Expanded decorrelating detector with reduced noise enhancement for multipath frequency-selective fading channels

Abstract – A novel hybrid multiuser detection scheme that jointly uses linear and nonlinear interference suppression techniques is developed for high-speed direct-sequence code-division multiple-access (DS/CDMA) communications in multipath frequency-selective fading channels. The detector detects signals in a symbol-by-symbol style. Conventional decorrelating detectors suffer from the noise enhancement problem, and the problem becomes more serious for dispersive multipath channels. The proposed detector uses interference cancellation (IC) technology to reduce the rank of the expanded signal subspace and hence it enjoys the advantages of the expanded decorrelating detector in terms of complete multiple access interference (MAI) and intersymbol interference (ISI) suppression and avoids its disadvantage in terms of noise enhancement. Meanwhile, for this new detection strategy, a novel Kalman filter-based adaptive power estimation algorithm is developed. Computer simulation shows dramatic performance gain in the new detector compared with other existing methods.