Energy Efficiency Analysis of Multistage Cooperation in Sensor Networks

Wireless sensor networks demand the implementation of energy-aware transmission protocols. Recently, cooperative protocols have been suggested for use in sensor networks since they typically require less transmit power than the direct transmission for the same error probability. For sensor networks with short range transmissions, however, the energy consumed in receiving transmissions from cooperative partners may exceed that of transmission energy when using cooperation. Hence it is not clear if such implementation is energy efficient. The objective of this work is to study energy efficiency of multistage cooperative networks that accounts for both the transmission reliability in terms of outage probability and the total network energy consumed (including the transmit as well as receive energy) to achieve this performance. We analyze the effect of node density, network topology and the number of cooperation stages on the energy efficiency of multistage relay networks using numerical results. With respect to serial equidistant network topology, we observe that the largest energy efficiency is obtained with three cooperation stages and just few relays in the medium SNR range while it is best to allocate five cooperation stages and large number of relays when transmit SNR is low. It is also observed that uniform relay distribution, a more practical approach in many scenarios, can improve energy efficiency of sensor network with five cooperation stages and large number of relays.