Spatial Multiplexing MIMO Visible Light Communications With Densely Distributed LEDs and PDs

Multiple-input multiple-output visible light communications (MIMO-VLC) have been considered as an advanced technique owing to the enhancement of communication capacity and reliability. However, the performance of MIMO-VLC highly depends on channel correlation, which means that the system performs worse when the channels are more highly correlated. Some studies have developed techniques to alleviate channel correlation and improve the performance of spatial multiplexing MIMO-VLC systems. However, these works have not considered situations where all LEDs and PDs are integrated into a compact structure. In this paper, a single-user spatial multiplexing MIMO-VLC system with densely distributed LEDs (light emitting diodes) and PDs (photodiodes) is proposed. Designs of optimal signal vectors and system structures are introduced, to fulfill multiplexing gains when LEDs and PDs are set close to each other respectively. Numerical simulations are carried out and the results illustrate that the proposed system can realize multiplexing gains over the system where LEDs and PDs are distributed densely, and also outperforms the traditional repetition coding (RC) technique.