Holographic Radio Interferometry for Target Tracking in Dense Multipath Indoor Environments

The Radio Interferometric Positioning System (RIPS) is a phase-based localization scheme that achieves high accuracy with low-cost devices. Indoor localization with RIPS is, however, a challenge due to dense multipath. In this paper, we propose holographic radio interferometry (HRI) to cope with multipath effect. HRI builds hologram out of phase measurements in radio interferometry for the mobile target. It is built on an important observation that spatial diversity induced by dense multipath resembles that induced by random noise. We implement HRI with GNU Radio/USRP N210 and test it in lab environments. With mobility data from only one step, HRI achieves a median positioning error of 21 cm, in contrast to 151 cm with the original RIPS. It is also verified that HRI is robust to errors in mobility data. The median positioning error is no more than 66 cm with a speed error of the target up to 15 cm/s and a direction error up to 2.5 degrees.