Capacity Comparison of Single- and Multi-Carrier VLC With ISI and Peak Power Constraint

Due to device characteristics, visible light communication (VLC) usually suffers inter-symbol interference and limited amplitude. In this paper, we focus on the combined impact of these two factors on capacity. We provide a fair comparison between single-carrier (SC) and multi-carrier (MC) modulations by adding cyclic prefixes and performing frequency-domain equalization at the receiving end. For SC modulation, two capacity lower bounds are obtained using entropy power inequality and suboptimal discrete input distribution, while an asymptotical upper capacity bound is obtained by applying the dual expression of capacity. For MC modulation, the nonlinear distortion is approximated as signal attenuation plus signal-independent noise via the Bussgang theorem, thereby obtaining the MC capacity. Numerical results show that for typical vehicle-to-vehicle VLC with high signal-to-noise ratios, SC modulation can achieve a higher rate than MC modulation.