An Energy-Efficient MAC-Layer Transmission Algorithm Considering Fading Channels for Cluster-Based Sensor Networks

Most of the existing MAC-layer protocols for sensor networks consider the status of wireless channel as time invariant. This assumption leads to reduced energy efficiency due to repeated transmissions particularly in nodes that experience deep channel fading. Multiple factors can be responsible for fading channels including other wireless activity in the surroundings, mobility, and geographic landscape. In this paper, we study the effect of fading channel for intra-cluster data transmission in cluster-based sensor networks that employ TDMA based channel access protocols. We propose an efficient MAC layer algorithm where the cluster head broadcasts a short message at the beginning of each frame. Each node within the cluster will transmit data in its assigned data slot when the detected received power of this broadcast message is above a certain threshold. By restraining a node from transmitting data in its assigned slot when its channel is in deep fading, the packet error rate is reduced and energy efficiency is greatly improved. By choosing the optimal threshold to maximize energy efficiency, our simulation results show that energy efficiency can be improved up to 400% considering the fading status of channel in different test scenarios. The proposed algorithm can be easily extended to contention based MAC protocols.