Coherence signal impact on the performance of a spatio-temporal GSC receiver for CDMA applications

The goal of adaptive beamforming is the reception of the desired signal in a specified direction and the cancellation of the interference signals without a priori knowledge of the interference environments. An efficient algorithm called generalized sidelobe canceller (GSC) was proposed (Rude, M.J. and Griffiths, L.J., Proc. IEEE ICASSP, p.968-71, 1989). However, one major problem is the desired signal cancellation that is caused by coherence between the desired signal and one or more interfering signals. We proposed a new spatio-temporal scheme based on GSC (Ghanem, K., Proc. IEEE Radio & Wireless Conf. p.119-22, 2003). The new receiver only prevents the desired signal cancellation but also provides robustness against channel variations. This paper presents the performance of the new efficient technique, combining spatial and temporal diversities, in coherent and non-coherent environments. Beamforming efficiency and convergence rates are investigated and presented. It is shown that the scheme performs well at higher interference levels, and, at the same time, the beamforming efficiency of the proposed technique presents a high robustness against signal coherence.