Distributed transmit beamforming: Performance improvement using a two-bit feedback scheme

In this paper a distributed transmit beamforming technique is proposed for time-varying wireless communication channels that improves the signal gain at the receiving terminal, and thus yielding an enhanced signal-to-interference-plus-noise ratio. In this regard, a two-bit feedback algorithm, with considerable gains in terms of received signal strength (RSS), is proposed for optimizing the phase synchronization of signals beamformed from distributed transmitters towards a moving receiver. It is shown that the proposed scheme can successfully capture the impact of time-varying wireless channels on the transmitted signals with reasonable accuracy such that an improved RSS is achieved at the receiver. Numerical experiments show that the proposed two-bit feedback scheme achieves an improved average RSS of about 37.9% and 29.7%, relative to the existing one-bit scheme and the improved one-bit feedback scheme respectively. Results also show that the proposed scheme requires a significantly reduced number of antennas to achieve an RSS equivalent to that of the one-bit feedback schemes.