Performance Analysis of Indoor Diffuse VLC MIMO Channels Using Angular Diversity Detectors

We consider specular and diffuse reflection models for indoor visible light communications using a mobile receiver with angular diversity detectors in multiple input multiple output (MIMO) channels. We aim to improve the MIMO throughput compared to vertically oriented detectors by exploiting multipath reflections from different surfaces in the room. We then evaluate data throughput across multiple locations in the small room by using repetition coding, spatial multiplexing, and spatial modulation approaches. In spatial modulation, we also propose a novel approach called adaptive spatial modulation. This makes use of channel matrix rank information to decide which TX/RX setup to be used, and is developed to cope with rank deficient channels. In a scenario, where the receiver is moving, channel gains are weak in some locations due to the lack of line of sight (LOS) propagation between transmitters and receivers. This effect is mitigated by employing adaptive modulation and coding together with per antenna rate control. We then compare the throughput for LOS only channels against LOS with specular or diffuse reflection conditions, for both vertical and angular oriented receivers. The results show that exploiting specular and diffuse reflections provide significant improvements in link performance.