7 for more information)

" The MS classmark (see Section 2.6 for more information).

The network uses this message to decide which call negotiationprocedures are required and whether to assign a TCH.

The BTS sends an establish_indication message to the BSC to

indicate that the MS has connected. The BSC stops the guardtimer, extracts the classmark information and initiates an SCCPconnection with the MSC.

The BSC sends an SCCP_connection_request message to theMSC. The MSC replies with an SCCP_connection_confirmmessage. This message can contain a classmark request or acipher mode command.

The signalling link is established between the MS and the MSC.


55/242


56/242

2 Call Set Up

56 / 240 3BK 02974 AAAA TQZZA Ed. 07

MS BTS BSC MSC

cm = ClassmarkTA = Timing Advancecipher= Encryption algorithm + ciphering keyDTX = Discontinuous transmission flags

Settranscoder

releaseSDCCH

TCHallocation

Set switchingpath

initiate SDCCHrelease

Figure 14 Normal Assignment for Mobile Originated Call


57/242


58/242

TCH Channel Activation

2 Call Set Up

58 / 240 3BK 02974 AAAA TQZZA Ed. 07

The BSC sends a physical_context_request message to the BTS,to find out the current power and timing advance being used bythe MS on the SDCCH. The BTS responds with aphysical_context_confirm message, containing the relevant

information.

Figure 15 shows the TCH channel activation process.

MS BTS BSC MSC

TA = Timing Advance

cipher = Encryption algorithm + ciphering keyDTX = Discontinuous transmission

TCHallocation

Figure 15 TCH Channel Activation

The BSC sends a channel_activation message to the BTS. Thiscontains:

" A description of the TCH to be used

" The MS timing advance to be applied

" The encryption algorithm and ciphering key (same as for

SDCCH assignment)

" A Discontinuous Transmission (DTX) indicator for uplink (notused) and downlink (see Section 5.2.4 for more information)

" The MS power to be used (see Section 5.2.2 for moreinformation)

" The BTS power to be used.

The BSC starts a timer, and waits for the BTS to acknowledge thatit has activated the channel.


59/242

2 Call Set Up

59 / 2403BK 02974 AAAA TQZZA Ed. 07

The BTS initializes its resources for the TCH, sets the cipheringmode, sends timing advance and power information to the MS onthe SACCH associated to the TCH, which is constantly monitoredby the MS. At the same time, the BTS sends a

channel_activation_acknowledgement message to the BSC.The BSC stops its timer and sends an assignment_commandmessage on the SDCCH to the MS. This instructs the MS to changeto the TCH.

When the MS receives the assignment_command message, itdisconnects the physical layer, and performs a local release to freethe LAPDm connection of the SDCCH.

Figure 16 shows the TCH channel assignment process.

MS BTS BSC MSC

Settranscoder

releaseSDCCH

Set switchingpath

Figure 16 TCH Channel Assignment

The MS then establishes the LAPDm connection (via the SABM onthe FACCH) for the TCH. The BTS sends an establish_indicationmessage to the BSC. It also sets the transcoder and its radio linkfailure detection algorithm. The BTS sends a layer 2acknowledgement to the MS. The MS sends anassignment_complete message to the BSC.

When the BSC receives the establish_indication message, itestablishes a switching path between the allocated Abis and Ainterface resources. When it receives the assignment_completemessage, it sends an assignment_complete message to the MSCand initiates release of the SDCCH (see Chapter 4 for moreinformation).


60/242

Connecting the Call

2 Call Set Up

60 / 240 3BK 02974 AAAA TQZZA Ed. 07

Once communication with the called party is established (butbefore the call is answered), the MSC sends an alerting messageto the MS. The MS generates a ring tone.

When the called party answers, the MSC sends a connectmessage to the MS. The MS responds with aconnect_acknowledgement message. The call is established.

Figure 17 shows the call connection process for a mobileoriginated call.

MS BTS BSC MSC

initiate SDCCHrelease

Figure 17 Call Connection for Mobile Originated Call


61/242


62/242

2 Call Set Up

62 / 240 3BK 02974 AAAA TQZZA Ed. 07

MS BTS BSC MSC

RADIO AND LINK ESTABLISHMENT PROCEDURERefer to Figure 10

Figure 18 Radio and Link Establishment for Mobile Terminated Call

2.3.2 Authentication and Cip

47936945 bss system description alcatel system

Documents