Energy Efficiency of Cooperative Relaying over a Wireless Link

Cooperation enhances the performance of wireless networks with fading channels. In this paper, we develop joint physical and network layer cooperative techniques in a simple network composed of a single source, a relay, and a destination, and focus on energy consumption as the performance criterion. Two transmission schemes are used at the network layer: (i) Simple Automatic Repeat Request (ARQ) and (ii) Random Network Coding (RNC). We also consider the use of Alamouti Space-time codes at the physical layer. For each of the proposed cooperative schemes, we consider the energy consumed per successfully delivered packet, and then find the optimal power values used by the source and the relay that minimize the energy consumed. Finally, we use the obtained optimal power values to compute the minimum stable throughput achieved at the source. Our results show that cooperation using Random Network Coding combined with Alamouti Coding at the physical layer achieves the best performance among the proposed schemes.