A New Class of DC-Free Run-Length Limited Codes

The conventional 4B6B run-length limited (RLL) code recommended by the IEEE 802.15.7 standard for visible light communication (VLC) is memory consuming as it must be stored at both the encoder and decoder; additionally, it can only be decoded through maximum likelihood (ML) decoding which is costly in terms of computational complexity. In this paper, a new class of structured DC-free RLL code without using lookup tables is proposed. A case study of the 4B6B code that achieves better error correction performance compared to the conventional 4B6B codes in a concatenated scheme, is investigated. Through simulations and analysis, it has been established that polar codes and convolutional codes concatenated with the proposed 4B6B code outperforms most existing schemes at high signal-to-noise ratio (SNR) in terms of bit-error rate (BER) and frame-error rate (FER). At a FER of $$10^{-4}$$ , the concatenated polar codes of length 128 with the proposed 4B6B code outperforms the same structure when using the traditional 4B6B code by 0.6 dB while maintaining the same complexity for encoding and decoding processes.