Data Rate and Illumination Performance of Sunlight Modulation Systems Using DLS

Sunlight offers not only illumination but also an eco-friendly solution for indoor optical wireless communication (OWC). This article presents a comprehensive investigation of sunlight modulation using the recently introduced dual-cell liquid crystal shutter (DLS), examining both communication and illumination aspects. We propose a system featuring a glass window equipped with a large array of DLS, including configurable active and non-active communication cells. Our study begins by formulating channel models for DLS configurations in downlink communication based on experimental measurements and thorough analysis. We then derive the illumination expression resulting from the generalized contribution of active and non-active communication cells. Building on these models, we analyze the channel capacity bounds of the proposed communication system and formulate an optimization problem to maximize channel capacity while meeting the minimum indoor illumination constraint. Simulation results demonstrate the superior channel capacity of the DLS-based system compared to conventional light-emitting diode (LED) communication systems. Furthermore, by dynamically adjusting the number of active DLS cells in a multiple DLS system, we achieve high communication throughput for receivers at various locations. Our findings reveal that the discrepancy between our theoretical predictions and empirical findings underscores the potential for elevating the data rate from tens of kbps to tens of Mbps.