VoIP Voice and Fax Signal Processing

Acknowledgments xix

About the Author xxi

Preface xxiii

Glossary xxvii

1 PSTN Basic Infrastructure, Interfaces, and Signals 1

1.1 PSTN CO and DLC 2

1.2 PSTN User Interfaces 3

1.3 Data Services on Telephone Lines 7

1.4 Power Levels and Digital Quantization for G.711 μA-Law 9

1.5 Significance of Power Levels on Listening 11

1.6 TR-57, IEEE-743, and TIA Standards Overview 13

2 VoIP Overview and Infrastructure 19

2.1 PSTN and VoIP 20

2.2 Typical VoIP Deployment Example 25

2.3 Network and Acoustic Interfaces for VoIP 26

2.4 VoIP Systems Working Principles 27

2.5 VoIP Signaling 41

3 Voice Compression 49

3.1 Compression Codecs 50

3.2 G.711 Compression 50

3.3 Speech Redundancies and Compression 60

3.4 G.726 or ADPCM Compression 60

3.5 Wideband Voice 62

3.6 G.729 Family of Low-Bit-Rate Codecs 63

3.7 Miscellaneous Narrow and Wideband Codecs 67

3.8 Codecs and Overload Levels 70

3.9 Voice Quality of Codecs 70

3.10 C-Source Code for Codecs 74

3.11 Codecs in VoIP Deployment 74

4 Generic VADCNG for Waveform codecs 76

4.1 VADCNG and Codecs 77

4.2 Generic VADCNG Functionality 78

4.3 Comfort Noise Payload Format 78

4.4 G.711 Appendix II VADCNG Algorithm 80

4.5 Power-Based VADCNG 83

4.6 VADCNG in Low-Bit-Rate Codecs 85

4.7 Miscellaneous Aspects of VADCNG 86

4.8 Summary on VADCNG 89

5 Packet Loss Concealment Techniques 91

5.1 Packet Loss Concealment Overview 91

5.2 Packet Loss Concealment Techniques 92

5.3 Transmitter- and Receiver-Based Techniques 94

5.4 Decoder-Only Based PLC Techniques 99

5.5 PLC Techniques Description 101

5.6 PLC for Low-Bit-Rate Codecs 108

5.7 PLC Testing 110

5.8 PLC Summary and Discussion 111

6 ECHO Cancellation 113

6.1 Talker and Listener Echo in PSTN Voice Call 114

6.2 Naming Conventions in Echo Canceller 119

6.3 Line and Acoustic Echo Canceller 120

6.4 Talker Echo Levels and Delay 123

6.5 Echo Cancellation in VoIP Adapters 127

6.6 Echo Path 131

6.7 Adaptation Filtering Algorithms 132

6.8 Echo Canceller Control Functions 137

6.9 Echo Cancellation in Multiple VoIP Terminals 144

6.10 Echo Canceller Testing 145

7 DTMF Detection, Generation, and Rejection 151

7.1 Specifications of DTMF Tones 152

7.2 DTMF Tones Generation 152

7.3 DTMF Detection 156

7.4 Goertzel Filtering with Linear Filtering 158

7.5 Tone Detection Using Teager and Kaiser Energy Operator 167

7.6 DFT or FFT Processing 171

7.7 DTMF Rejection 171

7.8 DTMF RFC2833 Processing 174

7.9 DTMF Testing 177

7.10 Summary and Discussions 178

8 Caller ID Features in VoIP 179

8.1 FSK Caller ID on PSTN 180

8.2 FSK Caller ID Data Transport Protocol 183

8.3 DTMF-Based Caller ID 188

8.4 Country-Specific Caller ID Overview 190

8.5 Caller ID in VoIP 191

8.6 Call Wait Caller ID 193

8.7 Caller ID on FXO Interfaces 198

8.8 Summary and Discussions 202

9 Wideband Voice Modules Operation 203

9.1 Wideband Voice Examples 204

9.2 Wideband VoIP Adapter 207

9.3 Wideband Voice Summary 214

10 Packetization—RTP, RTCP, and Jitter Buffer 215

10.1 Real-Time Protocol (RTP) 215

10.2 RTP Control Protocol (RTCP) 218

10.3 VoIP Packet Impediments 219

10.4 Jitter Buffer 222

10.5 Adaptive Jitter Buffer 224

10.6 Adapting to Delay Variations 228

10.7 AJB Algorithms Overview 230

10.8 Adaptive Jitter Buffer Implementation Guidelines 239

10.9 Fixed Jitter Buffer Implementation Guidelines 241

11 VoIP Voice—Network Bit Rate Calculations 242

11.1 Voice Compression and Bit Rate Overview 243

11.2 Voice Payload and Headers 244

11.3 Ethernet, DSL, and Cable Interfaces for VoIP 245

