Characterization of fast fading wireless vector channels

In mobile communications, smart antenna systems that utilize an antenna array and perform advanced signal processing techniques can suppress interference, increase channel capacity and improve link quality by selective reception/transmission at the base station. However in a fast fading environment where there is a relative motion between a mobile user and an antenna array, the ability of a smart antenna system to suppress the interference and to select the desired signal is fundamentally limited by the adverse nature of vector channels. In order to develop accurate vector channel models for fast fading environments, we first need to understand and characterize the variation of vector channel parameters. In this paper we present the results including spatial signatures, DOAs, and complex multipath fading parameters obtained by using a uniform circular array and 1.8 GHz smart antenna testbed in realistic wireless environments. The results show that DOAs change little within 2 lambda movement of the user in both line-of-sight (LOS) and non line-of-sight (NOLOS) scenarios. Correlation of spatial signatures are high in the LOS scenario, but decreases to as much as 50% in the NOLOS scenario.