Novel Soft Decoding Algorithm of RLL Codes for Secure Physical-Layer Visible Light Communications

This paper considers a novel efficient soft run-length limited (RLL) decoding algorithm in visible light communication (VLC) for efficient secure data transmission. Security transmission over the VLC channel can be achieved by the means of physical-layer security techniques, however, low efficient transmission performance is long-standing issue in VLC. Conventional RLL codes are used for dimming adjustments in VLC, existed hard-input hard-output (HIHO) RLL decoding and soft-input hard-output (SIHO) RLL decoding satisfied some valuable soft information. We proposed soft RLL decoding is one of soft-input soft-output (SISO) RLL decoding. In our receiver model, the posteriori probability matrix which contains all symbol probabilities is produced by the new RLL decoder, and it can be matched as the input of the soft RS decoder to enhance the throughput in the VLC system. Simulation results show that the BER and FER performances of our proposed method are always better than those of HIHO RLL decoding algorithm and SIHO RLL decoding algorithm.