Rake receiver performance on fading multipath channels in W-CDMA systems

A service specification of third generation wireless systems using wideband CDMA is to enable the delivery of data rates up to 2 Mbps to a single user on the downlink channel. One implication of such high data rates is the reduction of spreading gain, which results in increased multiple-access interference and also self-interference (SI). The latter is the result of multipath propagation and the imperfect autocorrelation properties of spreading sequences that must be used for despreading. In this paper, SI is estimated using a semi-analytical approach when the number of distinct multipath groups, each the vector sum of all multipath signals received within the delay resolution of the receiver, and their strengths are known. This in turn is used to predict bit error rates as a function of signal-to-noise ratio when a Rake receiver is used in a mobile terminal.