Analysis of RAKE receiver in W-CDMA systems with downlink beamforming

This paper presents an analysis of a RAKE receiver in a W-CDMA downlink. The base station employs transmit beamforming, while each user employs R-finger RAKE receiver under selective fading channels. Spreading sequences are composed of Walsh codes and a common long code based on 3GPP standardization. We derive an exact expression for the instantaneous signal-to-interference-plus-noise ratio (SINR) at the output of the RAKE receiver. In the derivation process, the effect of spreading sequences, downlink beamforming, and the RAKE receiver are taken into account. Simulation examples for a 4-finger RAKE receiver are given to verify the derived expression. Our expression can be applied to evaluate transmit beamforming as well as to evaluate the performance of the RAKE receiver.