Variant rate based cross layer time frame scheduling in wireless sensor networks

In this paper, a novel variable rate based time frame scheduling scheme is proposed to further reduce collisions and improve energy saving in wireless sensor networks. The MAC combines CSMA and TDMA functionalities, while obviating their shortcomings. After being assigned, slot 0 is preserved as the pre-schedule slot to inform neighbor nodes the schedule of the senders. During this pre-schedule slot, each node knows exactly the schedule of other neighbor nodes. Multi-rate and power scaling are adopted to achieve further energy saving by employing an acceptable rate rather than the maximum rate. Data rate is dynamically adjusted according to the traffic load of sending nodes in an energy efficient data rate to save energy. Compared with Z-MAC, performance in the present study proves to have better ability of local framing pre-schedule and multi-rate achieves better energy efficiency.