Tracking of a Periodic RF Transmitter with a Mobile Receiver: From Theory to Implementation

We propose a method to track a periodic RF transmitter using a mobile receiver. By estimating the difference in time-of-arrival (TOA) of the periodic messages at different locations along its trajectory, the receiver is able to estimate the transmitter location. A major challenge lies in separating the time offset due to receiver movement from the time offset due to local oscillator (LO) drift. We propose an adaptive filtering framework that is able to track both the LO drift and the RF transmitter simultaneously, using the receiver TOA measurements and the receiver locations as inputs. Furthermore, we propose an algorithm to optimize the receiver trajectory based on the posterior Cramér-Rao lower bound. Simulation results are presented to show the feasibility of the proposed method. Finally, the proposed method is implemented on a softwaredefined radio (SDR) testbed. Empirical experiments demonstrate that our approach can successfully track both a static and moving transmitter to within an accuracy of less than 1 m.