Performance of antenna arrays in an urban multi-path environment

The performance of an antenna array in a distributed fading environment depends on how the signal gets distributed in space. It is known that the scattering in an urban area mainly happens within a 100 wavelength radius around a mobile. Assuming that the base station antennas are above rooftop in urban areas, and approximately 1-2 kilometers from the mobile, the angular spread of the signal impinging on the array is on the order of 5-10 degrees, for a 1.8 GHz system. This angular spread results in a array response where the fading of the array elements is correlated along the array. We study how correlation effects the ability of the array to separate co-channel signals, and propose estimation algorithms which exploit this correlation. We derive the approximate theoretic performance of the array as a function of both angular spread and input SNR. Performance results are presented that compare the performance of different estimators, as well as the proposed theoretic performance, as a function of input SNR.