ZTE

ZTE Communications ›› 2016, Vol. 14 ›› Issue (2): 41-46.DOI: 10.3969/j.issn.1673-5188.2016.02.005

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LDPC Decoding for Signal Dependent Visible Light Communication Channels

YUAN Ming, SHA Xiaoshi, LIANG Xiao, JIANG Ming, WANG Jiaheng, ZHAO Chunming   

  1. National Mobile Communications Research Laboratory, Southeast University, Nanjing, 211189, China
  • Received:2015-11-17 Online:2016-04-01 Published:2019-11-27
  • About author:YUAN Ming (yuanming@seu.edu.cn) received his BE degree in electrical engineering from Southeast University, China in 2013. He is currently working toward an MS degree at the School of Information Science and Engineering, National Mobile Communications Research Laboratory (NCRL), Southeast University. His research interests include signal processing and visible light communications.
    SHA Xiaoshi (xiaoshisha@seu.edu.cn) received his BSc degree in information science from Southeast University in 2014 and is currently working toward an MS degree at NCRL, Southeast University. His research interests include channel coding and high throughput LDPC encoder and decoder implementation.
    LIANG Xiao (xiaoliang@seu.edu.cn) received his BSc, MS, and PhD degrees in communication and information engineering in 2000, 2005, and 2013, respectively, all from Southeast University. He is a lecturer with NCRL , Southeast University. His research interest is signal processing for communications and wireless networking.
    JIANG Ming (jiang_ming@seu.edu.cn) received his BSc, MS, and PhD degrees in communication and information engineering in 1998, 2003, and 2007, respectively, all from Southeast University. He is an associate professor with NCRL, Southeast University. His research interest is channel coding for wireless communications.
    WANG Jiaheng (jhwang@seu.edu.cn) received his BE and MS degrees from Southeast University in 2001 and 2006, respectively, and the PhD degree in electrical engineering from the Hong Kong University of Science and Technology, China in 2010. He is an associate professor with NCRL, Southeast University. From 2010 to 2011, he was with the Signal Processing Laboratory, ACCESS Linnaeus Center, KTH Royal Institute of Technology, Stockholm, Sweden. He also held visiting positions at the Friedrich- Alexander University Erlangen-Nürnberg, Nürnberg, Germany, and the University of Macau, China. His research interests mainly include optimization in signal processing, communication systems, and wireless networks. Dr. Wang serves as an associate editor for IEEE Signal Processing Letters. He is a recipient of the Humboldt Fellowship for Experienced Researchers, and a recipient of the Best Paper Award in WCSP 2014.
    ZHAO Chunming (cmzhao@seu.edu.cn) received his BS and MS degrees from Nanjing Institute of Posts and Telecommunications, China in 1982 and 1984, respectively. In 1993, he received the PhD degree from the Department of Electrical and Electronic Engineering, University of Kaiserslautern, Germany. He is a professor and vice director at NCRL, Southeast University. He has managed several key projects of Chinese Communications High Tech. Program. His research interests include communication theory, coding/decoding, mobile communications, and VLSI design. Dr. Zhao won the First Prize of National Technique Invention of China in 2011. He was awarded“Excellent Researcher”from the Ministry of Science and Technology, China.
  • Supported by:
    “973”project(2013CB329204); the National Natural Science Foundation of China(61223001, 61461136003, and 61571118)

