In this paper, we introduce a couple of hardware implementations of compact VLC transmitter and receiver for the first time. Compared with related works, our VLC transmitter is non-RLL one, that means flicker mitigation can be guaranteed even without RLL codes. In particular, we have utilized a centralized bit probability distribution of a prescrambler and a Polar encoder to create a non-RLL flicker mitigation solution. Moreover, at the receiver, a 3-bit soft-decision filter is proposed to analyze signals received from real VLC channel to extract log-likelihood ratio (LLR) values and feed them to the FEC decoder. Therefore, soft-decoding of Polar decoder can be implemented to improve the bit-error-rate (BER) performance of the VLC system. Finally, we introduce a novel very large scale integration (VLSI) architecture for the compact VLC transmitter and receiver; and synthesis our design under FPGA ASIC synthesis tools. Due to the non-RLL basic, our system has an evidently good code-rate and a reduced-complexity compared with other RLL-based receiver works. Also, we present FPGA and ASIC synthesis results of the proposed architecture with evaluations of power consumption, area, energy-per-bits and so on.
Table summarizes proposals related to FEC and flicker mitigation for VLC. The conventional solution is defined in the IEEE 802.15.7 standard, which employs Reed-Solomon (RS) codes, Convolutional Codes (CC) and RLL codes with hard-decoding of RLL codes (hard-RLL) @cite_8 . However, hard-RLL methods of inner RLL codes limit to hard-decoding of outer FEC codes @cite_8 @cite_10 @cite_5 ; consequently, the error-correction performance of the entire VLC system is restricted. Recently, soft-decoding RLL (soft-RLL) solutions have been proposed in @cite_7 @cite_3 @cite_2 @cite_1 . These techniques permit soft-decoding FEC algorithms to be applied to improve the bit-error-rate (BER) performance of the VLC system, but they also require heavy computational efforts, with many additions and multiplications.
@cite_7 @cite_8 @cite_1 @cite_3 @cite_2 @cite_5 @cite_10
2221939138 2105580634 2206502523 2742346654 2054470560
In this letter, we proposed a bit-level soft (BLS) run-length limited (RLL) decoding algorithm for visible light communication (VLC). Conventional RLL encoding is only used for dimming control, and the lack of effective RLL decoding is a long-standing issue in VLC systems. Therefore, an RLL decoding method that utilizes soft information from the channel to produce BLS output is proposed for enhancing the performance of the system. The BLS RLL decoder is conjugated with a Reed-Solomon decoder that can efficiently utilize bit-level information from RLL decoding output. The simulation results show that the bit error rate performance of our proposed RLL decoding provides a significant gain over that of the conventional RLL decoding and compares favorably with that of the referenced RLL decoding methods. Visible light communication refers to shortrange optical wireless communication using visible light spectrum from 380 to 780 nm. Enabled by recent advances in LED technology, IEEE 802.15.7 supports high-data-rate visible light communication up to 96 Mb s by fast modulation of optical light sources which may be dimmed during their operation. IEEE 802.15.7 provides dimming adaptable mechanisms for flicker-free high-data-rate visible light communication. In this letter, we propose a new decoding algorithm based on a soft-input soft-output run-length limited (RLL) decoder in visible light communication (VLC) with on–off keying (OOK) modulation and Reed–Solomon (RS) codes. Conventional RLL codes are used for dimming adjustments in VLC; however, in our receiver model, the posterior probability matrix 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. A significant advantage of our proposed method is that it leads to the enhancement of bit error rate (BER) and frame error rate (FER) performances without any change in the transmitter in VLC systems. The simulation results show that the majority of the BER and FER performances of our proposed method are better than those of hard-input hard-output RLL decoding and soft-input hard-output RLL decoding methods. In this letter, a new dimming control system with polar codes is proposed for visible light communication (VLC). The polar codes are concatenated with run-length limited codes and compensation symbols that can be used in VLC dimming control; moreover, puncturing is used to shorten the code length and improve coding efficiency. To compare the proposed system with the referenced systems, non-systematic and systematic polar codes are also considered. The simulation results show that our proposed system provides better performance than referenced systems, which use low-density parity-check codes or Reed–Solomon codes for dimming control. In this letter, we propose a new decoding algorithm based on a soft run-length limited (RLL) decoding in visible light communication (VLC) with on-off keying modulation and Reed-Solomon codes. Conventional RLL codes are used for dimming adjustments in VLC; however, in our receiver model, the proposed RLL decoder produces one or multiple candidates with greater probabilities to enhance the throughput in the VLC system. We also propose a selection method based on a cyclic redundancy check among multiple candidates. A significant advantage of our proposed method is that it leads to performance enhancement without any change in the transmitter in VLC systems. Simulation results show that the bit error rate of our proposed method is better than that of RLL hard decoding.