Distributed Beamforming with Sidelobe Control Using One Bit of Feedback

Distributed Beamforming (DBF) is a promising technique for energy-efficient uplink communications in Wireless Sensor Networks (WSNs). It is based on the fact that, by synchronizing their carrier phases precisely enough, sensor nodes can collaboratively form a beampattern with a stable mainlobe. However, the sidelobes of such beampattern depend on the actual node locations, possibly causing unacceptable interference levels to other Base Stations. In this paper, we propose a DBF scheme with Sidelobe Control (SC) which maximizes the beamforming gain in the direction of main BS while keeping the sidelobe levels in the directions of the unintended BSs below some prescribed threshold(s). The proposed algorithm operates with partial CSI at the BSs and it merely requires each BS to broadcast one bit of feedback to the sensor nodes. Performance is mainly assessed in terms of the beamforming gain and convergence speed, as a function of the number of unintended BS, their location and the actual values of the thresholds. A centralized solution obtained via numerical optimization is used as a benchmark.