Fast Phase Synchronization with Clustering and One-Bit Feedback for Distributed Beamforming in a Wireless Sensor Network

In this paper, we propose a fast phase synchronization method with clustering and one bit feedback for distributed beamforming in a wireless sensor network where multiple single-antenna nodes transfer their sensing data to a data collector. To transmit the data effectively, the distributed nodes should adjust their transmit signals' phase properly so that their signals are constructively added up at the data collector with a same phase, resulting in an increasing received signal strength (RSS). Accordingly, in conventional phase synchronization methods, the data collector broadcasts a common message with a single-bit feedback and, depending the feedback message, each node updates its transmit signal phase. Because, in such conventional methods, the phase are updated based on the random perturbation in a distributed way, the phases are slowly converged and the time required for the synchronization becomes large and it is more serious in a massively distributed sensor network. To overcome the problem, in the proposed method, we separate the distributed sensors into several clusters. Then, in the first stage, the phases in each cluster are synchronized with one-bit feedback and in the second stage, the inter-cluster phases are synchronized based on the grid-search with a one-bit feedback. Through the simulation, we verify that our proposed scheme has a shorter convergence time than the conventional scheme without any feedback overhead.