High Performance Mobile Ad hoc Networking
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DESCRIPTIONHigh Performance Mobile Ad hoc Networking. Herbert RubensBaruch Awerbuch firstname.lastname@example.org email@example.com. Johns Hopkins University Department of Computer Science. Wireless Communication Lab wireless.cs.jhu.edu. Presentation Overview. Mobile Ad hoc Networking Overview - PowerPoint PPT Presentation
<ul><li><p>High Performance Mobile Ad hoc NetworkingHerbert RubensBaruch Awerbuchherb@cs.jhu.edu firstname.lastname@example.orgJohns Hopkins UniversityDepartment of Computer ScienceWireless Communication Labwireless.cs.jhu.edu</p></li><li><p>Presentation OverviewMobile Ad hoc Networking OverviewResearch ContributionsRelated WorkThe Pulse ProtocolThe Medium Time MetricWave Relay System</p><p>Feel free to ask questions throughout the presentation!</p></li><li><p>Mobile Ad hoc NetworkA self configuring network of mobile routers connected by wireless linksThe routers may move freely, creating arbitrary network topologiesThe network topology can change rapidly and unpredictablyNodes communicate by wirelessly forwarding or relaying data through intermediate nodesThe network can be connected to the larger Internet or operate independentlyhttp://en.wikipedia.org/wiki/Mobile_ad-hoc_network</p></li><li><p>JHU Wave Relay Network</p></li><li><p>Node Locations Determine Topology </p></li><li><p>Mobile Ad hoc Networking Timeline19751995TodayDARPA Packet Radio NetworksAd hoc On-demandDistance Vector (AODV)Destination SequencedDistance Vector (DSDV)Dynamic SourceRouting (DSR)Burchfiel, J., Tomlinson, R., Beeler, M. (1975). "Functions and structure of a packet radio station". AFIPS: 245.Kahn, R. E. (January 1977). "The Organization of Computer Resources into a Packet Radio Network". IEEE Transactions on Communications COM-25 (1): 169178.Kahn, R. E., Gronemeyer, S. A., Burchfiel, J., Kunzelman, R. C. (November 1978). "Advances in Packet Radio Technology". Proceedings of IEEE 66 (11): 14681496.Jubin, J., and Tornow, J. D. (January 1987). "The DARPA Packet Radio Network Protocols". Proceedings of the IEEE 75 (1). Optimized Link-StateRouting Protocol (OLSR)1985Functions and Structure ofa Packet Radio StationMicrosoftFoundedAppleFoundedIntel4861991wwwAppleIIgsCDPlayerHerbertBenjaminRubens1979Windows3.0Y2K</p></li><li><p>Fundamental ChallengesComplex dynamics of a wireless linkContinuously fluctuating RF environment (without mobility!)Bit Error Rate= small packets more reliable then large packetsModulationDifferent modulations work better in different RF environmentsMulti-path, channel fading, delay spreadLink CapacityMobilityFurther increases wireless link dynamicsCreates hard transitions walk around a corner and everything changesIf all of the links are continuously changing, how do you select a set of links to form a path?</p></li><li><p>Research ObjectivesScalabilityDesign routing algorithms which scale to thousands of devices while minimizing control overheadRouting algorithm must perform under vehicular mobility, urban channel fading, and arbitrary communication patternsEfficiencySelected routes must:Maximize individual path capacityMinimize network resource consumptionContinuously adapt to changes</p></li><li><p>Research ContributionsMedium Time Metric (MTM)First route selection metric to consider multi-rate radiosProvably optimal route selection in small to medium sized networksExperimental results and simulated results validate approachPulse ProtocolExtremely scalable routing protocol designed for mobile networksOptimized for infrastructure access and peer-to-peer traffic patternsProtocol extensions provide integrated time synchronization and power savingSensor Network Pulse ProtocolDirectly trades route activation delay for power saving efficiencyOptimized for infrequently changing sensor network topologiesOptimized for sensor to collector traffic model</p></li><li><p>PublicationsMONET Journal The Medium Time Metric: High Throughput Route Selection in Multi-rate Wireless Networks </p><p>WONS 2005 