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A combining method of quasi-cyclic LDPC codes by the Chinese remainder theorem
Myung, Seho,Yang, Kyeongcheol IEEE 2005 IEEE communications letters Vol.9 No.9
In this paper we propose a method of constructing quasi-cyclic low-density parity-check (QC-LDPC) codes of large length by combining QC-LDPC codes of small length as their component codes, via the Chinese remainder theorem. The girth of the QC-LDPC codes obtained by the proposed method is always larger than or equal to that of each component code. By applying the method to array codes, we present a family of high-rate regular QC-LDPC codes with no 4-cycles. Simulation results show that they have almost the same performance as random regular LDPC codes.
Quasi-cyclic LDPC codes for fast encoding
Seho Myung,Kyeongcheol Yang,Jaeyoel Kim IEEE 2005 IEEE transactions on information theory Vol.51 No.8
<P>In this correspondence we present a special class of quasi-cyclic low-density parity-check (QC-LDPC) codes, called block-type LDPC (B-LDPC) codes, which have an efficient encoding algorithm due to the simple structure of their parity-check matrices. Since the parity-check matrix of a QC-LDPC code consists of circulant permutation matrices or the zero matrix, the required memory for storing it can be significantly reduced, as compared with randomly constructed LDPC codes. We show that the girth of a QC-LDPC code is upper-bounded by a certain number which is determined by the positions of circulant permutation matrices. The B-LDPC codes are constructed as irregular QC-LDPC codes with parity-check matrices of an almost lower triangular form so that they have an efficient encoding algorithm, good noise threshold, and low error floor. Their encoding complexity is linearly scaled regardless of the size of circulant permutation matrices.</P>
Offset and Normalized Min-Sum Algorithms for ATSC 3.0 LDPC Decoder
Myung, Seho,Park, Sung-Ik,Kim, Kyung-Joong,Lee, Jae-Young,Kwon, Sunhyoung,Kim, Jeongchang [Institute of Electrical and Electronics Engineers 2017 IEEE transactions on broadcasting Vol.63 No.4
<P>Offset min-sum algorithm (OMSA) and normalized min-sum algorithm (NMSA) are widely used in commercial LDPC decoders due to low complexity and reasonable performance. In this paper, we provide optimized offset and scaling values for those LDPC decoders based on Advanced Television Systems Committee (ATSC) 3.0 LDPC codes. Furthermore, according to extensive computer simulations, it is shown that the performance of the OMSA and NMSA with the obtained values is close to that of sum-product algorithm, even though the NMSA-based decoder may show a serious error floor due to a channel mismatch effect. Consequently, we recommend that the ATSC 3.0 transmitters use a concatenation of BCH outer code and LDPC inner code as channel coding, considering the use of NMSA for LDPC decoder in ATSC 3.0 receivers.</P>
Lifting methods for quasi-cyclic LDPC codes
Seho Myung,Kyeongcheol Yang,Youngkyun Kim IEEE 2006 IEEE COMMUNICATIONS LETTERS Vol.10 No.6
<P>In this paper, we present two simple methods to construct a quasi-cyclic LDPC (QC-LDPC) code of larger length by lifting a given QC-LDPC code. We show that its girth is always larger than or equal to that of the given QC-LDPC code. Applying the methods recursively, it is possible to construct a sequence of QC-LDPC codes generated from a single exponent matrix by proper floor or modulo operations. Simulation results show that they have no serious performance degradation, as compared with randomly constructed LDPC codes</P>
KSHV vPK inhibits Wnt signaling via preventing interactions between β-catenin and TCF4
Cha, Seho,Kang, Myung-Suk,Seo, Taegun Elsevier 2018 Biochemical and biophysical research communication Vol.497 No.1
<P><B>Abstract</B></P> <P>Viral factors interact with host cellular proteins, leading to dysregulation of signaling pathways. The Wnt pathway is known to participate in embryonic development and oncogenesis under dysregulation conditions. A downstream factor of the Wnt signaling pathway, β-catenin, activates T-cell factor (TCF)-dependent transcription, which contributes to cell proliferation and tumorigenesis. In this study, we demonstrated that viral protein kinase (vPK) encoded by Kaposi's sarcoma-associated herpesvirus inhibits the Wnt signaling pathway without affecting nuclear localization and expression of β-catenin. Coimmunoprecipitation and chromatin immunoprecipitation assays revealed that vPK interacts with β-catenin, reducing the binding affinity on TCF binding regions as well as interactions of β-catenin with TCF4. Overexpression of vPK led to reduced mRNA expression of cyclin D1, a well-known transcriptional product of Wnt signaling, suggesting that vPK effectively regulates the host signaling pathway through direct interactions with cellular proteins.</P> <P><B>Highlights</B></P> <P> <UL> <LI> vPK decreases LiCl-mediated activation of TCF-dependent transcription. </LI> <LI> vPK does not disrupt relocalization of β-catenin from the cytosol to nucleus. </LI> <LI> vPK disrupts interactions of β-catenin with the TCF4-binding region. </LI> <LI> vPK inhibits Wnt signaling via interactions with β-catenin. </LI> </UL> </P>
An Optimum Subcarrier and Bit Allocation Period Based on Mobile Speed for OFDM Systems
Kim, Seho,Kim, Hyung-Myung IEEE 2007 IEEE communications letters Vol.11 No.3
<P>A subcarrier and bit allocation period (SBAP) is proposed based on the mobile speed for OFDM systems. It is assumed that users have different SBAPs according to their mobile speeds. The overhead is considered while transmitting the subcarrier and bit assignment information (SBAI). The optimum SBAP of each user is determined such that the overall throughput including SBAI can be maximized. Simulation results show that the proposed scheme outperforms other schemes. It is also demonstrated that the proposed scheme is insensitive to an error in the estimation of mobile speeds</P>