An energy efficient pre-schedule scheme for hybrid CSMA/TDMA MAC in wireless sensor networks

In this paper, we propose a novel local framing preschedule scheme to improve energy saving in CSMA/TDMA hybrid MAC layer of wireless sensor network. This MAC combines CSMA and TDMA functionalities together, while obviates their shortcomings. Usually, in a hybrid CSMA/TDMA MAC such as ZMAC, all the receivers have to perform low power listening all the time to wait for in-coming data. Although low power listening scheme can achieve energy saving by reducing idle listening to some extent, it is much more beneficial with a scheme to smartly turn off the radio when the receiver does not receive any data. By introducing preschedule slot, all the nodes will know the neighbors' behavior in the upcoming slots. After the time slot assignment, senders advertise their traffic schedules to let neighbor nodes know which one will receive data, and what the amount of the data is. Since each node knows exactly the schedule of other neighbor nodes, it can sleep smartly when it has received all the data and does not have other task during this round. Our simulations have shown that such scheme of local framing pre-schedule has achieved much higher energy efficiency than other proposed hybrid CSMA/TDMA MACs such as Z-MAC.