7,668 research outputs found
Stopping Set Distributions of Some Linear Codes
Stopping sets and stopping set distribution of an low-density parity-check
code are used to determine the performance of this code under iterative
decoding over a binary erasure channel (BEC). Let be a binary
linear code with parity-check matrix , where the rows of may be
dependent. A stopping set of with parity-check matrix is a subset
of column indices of such that the restriction of to does not
contain a row of weight one. The stopping set distribution
enumerates the number of stopping sets with size of with parity-check
matrix . Note that stopping sets and stopping set distribution are related
to the parity-check matrix of . Let be the parity-check matrix
of which is formed by all the non-zero codewords of its dual code
. A parity-check matrix is called BEC-optimal if
and has the smallest number of rows. On the
BEC, iterative decoder of with BEC-optimal parity-check matrix is an
optimal decoder with much lower decoding complexity than the exhaustive
decoder. In this paper, we study stopping sets, stopping set distributions and
BEC-optimal parity-check matrices of binary linear codes. Using finite geometry
in combinatorics, we obtain BEC-optimal parity-check matrices and then
determine the stopping set distributions for the Simplex codes, the Hamming
codes, the first order Reed-Muller codes and the extended Hamming codes.Comment: 33 pages, submitted to IEEE Trans. Inform. Theory, Feb. 201
Permutation Decoding and the Stopping Redundancy Hierarchy of Cyclic and Extended Cyclic Codes
We introduce the notion of the stopping redundancy hierarchy of a linear
block code as a measure of the trade-off between performance and complexity of
iterative decoding for the binary erasure channel. We derive lower and upper
bounds for the stopping redundancy hierarchy via Lovasz's Local Lemma and
Bonferroni-type inequalities, and specialize them for codes with cyclic
parity-check matrices. Based on the observed properties of parity-check
matrices with good stopping redundancy characteristics, we develop a novel
decoding technique, termed automorphism group decoding, that combines iterative
message passing and permutation decoding. We also present bounds on the
smallest number of permutations of an automorphism group decoder needed to
correct any set of erasures up to a prescribed size. Simulation results
demonstrate that for a large number of algebraic codes, the performance of the
new decoding method is close to that of maximum likelihood decoding.Comment: 40 pages, 6 figures, 10 tables, submitted to IEEE Transactions on
Information Theor
Distance Properties of Short LDPC Codes and their Impact on the BP, ML and Near-ML Decoding Performance
Parameters of LDPC codes, such as minimum distance, stopping distance,
stopping redundancy, girth of the Tanner graph, and their influence on the
frame error rate performance of the BP, ML and near-ML decoding over a BEC and
an AWGN channel are studied. Both random and structured LDPC codes are
considered. In particular, the BP decoding is applied to the code parity-check
matrices with an increasing number of redundant rows, and the convergence of
the performance to that of the ML decoding is analyzed. A comparison of the
simulated BP, ML, and near-ML performance with the improved theoretical bounds
on the error probability based on the exact weight spectrum coefficients and
the exact stopping size spectrum coefficients is presented. It is observed that
decoding performance very close to the ML decoding performance can be achieved
with a relatively small number of redundant rows for some codes, for both the
BEC and the AWGN channels
Doped Fountain Coding for Minimum Delay Data Collection in Circular Networks
This paper studies decentralized, Fountain and network-coding based
strategies for facilitating data collection in circular wireless sensor
networks, which rely on the stochastic diversity of data storage. The goal is
to allow for a reduced delay collection by a data collector who accesses the
network at a random position and random time. Data dissemination is performed
by a set of relays which form a circular route to exchange source packets. The
storage nodes within the transmission range of the route's relays linearly
combine and store overheard relay transmissions using random decentralized
strategies. An intelligent data collector first collects a minimum set of coded
packets from a subset of storage nodes in its proximity, which might be
sufficient for recovering the original packets and, by using a message-passing
decoder, attempts recovering all original source packets from this set.
