A Hybrid SS-ToA Wireless NLoS Geolocation Based on Path Attenuation: Cramer-Rao Bound

Non-line-of-sight propagation in wireless localization systems leads to a challenging problem for the estimation of a mobile position. A hybrid idea has been considered as a promising approach to increase estimation accuracy. Existing methods, however, are formulated using separate measurements, necessitating different observation quantities, e.g. received signal and received signal strength, thus making the parameter estimation cumbersome. In this paper, we propose a new hybrid wireless geolocation model requiring only one observation quantity, namely the received signal. The attenuation model for transmit power from base stations is explored herein to capture propagation features in the received signal model. Fortunately, it also provides a more realistic approach to wireless geolocation. To investigate geolocation accuracy, the Cramer-Rao bound (CRB) is derived for the estimation error of the mobile position. For any value of path loss exponent, the obtained result provides a generalized form of the CRB for the usual time delay case. In small cells, e.g. office building picocells, numerical examples illustrate that the accuracy of mobile position estimation exploring path loss is improved comparing with that provided by the usual time delay method.