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Chapter 8 QOS ISSUES IN AD-HOC NETWORKS Prasun Sinha Computer and Information Science Ohio State University Columbus, OH 43210 prasun@cis.ohio-state.edu Abstract Support for QoS is integral to the design of ad-hoc networks. Fluctuations in channel quality effect the QoS metrics on each link and the whole end-to-end route. In addition, the interference from non-neighboring nodes effects the link quality. QoS is thus an essential component of ad-hoc networks. The QoS requirements arise at the application layer in the form of restrictions on values of certain QoS metrics. The most commonly studied QoS metrics are bandwidth, delay and jitter. Bandwidth is the QoS metric that has received the most attention in the QoS literature. The QoS requirements are typically met by soft assurances rather than hard guarantees from the network. Most mechanisms are designed for providing relative assurances rather than absolute assurances. This chapter presents solutions and approaches for supporting QoS in ad-hoc networks at the physical, MAC, and routing layers. It also presents approaches at other layers and describes future challenges that need to be addressed to design a QoS enabled ad-hoc network. Keywords: QoS, Ad-hoc, 802.11e 8.1 Introduction The need for supporting QoS in the Internet is evidenced by an increasing activity in the IETF community for supporting the Diffserv [3] architecture. The initial designers of the Internet moved away from the telephone network design where the intelligence was in the network and the end-terminals were comparatively dumb. The telephone network design however provides QoS in the form of guaranteed connection and quality of voice, once a call is established. The initial Internet design idea of keeping the network simple and moving the intelligence to the edge and the end-hosts, did help in the rapid growth of
230 QoS Issues in Ad-hoc Networks the Internet. But with proliferation of applications requiring some notion of guarantee of service from the network, it is becoming essential to support QoS in the Internet. Multimedia communication and VoIP (Voice over IP) are two such applications that are rapidly gaining popularity. The performance of these applications largely depends on the QoS assurances provided by the network. In ad-hoc networks, Quality of Service support is becoming an inherent necessity rather than an “additional feature” of the network. Following are the three main reasons that make a strong case for designing QoS enabled ad-hoc networks rather than adding such features as an afterthought. Wireless channel fluctuates rapidly and the fluctuations severely effect multi-hop flows. As opposed to the wired Internet, the capacity of the wireless channel fluctuates rapidly due to various physical layer phenomena including fading and multi-path interference. In addition, background noise and interference from nearby nodes further effect the channel quality. In ad-hoc networks, the end-to-end quality of a connection may vary rapidly as change in channel quality on any link may effect the end-to-end QoS metrics of multi-hop paths. Packets contend for the shared media on adjacent links of a flow. Contention between packets of the same stream at different nodes impacts the QoS metrics of a connection. Such contention arises as the wireless channel is shared by nodes in the vicinity. Unlike in the Internet, this phenomenon effects the QoS even in the absence of any other flow in the network. Interference can effect transmissions at nodes beyond the neighbors. Interference effects are pronounced in ad-hoc networks where typically a single frequency 1 is used for communication in the shared channel. In single-hop infrastructured wireless networks frequency planning is mostly used where nearby base-stations can be configured to function at different frequencies for reducing interference. Transmissions in the wireless media are not received correctly beyond the transmission range. But even beyond the transmission range, the remaining power may be enough to interfere with other transmissions. So, interference from nonneighboring nodes may result in packet drops. In order to support QoS on multi-hop paths, QoS must be designed for the end-to-end path as well as for each hop. The physical and MAC layers are responsible for QoS properties on a single-hop. The routing layer is responsible for QoS metrics on an end-to-end route. 1 In some recent studies such as [17], the use of multiple frequencies has been explored for ad-hoc networks.
