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IEEE 802.11 DCF Uses RTS-CTS exchange to avoid hidden terminal problem Any node overhearing a CTS cannot transmit for the duration of the transfer Uses ACK to achieve reliability Any node receiving the RTS cannot transmit for the duration of the transfer To prevent collision with ACK when it arrives at the sender When B is sending data to C, node A will keep quite A B C 270
Collision Avoidance With half-duplex radios, collision detection is not possible CSMA/CA: Wireless MAC protocols often use collision avoidance techniques, in conjunction with a (physical or virtual) carrier sense mechanism Carrier sense: When a node wishes to transmit a packet, it first waits until the channel is idle Collision avoidance: Once channel becomes idle, the node waits for a randomly chosen duration before attempting to transmit 271
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Mobile Ad Hoc Networks: Routing, MA
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Introduction Unicast routing Mult
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Coverage Not intended to be exhaus
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Mobile Ad Hoc Networks Formed by w
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Mobile Ad Hoc Networks (MANET) Mob
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Many Applications Personal area ne
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Many Variations Traffic characteri
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Challenges Limited wireless transm
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Research on Mobile Ad Hoc Networks
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Assumption Unless stated otherwise
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Why is Routing in MANET different ?
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Proactive protocols Routing Protoco
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Overview of Unicast Routing Protoco
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A Flooding for Data Delivery B H S
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A Flooding for Data Delivery B H
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Flooding for Data Delivery: Advanta
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Flooding of Control Packets Many p
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A B Route Discovery in DSR H S E C
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Route Discovery in DSR Destination
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Route Reply in DSR Route Reply can
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A B Data Delivery in DSR H DATA [S,
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DSR Optimization: Route Caching Ea
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A B Use of Route Caching [S,E,F,J,D
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Use of Route Caching: Can Reduce Pr
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Route Caching: Beware! Stale cache
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Dynamic Source Routing: Disadvantag
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Flooding of Control Packets How to
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X = last known location of node D,
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LAR Only nodes within the request
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LAR Variations: Adaptive Request Zo
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Location-Aided Routing The basic p
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Detour Routing Using Location Infor
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Distance Routing Effect Algorithm f
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Relative Distance Micro-Discovery R
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Geographic Distance Routing (GEDIR)
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Grid Location Service (GLS) [Li00Mo
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Query Localization [Castaneda99Mobi
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G F E B A S C D Query Localization:
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Broadcast Storm Problem [Ni99Mobico
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Solutions for Broadcast Storm Prob
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Solutions for Broadcast Storms Dis
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Ad Hoc On-Demand Distance Vector Ro
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A B Route Requests in AODV H S E C
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A B Route Requests in AODV H S E C
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A Reverse Path Setup in AODV B H S
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A B Route Reply in AODV H S E C I G
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A Forward Path Setup in AODV B H S
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Timeouts A routing table entry mai
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Route Error When node X is unable
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Link Failure Detection Hello messa
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Why Sequence Numbers in AODV A B C
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Summary: AODV Routes need not be i
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Link Reversal Algorithm [Gafni81] A
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Link Reversal Algorithm A B F C E G
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Link Reversal Algorithm Attempts t
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Partial Reversal Method A B F C E G
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Link Reversal Methods: Advantages
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Link Reversal in a Partitioned Netw
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Full Reversal in a Partitioned Netw
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Full Reversal in a Partitioned Netw
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Temporally-Ordered Routing Algorith
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E D Partition Detection in TORA A N
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E D Partition Detection in TORA A N
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E D Partition Detection in TORA A F
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E D Partition Detection in TORA A F
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TORA Design Decision TORA performs
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So far ... All nodes had identical
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Core-Extraction Distributed Ad Hoc
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Link State Propagation in CEDAR Th
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H G B CEDAR: Core Maintenance A C E
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H G B CEDAR Route Discovery A C E S
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Advantages CEDAR Route discovery/ma
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Proactive Protocols Most of the sc
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Optimized Link State Routing (OLSR)
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Optimized Link State Routing (OLSR)
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OLSR OLSR floods information throu
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Destination-Sequenced Distance-Vect
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Hybrid Protocols 171
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ZRP All nodes within hop distance
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B F ZRP: Example with Zone Radius =
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B F ZRP: Example with d = 2 A S C D
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LANMAR Routing to Nodes Within Scop
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LANMAR Routing to Nodes Outside Sco
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Geodesic Routing Without Anchors [B
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Routing Protocols discussed so far
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Other Routing Protocols Plenty of
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Power-Aware Routing [Singh98Mobicom
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Power-Aware Routing Possible modifi
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Associativity-Based Routing (ABR) [