Whenever the decoder stalls, the source packet which restarts decoding is
polled/doped from its original source node. The random-walk-based analysis of
the decoding/doping process furnishes the collection delay analysis with a
prediction on the number of required doped packets. The number of doped packets
can be surprisingly small when employed with an Ideal Soliton code degree
distribution and, hence, the doping strategy may have the least collection
delay when the density of source nodes is sufficiently large. Furthermore, we
demonstrate that network coding makes dissemination more efficient at the
expense of a larger collection delay. Not surprisingly, a circular network
allows for a significantly more (analytically and otherwise) tractable
strategies relative to a network whose model is a random geometric graph
์๋ก์ด ์์ค ์ฑ๋์ ์ํ ์๊ธฐ๋ํ ๊ตฐ ๋ณตํธ๊ธฐ ๋ฐ ๋ถ๋ถ ์ ์ ๋ณต๊ตฌ ๋ถํธ ๋ฐ ์ผ๋ฐํ๋ ๊ทผ ํ๋กํ ๊ทธ๋ํ LDPC ๋ถํธ์ ์ค๊ณ
ํ์๋
ผ๋ฌธ (๋ฐ์ฌ)-- ์์ธ๋ํ๊ต ๋ํ์ : ๊ณต๊ณผ๋ํ ์ ๊ธฐยท์ปดํจํฐ๊ณตํ๋ถ, 2019. 2. ๋
ธ์ข
์ .In this dissertation, three main contributions are given asi) new two-stage automorphism group decoders (AGD) for cyclic codes in the erasure channel, ii) new constructions of binary and ternary locally repairable codes (LRCs) using cyclic codes and existing LRCs, and iii) new constructions of high-rate generalized root protograph (GRP) low-density parity-check (LDPC) codes for a nonergodic block interference and partially regular (PR) LDPC codes for follower noise jamming (FNJ), are considered.
First, I propose a new two-stage AGD (TS-AGD) for cyclic codes in the erasure channel.
Recently, error correcting codes in the erasure channel have drawn great attention for various applications such as distributed storage systems and wireless sensor networks, but many of their decoding algorithms are not practical because they have higher decoding complexity and longer delay. Thus, the AGD for cyclic codes in the erasure channel was introduced, which has good erasure decoding performance with low decoding complexity. In this research, I propose new TS-AGDs for cyclic codes in the erasure channel by modifying the parity check matrix and introducing the preprocessing stage to the AGD scheme. The proposed TS-AGD is analyzed for the perfect codes, BCH codes, and maximum distance separable (MDS) codes. Through numerical analysis, it is shown that the proposed decoding algorithm has good erasure decoding performance with lower decoding complexity than the conventional AGD. For some cyclic codes, it is shown that the proposed TS-AGD achieves the perfect decoding in the erasure channel, that is, the same decoding performance as the maximum likelihood (ML) decoder. For MDS codes, TS-AGDs with the expanded parity check matrix and the submatrix inversion are also proposed and analyzed.
Second, I propose new constructions of binary and ternary LRCs using cyclic codes and existing two LRCs for distributed storage system. For a primitive work, new constructions of binary and ternary LRCs using cyclic codes and their concatenation are proposed. Some of proposed binary LRCs with Hamming weights 4, 5, and 6 are optimal in terms of the upper bounds. In addition, the similar method of the binary case is applied to construct the ternary LRCs with good parameters.
Also, new constructions of binary LRCs with large Hamming distance and disjoint repair groups are proposed. The proposed binary linear LRCs constructed by using existing binary LRCs are optimal or near-optimal in terms of the bound with disjoint repair group.
Last, I propose new constructions of high-rate GRP LDPC codes for a nonergodic block interference and anti-jamming PR LDPC codes for follower jamming.
The proposed high-rate GRP LDPC codes are based on nonergodic two-state binary symmetric channel with block interference and Nakagami- block fading. In these channel environments, GRP LDPC codes have good performance approaching to the theoretical limit in the channel with one block interference, where their performance is shown by the channel threshold or the channel outage probability. In the proposed design, I find base matrices using the protograph extrinsic information transfer (PEXIT) algorithm.
