Improved channel estimation schemes for DS-CDMA RAKE receiver with the use of multiuser interference canceller

Abstract

In this thesis, a standard pilot (or data)-assisted decoupled maximum likelihood (DEML) estimator is employed to estimate the multipath delays and channel coefficients of all users in asynchronous code division multiple access (CDMA) systems with Rayleigh faded multipath propagation medium. A recursive approach is incorporated into the estimator to spread the computational time over each processing window. Parallel interference cancellation (PIC) is deployed to detect the data. Later on in the thesis, the intermediate signals (cancelled from other undesired users and paths) from the PIC are exploited and fed back to estimator to refine the estimates of channel coefficients to give better overall performance. This proposed scheme works well under large number of propagation path. The time-variant channel mean-square-error in terms of fade rates and background noise level is also theoretically and numerically analyzed to obtain appropriate pilot length that can be used for simulation.