Resource-efficient channel estimation for DCO-OFDM based VLC systems

We consider a resource-efficient pilot design for visible light communication (VLC) system employing direct-current offset orthogonal frequency division multiplexing (DCO-OFDM). Firstly, we experimentally verify that the normalized channel gain vectors remain approximately the same at different locations under a line-of-sight (LOS) path between the transmitter and the receiver. Then, under the constant normalized subcarrier gain assumption, it is proved that a single pilot subcarrier is optimal to maximize the achievable rate without signal clipping. The impact of power budget and statistical channel characteristics is investigated regarding the optimal pilot position and the related achievable rate. We extend the pilot position optimization to a general case considering the light-emitting diode (LED) and power amplifier (PA) with a limited linear dynamic range. Assuming double-sided clipping, the impact of LED upper saturation voltage and statistical channel characteristics on the optimal pilot position and the achievable rate is investigated via the Bussgang theorem. Finally, under constant normalized link gain assumption, we propose a blind channel estimation approach based on the covariance of frequency-domain outputs. The convergence of the proposed channel estimation approaches based on constant normalized link gain is verified experimentally.