Measurements of spatial signature of an antenna array

A spatial signature is a response vector of an antenna array to a mobile unit at a certain location. The mobile subscribers at different locations exhibit different spatial signatures. The exploitation of spatial diversity (or difference of spatial signatures) is the basic idea of the so-called space-division-multiple-access (SDMA) scheme, which can be used to significantly increase the channel capacity and quality of a wireless communication system. Although the SDMA schemes have been studied by a number of researchers, most of these studies are based on theoretical analysis and computer simulations with ideal assumptions. Not much experimental study has been conducted on spatial signature variation due to nonideal perturbations in a real wireless communication environment. The purpose of this paper is to present our preliminary experimental results of spatial signature variation using our recently developed antenna array testbed. The results to be presented include the spatial signature variation with time and frequency and in several typical scenarios: (1) the mobile unit is stationary, so are its surroundings; (2) the mobile unit is stationary, but the surroundings vary; (3) the mobile unit moves in several different directions