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AD HOC NETWORKS Technologies and Pr
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AD HOC NETWORKS Technologies and Pr
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Contents List of Figures List of Ta
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Contents vii 4.7. Conclusions and F
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Contents ix 9.2. Potential Attacks
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List of Figures 1.1 Internet in the
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List of Figures xiii 6.3 COMPOW com
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List of Figures xv 9.1 9.2 An IDS a
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List of Tables 2.1 2.2 2.3 2.4 2.5
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Contributing Authors Samir R. Das i
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Preface Wireless mobile networks an
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Acknowledgments xxiii We wish to ex
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Chapter 1 AD HOC NETWORKS Emerging
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Introduction and Definitions 3 coul
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Introduction and Definitions 5 Secu
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Ad Hoc Network Applications 7 tunis
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Ad Hoc Network Applications 9 The d
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Ad Hoc Network Applications 11 Figu
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Design Challenges 13 example of cro
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Evaluating Ad Hoc Network Protocols
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Overview of the Chapters in this Bo
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Overview of the Chapters in this Bo
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Conclusions 21 1.6 Conclusions This
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Chapter 2 COLLISION AVOIDANCE PROTO
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Performance of collision avoidance
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Framework and Mechanisms for Fair A
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Conclusion 59 In the first part of
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Conclusion 61 [13] [14] [15] [16] [
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Chapter 3 ROUTING IN MOBILE AD HOC
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Flooding 65 vector and link state p
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Flooding 67 centralized approximati
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Proactive Routing 69 status of each
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Proactive Routing 71 Topology Broad
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On-demand Routing 73 reply packets
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On-demand Routing 75 during the lin
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Proactive Versus On-demand Debate 7
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Proactive Versus On-demand Debate 7
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Location-based Routing 81 to find a
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Location-based Routing 83 Figure 3.
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Concluding Remarks 85 relative meri
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Concluding Remarks 87 [14] [15] [16
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Concluding Remarks 89 [42] [43] [44
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Chapter 4 MULTICASTING IN AD HOC NE
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Introduction 93 The mobility of the
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Classifications of Protocols 95 red
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Multicasting Protocols 97 this sect
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Multicasting Protocols 99 as close
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Multicasting Protocols 101 In ODMRP
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Multicasting Protocols 103 hoc netw
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Multicasting Protocols 105 A member
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Multicasting Protocols 107 Figure 4
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Broadcasting 109 “talk” to a ra
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Broadcasting 111 broadcasted packet
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Protocol Comparisons 113 are cluste
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Overarching Issues 115 is user data
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Overarching Issues 117 and RTS/CTS
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Conclusions and Future Directions 1
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Conclusions and Future Directions 1
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Chapter 5 TRANSPORT LAYER PROTOCOLS
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TCP and Ad-hoc Networks 125 Modifie
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TCP and Ad-hoc Networks 127 mechani
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TCP and Ad-hoc Networks 129 timeout
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TCP and Ad-hoc Networks 131 to freq
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TCP and Ad-hoc Networks 133 Figure
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Transport Layer for Ad-hoc Networks
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Modified TCP 137 MAC layers without
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Modified TCP 139 Figure 5.6. TCP-EL
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TCP-aware Cross-layered Solutions 1
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Ad-hoc Transport Protocol 147 in it
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Ad-hoc Transport Protocol Figure 5.
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Summary 151 References [1] [2] [3]
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Chapter 6 ENERGY CONSERVATION Robin
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Energy Consumption in Ad Hoc Networ
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Energy Consumption in Ad Hoc Networ
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Communication-Time Energy Conservat
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Idle-time Energy Conservation 175 a
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Idle-time Energy Conservation 177 T
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Page 216 and 217: Conclusion 191 [6] [7] [8] [9] [10]
Page 218 and 219: Conclusion 193 [33] [34] [35] [36]
Page 222 and 223: Chapter 7 USE OF SMART ANTENNAS IN
Page 224 and 225: Smart Antenna Basics and Models 199
Page 226 and 227: Medium Access Control with Directio
Page 242 and 243: Routing with Directional Antennas 2
Page 248 and 249: Broadcast with Directional Antennas
Page 250 and 251: Broadcast with Directional Antennas
Page 252 and 253: Summary 227 [4] [5] [6] [7] [8] [9]
Page 256 and 257: Introduction 231 The concept of ad-
Page 258 and 259: Physical Layer 233 The 802.11a stan
Page 260 and 261: Medium Access Layer 235 neighbors,
Page 262 and 263: Medium Access Layer 237 Figure 8.5.
Page 264 and 265: QoS Routing 239 where is the number
Page 266 and 267: QoS at other Networking Layers 241
Page 268 and 269: Inter-Layer Design Approaches 243 8
Page 270 and 271: Conclusion 245 are specifically des
Page 272 and 273: Conclusion 247 [13] S. Mangold, S.
Page 274 and 275: Chapter 9 SECURITY IN MOBILE AD-HOC
Page 276 and 277: Potential Attacks 251 attacks, such
Page 278 and 279: Attack Prevention Techniques 253 9.
Page 280 and 281: Intrusion Detection Techniques 255
Page 290 and 291: Conclusion 265 an important and sti
Page 294 and 295: Index Ad hoc network multicast rout
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