Wi-Fi Telephony (eBook)

Front Cover 1
Wi-Fi Telephony: Challenges and Solutions for Voice over WLANs 4
Copyright Page 5
Contents 8
Acknowledgments 13
Acronyms 14
About the Authors 21
Chapter 1. The Telephony World 22
1.1 The Basics 22
1.2 Digitizing Speech 24
1.3 PSTN Architecture 27
1.4 Signaling 28
1.5 Voice and Wireless Networks 34
1.6 Summary 43
Chapter 2. The Data World 44
2.1 Introduction 44
2.2 Brief History 44
2.3 The OSI Seven-Layer Model 45
2.4 The IP Protocol 49
2.5 The TCP/IP Transport Layer 53
2.6 Other TCP/IP-Based Protocols 59
2.7 Conclusion 62
References 62
Chapter 3. Voice over IP 64
3.1 Introduction 64
3.2 Putting Voice Over Internet 68
3.3 VoIP Architectures 71
3.4 Signaling Protocols 73
3.5 Voice-over-IP Media 95
3.6 The Overall Picture 97
References 98
Chapter 4. Wireless Local Area Networks 100
4.1 Introduction 100
4.2 The Alphabet Soup 101
4.3 Network Architecture 103
4.4 802.11 Framing 107
4.5 Accessing the Medium 112
4.6 802.11 PHY 120
4.7 Power Save in 802.11 127
4.8 Conclusion 129
Chapter 5. VoWLAN Challenges 130
5.1 Introduction 130
5.2 VoWLAN 130
5.3 System Capacity and QoS 131
5.4 PCF 140
5.5 Admission Control 141
5.6 Security 142
5.7 Power Save 142
5.8 Roaming/Handoffs in 802.11 143
5.9 Summary 145
Chapter 6. QoS and System Capacity 146
6.1 Introduction 146
6.2 802.11e, WME and “Vanilla” WLANs 147
6.3 Traffic Categories 149
6.4 Transmission Opportunity 150
6.5 EDCF 152
6.6 HCF 156
6.7 Voice Data Coexistence 158
6.8 Achieving QoS for VoWLAN 158
6.9 System Capacity 161
6.10 Admission Control 164
6.11 Summary 167
Chapter 7. Security 168
7.1 Introduction 168
7.2 Key Establishment in 802.11 169
7.3 Anonymity in 802.11 170
7.4 Authentication in 802.11 171
7.5 Confidentiality in 802.11 177
7.6 Data Integrity in 802.11 180
7.7 Loopholes in 802.11 Security 183
7.8 WPA 184
7.9 WPA2 (802.11i) 196
7.10 Beyond 802.11 Security 203
7.11 Conclusion 213
Chapter 8. Roaming 214
8.1 The Need for Roaming 214
8.2 Types of Roaming 215
8.3 Roaming Issues 216
8.4 Roaming and Voice 218
8.5 Preparing to Roam: Scanning 220
8.6 When to Roam 226
8.7 Where to Roam 227
8.8 Reauthentication Delays 228
8.9 Inter-ESS Roaming 229
8.10 Future Enhancements 231
8.11 Conclusion 233
Chapter 9. Power Management 234
9.1 The Need for Power Management 234
9.2 Underlying Philosophy of Power Management 234
9.3 Designing for Power Management 236
9.4 Implementing Power Management 243
9.5 An Operational Perspective 253
9.6 Summary 255
Chapter 10. Voice over Wi-Fi and Other Wireless Technologies 256
10.1 Introduction 256
10.2 Ongoing 802.11 Standard Work 256
10.3 Wi-Fi and Cellular Networks 262
10.4 WiMax 272
10.5 VoWi-Fi and Bluetooth 273
10.6 VoWi-Fi and DECT 277
10.7 VoWi-Fi and Other Ongoing 802.x Wireless Projects 279
10.8 Conclusion 281
References 281
Index 282