On time-of-arrival positioning in a multipath environment

Wireless geolocation in a multipath environment is of particular interest for wideband communications. The conventional approach makes use of first-arriving signals only. In this paper, we investigate whether and under what conditions processing multipath delays should enhance the positioning accuracy. The best achievable positioning accuracy is evaluated in terms of the Cramer-Rao low bound (CRLB) and the generalized-CRLB (G-CRLB), depending on whether prior statistics of non-line-sight (NLOS) induced errors are available. We then show that such prior statics are critical to the accuracy improvement when the multipath delays are processed. Furthermore, the degree of accuracy enhancement depends on two major factors: the strength of multipath components and the variance of NLOS induced errors. The corresponding positioning receivers are also discussed. In previous work (Y. Qi and H. Kobayashi, Proc. 2002 IEEE Int. Conf. on Acoustic Speech and Sig. Proc., pp. 2473-2476, 2002, and Proc. IEEE Vehicle Tech. Conf., pp. 285-288, 2002), we developed an analysis of the time-of-arrival (TOA) positioning method in an NLOS environment, assuming single path propagation. The main results obtained there are extended and applied to the multipath case in this paper.