A channel estimation scheme for HACO-OFDM system-based visible light communications

For the first time, a channel estimation method for hybrid ACO-OFDM (HACO-OFDM) based visible light communications systems is proposed. The channel characteristics carried on the ACO-OFDM subcarriers are estimated by the least square (LS) method, and the channel response on the PAM-DMT subcarriers can be obtained by linear interpolation of which on the ACO-OFDM subcarriers. While considering the multipath channel in the paper, the simulation results show that the proposed scheme is able to estimate the channel effectively for HACOOFDM system. After equalization based on the results of the channel estimation, the average BER on the ACOOFDM branch will be lower than10^-3 when SNR>18.2dB, the average BER on the pulse-amplitude-modulated discrete multitone (PAM-DMT) branch will be lower than 10^-3 when SNR>19.4dB.