An Efficient Sensor-Node Selection Algorithm for Sidelobe Control in Collaborative Beamforming

Collaborative beamforming (CB), which forms a virtual antenna array from a number of distributed wireless nodes in wireless sensor networks (WSNs), can increase the transmission range, enhance energy efficiency, and prolong network lifetime. With perfect carrier phase synchronization, it has been revealed that CB guarantees a stable main lobe, regardless of the locations of the collaborative nodes. However, the sidelobe locations and the level of CB cannot be predicted due to random deployment of the nodes. A high-order sidelobe will cause severe interference to unintended receivers and degrade network capacity. Known sidelobe control methods suffer from exponential complexity with the number of unintended receivers. We tackle this by a novel algorithm that uses decentralized cross-entropy optimization (CEO) to search over different node combinations, which is proven to find the optimal solution with probability one. Simulation results verify the effectiveness of the proposed scheme and illustrate that the proposed scheme can achieve greater interference rejection at much lower complexity compared with a conventional method.