A wireless position location system using forward pilot signal

We propose a handset based TDOA position location system for a CDMA network. To avoid a critical modification of the handset, the proposed system exploits several delay lock loop (DLL) modules of fingers or off-line DLL modules to estimate the TOAs from the base stations. Since the synchronization performance of the DLL is degraded by the near-far effect in general, we adopt an interference cancellation technique, subtracting the reconstructed pilot signal from the received signal at the handset. It can increase the audibility and enhance the performance in estimating the TOAs of weak pilot signals from other base stations. Furthermore, the error in estimating the TOA is minimized by using an N-th order polynomial approximation. Through computer simulations, we showed that the proposed system has improved the performance in estimating parameters and locating positions