Effect of fading correlation on adaptive arrays in digital wireless communications

The effect of correlations among the fading signals at the antenna elements of an adaptive array in a digital wireless communication system is investigated. With an adaptive array, the signals received by multiple antennas are optimally weighted and combined to suppress interference and combat desired signal fading. A model of local scattering where the received multipath signals arrive within a given bandwidth is presented, and a closed-form expression for the correlation as a function of antenna spacing is derived. Results show that the degradation in performance with correlation in an adaptive array that combats fading and suppresses interference is only slightly larger than that for combating fading alone, i.e., with maximal ratio combining. This degradation is small, even with correlation as high as 0.5