Generation of Perfectly DC Balanced Codes for Visible Light Communications

In visible light communications (VLC), direct current (DC) level balancing is important to maintain constant illumination while the LEDs are being used for communication. In this paper, given codeword length of $n$ bits, we provide a relationship between maximum possible input bits, $k$, and $n$ for a perfectly DC balanced $kb/nb$ code. We propose an algorithm to generate the code book of these perfectly DC balanced codes that avoid flickering and maintain consistency in the brightness. The performance of the proposed codes is compared with several existing codes in terms of code rate, Hamming distance, frame error rate (FER), and bit error rate (BER). The numerical results show that the proposed codes provide perfect DC balance and perform better in terms of minimum Hamming distance, FER, and BER without significant loss in code rate. Further, we derive a lower bound on average Hamming distance for the proposed perfectly DC balanced codes for VLC.