Multiuser channel estimation for closely spaced multipath CDMA signals using the unscented Kalman filter

The paper introduces time delay and channel gain estimation for closely spaced multipaths in code division multiple access (CDMA) systems using the unscented Kalman filter (UKF). Given the non-linear dependency of the channel parameters on the received signals in multiuser/multipath scenarios, an iterative and non-linear filtering approach, namely UKF has been applied. The UKF produces channel estimates with the minimum mean-square error (MMSE) with an improved accuracy and consistency. A performance comparison with the conventional extended Kalman filter (EKF) has also been made. The UKF, which is a derivative-free Kalman filtering approach, avoids the errors associated with linearisation in the EKF. The Cramer-Rao lower bound (CRLB) has been derived for the proposed estimator and the simulation results clearly show that the UKF is simpler to implement and more resilient to near-far problem in CDMA networks.