  The millimeter-wave (mmWave)-based Wi-Fi sensing technology has recently
attracted extensive attention since it provides a possibility to realize higher
sensing accuracy. However, current works mainly concentrate on sensing
scenarios where the line-of-sight (LoS) path exists, which significantly limits
their applications. To address the problem, we propose an enhanced mmWave
sensing algorithm in the 3D non-line-of-sight environment (mm3NLoS), aiming to
sense the direction and distance of the target when the LoS path is weak or
blocked. Specifically, we first adopt the directional beam to estimate the
azimuth/elevation angle of arrival (AoA) and angle of departure (AoD) of the
reflection path. Then, the distance of the related path is measured by the fine
timing measurement protocol. Finally, we transform the AoA and AoD of the
multiple non-line-of-sight (NLoS) paths into the direction vector and then
obtain the information of targets based on the geometric relationship. The
simulation results demonstrate that mm3NLoS can achieve a centimeter-level
error with a 2m spacing. Compared to the prior work, it can significantly
reduce the performance degradation under the NLoS condition.