11.4 VoIP Voice Packets on a DSL Interface 249

11.5 VoIP Voice Packets on a Cable Interface 249

11.6 Bit Rate Calculation for Different codecs 253

11.7 Bit Rate with VADCNG 253

11.8 Bit Rate with RTCP, RTCP-XR, and Signaling 254

11.9 Summary on VoIP Bit Rate 254

12 Clock Sources for VoIP Applications 257

12.1 PSTN Systems and Clocks 259

12.2 VoIP System Clock Options 259

12.3 Clock Timing Deviations Relating to VoIP Packets 263

12.4 Measuring Clock PPM 266

12.5 Clock Drift Influence on Voice and Fax Calls 268

13 VoIP Voice Testing 269

13.1 Basic Test Setup 269

13.2 First-Level VoIP Manual Tests 272

13.3 Analog Front-End Voice Transmission Tests 274

13.4 Telephone Line Monitor for Tones and Timing Characteristics 274

13.5 MOS—PSQM, PAMS, and PESQ Measurements 275

13.6 Bulk Calls for Stress Testing 276

13.7 Network Impediments Creation 277

13.8 VoIP Packets Analysis 278

13.9 Compliance Tests 278

13.10 VoIP Interoperability 278

13.11 Deployment Tests 279

13.12 Voice Quality Certifications 280

13.13 VoIP Speech Quality Tests by the ETSI 280

13.14 User Operational Considerations 281

14 Fax Operation on PSTN, Modulations, and Fax Messages 282

14.1 Fax Machine Overview 284

14.2 Fax Image Coding Schemes 286

14.3 Fax Modulation Rates 290

14.4 PSTN Fax Call Phases 291

14.5 Fax and Modem Tones Basics 300

14.6 Tones Detection 303

14.7 Fax Modulations and Demodulations 309

14.8 V.21 Fax Modem 311

14.9 V.27ter Fax Modem 313

14.10 V.29 Modem 318

14.11 V.17 Modem 321

14.12 V.34 Fax Modem 325

14.13 V.21 HDLC Framing and Deframing 326

14.14 HDLC Messages in ECM 331

14.15 Summary and Discussions on Fax 332

15 Fax Over IP and Modem Over IP 333

15.1 Fax over IP Overview 333

15.2 Fax over IP Benefits 336

15.3 Fax Basic Functionality and Detecting Fax Call 337

15.4 T.38 Fax Relay 339

15.5 Fax Pass-Through 346

15.6 Fax over IP Interoperability Challenges 348

15.7 Modem Basic Functions on PSTN 356

15.8 Migrating Modem Functions to IP 358

15.9 Guidelines for Fax and Modem Pass-Through in VoIP 362

15.10 VoIP Fax Tests 365

16 Fax Over IP Payload Formats and Bit Rate Calculations 371

16.1 Overview on T.38 and G.711 Pass-Through Bit Rate 372

16.2 G.711 Fax Pass-Through Bit Rate 374

16.3 T.38 Basic Payload Bytes for V.27ter, V.29, V.17, and V.34 374

16.4 Overview on Redundant and Duplicate Fax Packets 376

16.5 T.38 IFP Packets 378

16.6 IFP over TCP (TCPIPIFP) 381

16.7 IFP over UDP 382

16.8 T.38 UDPTL-Based Bit Rate Calculation with Redundancy 387

16.9 Fax UDPTL-Based Bit Rate on Ethernet and DSL Interfaces 388

16.10 T.38 Bit Rate Recommendations 392

17 Country Deviations of the PSTN Mapped to VoIP 393

17.1 Country-Specific Deviations 394

17.2 Country-Specific Deviations on VoIP Interfaces 396

17.3 Call Progress Tones for Multiple Countries 399

17.4 Call Progress Tone Detectors 404

18 Voice Packets Jitter with Large Data Packets 406

18.1 ATM Cells and Transmission 408

18.2 IPQoS and Queuing Jitter on an Interface 410

19 VoIP on Different Processors and Architectures 414

19.1 VoIP on Personal Computers 415

19.2 VoIP on PC Add-On Cards 416

19.3 VoIP on Dedicated Processors 417

19.4 Operating System Aspects on Different Platforms 419

19.5 Voice Processing Complexity 422

20 VoIP Voice Quality 425

20.1 Voice Quality Measurements 426

20.2 E-model-Based Voice Quality Estimation 435

20.3 VoIP Voice Quality Considerations 446

20.4 VoIP Voice Quality Summary 459

20.5 Voice Quality Monitoring and RTCP-XR 459

20.6 Summary and Discussions 463

21 VoIP Voice FAQs 464

22 Basic Fax and Fax Over IP FAQs 484

Index 517