Voice Over 802.11

Contents
1 Overview of Vo802.11 1
Access 1
Switching 2
Transport 2
Vo802.11: Bypassing the Local Loop 3
Reference 4
2 802.11: Alternative Access 5
How Does WiFi Work? 5
How Data Is Transmitted Via Wireless Technology 6
The Significance of Spread Spectrum Radio 8
802.11 Variants 8
FHSS (802.11a) 9
DSSS 11
Orthogonal Frequency-Division Multiplexing 11
Carrier Multiplexing 13
MAC Concepts and Architecture 13
MAC Layer Services 13
Power Management and Time Synchronization 14
MAC Layer Architecture 14
MIB 17
DCF 18
PCF 18
IEEE 802.11 Architecture 19
IEEE 802.11 Components 21
Mobility 22
Conclusion 23
References 24
3 Voice over Internet Protocol 25
What Is VoIP? 25
Origins 25
How Does VoIP Work? 26
Protocols Related to VoIP 27
Signaling Protocols 28
H.323 28
SIP 29
What Is SIP? 30
SIP Architecture 30
Interworking with Other Multimedia Networks 36
H.323 Zone 37
Gateway Control Protocols 38
Media Gateway Control Protocol 39
SS7-Related Protocols 40
Routing Protocols 41
RIP 41
OSPF 41
SPF Algorithm 42
BGP 42
Resource Reservation Protocol 44
Transport Protocols 45
RTP 45
RTCP 46
Internet Protocol Version 6 46
Conclusion 47
References 47
4 Switching TDM and VoIP Networks 49
TDM Switching 49
Multiplexing 49
Voice Digitization 50
Signaling 55
Transport 58
Softswitch and Distributed Architecture: A “Stupid”
Network 59
Access 61
PC-to-PC and PC-to-Phone Applications 61
IP Phones (IP Handsets) Phone-to-Phone VoIP 61
Switching in IP Networks 66
Applications for Softswitch 69
Conclusion 74
References 75
5 Objections to Vo802.11 77
Objections Related to 802.11 77
QoS 77
Security 78
Range 78
Objections Related to Voice over IP 79
Reliability 79
Scalability 79
QoS 79
Signaling 79
Features and Applications 80
Conclusion 80
References 81
Vo802.11: Range Is a Matter of Engineering 83
Antennas 84
Factors Affecting Range 85
Sensitive Receivers 86
Amplifiers 86
The 802.11b Network at 20 to 72 Miles 87
Architecture: The Large Network Solution 87
MANs 88
Extending Range Via an Ad Hoc Peer-to-Peer Network 91
Conclusion: Range Is Not an Issue 94
References 96
7 Security and Vo802.11 97
SSID 98
WEP 98
MAC Address Filtering 100
Security Risks 100
WLAN Security Model 100
Interception 101
Fabrication 104
Modification 106
Replay 108
Reaction 109
Interruption 109
Denial of Service Attacks 109
Repudiation 111
Network Architecture 111
Mobility and Security 113
Security Policy: A Range of Options 113
802.11 Security Measures Beyond WEP 114
Wi-Fi Protected Access 114
802.1x and EAP Advanced Security 115
802.1x Network Port Authentication 116
EAP 117
VPNs 120
Point-to-Point Tunneling Protocol 122
Layer Two Tunneling Protocol 122
L2TP over IPsec 122
SSL 122
UPN-Related Security Protocols 123
Kerberos 123
Conclusion 125
References 126
8 Objections Due to Interference and QoS on Vo802.11
Wireless Networks 129
Interference 130
External Sources of Interference 131
Internal Sources of Interference 135
If You Want Interference, Call the Black Ravens 138
Line of Sight, Near Line of Sight, and Nonline of Sight 138
Fresnel Zone and Line-of-Sight Considerations 139
Importance of QoS on 802.11 Networks 140
Need for QoS in Wireless Networks 141
Challenges to Wireless QoS 141
Latency in Wireless Networks 141
QoS in 802.11 143
Legacy 802.11 MAC 143
DCF 144
PCF 148
Conclusion 153
References 153
9 Engineering Vo802.11 Networks for Maximum QoS 155
QoS on Vo802.11 Networks 155
Measuring Voice Quality in Vo802.11 156
Detractors to Voice Quality in Vo802.11 Networks 157
Factors Affecting QoS in Vo802.11 Networks 160