LDPC Decoding for Signal Dependent Visible Light Communication Channels

YUAN Ming, SHA Xiaoshi, LIANG Xiao, JIANG Ming, WANG Jiaheng, ZHAO Chunming   

  1. National Mobile Communications Research Laboratory, Southeast University, Nanjing, 211189, China
  • 作者简介:YUAN Ming (yuanming@seu.edu.cn) received his BE degree in electrical engineering from Southeast University, China in 2013. He is currently working toward an MS degree at the School of Information Science and Engineering, National Mobile Communications Research Laboratory (NCRL), Southeast University. His research interests include signal processing and visible light communications.
    SHA Xiaoshi (xiaoshisha@seu.edu.cn) received his BSc degree in information science from Southeast University in 2014 and is currently working toward an MS degree at NCRL, Southeast University. His research interests include channel coding and high throughput LDPC encoder and decoder implementation.
    LIANG Xiao (xiaoliang@seu.edu.cn) received his BSc, MS, and PhD degrees in communication and information engineering in 2000, 2005, and 2013, respectively, all from Southeast University. He is a lecturer with NCRL , Southeast University. His research interest is signal processing for communications and wireless networking.
    JIANG Ming (jiang_ming@seu.edu.cn) received his BSc, MS, and PhD degrees in communication and information engineering in 1998, 2003, and 2007, respectively, all from Southeast University. He is an associate professor with NCRL, Southeast University. His research interest is channel coding for wireless communications.
    WANG Jiaheng (jhwang@seu.edu.cn) received his BE and MS degrees from Southeast University in 2001 and 2006, respectively, and the PhD degree in electrical engineering from the Hong Kong University of Science and Technology, China in 2010. He is an associate professor with NCRL, Southeast University. From 2010 to 2011, he was with the Signal Processing Laboratory, ACCESS Linnaeus Center, KTH Royal Institute of Technology, Stockholm, Sweden. He also held visiting positions at the Friedrich- Alexander University Erlangen-Nürnberg, Nürnberg, Germany, and the University of Macau, China. His research interests mainly include optimization in signal processing, communication systems, and wireless networks. Dr. Wang serves as an associate editor for IEEE Signal Processing Letters. He is a recipient of the Humboldt Fellowship for Experienced Researchers, and a recipient of the Best Paper Award in WCSP 2014.
    ZHAO Chunming (cmzhao@seu.edu.cn) received his BS and MS degrees from Nanjing Institute of Posts and Telecommunications, China in 1982 and 1984, respectively. In 1993, he received the PhD degree from the Department of Electrical and Electronic Engineering, University of Kaiserslautern, Germany. He is a professor and vice director at NCRL, Southeast University. He has managed several key projects of Chinese Communications High Tech. Program. His research interests include communication theory, coding/decoding, mobile communications, and VLSI design. Dr. Zhao won the First Prize of National Technique Invention of China in 2011. He was awarded“Excellent Researcher”from the Ministry of Science and Technology, China.
  • 基金资助:
    “973”project(2013CB329204); the National Natural Science Foundation of China(61223001, 61461136003, and 61571118)

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Abstract: Avalanche photodiodes (APD) are widely employed in visible light communication (VLC) systems. The general signal dependent Gaussian channel is investigated. Experiment results reveal that symbols on different constellation points under official illuminance inevitably suffer from different levels of noise due to the multiplication process of APDs. In such a case, conventional log likely-hood ratio (LLR) calculation for signal independent channels may cause performance loss. The optimal LLR calculation for decoder is then derived because of the existence of non-ignorable APD shot noise. To find the decoding thresholds of the optimal and suboptimal detection schemes, the extrinsic information transfer (EXIT) chat is further analyzed. Finally a modified minimum sum algorithm is suggested with reduced complexity and acceptable performance loss. Numerical simulations show that, with a regular (3, 6) low-density parity check (LDPC) code of block length 20,000, 0.7 dB gain is achieved with our proposed scheme over the LDPC decoder designed for signal independent noise. It is also found that the coding performance is improved for a larger modulation depth.

Key words: VLC, APD, shot noise, LDPC code

摘要： Avalanche photodiodes (APD) are widely employed in visible light communication (VLC) systems. The general signal dependent Gaussian channel is investigated. Experiment results reveal that symbols on different constellation points under official illuminance inevitably suffer from different levels of noise due to the multiplication process of APDs. In such a case, conventional log likely-hood ratio (LLR) calculation for signal independent channels may cause performance loss. The optimal LLR calculation for decoder is then derived because of the existence of non-ignorable APD shot noise. To find the decoding thresholds of the optimal and suboptimal detection schemes, the extrinsic information transfer (EXIT) chat is further analyzed. Finally a modified minimum sum algorithm is suggested with reduced complexity and acceptable performance loss. Numerical simulations show that, with a regular (3, 6) low-density parity check (LDPC) code of block length 20,000, 0.7 dB gain is achieved with our proposed scheme over the LDPC decoder designed for signal independent noise. It is also found that the coding performance is improved for a larger modulation depth.

关键词: VLC, APD, shot noise, LDPC code