Dual-tone radio interferometric positioning systems using a single mobile anchor

In this paper, we propose a low-cost dual-tone radio interferometric positioning system using a single mobile anchor, named mDRIPS. There is no synchronization requirement between the mobile anchor and the target. In mDRIPS, the static target continuously transmits a dual-tone signal, and the mobile anchor receives the signal at different positions along its trajectory. The instability of the target clock is taken into account. An ESPRIT-type algorithm is developed to estimate frequencies of the dual-tone signal for the subsequent phase estimation. Furthermore, the time of arrival (TOA) is extracted from the phase estimate of the received dual-tone signal. After measuring several TOAs at different locations along the anchor's trajectory, the target can be located. The mDRIPS is robust to flat-fading channels. Since the frequency difference of the two tones of the dual-tone signal is designed to be smaller than the channel coherence bandwidth, the same fading effect on these two tones can be eliminated. Moreover, we investigate the integer ambiguity problem due to phase wrapping, and develop a localization algorithm to deal with a simplified ambiguity problem. Numerical results demonstrate the efficiency of the proposed mDRIPS.