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Preemptive Routing [Goff01MobiCom]
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Quality-of-Service Several proposa
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Multicasting in Mobile Ad Hoc Netwo
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Multicasting in MANET Need to take
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AODV Group Sequence Number In our
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Joining the Multicast Tree: AODV H
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Joining the Multicast Tree: AODV H
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Sending Data on the Multicast Tree
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Since J is not a leaf node, it must
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Leaving a Multicast Tree: AODV H C
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Handling a Link Failure: AODV Multi
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Merging Partitions: AODV If the ne
Page 219 and 220: Merging Partitions: AODV Assume th
Page 221 and 222: Q Merging Partitions: AODV B RREQ (
Page 223 and 224: Group Hello (update) Q Merging Part
Page 225 and 226: On-Demand Multicast Routing Protoco
Page 235 and 236: ODMRP No explicit join or leave pr
Page 237 and 238: Geocasting in Mobile Ad Hoc Network
Page 239 and 240: Geocasting [Navas97Mobicom] Navas
Page 241 and 242: Simple Flooding-Based Geocasting U
Page 243 and 244: Geocasting based on Location-Aided
Page 245 and 246: Geocast LAR If all routes between
Page 247 and 248: Anycasting with Modified TORA [Ko20
Page 249 and 250: DAG for Anycasting Since links bet
Page 251 and 252: Geocasting using Modified Anycastin
Page 253 and 254: Other Geocasting Schemes [Macwan01
Page 255 and 256: Some Related Work Content-based Mu
Page 257 and 258: Capacity of Fixed Ad Hoc Networks [
Page 259 and 260: Continues from last slide … Dela
Page 261 and 262: Measured Scaling Law [Gupta01] Mea
Page 263 and 264: Medium Access Control Protocols 263
Page 265 and 266: Hidden Terminal Problem Node B can
Page 267 and 268: Reliability Wireless links are pro
Page 269: IEEE 802.11 Wireless MAC Distribut
Page 273 and 274: B1 = 25 B2 = 20 cw = 31 DCF Example
Page 275 and 276: MAC Protocols: Issues Hidden Termi
Page 277 and 278: Binary Exponential Backoff in DCF
Page 279 and 280: IEEE 802.11 Distributed Coordinatio
Page 281 and 282: Fairness Issue Assume that initial
Page 283 and 284: MACAW Solution for Fairness When a
Page 285 and 286: Distributed Fair Scheduling (DFS) [
Page 287 and 288: Impact of Collisions After collisi
Page 289 and 290: Distributed Fair Scheduling DFS us
Page 291 and 292: Fairness in Multi-Hop Networks Not
Page 293 and 294: Balanced MAC degree of node j p_ij
Page 295 and 296: Balanced MAC Results show that it
Page 297 and 298: Estimation-Based Fair MAC Fair sha
Page 299 and 300: Proportional Fair Contention Resolu
Page 301 and 302: Sender-Initiated Protocols The pro
Page 303 and 304: Using Receiver’s Help in a Sender
Page 305 and 306: Receiver-Based Adaptive Rate Contro
Page 307 and 308: Capacity and MAC Protocols The MAC
Page 309 and 310: Energy Conserving MAC Since many m
Page 311 and 312: A Power Aware Multi-Access Protocol
Page 313 and 314: PAMAS PAMAS uses a control channel
Page 315 and 316: Another Proposal in PAMAS To avoid
Page 317 and 318: UDP on Mobile Ad Hoc Networks 317
Page 319 and 320: UDP Performance Several relevant s
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UDP Performance Difficult to ident
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Overview of Transmission Control Pr
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Transmission Control Protocol (TCP)
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Cumulative Acknowledgements A new
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Window Based Flow Control Sliding
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Window Based Flow Control Congesti
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How does TCP detect a packet loss?
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Retransmission Timeout (RTO) calcul
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Fast Retransmission Timeouts can t
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Congestion Avoidance and Control S
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Congestion Control On detecting a
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Congestion window (segments) 25 20
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ssthresh = Fast Recovery min(cwnd,
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Slow-start Congestion avoidance F
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Performance of TCP Several factors
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Random Errors May Cause Fast Retran
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Sometimes Congestion Response May b
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Burst Errors May Cause Timeouts If
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Impact of Transmission Errors TCP
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This Tutorial This tutorial consid
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Mobile Ad Hoc Networks Mobility ca
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Impact of Multi-Hop Wireless Paths
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Ideal Throughput f(i) = fraction o
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Impact of Mobility 20 m/s 30 m/s Id
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Actual throughput But not always
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mobility causes link breakage, resu
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B C A Why Does Throughput Improve?
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Network feedback How to Improve Thr
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Actual throughput Performance Impro
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Issues Network Feedback Network kn
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To Cache or Not to Cache Average sp
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Issues To Cache or Not to Cache Ca
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TCP Performance Two factors result
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Issues RTO After Route Repair Same
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Impact of Acknowledgements TCP Ack
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Security Issues 395
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Security Issues in Mobile Ad Hoc Ne
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Resurrecting Duckling [Stajano99]
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Secure Routing Establishing a Cert
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Techniques for Intrusion-Resistant
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Intrusion Detection [Zhang00Mobicom
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Packet Purse Model [Byttayn00MobiHo
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Existing Implementations Several i
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CMU Implementation: Lessons Learned
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BBN Implementation [Ramanathan00Wcn
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Link layer Implementation Issues: W
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Implementation Issues: Address Assi
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Implementation Issues: Security Ho
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Implementation Issues Only some is
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Distributed Algorithms for Mobile A
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Distributed Algorithms There is al
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Related Standards Activities 427
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Internet Engineering Task Force (IE
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Bluetooth [Haartsen98,Bhagawat00Tut
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Bluetooth: Piconet A channel is ch
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Bluetooth: Scatternet Several pico
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Open Issues in Mobile Ad Hoc Networ
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Related Research Areas Algorithms
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Thank you !! For more information,
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