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11 require sensing the channel even during backoff

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Unformatted text preview: of carrier sensing and power off the node during backoff Highly synchronized nature of the traffic causes no packet transfer at all in the absence of collision detection hardware Introduce random delay for transmission to unsynchronized the nodes Contribution of this paper are as follows: A Transmission Control Scheme for Media Access in Sensor Networks [Woo+, 2003] Backoff Mechanism: o o o Used to reduce the contention among the nodes In the sensor networks, traffic is a superposition of different periodic streams Apply back off as a phase shift to the periodicity of the application so that the synchronization among periodic streams of traffic can be broken Contention-based Mechanism o o o o Explicit control packets like RTS and CTS are used to avoid contention ACKS indicate lack of collision Use of lot of control packets reduces bandwidth efficiency ACKS can be eliminated by hearing the packet transmission from its parent to its upstream which serves as an ACK for the downstream node A Transmission Control Scheme for Media Access in Sensor Networks [Woo+, 2003] Rate Control Mechanism o o The competition between originating traffic and route-thru traffic has a direct impact in achieving the fairness goal. MAC should control the rate of originating data of a node in order to allow route-thru traffic to access the channel and reach the base station and some kind of progressive signaling for route-thru traffic such the rate is controlled at the origin. A passive implicit mechanism is used to control the rate of transmission of both...
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