EKF based LOS Estimation with Interference Cancellation for WCDMA Mobile Positioning

In WCDMA mobile phone positioning, one method to compute the terminal location in two dimensions is to use the Line-Of-Sight (LOS) distance between the mobile and at least three participating Base Stations (BSs). Correct estimation of the LOS delay will ensure correct estimation of the mobile position. However, delay estimation is still a challenging topic when the successive paths are spaced at less than one chip distance (closely-spaced paths) and in presence of strong interference in the system (interference from other BSs and from the users of the same BS). In this paper we introduce a scheme for estimating the LOS delay based on the Extended Kalman filter (EKF) with parallel interference cancellation. The scheme, which combines 2 parallel EKF, consists on estimating the parameters of the interference and of the desired user (delays and channel coefficients) and can be generalized to NBS+1 EKF, where NBS is the number of BSs included in the localization procedure. The simulation results show that the proposed technique can be used efficiently in multiuser multicell WCDMA systems.