Codes for DC Balance and Dimming Control in Visible Light Communications

Thummaluri, Uday Reddy and Natarajan, Lakshmi Prasad (2018) Codes for DC Balance and Dimming Control in Visible Light Communications. Masters thesis, Indian Institute of Technology Hyderabad.

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In visible light communications (VLC), direct current (DC) level balancing is important to maintain constant illumination while the light emitting diodes are being used for communication. In this thesis, perfectly DC balanced codes which have equal number of zeros and ones in all their codewords are proposed. 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 codebook of these perfectly DC balanced codes that avoid ickering 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 than existing codes in terms of minimum Hamming distance, FER, and BER without signi�cant loss in code rate. We also derive a lower bound on average Hamming distance for the proposed perfectly DC balanced codes for VLC. In VLC, dimming control is required to maintain desired ambiance. For dimming control, addition of compensation symbols (CS) at the end of the runlength limited (RLL) codes has been proposed in the literature. In this thesis, we propose novel RLL codes for VLC that utilize these CS to improve the BER performance in addition to providing dimming control. For various dimming factors, we compare the BER performance and mutual information of the proposed and existing codes to show that the proposed codes result in improved performance. A brief discussion on high rate codes for VLC is also presented.

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IITH Creators:
IITH CreatorsORCiD
Natarajan, Lakshmi Prasad
Item Type: Thesis (Masters)
Uncontrolled Keywords: Visible Light Communication, DC Balance, Diming Control, Hamming Distance, Mutual Information
Subjects: Electrical Engineering
Divisions: Department of Electrical Engineering
Depositing User: Team Library
Date Deposited: 03 Jul 2018 04:42
Last Modified: 22 May 2019 07:08
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