A Novel MAC Approach to Combating Fading Channel for Wireless Sensor Networks

Networking together hundreds or thousands of small and cheap wireless sensor nodes requires highly energy-aware communication protocols at each layer, and much research work has been done to address this issue. However, the time-varying nature of the wireless channel also has a significant influence on the communication energy consumption, and this has long been ignored in most existing state-of-the-art energy saving protocols, thus resulting in unnecessary waste of precious battery energy. Due to this, to judiciously handle the energy management, we propose a channel adaptive energy management protocol, namely, CAEM, that can exploit this time-varying property of the wireless link, by leveraging on the synergistically cross-layer interaction between physical and MAC layers. Specifically, in CAEM, by using a previously proposed adaptive channel coding and modulation scheme, which allows a sensor terminal to dynamically adjust the data throughput via changing the amount of error protection incorporated, sensor node can intelligently access the wireless medium, according the current wireless link quality, estimated available bandwidth, and the traffic load, to realize an efficient utilization of the energy. Thus through a jointly cross layer design across the MAC layer and physical layer, CAEM can reduce the energy consumption as much as 30%, compared with traditional protocols without channel adaptation. Moreover, extensive simulation shows that CAEM is more efficient in channel utilization, in that higher network throughput is realized under heavy traffic load.