Spectral Efficient and High Performance LiFi Color Dimming

This paper presents a color dimming (CD) method for Light Fidelity (LiFi), enabling the ability to change the color of a light-emitting-diode (LED) and adjust the brightness of the light. The proposed CD scheme targets both high spectral efficiency and high signal-to-noise ratio (SNR). In order to achieve a high spectral efficiency, a superposition modulation scheme called augmented spectral efficiency discrete multi-tone (ASE-DMT) is used with multi-layer modulation and iterative detection. In order to achieve a high SNR, different modulation layers of ASE-DMT are loaded onto different LEDs. This is called a multi-layer multi-output modulation (MLMO) scheme. The proposed MLMO scheme supports single photodiode (PD) demodulation, thus reducing the receiver complexity. Results show that red/green/blue channels can adjust their brightness levels independently within a brightness range of 16\% to 84\% to produce a mixed color. Within the operating color plane, the proposed MLMO ASE-DMT provides a consistently high SNR of up to 33~dB, which is 8.3~dB higher than the typical ASE-DMT with multi-layer single-output modulation (MLSO).
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