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

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Idle-time Energy Conservation 177 The goal of any device suspension protocol is to only remain awake when there is active communication for a node and otherwise suspend. In general, active communication is defined to be communication, unicast, multicast or broadcast, that originates from or is destined to a node. However, many ad hoc routing protocols take advantage of the fact that all communication in an ad hoc network is inherently broadcast and snoop on communication in their neighborhood to populate their routing tables. Allowing a node to suspend its device limits the node’s ability to snoop on communication between neighboring nodes. To date, there has been little evaluation of the impact of device suspension on route caching. When a communication device is suspended, the node is effectively cut off from the rest of the network. While it is relatively simple to resume the device when the node has packets to send, the challenge comes from dealing with packets destined to a node with a suspended communication device. Two major problems arise when the destination device is suspended. First, sending nodes must know when the receiving node’s communication device is suspended. If the receiver is active, the sender should transmit immediately. If the receiver is suspended, the sender should buffer the packet and wait until the receiver wakes up to transmit it. Packets destined to a suspended device experience delay on the order of the length of time the device spends suspended before it resumes to check for pending transmissions. If the receiver is suspended for too long, the sender’s buffers could fill up, eventually causing the packet to be dropped. If the sender thinks a suspended receiver is active, the sender tries to transmit the packets with no success, unnecessarily wasting its own energy and potentially dropping the packets because it thinks the receiver is not in range. Second, the suspended device can only guess when there are packets destined for the node. If it resumes when there are none, it again wastes energy listening to an idle channel. If it waits too long to resume, pending packets are unnecessarily delayed or even dropped. Since both the sender and receiver must be awake to transmit and receive, it is necessary to ensure an overlap between awake times for nodes with pending communication. We discuss two types of protocols used to manage the suspend/resume cycles for individual nodes: periodic resume and triggered resume. Periodic Resume. A simple technique for managing the suspend/resume cycles for nodes is to allow the nodes to suspend most of the time and to resume periodically to check for pending transmissions. If no packets are destined for a node when it checks, the node can again suspend its device. If a node has some packets destined for it, it remains awake until there are no more packets or until the end of the cycle. Nodes can be notified of pending transmissions through an out-of-band control channel (i.e., part of the channel is reserved for
178 Energy Conservation Figure 6.8. IEEE 802.11 Power-save Mode control messages) [26] [17] [65] or through in-band signaling [71]. The success of a periodic resume approach is to ensure that nodes that want to communicate with each other are awake at the same time to coordinate the notification and ensure that the receiver remains awake to receive the pending transmission. We discuss two approaches to periodic resume: synchronous and asynchronous. Synchronous. If the periods of all nodes in the ad hoc network are synchronized, all nodes are guaranteed to have overlapping awake times, and so can easily have overlapping out-of-band channels for notification. Such a synchronized solution is specified in IEEE 802.11 Power Save Mode (PSM) [26], which also provides low-level support for buffering packets for sleeping nodes and synchronizing nodes. In power-save mode, all nodes in the network are synchronized to wake up at the beginning of a beacon interval (see Figure 6.8). To maintain synchronization, beacon messages are sent at the beginning of every beacon interval. Synchronization in single-hop networks only requires the transmission of one beacon per interval. To determine if and when to send a beacon, nodes use a random backoff algorithm. Any node that hears another node’s beacon before it sends its own cancels its beacon and synchronizes to that beacon. This algorithm has been proposed for use in multiple-hop wireless networks. While there is the possibility that the algorithm will not converge in dynamic environments, the randomness of the algorithm should enable convergence in many environments. Broadcast, multicast or unicast packets to a power-saving node are first announced during the period when all nodes are awake. The announcement is done via an ad hoc traffic indication message (ATIM) inside a small interval at the beginning of the beacon interval called the ATIM window. Channel access and contention resolution for communication during the ATIM window follow the same rules as during normal communication. A node that receives a directed ATIM during the ATIM window (i.e., it is the designated receiver) sends an ac-
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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
Page 152 and 153: TCP and Ad-hoc Networks 127 mechani
Page 154 and 155: TCP and Ad-hoc Networks 129 timeout
Page 156 and 157: TCP and Ad-hoc Networks 131 to freq
Page 158 and 159: TCP and Ad-hoc Networks 133 Figure
Page 160 and 161: Transport Layer for Ad-hoc Networks
Page 162 and 163: Modified TCP 137 MAC layers without
Page 164 and 165: Modified TCP 139 Figure 5.6. TCP-EL
Page 166 and 167: TCP-aware Cross-layered Solutions 1
Page 172 and 173: Ad-hoc Transport Protocol 147 in it
Page 174 and 175: Ad-hoc Transport Protocol Figure 5.
Page 176 and 177: Summary 151 References [1] [2] [3]
Page 178 and 179: Chapter 6 ENERGY CONSERVATION Robin
Page 180 and 181: Energy Consumption in Ad Hoc Networ
Page 182 and 183: Energy Consumption in Ad Hoc Networ
Page 184 and 185: Communication-Time Energy Conservat
Page 200 and 201: Idle-time Energy Conservation 175 a
Page 204 and 205: Idle-time Energy Conservation 179 k
Page 206 and 207: Idle-time Energy Conservation 181 F
Page 210 and 211: Idle-time Energy Conservation 185 t
Page 212 and 213: Idle-time Energy Conservation 187 c
Page 216 and 217: Conclusion 191 [6] [7] [8] [9] [10]
Page 218 and 219: Conclusion 193 [33] [34] [35] [36]
Page 220 and 221: Conclusion 195 [59] [60] [61] [62]
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
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Summary 227 [4] [5] [6] [7] [8] [9]
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Chapter 8 QOS ISSUES IN AD-HOC NETW
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Introduction 231 The concept of ad-
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Physical Layer 233 The 802.11a stan
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Medium Access Layer 235 neighbors,
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Medium Access Layer 237 Figure 8.5.
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QoS Routing 239 where is the number
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QoS at other Networking Layers 241
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Inter-Layer Design Approaches 243 8
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Conclusion 245 are specifically des
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Conclusion 247 [13] S. Mangold, S.
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Chapter 9 SECURITY IN MOBILE AD-HOC
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Potential Attacks 251 attacks, such
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Attack Prevention Techniques 253 9.
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Intrusion Detection Techniques 255
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Conclusion 265 an important and sti
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Conclusion 267 [24] [25] [26] [27]
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Index Ad hoc network multicast rout
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