Also, the proposed new constructions of anti-jamming partially regular LDPC codes is based on follower jamming on the frequency-hopped spread spectrum (FHSS). For a channel environment, I suppose follower jamming with random dwell time and Rayleigh block fading environment with M-ary frequnecy shift keying (MFSK) modulation. For a coding perspective, an anti-jamming LDPC codes against follower jamming are introduced. In order to optimize the jamming environment, the partially regular structure and corresponding density evolution schemes are used. A series of simulations show that the proposed codes outperforms the 802.16e standard in the presence of follower noise jamming.์ด ๋
ผ๋ฌธ์์๋, i) ์์ค ์ฑ๋์์ ์ํ ๋ถํธ์ ์๋ก์ด ์ด๋จ ์๊ธฐ๋ํ ๊ตฐ ๋ณตํธ๊ธฐ , ii) ๋ถ์ฐ ์ ์ฅ ์์คํ
์ ์ํ ์ํ ๋ถํธ ๋ฐ ๊ธฐ์กด์ ๋ถ๋ถ ์ ์ ๋ณต๊ตฌ ๋ถํธ(LRC)๋ฅผ ์ด์ฉํ ์ด์ง ํน์ ์ผ์ง ๋ถ๋ถ ์ ์ ๋ณต๊ตฌ ๋ถํธ ์ค๊ณ๋ฒ, ๋ฐ iii) ๋ธ๋ก ๊ฐ์ญ ํ๊ฒฝ์ ์ํ ๊ณ ๋ถํจ์จ์ ์ผ๋ฐํ๋ ๊ทผ ํ๋กํ ๊ทธ๋ํ(generalized root protograph, GRP) LDPC ๋ถํธ ๋ฐ ์ถ์ ์ฌ๋ฐ ํ๊ฒฝ์ ์ํ ํญ์ฌ๋ฐ ๋ถ๋ถ ๊ท ์ผ (anti-jamming paritally regular, AJ-PR) LDPC ๋ถํธ๊ฐ ์ฐ๊ตฌ๋์๋ค.
์ฒซ๋ฒ์งธ๋ก, ์์ค ์ฑ๋์์ ์ํ ๋ถํธ์ ์๋ก์ด ์ด๋จ ์๊ธฐ๋ํ ๊ตฐ ๋ณตํธ๊ธฐ๋ฅผ ์ ์ํ์๋ค. ์ต๊ทผ ๋ถ์ฐ ์ ์ฅ ์์คํ
ํน์ ๋ฌด์ ์ผ์ ๋คํธ์ํฌ ๋ฑ์ ์์ฉ์ผ๋ก ์ธํด ์์ค ์ฑ๋์์์ ์ค๋ฅ ์ ์ ๋ถํธ ๊ธฐ๋ฒ์ด ์ฃผ๋ชฉ๋ฐ๊ณ ์๋ค. ๊ทธ๋ฌ๋ ๋ง์ ๋ณตํธ๊ธฐ ์๊ณ ๋ฆฌ์ฆ์ ๋์ ๋ณตํธ ๋ณต์ก๋ ๋ฐ ๊ธด ์ง์ฐ์ผ๋ก ์ธํด ์ค์ฉ์ ์ด์ง ๋ชปํ๋ค. ๋ฐ๋ผ์ ๋ฎ์ ๋ณตํธ ๋ณต์ก๋ ๋ฐ ๋์ ์ฑ๋ฅ์ ๋ณด์ผ ์ ์๋ ์ํ ๋ถํธ์์ ์ด๋จ ์๊ธฐ ๋ํ ๊ตฐ ๋ณตํธ๊ธฐ๊ฐ ์ ์๋์๋ค. ๋ณธ ์ฐ๊ตฌ์์๋ ํจ๋ฆฌํฐ ๊ฒ์ฌ ํ๋ ฌ์ ๋ณํํ๊ณ , ์ ์ฒ๋ฆฌ ๊ณผ์ ์ ๋์
ํ ์๋ก์ด ์ด๋จ ์๊ธฐ๋ํ ๊ตฐ ๋ณตํธ๊ธฐ๋ฅผ ์ ์ํ๋ค. ์ ์ํ ๋ณตํธ๊ธฐ๋ perfect ๋ถํธ, BCH ๋ถํธ ๋ฐ ์ต๋ ๊ฑฐ๋ฆฌ ๋ถ๋ฆฌ (maximum distance separable, MDS) ๋ถํธ์ ๋ํด์ ๋ถ์๋์๋ค. ์์น ๋ถ์์ ํตํด, ์ ์๋ ๋ณตํธ ์๊ณ ๋ฆฌ์ฆ์ ๊ธฐ์กด์ ์๊ธฐ ๋ํ ๊ตฐ ๋ณตํธ๊ธฐ๋ณด๋ค ๋ฎ์ ๋ณต์ก๋๋ฅผ ๋ณด์ด๋ฉฐ, ๋ช๋ช์ ์ํ ๋ถํธ ๋ฐ ์์ค ์ฑ๋์์ ์ต๋ ์ฐ๋ (maximal likelihood, ML)๊ณผ ๊ฐ์ ์์ค์ ์ฑ๋ฅ์์ ๋ณด์ธ๋ค. MDS ๋ถํธ์ ๊ฒฝ์ฐ, ํ์ฅ๋ ํจ๋ฆฌํฐ๊ฒ์ฌ ํ๋ ฌ ๋ฐ ์์ ํฌ๊ธฐ์ ํ๋ ฌ์ ์ญ์ฐ์ฐ์ ํ์ฉํ์์ ๊ฒฝ์ฐ์ ์ฑ๋ฅ์ ๋ถ์ํ๋ค.
