Performance evaluation of advanced receivers for WCDMA downlink detection

The performance of the conventional RAKE receiver is known to be limited in time-dispersive propagation environments due to intersymbol and multiple access interference caused by delayed replicas of the transmitted signal. Especially, at high data rates, i.e. with low spreading factors, not only does the interference rejection capability of the RAKE receiver decrease but also the diversity gain from combining the multipath components is drastically reduced. Therefore, in 3rd generation mobile radio systems based on direct-sequence code-division multiple access, the employment of more sophisticated demodulation techniques is indispensable for the provision of high data rates with a reasonable error performance. A comparison between three advanced WCDMA downlink detection algorithms is presented. Both uncoded and coded error performances in different scenarios are considered. Our simulation results indicate that almost the same performance level can be achieved by all three algorithms. Thus, the decision on which algorithm to use mainly depends upon implementation issues.