Nonlinear multiuser parameter estimation and tracking in CDMA systems

This paper presents a joint channel coefficient and time-delay tracking technique for code-division multiple-access (CDMA) systems. Due to the highly nonlinear nature of time delay estimation, an iterative nonlinear filtering algorithm, called the "unscented filter" (UF), is employed. The UF can provide a better alternative to nonlinear filtering than the conventional extended Kalman filter (EKF) since it avoids errors associated with linearization. The Cramer-Rao lower bound is derived for the estimator, and computer simulations show that it provides a more viable means for tracking time-varying amplitudes and delays in CDMA communication systems than estimators based on the EKF.