Towards mmWave Localization with Controllable Reflectors in NLoS Scenarios

Millimeter wave (mmWave) signal-based localization is a promising scheme due to high precision in the lineof-sight (LoS) scenarios. However, even small obstacles would hinder mmWave localization by blocking the LoS paths, and environment reflection-based schemes under non-LoS (NLoS) scenarios couldn’t guarantee the precision. In this paper, we investigate mmWave NLoS localization scheme based on recent fast-growing research for specialized mmWave reflectors. Our system uses multiple reflectors in the environment to act as anchors for target localization. Firstly, we propose a two-phase reflector discovery mechanism to let transmitter identify the reflectors and estimate their positions as well. Secondly, we introduce a hashing-based beam alignment method with logarithmic complexity to obtain the relative relationship among reflectors and the target. Lastly, we put forward a triangulation-based method for target localization, along with credit-based fusing mechanism to handle the possible imprecise estimated reflector positions. Extensive experiments are carried out to evaluate the proposed scheme. The results demonstrate the effectiveness of the proposed system, which achieves 50% average improvement over environment reflection-based methods. Furthermore, the proposed hashing-based beam alignment process dramatically reduces the time-consumption as compared with baseline using exhaustive search, e.g., 18x, 37x and 40x reductions are observed with 1, 4 and 7 reflectors, respectively.