The Pulse Protocol: Mobile Ad hoc Network Performance Evaluation</p><p>MILCOM 2004 The Pulse Protocol: Sensor Network Routing and Power Saving</p><p>INFOCOM 2004 The Pulse Protocol: Energy Efficient Infrastructure Access</p><p>WONS 2004 High Throughput Route Selection in Multi-rate Wireless NetworksESAS 2006 Dynamics of Learning Algorithms for the On-Demand Secure Byzantine Routing Protocol</p><p>SECURECOM 2005 On the Survivability of Routing Protocols in Ad Hoc Wireless Networks</p><p>NDSS 2005 Secure Multi-hop Infrastructure Access</p><p>INFOCOM 2005 Provably Competitive Adaptive Routing</p><p>IZS 2004 Swarm Intelligence Routing Resilient to Byzantine Adversaries</p><p>WiSE 2002 An On-Demand Secure Routing Protocol Resilient to Byzantine Failures Relevant to ThesisOther work</p></li><li><p>Existing ApproachesSourceReceiversDestination Multi-path fading & shadowing Rapidly changing channel conditions On-demand protocols have no prior knowledge of channels conditions A RREQ packet provides only a single sample of a complex distributionReactive On-Demand Protocols (AODV, DSR) Channel is continuously changing Continuous flooding from every node in the network Hello Protocol detects link changesProactive Link State Protocols (OLSR, TBRPF)Urban Channel EnvironmentYou can not accurately track channel with control packets!</p></li><li><p>How Often Does Connectivity Change?10% of min-hop paths fail within 1.3 secondsAfter 5 seconds 25% of min-hop paths have failedOn-Demand routes may only work for a short period of timeLink State Protocols need to flood every time a link changesThese simulations only consider changes from connected not connected (in free space)What about changes in link speed? Reliability? Hard transitions in a real environment? Fast-fading and urban channel effects?Connectivity is continuously changing at an extremely fast rate!Simulation: 100 Nodes 1000m x 1000m area Random Waypoint Mobility (Max Speed=20m/s) Calculate All-to-All shortest path initially, then track how long until the route fails</p></li><li><p>Pulse Protocol OutlinePulse Protocol OverviewScalable multi-hop ad hoc routing protocolBased on Tree RoutingTree Routing vs. Direct Routing</p></li><li><p>The Pulse ProtocolProactive ComponentTracks minimum amount of information to avoid flooding for route establishment and maintenancePeriodic flood operation (similar to Hello Protocol)Proactively rebuilds spanning treeEstimates neighbors, density, SNR, loss rates, capabilities, number of radios, MTM metricOn-Demand ComponentRoute establishmentUsing only UNICASTS!Gratuitous mechanismNeighbors promiscuously monitor packetsMetric tracked at the speed of data packets NOT control packets!Path switches as metrics changeLocal changes in connectivity only generate local trafficUnlike BOTH on-demand and link state protocols</p></li><li><p>Ad hoc Nodes</p></li><li><p>Network Connectivity</p></li><li><p>Pulse Flood</p></li><li><p>Spanning Tree</p></li><li><p>Source and Destination Need to Establish a Path</p></li><li><p>Pulse Response Sent to Root</p></li><li><p>Destination Paged on Next Pulse</p></li><li><p>Destination Sends Pulse Response</p></li><li><p>Path Option 1: Through the RootThrough the Root Path9 HopsShortest Path2 HopsThis option is inefficient! It is not necessary to go to the root. Better routes already exist!</p></li><li><p>Path Option 2: Tree TraversalTree Traversal Path5 HopsShortest Path2 Hops</p></li><li><p>Path Option 3: Tree ShortcutTree Shortcut Path3 HopsShortest Path2 HopsThis is the initially selected path of the Pulse protocol.