See and Beam: LiDAR-Guided Passive Reflection for Reliable Indoor mmWave Connectivity

Millimeter-wave (mmWave) links promise multi-gigabit rates but degrade sharply in non-line-of-sight (NLoS) indoor settings. This paper introduces a LiDAR-guided adaptive beamforming framework that dynamically steers the transmit beam to optimize NLoS coverage based on user location. A LiDAR sensor co-located with the transmitter detects the user position in an L-shaped corridor and determines the corresponding angle of departure (AoD) for reflection toward the user. A mirror and glossy metallic reflector placed at the corridor corner provide a common reflection path for both LiDAR and mmWave signals, enabling precise beam alignment without exhaustive angular scanning. Experimental results show that the proposed LiDAR-assisted adaptive beamforming enhances the minimum received signal strength by up to 12 dB compared to fixed-beam transmission. The findings demonstrate that common indoor surfaces capable of reflecting both LiDAR and mmWave signals can be effectively leveraged to extend and optimize coverage.