Channel estimation and tracking for MC-CDMA signals

This paper investigates the impact of channel estimation errors in the uplink and downlink of a multicarrier code-division multiple-access system. Pilot blocks are periodically inserted into the downlink data stream to perform a least-squares channel estimation. It is shown that a single-user minimum-mean-square-error (MMSE) detector endowed with the proposed channel estimator has relatively low complexity, good performance and is robust to estimation errors even under full-loaded conditions. In the uplink scenario channel estimates are computed through a least-mean-square algorithm and are passed to a linear MMSE multiuser detector or a parallel interference cancellation (PIC) receiver. Simulations indicate that in this case the system performance depends heavily on the quality of the channel estimates, meaning that they are particularly critical.