• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.7
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• pp.1-8
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• 2008

Low Density Parity Check codes(LDPC) are recently focused on communication systems due to its good performance. The standard of WiBro has also included LDPC codes as a channel coding. The weak point of implementation for LDPC encoder is that conventional binary Matrix Vector Multiplier has many clock cycles which limit throughput. In this paper, we propose semi-parallel architecture by using cyclic shift registers and exclusive-OR without conventional Matrix Vector Multipliers over the standard parity check matrices with Circulant Permutation Matrices(CPM). Furthermore, multi-rate encoder is designed by using proposed architecture. Our encoder with multi-rate for IEEE 802.16e LDPC has lower clock cycles and higher throughput.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.5C
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• pp.532-538
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• 2003

In this paper we have investigated a novel approach applying low-density parity-check coding to a COFDM-CDMA system, which operates in a multi-path fading mobile channel. Developed as a linear-block channel coder, the LDPC code is known for a superior signal reception capability in AWGN and/or flat fading channels with respect to increased encoding rates, however, its performance degrades when the communication channel becomes multi-path fading. For a typical multi-path fading mobile channel with a SNR of 16㏈ or lower. in order to obtain a BER lower than 1 out of 10000, the LDPC code with encoding rates below 1:3 requires not only the inherent parity check information but also the piloting information for refreshing front-end equalizer taps of COFDM-CDMA, periodically. For instance, while the 1:3-rate LDPC coded transmission symbol is consisted of data bits and parity-check bits in 1 to 3 proportion, on the other hand, in the proposed method the same rate LDPC transmission symbol contains data bits, parity check bits, and pilot bits in 1 to 2 to 1 proportion, respectively. The included pilot bits are effective not only for channel estimation and channel equalization but for symbol decoding by assisting the parity-check bits, hence, improving SNR vs BER performance over the conventional 1:3-rate LDPC code. The proposed system performance has been verified using computer simulations in multi-path, Rayleigh fading channels, and the results show us that the proposed method out-performs the general LDPC channel coding methods in terms of SNR vs BER measurements.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.4
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• pp.659-665
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• 2015

Recent studies on network coding scheme for increasing transmission efficiency of the network has been actively conducted. In this paper, we apply RLNC in sub-packet unit and propose a joint scheme of sub-packet level network coding and LDPC code. The proposed method can have similar ability of network coding and obtain further error correction capability. The simulation results show that the proposed one enhances error correction capability compared to the case using only LDPC when extra packets are received.

• Journal of Convergence Society for SMB
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• v.6 no.4
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• pp.99-106
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• 2016

In this paper, we propose an adaptive FEC scheme in visible light communication using white LED. To this end, we investigate the red, green and blue mixing ratio of white LED in order to achieve the white color, and the mixing ratio of those wavelength can be defined as 4 types. Based on those properties, the FEC technique is applied to the wavelength band with the lowest mixing ratio according to mixing ratio types. At that point, we use a LDPC channel coding scheme as the FEC technique. Therefore, the proposed system can mitigate the reduction of data rate and improve total BER performance.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.9 s.351
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• pp.31-37
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• 2006

Low-density parity-check (LDPC) codes are recently emerged due to its excellent performance. The standard for European high definition satellite digital video broadcast, DVB-S2 has adopted LDPC codes as a channel coding scheme. This paper proposes a DVB-S2 LDPC decoder architecture using a hybrid parity check matrix which is efficient in hardware implementation for both decoders and encoders. The hybrid H-matrices are constructed so that both the semi-random technique and the partly parallel structure can be applied to design encoders and decoders. Using the hybrid H-matrix scheme, the architecture of LDPC decoder for DVB-S2 can be very practical and efficient. In addition, we show a new Variable Node processor Unit (VNU) architecture to reuse the VNU for various code rates and optimized block memory placement to reuse. We design a DVB-S2 LDPC decoder of code rate 1/2 usng the proposed architecture. We estimate the performance of the DVB-S2 LDPC decoder and compare it with other decoders.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.12
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• pp.2791-2797
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• 2010

In recent years, the goal of providing high speed wireless data services has generated a great amount of interest among the research community. Several researchers have shown that the capacity of the system, in the presence of flat Rayleigh fading, improves significantly with the use of combined MIMO and LDPC. To feed the soft values to LDPC decoder, the soft values must be calculated from multiple transmitter and receiver antennas in Rayleigh fading channel. It requires high computational complexity to get the soft symbols by increasing number of transmitter and receiver antennas. Therefore, this thesis proposed on effective algorithm for calculation of soft values from multiple antennas based on LLR. As result, This thesis shows that maximum 61% of computational complexity is reduced with a little loss of performance.

• 전자공학회논문지 IE
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• v.43 no.4
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• pp.115-121
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• 2006

In this paper, we proposed about data error check and correction on channel transmission in the communication system. LDPC codes are used for minimizing channel errors by modeling AWGN Channel as a VDSL system. Because LDPC Codes use low density parity bit, mathematical complexity is low and relating processing time becomes shorten. Also the performance of LDPC code is better than that of turbo code in long code word on iterative decoding algorithm. This algorithm is better than conventional algorithms to correct errors, the proposed algorithm assigns weights for errors concerning parity bits. The proposed weighted Bit-flipping algorithm is better than the conventional Bit-flipping algorithm and we are recognized improve gain rate of 1 dB.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.6
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• pp.42-47
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• 2008

In this article a novel constant amplitude precoding for impulse UWB system is proposed. According to IEEE 802.15.4a, impulse UWB can be used in indoor localization and sensor data transmission. Most USN(ubiquitous sensor networks) needs multiple access. However impulse UWB system has a limited capability to detect superpositioned signal induced by multiple access. To overcome this problem we have adopted the concept of CAMC(Constant Amplitude Multi-Code) deviced by Wada and Kim. The proposed system consists of systematic constant amplitude precoding and LDPC decoding. And this system shows a good BER performance in computer simulation.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.2271-2272
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• 2008

Recently, LDPC codes received a lot of attention in 4G. LDPC codes perform good error correction at high SNR. But LDPC codes are complex design and not good at low SNR. At low SNR, convolution codes and turbo codes show more good performance than LDPC codes. The main subject presented in this study is that parallel encoding and decoding according to SNR. The system chooses convolution codes at low SNR and chooses LDPC codes at high SNR.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5A
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• pp.436-444
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• 2005

Unitary matrix modulation (UMM) is investigated in multiple antennas system that is called unitary space-time modulation (USTM). In an OFDM, the diagonal components of UMM with splitting over the coherence bandwidth (UMM-S/OFDM) have been proposed. Recently LDPC code is strongly attended and studied due to simple decoding property with good error correction property. In this paper, we propose LDPC coded UMM-S/OFDM for increasing the system performance. Our proposed system can obtain frequency diversity using UMM-S/OFDM like USTM/OFDM, and large coding gain using LDPC code. The superior characteristics of the proposed UMM-S/OFDM are demonstrated by extensive computer simulations in multi-path Rayleigh fading channel.