Near optimum decentralized linear receiver for the forward link of W-CDMA mobile systems over frequency-selective fading channels

We derive and analyze an advanced decentralized (single-user) linear receiver for wideband code-division multiple-access (W-CDMA) systems operating in frequency-selective fading channels. We focus particularly on the forward link whose performance needs improvement for third-generation (3G) mobile radio systems and beyond. By considering the forward link specific characteristics a near optimum decentralized linear receiver, here called an "MMSE combiner", is proposed, which optimally (based on MMSE criterion) combines the advantages of both a matched filter RAKE receiver (used to compensate for multipath fading) and an inverse filter linear equalizer (acts to suppress MAI). That is, the proposed receiver consists of the matched filter (RAKE receiver) and inverse filter in parallel, followed by a linear (MMSE-based) combiner. The resulting receiver structure is relatively simple, as are other sub-optimal single-user receivers, and does not require any knowledge of other active users' CDMA codes. The receiver treats both multiple-access interference (MAI) and intersymbol interference (ISI) as noise. Monte-Carlo simulation results are given showing that the performance of the proposed MMSE combiner nearly approaches that of the optimum decentralized linear receiver.