CDMA multiuser detection based on state-space estimation techniques

We propose a new space-time multiuser receiver for CDMA wireless systems. The receiver is based on the fixed-lag smoothed estimator which occurs in the well-researched area of state-space estimation. The receiver can work with long codes as opposed to most other multiuser detectors that require cyclic spreading codes. It is also naturally suited for adaptation and can be used with time-varying (Doppler spread) multipath channels. All the desired users are decoded simultaneously with little decoding delay. The approach assumes that a reliable channel estimate is available which in practice can be obtained from training symbols. We also briefly study the computational complexity of the receiver.