Roaming in wireless networks

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A cell phone's roaming feature allows the user to get service when traveling beyond the boundaries of his/her service provider. Wireless service providers make approximately 30% of their operating profit from roaming. But despite being a major source of income, roaming suffers from a number of technological problems in the handoff between networks. Signal strength is wildly variable, calls are frequently dropped, and quality of service is poor. Based upon training courses the author teaches at Agilent and Hewlett-Packard, this is the first book to give communications engineers the know-how to faultlessly design and manage roaming services.

Author Notes

Shahid K. Siddiqui is Principal Consultant working with Agilent Technologies in Malaysia. He has 20 years of experience in diverse areas of telecommunication including research and development, validation, test and measurement, and operations support systems. He works closely with wireless service providers delivering consulting and training. He has developed and taught technical training courses on digital switching, signaling, and wireless communication, and delivered numerous seminars.

Preface	p. x
Acknowledgments	p. xii
Chapter 1 Roaming and Wireless Networks	p. 1
1.1 National and International Roaming	p. 2
1.2 Interstandard Roaming	p. 2
1.3 Prepaid and Postpaid Subscriber Roaming	p. 3
1.4 Basic Structure of Roaming	p. 4
1.5 Roaming Services	p. 6
Chapter 2 CCS7 in Wireless Networks	p. 7
2.1 Signaling-An Introduction	p. 7
2.2 CCS7 Network Architecture	p. 8
2.3 Message Transfer Part	p. 10
2.3.1 MTP Level 1	p. 10
2.3.2 MTP Level 2	p. 10
2.3.3 MTP Level 3	p. 12
2.4 ISDN User Part	p. 15
2.5 Signaling Connection and Control Part	p. 20
2.5.1 Connectionless signaling	p. 21
2.5.2 Connection-oriented signaling	p. 22
2.5.3 SCCP message format	p. 23
2.5.4 SCCP routing control	p. 24
2.5.5 SCCP management	p. 25
2.6 Transaction Capabilities Application Part	p. 26
2.6.1 Structure of TCAP	p. 27
Bibliography	p. 30
Chapter 3 Global System for Mobile Communication (GSM)	p. 31
3.1 Brief History of Early Cellular Networks	p. 31
3.1.1 Limitations of early cellular technologies	p. 32
3.1.2 Roaming and early cellular networks	p. 32
3.2 GSM Overview	p. 32
3.3 GSM Offered Services	p. 33
3.3.1 Bearer service	p. 34
3.3.2 Teleservices	p. 34
3.3.3 Supplementary services	p. 34
3.4 System Architecture	p. 34
3.4.1 Mobile station	p. 35
3.4.2 Base station subsystem	p. 40
3.4.3 Network switching system	p. 42
3.5 GSM Interfaces and Protocols	p. 46
3.5.1 Air interface	p. 46
3.5.2 Abis interface	p. 53
3.5.3 A interface	p. 59
3.5.4 Inter-MSC signaling	p. 62
3.6 Scenarios	p. 67
3.6.1 Mobility management	p. 67
3.6.2 Call establishment	p. 74
Bibliography	p. 82
Chapter 4 General Packet Radio Service	p. 83
4.1 GPRS Overview	p. 83
4.2 GPRS Services	p. 84
4.2.1 Horizontal applications	p. 84
4.2.2 Vertical applications	p. 84
4.3 GPRS Network Architecture	p. 84
4.3.1 GPRS terminals	p. 86
4.3.2 GPRS BSS-Packet control unit	p. 86
4.3.3 GPRS support nodes	p. 87
4.4 Interfaces and Protocols	p. 91
4.4.1 User plane	p. 91
4.4.2 Signaling plane	p. 95
4.5 GPRS Identities	p. 97
4.5.1 P-TMSI	p. 98
4.5.2 TLLI	p. 98
4.5.3 NSAPI	p. 98
4.5.4 TEID	p. 99
4.6 GPRS Procedures	p. 99
4.6.1 Mobility management	p. 99
4.6.2 Session management	p. 106
4.6.3 Security function	p. 111
Bibliography	p. 113
Chapter 5 Third Generation Networks	p. 115
5.1 3G Specifications	p. 115
5.2 UMTS Network Architecture	p. 116
5.2.1 3GPP Release 99	p. 117
5.2.2 Release 4 architecture	p. 118
5.2.3 Release 5 architecture	p. 119
5.3 UMTS Interfaces and Protocols	p. 120
5.3.1 UTRAN interfaces and protocol structure	p. 120
5.3.2 System network protocols	p. 125
5.4 Example UMTS Procedures	p. 128
5.4.1 Mobile-originated circuit-switched calls	p. 128
5.4.2 Mobile-originated packet-switched calls	p. 133
Bibliography	p. 135
Chapter 6 Roaming in a GSM Network	p. 137
6.1 Inter-PLMN Signaling Network	p. 137
6.1.1 Inter-PLMN addressing	p. 139
6.1.2 Address format	p. 139
6.2 Communication Between a VPLMN VLR and an HPLMN HLR	p. 143
6.3 Roaming Procedures	p. 145
