Achievable rate analysis for post- and pre-equalization in DCO-OFDM VLC with limited dynamic range

Abstract In visible light communication (VLC) that uses direct-current-biased optical orthogonal frequency division multiplexing (DCO-OFDM), the channel equalization can be done by dividing the channel gain of each subcarrier either at the receiver or the transmitter, termed as post- and pre-equalization, respectively. This paper aims to analyze the achievable rates of post- and pre-equalization in DCO-OFDM VLC. First, we theoretically reveal that the achievable rate of pre-equalization is greater than or equal to that of post-equalization within the same dynamic range, and the equality holds if and only if the VLC channel is flat. Then, we obtain the gap of achievable rate between post- and pre-equalization, which interestingly obeys the form of Kullback-Liebler (KL) divergence. We discuss the influence of the 3-dB bandwidth of VLC channel on the gap, and obtain the asymptotic gap as the signal-to-noise ratio (SNR) tends to infinity. Finally, the correctness of the theoretical results is verified via numerical simulations. In addition, experimental measurements are conducted in our actual VLC platform to further verify the theoretical results. The measurement results approximately match with the simulation results.