The Performance of a Null-Steering Beamformer in Correlated Rayleigh Fading

We consider the performance of a null-steering adaptive beamformer in a distributed Rayleigh fading environment. To determine the beamformer coefficients, the signal and interference array response vectors must be estimated. An estimator that makes use of the knowledge of the spatial distribution of the signal is proposed and compared with other estimators that do not use this information. As the angular spread of the signal increases, the value of this information is reduced, until, for the case of isotropic scattering, the estimate that uses the spatial distribution is equivalent to the estimate that does not. Performance results are presented that compare the performance of the different estimators. We derive closed-form expressions for the signal-to-interference-plus-noise ratio (SINRO) and probability of error for the case where the training data are orthogonal.