• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.1A
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• pp.34-42
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• 2012

Low density parity check (LDPC) code is widely used, since it shows superior performance close to Shannon limit and its decoding complexity is lower than turbo code. Recently, it is used as a channel code to decode Wyner-Ziv frames in distributed video coding (DVC) system. In this paper, we propose an efficient method to design the parity check matrix H of LDPC codes. In order to apply LDPC code to DVC system, the LDPC code should have rate compatibility. Thus, we also propose a method to merge check nodes of LDPC code to attain the rate compatibility. LDPC code is designed using ACE algorithm and check nodes are merged for a given code rate to maximize the error correction capability. The performance of the designed LDPC code is analyzed extensively by computer simulations.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.8 s.338
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• pp.1-10
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• 2005

In this paper, the explicit low density codes construction from the generalized permutation matrices related to algebra theory is investigated, and we design several Jacket inverse block matrices on the recursive formula and permutation matrices. The results show that the proposed scheme is a simple and fast way to obtain the low density codes, and we also Proved that the structured low density parity check (LDPC) codes, such as the $\pi-rotation$ LDPC codes are the low density Jacket inverse block matrices too.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.1C
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• pp.1-8
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• 2005

In this paper, we present a novel LDPC code construction called as semi-algebra low density parity check(LDPC) codes which is one kind of deterministic LDPC code based on dual-diagonal sub-matrix. The constructing method results in a class of high rate LDPC codes. Codes in this class have a large girth and good minimum distances. Furthermore, they can be implemented by simple parallel array architecture using cyclic shift register and perform well with the iterative decoding.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.10
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• pp.852-857
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• 2013

In this paper we propose a design algorithm for nonbinary LDPC (low-density parity-check) codes with low error-floors. The proposed algorithm determines the nonbinary values of the nonzero entries in the parity-check matrix in order to maximize the binary minimum distance of the designed nonbinary LDPC codes. We verify the performance of the designed nonbinary LDPC codes in the error-floor region by Monte Carlo simulation and importance sampling over BPSK (binary phase-shift keying) modulation.

• Proceedings of the KIEE Conference
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• 2006.07d
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• pp.2023-2024
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• 2006

1962년 Gallager에 의해 처음 제안된 LDPC 부호는 복호를 수행하는 부호방식으로 패리티 행렬(H)의 대부분이 0으로 구성되어 복호시에 적은 연산량을 요구하며, shannon의 한계에 도달하는 복호 능력으로, 차세대 통신의 주된 부호 방식으로 고려되고 있다. 하지만, LDPC는 부호화에 있어서 여타 다른 부호방식에 비해 복잡한 특성을 가지고 있으므로, 이를 개선하기 위한 부호방식의 적용이 필요하다. 본 논문에서는 효율 적인 부호화를 위하여 Dual-diagonal H parity행렬을 구성 하고, 쉽게 부호 길이를 확장 할 수 있는 Quasi-Cyclic 방식을 적용한 복호기를 구현하였다.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.2
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• pp.35-39
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• 2011

Error correcting codes with easy variability in code rate and codeword length in addition to powerful error correcting capability are required for present and future mobile multimedia communication systems. And low complexity is also needed for the compact mobile terminals. In general, the irregular random LDPC(low-density parity-check) code is known to have the superior performance among various LDPC codes. But it has inefficiency since the various parity check matrices for various services should be stored for encoding and decoding. The structured LDPC codes which can easily provide various rates and lengths are studied recently. Therefore, the flexibility, memory size, and error performance of various structured LDPC codes are compared and analyzed in this paper. And the most appropriate structured LDPC code is also suggested.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12C
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• pp.1143-1149
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• 2006

In this paper, the modified iterative decoding algorithm[8] by partitioning check nodes is applied to low-density parity-check(LDPC) codes in IEEE 802.16e standards, which gives us the improvement for convergence speed of decoding. Also, the new method of check node partitioning which is suitable for decoding of the LDPC codes in IEEE 802.16e system is proposed. The improvement of convergence speed in decoding reduces the number of iterations and thus the computational complexity of the decoder. The decoding method by partitioning check nodes can be applied to the LDPC codes whose decoder cannot be implemented in the fully parallel processing as an efficient sequential processing method. The modified iterative decoding method of LDPC codes using the proposed check node partitioning method can be used to implement the practical decoder in the wireless communication systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4C
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• pp.310-317
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• 2006

In this paper, we propose a new sequential message-passing decoding algorithm of low-density parity-check (LDPC) codes by partitioning check nodes. This new decoding algorithm shows better bit error rate(BER) performance than that of the conventional message-passing decoding algorithm, especially for small number of iterations. Analytical results tell us that as the number of partitioned subsets of check nodes increases, the BER performance becomes better. We also derive the recursive equations for mean values of messages at variable nodes by using density evolution with Gaussian approximation. Simulation results also confirm the analytical results.

• Smart Media Journal
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• v.2 no.2
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• pp.39-43
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• 2013

In this paper, we suggest a new technique for WPC parity-check matrix (H-matrix) generation and a corresponding decoding process. The key idea is to construct WPC H-matrix by using a convolutional encoder. It is easy to have many different coderates from a mother code with convolutional codes. However, it is difficult to have many different coderates with LDPC codes. Constructing LDPC Hmatrix based on a convolutional code can easily bring the advantage of convolutional codes to have different coderates. Moreover, both LDPC and convolutional decoding algorithms can be applied altogether in the decoding part. This process prevents the performance degradation of short-length WPC code.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.10C
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• pp.758-763
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• 2008

We introduce a noise-predictive turbo equalization using noise filter in perpendicular magnetic recording(PMR) channel. The noise filter mitigates the colored noise in high-density PMR channel. In this paper, the channel detectors used are SOVA (Soft Output Viterbi Algorithm) and BCJR algorithm which proposed by Bahl et al., and the outer decoder used is LDPC (Low Density Parity Check) code that is implemented by sum-product algorithm. Two kinds of LDPC codes are experimented. One is the 0.5Kbyte (4336,4096) LDPC code with the code rate of 0.94, and the other is 1Kbyte (8432,8192) LDPC code with the code rate of 0.97.