Modeling and compensating dynamic nonlinearities in LED photon-emission rates to enhance OWC

LEDs can be modulated at relatively high speeds to support wireless optical data communication (OWC). Yet, particularly LEDs optimized for illumination act as a non-linear low-pass communication channel. It has become clear in recent literature that their non-linearity and low-pass behavior cannot be seen as two separable, cascaded mechanisms. Although standard nonlinear equalizer schemes, e.g. based on Volterra Series, have been proposed and tested before, our recent research results show that a more dedicated approach in which we specifically analyze the hole-electron recombination mechanisms, yield a very effective and computationally-efficient compensation approach. In this manuscript, we will review the non-linear differential equations for photon emissions, its electrical equivalent circuit and a discrete-time variant with delays and non-linearities. This can be inverted, in the sense that we can actively eliminate or mitigate the non-linear dynamic LED distortion by adequate signal processing. We propose an aggressive simplification of the compensation circuit that allows us to use a relatively simple structure with only a couple of parameters.