Multiuser Precoded MIMO Visible Light Communication Systems Enabling Spatial Dimming

In this article, a new indoor multiuser (MU) multiple-input-multiple-output (MIMO) visible light communication (VLC) system is proposed, where the dynamic range of the light emitting diodes (LED-DR) and illumination requirements are taken into consideration. Exploiting the characteristics of LED-DR and the block diagonalization precoding (BDP) technique, we design a weight-adjusted BDP (WA-BDP) scheme that can exploit the LED-DR to offer a high performance in terms of bit error rate (BER). Moreover, utilizing the LED array equipped with a number of LEDs, a spatial dimming (SD) mechanism based on LED selection is employed to fulfill the uniform illumination requirement for typical indoor scenarios. Finally, we combine the WA-BDP technique and SD to form the proposed spatially-dimmed, weight-adjusted block diagonalization precoded (SD-WA-BDP) MU-MIMO-VLC system, where the LED-DR is fully utilized to support simultaneous illumination and communication. In addition, two options of the SD-WA-BDP scheme are developed to manage the performance and complexity tradeoff. Simulation results demonstrate the superiority of the proposed scheme.