Energy-constrained slot-amplitude modulation with dimming support

This letter proposes a modulation scheme that combines both pulse slots and amplitudes in a flexible manner to obtain a desired level of flicker-free dimming while efficiently conveying information for visible light communication. The scheme is referred to as energy-constrained slot-amplitude modulation (ECSAM). Specifically, the total energy for every macro-symbol, containing multiple pulse slots, is fixed at a level that depends on the requested dimming target by adjusting the number of active slots and their amplitude levels. By allocating a fixed amount of energy for every marco-symbol, of a period smaller than the human eye's integrating time, ECSAM also ensures flicker-free data transmission for eye safety. The performance of ECSAM in terms of error rate and spectral efficiency is evaluated numerically. Measurement of the error rate, obtained from an experimental test-bed, is reported at distances ranging from 20 to 100 cm. Results show that ECSAM supports a continuous and wide range of dimming with high-spectral efficiency and low error rate compared with conventional techniques.