  Visible light communications (VLC) have recently attracted a growing interest
and can be a potential solution to realize indoor wireless communication with
high bandwidth capacity for RF-restricted environments such as airplanes and
hospitals. Optical based orthogonal frequency division multiplexing (OFDM)
systems have been proposed in the literature to combat multipath distortion and
intersymbol interference (ISI) caused by multipath signal propagation. In this
paper, we present a robust timing synchronization scheme suitable for
asymmetrically clipped (AC) OFDM based optical intensity modulated direct
detection (IM/DD) wireless systems. Our proposed method works perfectly for
ACO-OFDM, Pulse amplitude modulated discrete multitone (PAM-DMT) and discrete
Hartley transform (DHT) based optical OFDM systems. In contrast to existing
OFDM timing synchronization methods which are either not suitable for AC OFDM
techniques due to unipolar nature of output signal or perform poorly, our
proposed method is suitable for AC OFDM schemes and outperforms all other
available techniques. Both numerical and experimental results confirm the
accuracy of the proposed method. Our technique is also computationally
efficient as it requires very few computations as compared to conventional
methods in order to achieve good accuracy.
