Space-time receivers for CDMA systems

This paper discusses blind spatial channel estimation techniques for single user space-time CDMA receivers. The proposed receiver structure consists of beamformers in front followed by the generalized sidelobe canceler (GSC)-based time domain interference cancelers. We propose two spatial channel estimation techniques using the power method (PM): (i) the covariance method (CM) in which the data covariance matrix of the despread array output is applied to the PM to compute the spatial channel as its principal eigenvector and (ii) decision-directed and differentially-formed covariance matrix-based method (DDCM) which utilizes the decision feedback from the time domain filter to estimate the effective interference-free covariance matrix of the spatial channel using the differentially-formed covariance matrix of the array output. The simulation results show the both techniques can estimate the spatial channels reliably under the assumption of mild power control and DDCM could do so even in the “near-far situation”, outperforming the conventional either only time-domain or space-domain receivers in BER performance in the Rayleigh fading channel