</p></li><li><p>Path Optimization: Gratuitous ReplySelected Path2 HopsShortest Path2 HopsNode sends gratuitous reply</p></li><li><p>Proactive Route Maintenance</p></li><li><p>Proactive Route Maintenance</p></li><li><p>Tree Routing vs. Direct RoutingDirect RoutingAttempts to initially discover the shortest pathRequires large overheadLink state tracks every link in the network regardless of whether it is useda shortest path spanning tree for every node in the networkOn-Demandfloods the network to establish a route re-floods when ever the path breaksa shortest path spanning tree for all nodes transferring dataTree RoutingProactively rebuilds a single spanning tree on top of the networkBoot straps communication off of the tree routeRoute are not initially the direct shortest path, but routing mechanism allows the path to converge towards the shortest pathActive destinations can be reached without flooding the networkEfficient operation for realistic traffic patterns</p></li><li><p>Pulse Protocol ConceptsAggregation for scalabilitySpanning tree represents a compressed view of the network topologyPro-active component maintains the minimum amount of information to allow efficient route establishmentDe-Aggregation for efficiencyThe routing metric is tracked at the speed of the data flowChanges to the metric are only reported locallyRoutes are continuously adjusted as the metrics changeHigh speed accurate route tracking is essentially an on-demand decompression of the topology However, it occurs ONLY in areas of the network with active data flowsResult: a scalable routing structure which tracks paths at the speed of the data flow</p></li><li><p>Internet Gateway Example All nodes routing to centrally located internet gateway Best possible case for Pulse Protocol Pulse source is designated as the centrally located gateway Representative of Pulse internet access deployment at JHU Similar to DoD Reach Back modelRepresentative of most commonreal-world communication model</p></li><li><p>Delivery Ratio Simulations Pure peer-to-peer communication pattern Pulse source is an arbitrary mobile node</p></li><li><p>SNS Scalability SimulationSize: 10 km x 10 kmNodes: 5,000 Speed: 1 m/sTraffic: 5 MbpsDelivery Ratio: 97.2%10 km10 km 100 stationary backbone nodes were arranged in a 10 by 10 grid 5000 nodes were randomly placed and moved randomly Exponential random traffic pattern was used A network of 5,000 nodes could contain up to 25 million wireless links.Links: 50,000 on average</p></li><li><p>Scalability CalculationsWave Relay MTU = 3200 bytesPulse Interval = 200 ms (5 per second)Average P2P route setup latency = 100 msHeaders = 100 bytes 3100 bytes remaining3100 / 6 (MAC addr) = 516 pages per packet are possible516 * 5 = 2,580 route establishments per second (P2P)154,800 connections established per minute150,000 = # of troops in Iraq1% of troops open a P2P connection each second = 1,500/secMIT Campus Network3,000 802.11g APs in 0.5 square milesEach AP Beacons 10 times per second(Double the Pulse Interval)</p></li><li><p>Medium Efficiency vs. Packet SizeTransmitting small packets inefficiently utilizes medium timeOn-demand Protocol RREQsLink State UpdatesARP TrafficVoIP CallsExisting Protocols Flood these small messages which severely limits the total network capacityThe Pulse Protocol aggregates network wide broadcasts, multicasts, routing updates, spanning tree construction, neighbor information, asymmetry detection, active route tracking, MTM metrics, leader election, into large packets (up to 3,200 bytes).The Pulse Protocol attempts to maximize the efficiency of the network</p><p> Packets transmitted at 54 Mbps link speed</p></li><li><p>Medium Time Metric Outline Why do wireless radios operate at multiple rates?Minimum Hop Metric shortcomingsMedium Time Metric</p></li><li><p>Advantage of Multi-Rate?Direct relationship between communication rate and the channel quality required for that rateAs distance increases, channel quality decreasesTherefore: tradeoff between communication range and link speedMulti-rate provides flexibility1 Mbps2 Mbps5.5 Mbps11 Mbps 802.11g 1,2,5,6,11,12,18,24,36,48,54 Mbps 802.11n (draft) A lot more! Up to 300 Mbps.