Adaptive multiuser bootstrapped decorrelating CDMA detector in asynchronous unknown channels

For personal, indoor, and mobile wireless radio communications (PIMRC) uplink multiuser CDMA channels, received signals are time asynchronous, and suffer from amplitude fading. The relative signals´ bit delays, energy variations, and hence the cross-correlation matrix of the received signal, are unknown. Using a novel adaptive algorithm, we propose in this paper a decorrelating detector suitable for particular CDMA uplink channels. The proposed asynchronous CDMA adaptive decorrelator consists of a bank of matched filters (matched to the users´ signature sequences), followed by a sampler at the bit-rate of 1/T and controllable weights. It is near-far resistant, and can be used by itself if signal-to-noise ratios are high, or as a first stage in the two-stage adaptive canceller previously proposed for the synchronous CDMA case