๋ ๋ฒ์งธ๋ก, ๋ถ์ฐ ์ ์ฅ ์์คํ
์ ์ํ ์ํ ๋ถํธ ๋ฐ ๊ธฐ์กด์ ๋ถ๋ถ ์ ์ ๋ณต๊ตฌ ๋ถํธ (LRC)๋ฅผ ์ด์ฉํ ์ด์ง ํน์ ์ผ์ง ๋ถ๋ถ ์ ์ ๋ณต๊ตฌ ๋ถํธ ์ค๊ณ๋ฒ์ ์ ์ํ์๋ค. ์ด๊ธฐ ์ฐ๊ตฌ๋ก์, ์ํ ๋ถํธ ๋ฐ ์ฐ์ ์ ํ์ฉํ ์ด์ง ๋ฐ ์ผ์ง LRC ์ค๊ณ ๊ธฐ๋ฒ์ด ์ฐ๊ตฌ๋์๋ค. ์ต์ ํด๋ฐ ๊ฑฐ๋ฆฌ๊ฐ 4,5, ํน์ 6์ธ ์ ์๋ ์ด์ง LRC ์ค ์ผ๋ถ๋ ์ํ๊ณผ ๋น๊ตํด ๋ณด์์ ๋ ์ต์ ์ค๊ณ์์ ์ฆ๋ช
ํ์๋ค. ๋ํ, ๋น์ทํ ๋ฐฉ๋ฒ์ ์ ์ฉํ์ฌ ์ข์ ํ๋ผ๋ฏธํฐ์ ์ผ์ง LRC๋ฅผ ์ค๊ณํ ์ ์์๋ค. ๊ทธ ์ธ์ ๊ธฐ์กด์ LRC๋ฅผ ํ์ฉํ์ฌ ํฐ ํด๋ฐ ๊ฑฐ๋ฆฌ์ ์๋ก์ด LRC๋ฅผ ์ค๊ณํ๋ ๋ฐฉ๋ฒ์ ์ ์ํ์๋ค. ์ ์๋ LRC๋ ๋ถ๋ฆฌ๋ ๋ณต๊ตฌ ๊ตฐ ์กฐ๊ฑด์์ ์ต์ ์ด๊ฑฐ๋ ์ต์ ์ ๊ฐ๊น์ด ๊ฐ์ ๋ณด์๋ค.
๋ง์ง๋ง์ผ๋ก, GRP LDPC ๋ถํธ๋ Nakagami- ๋ธ๋ก ํ์ด๋ฉ ๋ฐ ๋ธ๋ก ๊ฐ์ญ์ด ์๋ ๋ ์ํ์ ์ด์ง ๋์นญ ์ฑ๋์ ๊ธฐ๋ฐ์ผ๋ก ํ๋ค. ์ด๋ฌํ ์ฑ๋ ํ๊ฒฝ์์ GRP LDPC ๋ถํธ๋ ํ๋์ ๋ธ๋ก ๊ฐ์ญ์ด ๋ฐ์ํ์ ๊ฒฝ์ฐ, ์ด๋ก ์ ์ฑ๋ฅ์ ๊ฐ๊น์ด ์ข์ ์ฑ๋ฅ์ ๋ณด์ฌ์ค๋ค. ์ด๋ฌํ ์ด๋ก ๊ฐ์ ์ฑ๋ ๋ฌธํฑ๊ฐ์ด๋ ์ฑ๋ outage ํ๋ฅ ์ ํตํด ๊ฒ์ฆํ ์ ์๋ค. ์ ์๋ ์ค๊ณ์์๋, ๋ณํ๋ PEXIT ์๊ณ ๋ฆฌ์ฆ์ ํ์ฉํ์ฌ ๊ธฐ์ด ํ๋ ฌ์ ์ค๊ณํ๋ค. ๋ํ AJ-PR LDPC ๋ถํธ๋ ์ฃผํ์ ๋์ฝ ํ๊ฒฝ์์ ๋ฐ์ํ๋ ์ถ์ ์ฌ๋ฐ์ด ์๋ ํ๊ฒฝ์ ๊ธฐ๋ฐ์ผ๋ก ํ๋ค. ์ฑ๋ ํ๊ฒฝ์ผ๋ก MFSK ๋ณ๋ณต์กฐ ๋ฐฉ์์ ๋ ์ผ๋ฆฌ ๋ธ๋ก ํ์ด๋ฉ ๋ฐ ๋ฌด์์ํ ์ง์ ์๊ฐ์ด ์๋ ์ฌ๋ฐ ํ๊ฒฝ์ ๊ฐ์ ํ๋ค. ์ด๋ฌํ ์ฌ๋ฐ ํ๊ฒฝ์ผ๋ก ์ต์ ํํ๊ธฐ ์ํด, ๋ถ๋ถ ๊ท ์ผ ๊ตฌ์กฐ ๋ฐ ํด๋น๋๋ ๋ฐ๋ ์งํ (density evolution, DE) ๊ธฐ๋ฒ์ด ํ์ฉ๋๋ค. ์ฌ๋ฌ ์๋ฎฌ๋ ์ด์
๊ฒฐ๊ณผ๋ ์ถ์ ์ฌ๋ฐ์ด ์กด์ฌํ๋ ํ๊ฒฝ์์ ์ ์๋ ๋ถํธ๊ฐ 802.16e์ ์ฌ์ฉ๋์๋ LDPC ๋ถํธ๋ณด๋ค ์ฑ๋ฅ์ด ์ฐ์ํจ์ ๋ณด์ฌ์ค๋ค.Contents
Abstract
Contents
List of Tables
List of Figures
1 INTRODUCTION
1.1 Background
1.2 Overview of Dissertation
1.3 Notations
2 Preliminaries
2.1 IED and AGD for Erasure Channel
2.1.1 Iterative Erasure Decoder
2.1.1 Automorphism Group Decoder
2.2. Binary Locally Repairable Codes for Distributed Storage System
2.2.1 Bounds and Optimalities of Binary LRCs
