Two-Way Range Estimation Utilizing Uplink and Downlink Channels Dependency

Range estimation between a base station (BS) and target that are unsynchronized in time is obtained by two-way ranging where both sides are transmitting and receiving. In the conventional two-way range estimation approach, the time of arrivals at BS and target are estimated separately and thus correlation between the uplink and downlink channels is ignored. In this paper, we develop a maximum likelihood range estimator, in multipath conditions, where the received signals distribution is approximated as Gaussian and the time of arrivals at BS and target are jointly estimated. The estimator is convenient for implementation and utilizes the uplink and downlink statistical dependency and, hence, obtains a performance advantage over the conventional suboptimal approach. An analytical analysis of the estimator is also developed, which is used to gain insight on the estimator performance.