Semi-blind Channel Estimation for DCO-OFDM VLC Systems

In this paper, we propose a closed form (CF) based channel estimation approach for direct current biased optical-orthogonal frequency division multiplexing (DCO-OFDM) visible light communication (VLC) systems. This is the first work to utilize light emitting diode (LED)'s limited bandwidth to reduce the number of pilots while maintaining good performance. A comb-type pilot pattern is employed, requiring a small number of pilots on few DCO-OFDM subcarriers and blocks. It is high spectral efficiency, as a large number of pilots on all subcarriers and some blocks are not required as in a block-type pilot pattern. The proposed CF approach performs the line-of-sight (LoS) channel estimation and LED's limited bandwidth estimation in a CF via two formulated functions on two subcarriers. Simulation results show that the proposed CF approach provides bit error ratio (BER) and mean square error (MSE) performances better than the block-type pilot based methods in the literature, requiring less pilots.