Post-Equalization Technique to Mitigate LED Nonlinearity in VLC Systems

A LMS-based adaptive post-equalizer O-OFDM system and an adaptive decision feedback post-equalizer (ADFE) O-OFDM system are proposed for mitigating LED nonlinear distortion in the VLC system. Compared with the traditional pre-equalization scheme, this scheme does not require additional physical circuits at the transmitter and only needs some computing resources at the receiver, which improves the cost efficiency of the system. Bit error rate (BER) is used as the performance evaluation index to analyze the improvement effect of the above equalizers on LED nonlinearity, and the influence of the number of taps of the equalizer on the equalization effect is also studied. The simulation results show that both post-equalizers can suppress LED nonlinearity, and the ADFE equalizer performs better than the LMS-based adaptive post-equalizer.