Channel estimation and multiuser detection for long code CDMA

In a long code CDMA system, a subspace technique is directly applied to downlink channel estimation when spatial/temporal diversity is available. Detection of the desired user is performed by typical linear techniques after the channel is estimated Since the method depends on eigenvalue decomposition on the data covariance matrix, which is typically estimated from finite data samples, the optimal solution is then perturbed. Therefore, the statistical performance of both the channel estimator and the detectors is analyzed based on a perturbation technique. It is further justified by numerical examples.