Energy-efficiency of cooperative diversity techniques in wireless sensor networks

This paper presents an investigation of the energy efficiency of two major cooperative diversity techniques in short-range wireless sensor networks: virtual-MISO (multiple-input-single-output) and decode-and-forward. The total energy consumption of a cooperative system consists of the transmission energy, the transceiver circuit energy and the local communication energy cost. In virtual-MISO explicit local communication precedes the long-haul cooperative transmission, whereas in decode-and-forward nodes cooperate by overhearing and repeating each other's long-haul transmissions. Our energy analysis shows that decode-and-forward is overall the more energy-efficient cooperative scheme. We also show that cooperation can yield large energy savings compared to traditional SISO (single-input-single-output) communication, even when the local distance between cooperating nodes is increased and becomes comparable to the long-haul distance. Given specific local and long-haul distance ranges, we formulate the recommended cooperation strategy in terms of the number of cooperating partners to employ for optimal energy-efficiency.