Adaptive space-frequency RAKE receivers for WCDMA

Adaptive space-frequency rake receivers use maximum ratio combining and multi-user interference suppression to obtain a considerable increase in performance in DS-CDMA systems such as WCDMA. To this end, the signal-plus-interference-and-noise and the interference-plus-noise space-time covariance matrices are estimated. The computational complexity is reduced significantly by transforming the covariance matrices into the space-frequency domain and by omitting noisy space-frequency bins. The optimum weight vector for symbol decisions is the ”largest” generalized eigenvector of the resulting matrix pencil. By iteratively updating the optimum weight vector slot by slot, real-time applicability becomes feasable while the fast fading is still tracked. The performance and the computational complexity depend on the number of space-frequency bins, antenna elements, and iterations. Therefore, the performance can easily be scaled with respect to the available computational power.