Sparse array spatial diversity with dual-size spatial invariances to mitigate fading-channel effects

A novel sparse array geometry embedding two sizes of spatial invariances is proposed for extended-aperture spatial diversity using a new ESPRIT-based algorithm. This novel direction-finding method extends the array aperture without additional antennas, irregular inter-element spacings, nor any cyclic ambiguity in the final arrival angle estimates. The half-wavelength invariance yields unambiguous but high-variance DOA estimates to disambiguate low-variance but cyclically ambiguous estimates obtained using the larger invariance. This novel approach facilitates (1) multipath de-correlation (independent fading), (2) coherent summation of multipaths from the same source, and (3) down-link beamforming from the base-station to the mobile. Under one simulation scenario involving two closely spaced time-delayed multipaths in frequency-selective slow-fading, the proposed algorithm offers an impressive 80% reduction in the standard deviation and bias. Any additional computation needed by this method may be performed in parallel, thereby requiring no serious increase in the overall computational time