Energy Efficiency of Visual Light Communications

Visible Light Communication (VLC) utilizes lighting technology based on Light Emitting Diodes (LEDs) to provide high-speed and low-cost wireless communications. The unlicensed spectrum of visible light allows high rate VLC to achieve high performance and flexibility. Moreover, VLC can offer new functionalities beyond simple illumination, such as intelligent sensing and control, adaptive ambient atmosphere rending and building management.

VLC is supposed not to significantly jeopardize the power efficiency of LED illumination. We study the popular buck converters as LED driver and we assume that this circuit also takes care of dimming.

PhD student Deng Xiong and Jean-Paul Linnartz studied amplitude modulation of a Manchester encoded signal. As can be seen from efficiency modeling of the circuit for implementing the full-depth (on-off) modulation provided, VLC can obtain a decent BER performance but at the cost of severe efficiency penalty.

In particular it relevant to achieve with VLC the same state of art efficiencies of switched mode power supplies (SMPSs) used in LED lamps without data communication. By adapting the SMPS to operate at two illumination levels, we can create VLC with high power efficiency.

Our paper [*] analyzes the BER for Manchester encoded amplitude modulation. We introduce the modulation index that describes the difference between the high and low illumination levels. Hence, besides the duty cycle, this paper studies not only modulation-index-related current fluctuations but also time-dependent (Poisson) noise, the variance of which fluctuates with the received amount of light. Moreover, it models two buck converter circuits, which we refer to as slow modulation and binary shunting.

[*] Performance Comparison for Illumination and Visible Light Communication System using Buck Converters, Xiong Deng, Yan Wu, Kumar Arulandu†, Guofu Zhou, Jean-Paul M. G. Linnartz