Cramer-Rao bounds for time of arrival estimation in cellular systems

The accuracy limits of TOA estimation over multipath channels are of interest for position estimation in cellular networks. The Cramer-Rao lower bound (CRLB) has been used for this purpose. Prior work on CRLB computation for TOA estimation has implicitly assumed that all channel parameters are to be estimated. It is shown in this paper that this approach is not suitable for estimating the performance achievable in a positioning context. This paper focuses on the CRLB for TOA estimation when only the delay of the first path is estimated. Bounds are computed for suburban and urban environments using realistic CODIT-based channel models. Further, a tighter bound is derived for channels whose amplitudes have a Rayleigh density function.