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Unformatted text preview: o very different traffic characteristics from that found in conventional computer networks Highly constrained resources and functionality Small packet size Deep multi-hop dynamic topologies The network tends to operate as a collective structure, rather than supporting many independent point-to-point flows Traffic tends to be variable and highly correlated Little or no activity/traffic for longer periods and intense traffic over shorter periods A Transmission Control Scheme for Media Access in Sensor Networks [Woo+, 2003] Major factors to be considered in the design of MAC: Communication efficiency in terms of energy consumed per each packet
o o Communication by radio channel consumes the highest energy Transmit , receive and idle consume roughly the same amount of energy Fairness of the bandwidth allocated to each node for end to end data delivery to sink
o o o Each node acts as a router as well as data originator resulting in two kinds of traffic The traffics compete for the same upstream bandwidth Hidden nodes Contention at the upstream node may not be detected and results in significant loss rate Efficient channel utilization A Transmission Control Scheme for Media Access in Sensor Networks [Woo+, 2003] Major factors to be considered in the design of MAC: The routing distance and degree of intermediate competition varies widely across the network The cost of dropping a packet varies with place and the packet Listening mechanism:
o o o o o o Listening is effective when there are no hidden nodes It comes at an expense of energy cost as the radio must be on to listen Many protocols such as IEEE 802.11 require sensing the channel even during backoff Shorten the length...
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- Spring '08