Ad Hoc Networks : Technologies and Protocols - University of ...

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Introduction 231 The concept of ad-hoc networking is not tied to any particular single-hop wireless technology. However, with increasing deployments of Wireless LAN (WLAN) devices at homes, offices and public hotspots, the term wireless is becoming synonymous with “Wireless LANs”. Currently in the market there are products conforming to two competing WLAN standards, namely IEEE 802.11a and IEEE 802.11b. These standards differ from the original IEEE 802.11 standard in the specification of the physical layer. However, the MAC layer is unchanged in all these three protocols. In this chapter, we use 802.11 to collectively refer to the three standards. High speed (up to 54 Mbps with 802.11a), decreasing prices (Wireless Network Interface Cards are priced below $50) and proliferation of wireless integrated handheld devices, are the three main reasons for its popularity. Most researchers assume CSMA/CA based 802.11 (specifies Medium Access (MAC) and Physical layers) to be the underlying wireless technology for ad-hoc networks. In this chapter we will also assume that 802.11 is the underlying technology. Researchers are also actively exploring the use of other medium access techniques such as TDMA [19], for ad-hoc networks. More recently, there has been a growing interest in applying ad-hoc networking techniques to different environments, such as acoustic ad-hoc networks [21] for marine exploration. Figure 8.1 shows a Wireless LAN and Figure 8.2 an ad-hoc network. The 802.11 standard has two modes of operation, namely the Infrastructure mode and the ad-hoc mode. These modes correspond to the WLAN and ad-hoc configurations respectively. In the WLAN configuration nodes communicate only via the access-point (AP). In the ad-hoc configuration, nodes communicate via multi-hop peer-to-peer wireless links formed by virtue of proximity with other nodes. Figure 8.1. Wireless LAN Figure 8.2. Ad-hoc Network The rest of the chapter is organized as follows. Section 8.2 provides a definition of QoS and a discussion on QoS metrics. Section 8.3 presents QoS issues in the design of the physical layer. Section 8.4 discusses QoS support at the MAC layer in WLANs and ad-hoc networks. Section 8.5 describes various
232 QoS Issues in Ad-hoc Networks solutions for QoS routing in ad-hoc networks. Section 8.6 discusses other QoS approaches at transport and higher layers. Frameworks that span more than one networking layers are discussed in Section 8.7. Section 9 presents some future challenges in the design of QoS enabled Ad-hoc Networks and concludes the chapter. 8.2 Definition of QoS So far we have been discussing about QoS in an abstract sense. But, what is QoS? What are the QoS metrics? Quality of service refers to different notions at different networking layers. At the physical layer, QoS refers to the data rate and packet loss rate on wireless links, which is a function of the channel quality. With continuously varying channel quality, it is impossible to maintain constant data rate and low packet loss rate. At the MAC layer, QoS is related to the fraction of time a node is able to successfully access and transmit a packet. At the routing layer, end-to-end QoS metrics would depend on the metrics at each hop of a multi-hop route. The routing layer must try to compute and maintain routes that satisfy the QoS requirement for the lifetime of a connection. The transport and upper layers could include support for QoS if the routing layer is not able to meet the QoS requirements. Bandwidth, delay and jitter are the three commonly studied QoS metrics. However, the problem of QoS in ad-hoc networks is more challenging than in wired networks as described in Section 8.1. As a result there has been little work on supporting delay and jitter; and most of the focus has been on providing bandwidth assurances. Various mechanisms have been proposed to estimate the amount of bandwidth in CSMA/CA (Carrier Sense Multiple Access) networks [8] and TDMA networks [12]. For ad-hoc networks, it is difficult to provide hard QoS guarantees due to fluctuations in the wireless channel and interference from non-neighboring nodes. It is therefore easier to design solutions where QoS support from the network is in the form of soft-assurances [18] rather than hard guarantees. For the same reasons, relative assurances are more common than absolute assurances. Most of this chapter refers to soft-assurances for QoS metrics, unless stated otherwise. 8.3 Physic al Layer One of the fundamental challenges in wireless networks is the continuously changing physical layer properties of the channel. The physical layers of 802.11a and 802.11b can support multiple data rates. Depending on the channel quality the data rate can be altered to keep the bit error rate acceptable, as high data rates are also prone to high bit error rates.
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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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Idle-time Energy Conservation 179 k
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Page 216 and 217: Conclusion 191 [6] [7] [8] [9] [10]
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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
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Page 248 and 249: Broadcast with Directional Antennas
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Page 252 and 253: Summary 227 [4] [5] [6] [7] [8] [9]
Page 254 and 255: Chapter 8 QOS ISSUES IN AD-HOC NETW
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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