Optimization of LED's SAHPs to simultaneously enhance SNR uniformity and support dimming control for visible light communication

In this paper, we propose a method to enhance signal to noise ratio (SNR) uniformity and simultaneously support dimming control via optimization of LEDs' semi-angle at half power (SAHP) for visible light communication (VLC) systems. The uniformity of SNR performance is analyzed. Subcarrier-4pulse position modulation (SC-4PPM) is employed to supply light brightness control. Performance evaluation demonstrates that the overall SNR variation can be managed within 0.5 dB and the lowest SNR can be improved by nearly 5 dB for different dimming factors. A linear dimming control model is presented for the modulation parameters under optimal conditions. Tolerance analysis shows that our method is robust against practical parameters deviations. Feasibility evaluations show that the optimization demonstrates better performance than the non-optimized situations, both in SNR value and its distribution for various LED powers, receiver FOVs (field of view), LED numbers and room dimensions.