Node selection for sidelobe control in collaborative beamforming for wireless sensor networks

Collaborative beamforming (CB) is a new technique for energy-efficient long-distance communications in wireless sensor networks (WSNs). It is based on the fact that the distributed nodes of a WSN can synchronize their carrier phases to form a beampattern with a stable mainlobe (independent on the node locations). However, sidelobes of such beampattern are found to be severely dependent on the particular node locations. High level sidelobes can cause unacceptable interference to unintended base stations and access points (BSs/APs). Therefore, controlling the sidelobes of CB has the potential to increase the network capacity and wireless channel availability. In this paper, we propose node selection for CB sidelobe control. A selection algorithm with low implementation complexity is developed to search over different node combinations. It aims at minimizing the interference at unintended BSs/APs. The performance of the proposed algorithm is analyzed in terms of the average number of trials and the achieved interference suppression. Simulation results match the analytical approximations and show the effectiveness of node selection for limiting the interference.