</p></li><li><p>Effect of Transmission on SHARED Wireless MediumSourceDestinationRequest to Send (RTS)Clear to Send (CTS)DATAACK12345678XXXXXXX</p></li><li><p>Challenge to the Routing ProtocolMust select a path from Source to DestinationLinks operate at different speedsFundamental TradeoffFast/Short links = low range = many hops/transmissions to get to destinationSlow/Long links = long range = few hops/transmissions</p></li><li><p>Minimum Hop Metric(Traditional Technique)Not designed for multi-rate networksA small number of long slow hops provide the minimum hop pathThese slow transmissions occupy the medium for long times, blocking adjacent sendersSelecting nodes on the fringe of the communication range results in reduced reliability</p></li><li><p>New Approach: Medium Time Metric (MTM)Assigns a weight to each link proportional to the amount of medium time consumed by transmitting a packet on the linkEnables the Pulse protocol to discover the path that minimizes total transmission time</p></li><li><p>MTM ExampleSourceDestination11 Mbps5.5 Mbps2 Mbps1 Mbps10.85 Mbps2.5ms3.7ms7.6ms13.9ms11 Mbps5.5 Mbps2 Mbps1 Mbps13.9msMedium Time Usage4.55 Mbps3.17 Mbps1.54 Mbps0.85 MbpsPath ThroughputPath Medium Time Metric (MTM)= 13.9 msLink Throughput</p></li><li><p>MTM ExampleSourceDestination11 Mbps5.5 Mbps2 Mbps1 Mbps5.5 + 211.04 Mbps0.85 Mbps2.5ms3.7ms7.6ms13.9ms11 Mbps5.5 Mbps2 Mbps1 Mbps7.6ms3.7ms13.9ms= 11.3 msMedium Time Usage4.55 Mbps3.17 Mbps1.54 Mbps0.85 MbpsPath ThroughputPath Medium Time Metric (MTM)= 13.9 msLink Throughput</p></li><li><p>MTM ExampleSourceDestination11 Mbps5.5 Mbps2 Mbps1 Mbps11 + 25.5 + 211.15 Mbps1.04 Mbps0.85 Mbps2.5ms3.7ms7.6ms13.9ms11 Mbps5.5 Mbps2 Mbps1 Mbps2.5ms7.6ms7.6ms3.7ms13.9ms= 10.1 ms= 11.3 msMedium Time Usage4.55 Mbps3.17 Mbps1.54 Mbps0.85 MbpsPath ThroughputPath Medium Time Metric (MTM)= 13.9 msLink Throughput</p></li><li><p>MTM ExampleSourceDestination11 Mbps5.5 Mbps2 Mbps1 Mbps11 + 1111 + 25.5 + 212.38 Mbps1.15 Mbps1.04 Mbps0.85 Mbps2.5ms3.7ms7.6ms13.9ms11 Mbps5.5 Mbps2 Mbps1 Mbps2.5ms2.5ms2.5ms7.6ms7.6ms3.7ms13.9ms= 5.0 ms= 10.1 ms= 11.3 msMedium Time Usage4.55 Mbps3.17 Mbps1.54 Mbps0.85 MbpsPath ThroughputPath Medium Time Metric (MTM)= 13.9 msLink Throughput</p></li><li><p>MTM AdvantagesPaths which minimize network utilization, maximize network capacityGlobal optimum under complete interferenceExcellent heuristic in even larger networksAvoiding low speed links inherently provides increased route stabilityHigh speed links operate with greater margin and are more elastic under changesExperimental results show up to 17 times greater throughput using MTM in 802.11g networks</p></li><li><p>Wave Relay Systemand Test-bed</p></li><li><p>Wave Relay Test-bedOver 50 Wave Relay Routers deployed across JHU CampusUrban City EnvironmentInternet Access, Ad hoc Access Points, Voice over IPMobility testing from automobilesOver 100 JHU students simultaneously use network each day for Internet AccessSystem tested at Holcim Industrial Plant (Chicago, IL)Complex propagation environment Enabled real-time industrial process controlCurrently Deployed Custom ApplicationsMilitary Distributed Battlefield MappingGPS based interactive mapEventual reliabilityLocality Specific Messaging SystemGPS based messaging systemMessages targeted to any user at a specific location</p></li><li><p>Wave Relay DevicePulse Protocol [Infocom04, Milcom04, WONS05]Scalable ad hoc routing protocolActive path trackingBased on Tree Routing strategyMedium Time Metric [MONET,WONS04]High Throughput Path SelectionIncreased Path ElasticityEfficient Multi-rate OperationLeader Election Algorithm Handles merge, partition, failureEmbedded Linux Distribution Less then 8 MB storage requirementLinux Kernel Module 2.4 and 2.6 compatibilityOperates at layer 2Distributed virtual switch architecture provides seamless bridging</p><p>Embedded Single Board ComputerIntel IXP425 Network ProcessorOn-chip Cryptographic Accelerator64 Mb Ram onboard4 mini-PCI interfacesDual 10/100 EthernetCompact flash interfaceSerial port / JTAG / GPIOHardware WatchdogPower over Ethernet+9V to +48V DC InputAtheros 802.11g/b Wireless Card400 mW (26 dBm) output power16 MB Intel Strata FlashStores OS & Wave Relay softwareGarmin GPS 16 receiverLi-Ion Battery Pack~20 hours continuous runtimeIndustrial NEMA 67 Enclosure4 N-type antenna mounts2 Et...</p></li></ul>
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