Adaptive signal processing techniques for short-code CDMA

The use of short, or repeated, spreading codes for direct-sequence (DS)-code-division multiple access (CDMA) enables the application of adaptive filtering techniques for interference mitigation. An attractive property of these techniques is that given a training sequence, little additional side information is required for estimation of the optimal filter. We describe some previously proposed adaptive filtering methods for short-code DS-CDMA, including reduced-rank filtering for fast convergence and tracking, adaptive decision-feedback multiuser detectors, and joint transmitter-receiver adaptation.