AsOR: an energy efficient multi-hop opportunistic routing protocol for wireless sensor networks over Rayleigh fading channels

In this paper, we describe an efficient and energy conservative unicast routing technique for multi-hop wireless sensor networks over Rayleigh fading channels, which we shall refer to as assistant opportunistic routing (AsOR) protocol. In contrast to previous works, this protocol is presented from a systematic energy conservation perspective. During the source-destination transmission, the AsOR protocol forwards the data stream through a sequence of nodes, which are classified as three different node sets, namely, the frame node, the assistant node and the unselected node. The frame nodes are indispensable to decode-and-forward while the assistant nodes provide protections for unsuccessful opportunistic transmissions. Based on the AsOR protocol, each predetermined route can be divided into several disjoint segments, and we establish a mathematical model to characterize the energy consumptions for each node in one segment. Furthermore, we provide a method for selecting the optimal value N*, the number of nodes in one transmission segment, which can lead to the minimum average energy consumption. Numerical results will confirm that the proposed protocol is energy conservative compared with other two traditional routing protocols both in slow and fast Raleigh fading channels and that the method for searching the optimal value N* is efficient. Finally, robustness analysis for the theoretical results are presented.