VoLTE and ViLTE
Voice and Conversational Video Services over the 4G Mobile Network

This book presents the architecture of two networks that make up the backbone of the telephone service VoLTE and video service ViLTE. The 4G mobile network makes it possible to construct bearers through which IP packets, containing either telephone signals (SIP, SDP) or voice or video media (RTP stream), are transported.

The IMS network performs the processing of the telephone signal to provide VoLTE and ViLTE services, including call routing and the provision of additional services. Different procedures are described: the set-up and termination of a session, interconnection with third-party networks, roaming and intra-system handover.

The inter-system handover PS-CS is a special case that occurs when the mobile loses 4G network coverage over the course of a session. The e-SRVCC mechanism enables continuity of the service during the switch of the telephone communication to the 2G or 3G networks. The SMS service for short messages, which is a special telephone service in itself, is provided by two structures, one relying on the IMS network, and a second on the CSFB functionality.

Preface ix

List of Abbreviations xv

Chapter 1. Network Architecture 1

1.1. EPS network 1

1.1.1. Functional architecture 1

1.1.2. Protocol architecture 5

1.1.3. Bearers 8

1.2. IMS network 12

1.2.1. Functional architecture 12

1.2.2. Protocol architecture 17

1.3. Databases 18

1.3.1. Functional architecture 18

1.3.2. Protocol architecture 18

1.4. Charging associated with IMS network 19

1.4.1. Functional architecture 19

1.4.2. Protocol architecture 21

1.5. PCC function 21

1.5.1. Functional architecture 21

1.5.2. Protocol architecture 22

1.6. DIAMETER routers 23

1.7. ENUM system 24

1.8. IPX network 25

Chapter 2. Signaling Protocols 27

2.1. NAS protocol 27

2.1.1. EMM messages 28

2.1.2. ESM messages 30

2.2. RRC protocol 32

2.2.1. System information 36

2.2.2. Control of RRC connection 37

2.2.3. Measurement report 39

2.3. S1-AP protocol 40

2.3.1. Context management 42

2.3.2. Bearer management 43

2.3.3. Mobility management 43

2.3.4. S1-MME interface management 45

2.4. X2-AP protocol 45

2.4.1. Mobility management 46

2.4.2. Load management 47

2.4.3. X2 interface management 48

2.5. GTPv2-C protocol 49

2.5.1. Bearer management 51

2.5.2. Mobility management 52

2.6. SIP protocol 53

2.6.1. Requests 53

2.6.2. Responses 57

2.7. SDP protocol 60

2.8. DIAMETER protocol 61

2.8.1. Application to EPS network 61

2.8.2. Application to IMS network 62

2.8.3. Application to PCC function 64

Chapter 3. Basic Procedures 69

3.1. Attachment 69

3.2. Registration 75

3.3. Deregistration 84

3.4. Detachment 85

3.5. Establishment of VoLTE session 87

3.5.1. Originating side 87

3.5.2. Terminating side 94

3.6. Termination of VoLTE session 98

3.6.1. Initiated side 99

3.6.2. Received side 100

3.7. Establishment of ViLTE session 101

3.8. Termination of ViLTE session 104

3.9. Emergency call 106

Chapter 4. Radio Interface Procedures 109

4.1. Radio interface 109

4.1.1. Data link sub-layer 110

4.1.2. Logical channels 113

4.1.3. Transport channels 114

4.1.4. Physical layer 114

4.1.5. Physical signals 121

4.1.6. Physical channels 122

4.2. Procedures 124

4.2.1. Access control 124

4.2.2. Data transfer 130

Chapter 5. Service Profiles 147

5.1. Subscription data 147

5.1.1. Subscription to the EPS network 147

5.1.2. Subscription to the IMS network 148

5.2. VoLTE profile service 150

5.2.1. Supplementary telephone services 150

5.2.2. Audio flow 167

5.3. ViLTE profile service 170

5.3.1. Supplementary conversational video service 170

5.3.2. Video flow 171

Chapter 6. Interconnections 173

6.1. Interconnection CS network 173

6.1.1. Functional architecture 173

6.1.2. Protocol architecture 175

6.1.3. Session establishment 181

6.1.4. Session termination 190

6.2. Interconnection with IMS network 192

6.2.1. Functional architecture 192

6.2.2. Session establishment 193

Chapter 7. Handover 199

7.1. Introduction 199

7.2. Handover based on X2 201

7.2.1. Handover based on X2 without relocation 201

7.2.2. Handover based on X2 with relocation 205

7.3. Handover based on S1 207

7.3.1. Handover based on S1 without relocation 207

7.3.2. Handover based on S1 with relocation 211

7.4. PS-PS inter-system handover 218

7.4.1. Functional architecture 218

7.4.2. Procedure. 220

Chapter 8. Roaming 223

8.1. Functional architecture 223

8.1.1. Roaming applied to the EPS network 223

8.1.2. Roaming applied to the IMS network 224

8.2. Procedures 228

8.2.1. Session establishment for nominal routeing 228

8.2.2. Session establishment for optimal routeing 235

Chapter 9. Service Centralization and Continuity 243

9.1. ICS function 243

9.1.1. Functional architecture 243

9.1.2. Procedures 246

9.2. e-SRVCC function 255

9.2.1. Functional architecture 255

9.2.2. Procedures 260

Chapter 10. Short Message Service 273

10.1. Message structure 273

10.1.1. SM-TL layer 274

10.1.2. SM-RL layer 275

10.1.3. SM-CL layer 275

10.2. SMS over SGsAP 276

10.2.1. Functional architecture 276

10.2.2. Procedures 277

10.3. SMS over SIP 282

10.3.1. Functional architecture 282

10.3.2. Procedures 283

Bibliography 289

Index 295

André Perez is a consultant and teacher in networks and telecommunications. He works with industrialists and operators regarding architecture studies and leads training on the 4G and IMS networks for NEXCOM SYSTEMS.