Should Analogue Pre-Equalisers be Avoided in VLC Systems?

Visible light communication (VLC) systems are highly constrained by the limited 3-dB bandwidth of light-emitting diodes (LEDs). Analogue pre-equalisers have been proposed to extend the LED's bandwidth at the cost of reduced signal-to-noise ratio (SNR). Compared with the pre-equaliser, the multi-carrier modulation with bit-loading can efficiently use the spectrum beyond the LED's raw 3-dB bandwidth without incuring SNR penalties by employing multiple narrow quasi-flat sub-bands to eliminate the need for equalisation. In this work we show by means of theoretical and experimental investigation that VLC with multi-band carrierless amplitude and phase modulation with bit-loading can outperform VLC with analogue pre-equalisers.