Joint adaptive channel gain estimator and multiuser detector for asynchronous CDMA time-variant multipath channels

CDMA proves to be an attractive method for multiuser communication due to its potential capacity increase and anti-multipath fading capability. However, its performance is limited by the existence of multiple access interference energy (MAI), which results in the so called near-far problem. To reduce the MAI effect, different multiuser detection methods have been proposed. Many of these methods require the amplitudes and relative delays of the users signals to be either a-priori known or accurately estimated. A number of algorithms that jointly perform this estimation and detection have been investigated. These algorithms, however, generally require a high computational effort. In this paper, we present a joint adaptive channel gain estimator and decorrelator, which has a significantly lower complexity. The performance of this joint adaptive structure is evaluated using simulations in multipath channels, both variant and invariant.