Smart Antenna Testbed for Mobile Wireless Systems

Abstract

A software radio-based test bed has been built and operated to collect experimental data related to smart antenna performance. Environmental data on radio channel characteristics as well as comparative data on different types of smart antenna algorithms were gathered and analyzed. To make realistic predictions of “smart” antenna performance, statistical characterizations of multipath propagation and interference were performed in the suburban Washington, D. C. area using data collected on coherent eight-channel software radio equipment built to geolocate mobile cellular phones. Analysis of the data yields estimates of the probabilities of encountering a given number of co-channel interferors or multipath components. The distributions of interference and multipath components as a function of relative power and angle are also presented. Preliminary results suggest that multipath fading, and not interference, is a dominant mode of signal degradation. Another variant of the software radio was constructed to evaluate different C/I measurement algorithms and to compare different smart antenna algorithms. Comparisons of performance for fully adaptive algorithms vs. switched fixed beams in an suburban/urban environment is presented.