LED Modelling for Efficient LiFi Modulator Design to Accelerate OOK

This paper studies the response of a Light Emitting Diode (LED) to a stepwise change of the power delivered by a current or voltage supply. This study contributes to the design of efficient electronic circuits to generate On-Off Keying modulation for optical wireless communication using LEDs as an emitter. We combine the Shockley diode equation with the ABC model for electron-hole recombination to propose a new model for rise and fall curves. The fall curve differs for an open or shunted LED, as in the latter case, the carriers (electrons and holes) are pulled out of the LED junction. We quantify these effects and exploit this difference to propose a tristate optimized modulator circuit, which is highly power efficient. In this design, we allow modulating currents to be switched a bit earlier or later than then the bit transition itself.