Blind Adaptive Decorrelating RAKE (DRAKE) Downlink Receiver for Space-Time Block Coded Multipath CDMA

A downlink receiver is proposed for space-time block coded CDMA systems operating in multipath channels. By combining the powerful RAKE receiver concept for a frequency selective channel with space-time decoding, it is shown that the performance of mobile receivers operating in the presence of channel fading can be improved significantly. The proposed receiver consists of a bank of decorrelating filters designed to suppress the multiple access interference embedded in the received signal before the space-time decoding. The new receiver performs the space-time decoding along each resolvable multipath component and then the outputs are diversity combined to obtain the final decision statistic. The proposed receiver relies on a key constraint imposed on the output of each filter in the bank of decorrelating filters in order to maintain the space-time block code structure embedded in the signal. The proposed receiver can easily be adapted blindly, requiring only the desired user’s signature sequence, which is also attractive in the context of wireless mobile communications. Simulation results are provided to confirm the effectiveness of the proposed receiver in multipath CDMA systems.