Improving QoS in IP Routers and Gateways 160
Measures for Delivering Optimal QoS on Vo802.11
Networks 161
Voice Codecs Designed for Vo802.11 Networks 167
Conclusion 170
References 170
10 Scalability in Wireless VoIP Networks 171
Bandwidth Considerations for Wireless VoIP 171
Importance of Bandwidth to Scalability 172
Which 802.11 Protocols Are Best for Which Vo802.11
Applications? 173
802.11b 173
802.11a 173
802.11g 173
Why Frequency Bands Are Important 174
Path Loss Illustrated 174
Receiving Antenna Gain 174
Link Margin 175
Diffraction Losses 175
Coax and Connector Losses 175
Frequency Reuse Planning for Vo802.11 Networks 175
Frequency Reuse at 2.4 GHz 176
Frequency Reuse at 5 GHz 176
Frequency Allocation 178
FCC Regulations and Power of Vo802.11 Transmissions 179
Point-to-Multipoint Links 179
Point-to-Point Links 179
Limitations in the AP 180
Scalability in VoIP Switching 181
Conclusion 182
References 182
11 Vo802.11 Reliability 183
Understanding Reliability 183
How Availability Is Calculated 184
Reliability in Wireless Access in a Vo802.11 Network 186
Redundancy in Vo802.11 Networks 186
Repairability 187
Recoverability 187
Achieving the “Five 9s” with a Vo802.11 Softswitch 187
NEBS 190
Power Availability 190
Conclusion 192
References 192
12 Vo802.11 Features and Applications 193
Features in the Legacy PSTN 194
Features and Signaling 194
SCE 195
APIs 196
APIs and Services 196
XML 197
SIP: Architecture for Enhanced Services in Softswitched
Vo802.11 Networks 197
Media Servers 198
Application Servers 198
Architecture 199
Interface Between Call Control and Application Server 199
Application Server Interactions 200
Vo802.11 Networks and E911 and CALEA
Requirements 201
E911 201
CALEA 202
Vo802.11 Applications Made Possible by Softswitch
Features 203
Web Provisioning 203
Voice-Activated Web Interface 203
The Big “So What!?” of Enhanced Features in
Vo802.11 Networks 203
Example of a Wireless Killer App: I-Mode 204
Conclusion 204
References 205
13 Regulatory Considerations for Vo802.11 Networks 207
Current Regulatory Environment for 802.11 207
Power Limits 208
Interference 209
Laws on Antennas and Towers 214
FCC Preemption of Local Law 214
Height Limitations 214
Regulatory Issues Concerning VoIP 214
Conclusion 215
References 216
14 Economics of Vo802.11 Networks 217
Vo802.11 Works: Case Studies 217
Medical 217
Education 219
Financial Services 221
Manufacturing and Warehousing 222
WISPs 222
Vo802.11 Telephone System Cost Justification in the
Workplace 223
Platform Costs 224
MAC 224
Saving Time and Money in Health Care 225
Supervisor Time Savings 226
Efficiencies in Maintenance of the Production Line 227
Cost Savings with Regard to Long-Distance Customers 228
Interoffice Telephony 228
Enterprise Conclusion 228
Lower Barrier to Entry 229
Considerations in Bypassing the PSTN with Vo802.11 229
Conclusion 230
References 231
15 Conclusion: Vo802.11 Is the Future of Voice
Communications 233
Potential for a New Regulatory Regime 233
FCC New Spectrum Policy 233
Problem Areas in Spectrum Management and Their
Solutions 234
Projections: Futurecasting for Vo802.11 240
Disruptive Technology 240
How Vo802.11 Will Disrupt the Telephone Industry 241
Cheaper 241
Simpler 241
Smaller 242
More Convenient to Use 242
Deconstruction 243
Deconstruction of Service Providers 243
Goetterdaemmerung or Creative Destruction in the
Telecommunications Industry 244
References 245
About the Author 247
Index 249

Download this book click here
Another Computer Network books click here
Another Multimedia books click here