How The Mac Is A Medium Access Control Protocol

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Introduction : This paper discusses about the S-MAC , which is a Medium Access Control Protocol used in wireless sensor networks . The protocol proposed in the paper is mainly inspired by PAMAS . The important goals of this protocol is to conserve energy and configure by itself or known as scalability . It is entirely different from traditional mac protocols like ieee 802.11. The protocol uses three primary techniques to support energy conserving and self-configuration . they periodically sleep to minimize energy consumption , then formation of virtual clusters by neighbor nodes for auto synchronization on sleep times and radios are also set to sleep during transmissions of other node . Then S-mac uses message passing and in-channel…show more content…
2) periodic listen and sleep : in this the listen time is reduced by letting go the node into periodic sleep . a) basis scheme : in this node goes to sleep for a specified time and then wakes up to listen if any node wants to communicate with it . A timer is set during sleep and the radio of the node is also turned off . A periodic synchronization is between neighbor nodes for their correct clock timings . Two techniques are used to synchronization one is timestamps exchanged are relative other than being absolute. Another technique is listen is period is longer than clock error or drift . To reduce control overhead neighbor nodes should be preferred to synchronize together . to be noted that all neighboring nodes cant synchronize together . then all nodes broadcast their schedule to all its immediate neighbors this for ensuring that all neighbor can talk with different schedule times . If multiple nodes want to talk to a node , this can be done by contention mechanism using request to send and clear to send packets . here first come first serve basis , node which send first will grab the medium . here the formation of nodes are done in flat topology . b) choosing and maintaining schedules : each node maintains its own schedule table where its neighbor nodes schedule are stored. First node listens for a particular time , if it is not hearing from another node it randomnly goes to sleep with broadcasting a SYNC message .
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