Collaborative beamforming in wireless sensor networks

Collaborative beamforming (CB) is an energy efficient transmission scheme in wireless sensor networks (WSNs). Despite the promising aspects of CB, its practical implementation remains largely unexplored and the challenges, namely frequency, phase, and data synchronization, must be addressed for successful deployment. We propose a CB protocol with a compatible transceiver architecture. The protocol uses a phase-locked loop (PLL) continuously operating in closed-loop for frequency synchronization, a local two-way phase estimation and remote one-way calibration technique for phase synchronization, and a data entrainment technique to achieve data synchronization with minimal data traffic. The efficiency analysis including carrier jitter demonstrates the feasibility of the proposed CB protocol.