Synchronization of carrierless amplitude and phase modulation in visible light communication

Abstract

Carrierless amplitude and phase modulation (CAP) has been widely employed in visible light communication (VLC) as a result of its implementation simplicity. While the simplicity of CAP receiver results in the elimination of carrier recovery, it also leads to significant increase in CAP sensitivity to timing jitter. In this paper, a novel correlation-based synchronization algorithm whose synchronization sequence is obtained from the CAP pulse shaping filter has been proposed for a joint bit and frame synchronization at the CAP receiver. The proposed ‘CAP-filter’ synchronization sequence is particularly suitable for optical wireless communication. The performance of the ‘CAP-filter’ synchronization technique is evaluated with both theoretical and simulation analysis. It is shown that while a timing jitter of 0.15T results in failure of communication for unsynchronized CAP at a BER of 0.5, the proposed ‘CAP-filter’ algorithm achieved perfect synchronization with a BER performance matching that of CAP with no jitter. This performance is reported for both low and high constellation order and in all the SNR regimes considered. Finally, the viability of the ‘CAP-filter’ synchronization algorithm in VLC systems is demonstrated through laboratory experiment.