Residual energy-aware collaborative transmission beamforming in wireless sensor networks

Energy-Efficient transmission techniques are very important for extending the lifetime of a wireless sensor network (WSN) given that recharging batteries of a large number of WSN nodes is a very difficult and expensive operation. Collaborative transmission beamforming (CTB) saves energy consumed by each node by distributing between different WSN nodes the required total power transmission to get a desired bit error rate (BER) at the receiver. Moreover, by coherently combining the different signals transmitted by the WSN nodes, CTB increases the signal strength in the direction of the receiver, therefore decreases the total power transmission of the WSN. In this paper, we propose a new CTB technique that minimizes the total power transmission of the WSN while balancing the residual energy in different nodes. By solving this multi-objective optimization problem, we show that the WSN lifetime can be improved up to 30 % compared to the basic CTB algorithm, which aims at minimizing the total power transmission without taking into account the residual energy.