On the performance improvement through the use of parallel interference cancellation in channel estimation for multipath CDMA systems

A decoupled maximum likelihood (DEML) estimator is employed to estimate the multipath delays and channel coefficients of all users. This estimator starts with a training mode then reverts to a decision-directed mode. In the training mode, the initial values of multipath delays and channel coefficients of all users are estimated. These initial parameters are used for parallel multiuser interference cancellation. Once the multiuser interference is cancelled, the signal is fed back to the estimator for fine estimation of delays and channel coefficients of all users. These fine estimates are used for the next symbol interval. This process continues in the decision-directed modes. The performance of channel estimation with interference cancellation has shown considerable improvement under multipath environments compared to the one without interference cancellation. Conclusively, the proposed scheme removes the intersymbol interference (ISI) resulting from multipath propagation and obtains more accurate channel estimates for further data detection. Finally, analysis is done to justify the simulation results.