Time-reversal indoor positioning with centimeter accuracy using multi-antenna WiFi

In this paper, we propose an indoor positioning system (IPS) that achieves centimeter accuracy in a complex indoor environment using time-reversal (TR) technique with a single pair of off-the-shelf multi-antenna WiFi devices. The proposed IPS can work under both line-of-sight (LOS) and non-line-of-sight (NLOS) environment. Leveraging the spatial diversity on the multi-antenna WiFi device, the proposed IPS creates a large effective bandwidth to mitigate the ambiguity between different locations due to the limited bandwidth in WiFi systems. The proposed IPS obtains channel frequency responses (CFRs) from different antenna links at locations-of-interest in the offline phase. In the online phase, it captures instantaneous CFR which is compared against CFRs in the offline phase by fusing the time-reversal resonating strength (TRRS) calculated at each link. Finally, the location is determined according to the TRRS. Extensive experiment results in an office environment demonstrate true positive rates of 99.93% and 100% while only incurring false positive rates of 1.56% and 1.80% under LOS and NLOS conditions, respectively.