Y. Qi and H. Kobayashi (USA)
achievable bounds, Cramer-Rao Lower Bound, non-line of-sight geolocation
Non-line-of-sight (NLOS) geolocation becomes an impor tant issue with the fast development of mobile communi cations in recent years. Several methods have been pro posed to address this problem. But we believe that a more comprehensive study on the best geolocation accuracy that these methods may possibly achieve is imperative. In [1], we developed a unified analysis of the Cramer-Rao Lower Bound (CRLB) applicable to NLOS geolocation. How ever, our further study reported here shows that the CRLB is not achievable in general cases. In this paper, we first present a new result on achievable bounds for NLOS geolo cation with time-of-arrival (TOA), maximum likelihood es timation (MLE) and signal strength (SS) based positioning methods. Their physical interpretation is consistent with that of the CRLB and provides an insightful direction to wards construction of NLOS geolocation algorithms. We then evaluate the difference between the achievable bound and the CRLB obtained earlier, and verify quantitatively that the CRLB can only be achieved in some specific cases, e.g., when the signal-to-noise ration (SNR) is same for the signals received at each base station. Some numerical re sults are reported based on simulation experiments.
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