Authors : Kyuntak Kim, Kyujin Lee and Kyesan Lee
Abstract: In order to simultaneously provide effective lighting and communication services, this study proposes an effective dimming coding scheme combined with a Direct Sequence Spread Spectrum (DSSS) technique in Visible Light Communication (VLC). In previous researches, Zero Reduction Code (ZRC) based on On-Off Keying (OOK) modulation were proposed for effective dimming control, and that achieved better Bit Error Rate (BER) performance and brightness than conventional dimming control scheme such as manchester and 8B/10B codes. However, there is a problem that the error probability was increased in decoding process because ZRC was also a kind of block codes. To solve this problem, the proposed ZRC coding scheme can reduce the input pattern of code sets to the encoder by using the DSSS technique. The DSSS technique uses the specific orthogonal codes, so, the spread chip sequence with a specific pattern can be inputted into the ZRC encoder. Based on this characteristic the number of decision regions can be decreased and that can be led to reduction of the error probability in decoding process. In addition, the proposed scheme can achieve the enhanced dimming level because the available ZRC sets are less restrictive than the conventional ZRC coding scheme. The experiment results indicate that the proposed scheme is able to improve the BER and dimming performance in comparison with the conventional ZRC coding scheme.
Kyuntak Kim, Kyujin Lee and Kyesan Lee, 2018. Improvement of Dimming and Transmission Efficiencies Based on Direct Sequence Spread Spectrum Scheme in Optical Wireless Communication. Journal of Engineering and Applied Sciences, 13: 2971-2977.