Collision-Minimizing CSMA and its Applications to Wireless Sensor Networks

Y. C. Tay, Kyle Jamieson Hari Balakrishnan,
IEEE Journal on Selected Areas in Communications 22:6 (2004), 1048–1057

Recent research in sensor networks, wireless location systems, and power-saving in ad hoc networks suggests that some applications wireless traffic be modeled as an event-driven workload: a workload where many nodes send traffic at the time of an event, not all reports of the event are needed by higher-level protocols and applications, and events occur infrequently relative to the time needed to deliver all required event reports. We identify several applications that motivate the event-driven workload, and propose a protocol that is optimal for this workload.

Our proposed protocol, named CSMA/p*, is non-persistent CSMA with a carefully-chosen non-uniform probability distribution p* that nodes use to randomly select contention slots. We show that CSMA/p* is optimal in the sense that p* is the unique probability distribution that minimizes collisions between contending stations. CSMA/p* has knowledge of N. We conclude with an exploration of how p* could be used to build a more practical MAC protocol via a probability distribution with no knowledge of N that approximates p*.

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