On Routing in Multichannel Wireless Mesh Networks: Challenges and Solutions指導教授：林永松 老師 資管碩一 謝友仁Tehuang Liu and Wanjiun Liao, National Taiwan UniversityIEEE Networks, 2008*1NTU IM OPLABAuthorWanjiun Liao(廖婉君) received her Ph.D. degree in electrical engineering from the University of Southern California, Los Angeles, in 1997. She joined the Department of Electrical Engineering, at National Taiwan University, as an assistant professor in 1997. Since August 2005 she has been a full professor.nHer research interests includeqwireless networksqmultimedia networksqbroadband access networksnShe is currently an Associate Editor ofqIEEE Transactions on Wireless CommunicationsqIEEE Transactions on MultimedianShe has received many research awardsqBest Student Paper Award at the First IEEE International Conferences on Multimedia and Expo (ICME) in 2000qBest Paper Award at the First IEEE International Conferences on Communications, Circuits and Systems (ICCCAS) in 2002qK. T. Li Young Researcher Award of ACM in 2003qDistinguished Research Award from National Science Council in Taiwan in 2006Date2NTU IM OPLABAuthor (contd)Tehuang Liu (劉得煌) received a B.S. degree in electrical engineering from National Taiwan University, Taipaei, in 2003 and is currently a Ph.D. candidate in the Department of Electrical Engineering, National Taiwan University. nHis research interests includeqrouting protocolsqchannel assignment mechanismsqperformance modeling in wireless mesh networksDate3NTU IM OPLABOverviewn Abstract n Introduction n ChallengesqNeed for a New Routing MetricqLoad Distribution among ChannelsqDependence on Channel AssignmentqCross-Layer Design of Routing and MAC n Routing MetricsqWCETTqNBLC n Performance Comparison n Open Research IssuesqQoS RoutingqMultipath RoutingqMulticast Routing n ConclusionDate4NTU IM OPLAB1.Abstract*5NTU IM OPLABAbstractnEmploying multiple channelsqthe problem of capacity degradation in multihop wireless networks. nExisting routing schemesqinefficient routing paths in multichannel WMNs.nTo fully exploit the capacity gainqthe availability of multiple channelsqdistribute traffic loadnWe highlightqthe challenges in designing routing algorithmsqexamine existing routing metrics that are designed for multichannel WMNsDate6NTU IM OPLAB2.Introduction*7NTU IM OPLABIntroductionnThe major challengeqto conquer the degradation of capacity due to the interference problemnMultiple channels is an effective approachqconcurrent transmissions on nonoverlapping channelsnThe multichannel environment introduces new research challengesqroutingqschedulingqallocating wireless channelsnIn this article we focus on the routing problem in multichannel WMNsqwhich nodes to includeqwhich channel to use on each linknTo fully exploit the availabilityqthe existence of channel diversity on a path in the networkDate8NTU IM OPLABIntroduction (contd)nEach node can transmit or receive data on two nonoverlapping channels simultaneouslyDate9NTU IM OPLABIntroduction (contd)nThe routing problem in multichannel WMNs is exacerbatedqthe network topology is determined by the channel assignmentnRouting paths between any two nodes qrestricted by channel assignmentnWith an improper channel assignment algorithmqwell designed routing algorithm may become uselessDate10NTU IM OPLAB3.Challenges3.1 Need for a New Routing Metric 3.2 Load Distribution among Channels 3.3 Dependence on Channel Assignment 3.4 Cross-Layer Design of Routing and MAC*11NTU IM OPLABChallenges Need for a New Routing MetricnEach radio interface on adjacent links can be assigned a different channelqthe interference among links can be eliminated qthe network capacity can be improvednThe routing metric is a criterion to judge the “goodness” of a path in routing algorithms.nThe most typical routing metric for multihop wireless networks is the hop countqcannot capture the quality of a pathnRadio-aware routing metricqincorporates the link conditionDate12NTU IM OPLABChallenges (contd) Need for a New Routing MetricnRouting metric which accounts forqmultirate capabilityqInterferencenIn multichannel WMNs the channel diversity is another key factorqwhich nodes this path comprisesqwhich channels the links of this path are tunednIncorporating channel diversity into the routing metricqHow to balance the trade-off between network throughput and per-node throughputqHow to quantify the channel diversity of a pathDate13NTU IM OPLABChallenges (contd) Need for a New Routing MetricnTo expand on these two issuesDate14NTU IM OPLAB3.Challenges3.1 Need for a New Routing Metric 3.2 Load Distribution among Channels 3.3 Dependence on Channel Assignment 3.4 Cross-Layer Design of Routing and MAC*15NTU IM OPLABChallenges (contd) Load Distribution among ChannelsnWithout accounting for the traffic load among channelsqdegrading network utilizationnTo avoid this problem, multichannel routing algorithms should compare different possible routesqan exponential number of such combinations may exist -