6.3.1 Location update in a visited network	p. 145
6.3.2 Roamer authentication in visited network	p. 150
6.3.3 Provide roaming number	p. 152
6.3.4 Cancel location	p. 158
6.3.5 Purge MS	p. 158
6.3.6 Restore data	p. 158
6.4 Roaming Call Scenarios	p. 161
6.4.1 Roamer-originated call	p. 161
6.4.2 Roamer-terminated call	p. 161
6.5 Short Message Service (SMS)	p. 164
6.5.1 Roamer-originated SM	p. 164
6.5.2 Roamer-terminated SM	p. 167
6.5.3 MAP v2 procedures	p. 170
Bibliography	p. 170
Chapter 7 Roaming in GPRS and 3G Networks	p. 171
7.1 Inter-PLMN Connectivity	p. 171
7.1.1 Inter-PLMN backbone network	p. 172
7.1.2 Inter-PLMN data connectivity alternatives	p. 174
7.1.3 GPRS roaming eXchange	p. 175
7.1.4 Border gateway protocol version 4	p. 176
7.2 Access Point Name	p. 177
7.2.1 APN network identifier	p. 178
7.2.2 APN operator identifier	p. 178
7.2.3 Wild card APN	p. 179
7.3 APN Resolution	p. 179
7.3.1 GPRS and DNS	p. 179
7.3.2 APN resolution using DNS in the HPLMN	p. 180
7.3.3 APN resolution using DNS in the VPLMN	p. 181
7.4 Roaming Scenarios	p. 182
7.4.1 GPRS attach in a visited network	p. 182
7.4.2 PLMN and ISP roaming	p. 184
7.4.3 PDP context activation using HGGSN	p. 184
7.4.4 PDP context activation using VGGSN	p. 187
Bliography	p. 188
Chapter 8 Roaming Implementation for Prepaid	p. 189
8.1 Prepaid Roaming Using USSD Callback	p. 190
8.1.1 USSD string coding	p. 192
8.1.2 USSD request handling-general concept	p. 192
8.1.3 Roamer initiated USSD operation	p. 193
8.1.4 Network initiated USSD operations	p. 197
8.1.5 Prepaid roaming-USSD callback scenario	p. 203
8.2 Prepaid Roaming Using CAMEL	p. 205
8.2.1 CAMEL architecture	p. 206
8.2.2 Points in call and detection points	p. 212
8.2.3 CAMEL subscriber information	p. 213
8.2.4 Basic call state model	p. 219
8.2.5 CAMEL information flow	p. 223
8.2.6 Prepaid roaming-CAMEL call scenario	p. 228
Bibliography	p. 234
Chapter 9 Inter-PLMN Roaming Testing	p. 235
9.1 Overview of IREG Testing	p. 235
9.1.1 Internetwork connectivity	p. 236
9.1.2 End-to-end functional testing	p. 237
9.2 IREG Testing-Test Setup	p. 238
9.2.1 GSM roaming test setup	p. 238
9.2.2 GPRS roaming test setup	p. 239
9.3 IREG Tests	p. 241
9.3.1 GSM basic service tests	p. 241
9.3.2 GSM supplementary services tests	p. 246
9.3.3 GSM SMS tests	p. 248
9.3.4 GSM SS and ODB tests	p. 249
9.3.5 GPRS attach	p. 251
9.3.6 GPRS PDP context tests	p. 251
9.3.7 GPRS SMS tests	p. 254
9.3.8 GPRS operator control of service	p. 254
9.3.9 Other tests	p. 255
9.4 IREG Tester	p. 255
Bibliography	p. 256
Chapter 10 Roaming Service Management and Troubleshooting Faults	p. 259
10.1 Quality of Service-General Concepts	p. 260
10.1.1 Service-independent quality indicators	p. 260
10.1.2 Service-dependent quality indicators	p. 261
10.1.3 Quality indicators by services	p. 262
10.2 Roaming Service Quality	p. 267
10.3 Proactive Service Monitoring	p. 267
10.3.1 Roaming service monitoring using active probes	p. 269
10.3.2 Roaming service monitoring using passive probes	p. 272
10.4 Troubleshooting Roaming Faults	p. 273
10.4.1 Common network problems	p. 273
10.4.2 Information gathering on symptoms	p. 274
10.4.3 Diagnostic tools	p. 275
10.4.4 Understanding protocol errors	p. 276
Bibliography	p. 288
Chapter 11 Billing and Settlement	p. 289
11.1 Roaming Billing Standards	p. 289
11.2 Transferred Account Procedures	p. 290
11.2.1 TAP3 and earlier versions	p. 291
11.2.2 TAP-in and TAP-out processes	p. 292
11.2.3 Reject and return process	p. 292
11.3 Role of Clearinghouses	p. 295
Bibliography	p. 297
Chapter 12 Roaming Value-Added Services	p. 299
12.1 Optimal Routing	p. 300
12.1.1 Implementation	p. 300
12.2 Welcome and Other Information SMS	p. 306
12.2.1 Implementation	p. 306
12.3 Short Dial Codes	p. 308
12.3.1 Implementation	p. 308
12.4 Missed-Call Information While Roaming	p. 308
12.4.1 Implementation	p. 310
12.5 Other Services	p. 312
Chapter 13 Roaming-Current and Future Enhancements	p. 313
13.1 WLAN Overview	p. 313
13.2 PLMN-WLAN Roaming	p. 315
13.3 WLAN-PLMN Interworking	p. 316
13.3.1 WLAN UE	p. 316
13.3.2 AAA server	p. 317
13.3.3 Packet data gateway	p. 317
13.4 Roaming Scenarios	p. 318
Bibliography	p. 319
Index	p. 321

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