Zero-feedback open-loop distributed transmit beamforming

Abstract

This paper presents a novel open-loop distributed transmit beamforming technique, where no collaboration or feedback from the receiver is required. In general, distributed transmit beamforming without receiver collaboration can be performed by observing a reference signal, together with positional information of individual array nodes. This approach is usually impractical due to the stringent accuracy requirement on positional information. We propose a practically feasible approach to substantially relax this requirement by combining observations from multiple reference signals. The scheme is highly practical since reference signals can be observed from existing broadcast stations, while the beamforming solution can be computed with low complexity. Our numerical results show that significant beamforming gains are achievable with relatively imprecise positional information.