Effect of the Color Temperature of LED lighting on the sensing ability of Visible Light Communications

This paper studies the effect that the color temperature of an LED lamp has on the ability of a Visible Light Communication (VLC) system to detect different events, which could be the presence, position, and/or color of an object in the sensing area. The proposed VLC-based monitoring system takes advantage of the Channel State Information (CSI) that the VLC receiver estimates regularly for OFDM equalization, and makes use of K-means++ clustering to estimate the number of events that can be identified in the collected CSI data. The color temperature of the LED lighting is varied by changing the fraction of the total radiant flux emitted by Cool-White and Red-Orange LEDs, respectively, enabling to obtain a complete palette of white light that ranges from warm reddish (2600 K) to cool blueish (6200 K). The experimental evaluation is carried out with the aid of a software-defined VLC demonstrator, and shows that the sensing performance when using the reflected VLC signal to estimate the position of the object does not vary notably with the color temperature of the LED lamp. In contrast, the use of white light with high Color Rendering Index provides better results when the objective is to identify the color signature that different objects create when placed in the sensing area.