A novel scheme for demodulation of ACO-OFDM in the presence of DC offset

Asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) has become one of the most promising technologies for high speed optical wireless communications (OWCs). However, as a key challenge, improving the demodulation performance of ACO-OFDM in practical systems has not been well addressed. Most established demodulation schemes suffer from performance degradation either due to discarding of even sub-carriers or interference of direct current (DC) offset, which is one of the most common impairments in practical OWC systems. Up to our awareness, there was only one established scheme (Dissanayake and Armstrong, 2011 [1]) that addressed ACO-OFDM demodulation in the presence of DC offset, but it requires relatively high computation efforts. To deal with the challenge, we propose a novel demodulation scheme for ACO-OFDM in this paper. By making use of the virtual clean window (VCW), we develop methods to estimate and eliminate DC offset, so that the even sub-carriers of ACO-OFDM can be explored to improve demodulation performance even in the presence of DC offset. Compared with the scheme presented in (Dissanayake and Armstrong 2011 [1]), the proposed scheme significantly reduces processing complexity. Simulation results are given to demonstrate the performance of the proposed scheme.