Subspace Methods for Blind Fractionally-Spaced Equalization of Distributed Phase-Shift Beamforming Signals

This work investigates different subspace-based approaches for the equalization of signals transmitted from phase shift Distributed Beamforming systems. While phase shifters have been shown to be capable of enabling distributed beamforming by providing carrier coherence, it does not address mismatches in symbol timing, resulting in potentially significant levels of intersymbol interference. Using fractionally spaced receivers and the singular value decomposition of the channel matrix, we design linear and nonlinear equalization methods to combat the distortion induced by this symbol timing mismatch. We show that when linear equalization is not practical, a Causal Minimum Noise Decision Feedback Equalizer would provide us with better symbol error performance when operating with high signal-to-noise ratio, and we provide a lower bound on the error rate of this proposed equalization method.