Mobile Assister Based Collaborative Beamforming for Distributed Sensor Networks

This paper addresses distributed transmit beamforming problems based on a mobile assister node. Assuming that the distance to the receiver and the direction-of-destination (DoD) can be estimated, a stop-and-go strategy is proposed for a mobile assister node such that it moves gradually along the direction towards the receiver and provides SNR feedback information for transmitters. By receiving the SNR feedback information at each step, the transmitting sensors update their phases to maximize the SNR at the assister end. We then show that when the assister node reaches a threshold distance, the maximum SNR at the assister implies an approximate optimum SNR at the receiver end. Thus, the transmit beamforming problem is solved though the receiver initially is out of the communication range of the transmitters and is not able to provide SNR feedback information.