A Novel Hybrid Dimming Control Scheme for Visible Light Communications

A dimming control scheme that combines analog dimming and spatial dimming is proposed. The basic idea of the combined scheme is that both the direct current bias level of each individual light-emitting diode (LED) and the number of glared LEDs are simultaneously adjusted to achieve a required dimming level. Besides, we design a space constellation to transmit additional information in spatial domain without compromising uniform illumination constraint, and this essentially improves the performance of the system. A maximum-a-posteriori probability estimator is also designed to estimate the received time domain and spatial domain signals. Since two degree of freedoms are simultaneously exploited for dimming control, the proposed scheme outperforms conventional dimming schemes, which only focus on signal domain design, and this is verified by simulation results. To the best of authors' knowledge, this is the first design that effectively utilizes multidomain resources to achieve dimming control for visible light communications.