Optimal multiuser detection of bandlimited DS-CDMA signals, distorted by time-varying, frequency-selective multipath channels

We have addressed the problem of optimum multiuser detection for bandlimited signals distorted by a time-varying, frequency selective channel, and corrupted by additive Gaussian noise. We have derived the MLSE receiver for this channel using the familiar concept of matched filtering. A performance analysis for Rayleigh fading and white noise is in good agreement with simulations. We propose this optimal multiuser receiver as a benchmark for comparing the performance of other detectors. Many other receivers exhibit a BER floor in fast time varying channels and therefore are unsuitable as a reference. As a final note, realisations of the optimal receiver using different metrics, for example, the squared Euclidean distance metric, can be derived easily