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WUSTL CSE 574S - Ad Hoc Networks

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Ad Hoc Networks: Issues and RoutingOverviewAd Hoc Networks: CharacteristicsAd Hoc Networks: ApplicationsSensor NetworksIssues in Ad Hoc NetworksCellular vs. Ad HocAd Hoc: Media Access ControlAd Hoc Routing: RequirementsClassification of Routing ProtocolsRouting in Wired Networks: ReviewOLSROLSR: ExampleSelection of MPRDynamic Source Routing (DSR)DSR: ExampleAODVAODV (Cont)AODV: ExampleSummaryReading AssignmentOptional ReadingHomework14-1©2006 Raj JainCSE574sWashington University in St. LouisAd Hoc Networks: Ad Hoc Networks: Issues and RoutingIssues and RoutingRaj Jain Washington University in Saint LouisSaint Louis, MO [email protected] slides are available on-line at:http://www.cse.wustl.edu/~jain/cse574-06/14-2©2006 Raj JainCSE574sWashington University in St. LouisOverviewOverviewCharacteristics, Applications, IssuesCellular vs. Ad HocRouting: Requirements, parameters, classificationDynamic Source Routing (DSR)Ad Hoc On-demand Distance Vector (AODV)Optimized Link State Routing (OLSR)14-3©2006 Raj JainCSE574sWashington University in St. LouisAd Hoc Networks: CharacteristicsAd Hoc Networks: CharacteristicsNo Fixed InfrastructureDynamic Topology (Mobility)Multi-hopping: Obstacles, spectrum reuse, energy conservationSelf-Organization: Addressing, routing, clustering, location, power controlEnergy conservationScalability: Thousands of nodesSecurity: LimitedBandwidth constrained: Congestion is a normRef: RFC250114-4©2006 Raj JainCSE574sWashington University in St. LouisAd Hoc Networks: ApplicationsAd Hoc Networks: ApplicationsEmergency, DisastersWearable computingBattlefield: Unmanned ground/airborne/underwater vehiclesHybrid: Multi-hop cellularWireless Mesh NetworksSensor Networks14-5©2006 Raj JainCSE574sWashington University in St. LouisSensor NetworksSensor NetworksA large number of low-cost, low-power, multifunctional, and small sensor nodes consisting of sensing, data processing, and communicating componentsKey Issues:1. Scalability2. Power consumption3. Fault tolerance4. Data Fusion5. Traffic: Low throughput, Delay sensitiveInternetSensor FieldSinkTask Manager14-6©2006 Raj JainCSE574sWashington University in St. LouisIssues in Ad Hoc NetworksIssues in Ad Hoc Networks1. Medium Access: Distributed, no time sync, directional antennas2. Routing: Route acquisition delay, quick reconfig, loop free3. Multicasting: Common in Ad-Hoc, Emergency/military4. Transport Layer: Frequent path breaks5. QoS6. Self-organization: Neighbor discovery, report link failures7. Security: DoS, jamming, energy depletion8. Energy management: Transmission Power, battery monitoring, processor power9. Addressing and Service Discovery: Global10. Pricing Scheme: Incentives for relaying14-7©2006 Raj JainCSE574sWashington University in St. LouisCellular vs. Ad HocCellular vs. Ad HocCellular Network Ad Hoc Networks Fixed Infrastructure Infrastructure-less Single-hop wireless links Multi-hop wireless links Centralized routing Distributed Routing Base station: Single point of failure Resilient Seamless connectivity Mobility  Frequent link breaks High cost and long deployment time Quick and cost effective setup Commercial sector Defense, Emergency, Disaster Simple Mobile, Complex Base All complexity in Mobile No forwarding fairness issues Fairness: own vs other’s traffic Time Sync  TDMA Time Sync difficult  CSMA Static frequency reuse (cells) Dynamic freq reuse  CSMA14-8©2006 Raj JainCSE574sWashington University in St. LouisAd Hoc: Media Access ControlAd Hoc: Media Access ControlFully distributed operation. CSMA.Hidden Node: Reachable from a receiving end of a link but not from the transmitting end. A cannot hear C, but can interfere with its transmissions to BExposed Node: Other nodes in the vicinity cannot talk.When B is talking to A, C cannot talk to DUse of Directional Antennas, Steer-able antennasMultiple Access Collision Avoidance (MACA): Use RTS/CTS with Binary Back off, e.g., 802.11ABCABCD14-9©2006 Raj JainCSE574sWashington University in St. LouisAd Hoc Routing: RequirementsAd Hoc Routing: RequirementsFully distributedGlobal state (all nodes-all time) maintenance expensive  LocalizedLoop-Free routingMinimize route acquisition delay: ProactiveQuick route reconfiguration: Adaptive to Frequent changes. Changes in unrelated parts should not impact a node.Energy conservation: Sleep periodsUnidirectional Link SupportMinimize:Bits Transmitted/Bits Delivered = Avg hopsControl bits/data bits = OverheadControl packets/data packets = Overhead14-10©2006 Raj JainCSE574sWashington University in St. LouisClassification of Routing ProtocolsClassification of Routing ProtocolsRouting Updates:Proactive: Before neededReactive: On-demandHybrid: Combined. Know neighbors. Others on-demand.Temporal Information:Past HistoryPrediction:Based on node lifetime, locationTopology Organization:Flat: Global addresses as in 802.11Hierarchical: Geographical or Hop distanceResource Optimization:Power-Aware: Local or global battery powerGeographical info basedEfficient FloodingMurthy and Manoj list 40+ routing schemes for Ad-hoc nets.14-11©2006 Raj JainCSE574sWashington University in St. LouisRouting in Wired Networks: ReviewRouting in Wired Networks: Review1. Distance Vector:Each node sends its complete table (distances to all nodes in the network) to its neighbors Large vectors to small number of nodesUse Dijkstra’s algorithm to compute the shorted pathRouting Information Protocol (RIP) is a distance vector protocol2. Link State: Each nodes sends its link information (distances to its neighbors) to all nodes in the network Small vectors to large number of nodesUse Bellman-Ford to compute the shortest pathOpen Shorted Path First (OSPF) is a link state routing protocol14-12©2006 Raj JainCSE574sWashington University in St. LouisOLSROLSROptimized Link State Routing Protocol Proactive  Routes are prepared before neededOptimize  Min flooding duplication in highly connected netsAsk only a subset of your neighbors to forward your link statesThis is subset is your "Multipoint Relay" (MPR)If X is your MPR, you are X's "MPR selector"Each MPR has a set of MPR selectorsEach node sends LS to all its neighborsMPRs forward LS of their MPR selectorsOther neighbors use the information to compute


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WUSTL CSE 574S - Ad Hoc Networks

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