Cramer-Rao bound for location estimation of a mobile in asynchronous DS-CDMA systems

Commercial applications for the location of subscribers of wireless services continue to expand. Consequently, finding the Cramer-Rao bound (CRB), which serves as an optimality criterion for the location estimation problem, is of interest. We derive the CRB for the estimation of channel parameters and mobile position in an asynchronous direct sequence code division multiple access (DS-CDMA) system operating over fading channels. It is assumed that the location estimates are obtained from the bearings and/or propagation delays estimated at one or more cluster(s) of antenna arrays of arbitrary geometry. Among other applications, the CRB on the positioning accuracy may serve as a design tool to find an optimum antenna placement, or to evaluate the practicability of a legal demand for emergency location.