2.2.2 Existing Optimal Constructions of Binary LRCs
2.3 Channels with Block Interference and Jamming
2.3.1 Channels with Block Interference
2.3.2 Channels with Jamming with MFSK and FHSS Environment.
3 New Two-Stage Automorphism Group Decoders for Cyclic Codes in the Erasure Channel
3.1 Some Definitions
3.2 Modification of Parity Check Matrix and Two-Stage AGD
3.2.1 Modification of the Parity Check Matrix
3.2.2 A New Two-Stage AGD
3.2.3 Analysis of Modification Criteria for the Parity Check Matrix
3.2.4 Analysis of Decoding Complexity of TS-AGD
3.2.5 Numerical Analysis for Some Cyclic Codes
3.3 Construction of Parity Check Matrix and TS-AGD for Cyclic MDS Codes
3.3.1 Modification of Parity Check Matrix for Cyclic MDS Codes .
3.3.2 Proposed TS-AGD for Cyclic MDS Codes
3.3.3 Perfect Decoding by TS-AGD with Expanded Parity Check Matrix for Cyclic MDS Codes
3.3.4 TS-AGD with Submatrix Inversion for Cyclic MDS Codes . .
4 New Constructions of Binary and Ternary LRCs Using Cyclic Codes and Existing LRCs
4.1 Constructions of Binary LRCs Using Cyclic Codes
4.2 Constructions of Linear Ternary LRCs Using Cyclic Codes
4.3 Constructions of Binary LRCs with Disjoint Repair Groups Using Existing LRCs
4.4 New Constructions of Binary Linear LRCs with d โฅ 8 Using Existing LRCs
5 New Constructions of Generalized RP LDPC Codes for Block Interference and Partially Regular LDPC Codes for Follower Jamming
5.1 Generalized RP LDPC Codes for a Nonergodic BI
5.1.1 Minimum Blockwise Hamming Weight
5.1.2 Construction of GRP LDPC Codes
5.2 Asymptotic and Numerical Analyses of GRP LDPC Codes
5.2.1 Asymptotic Analysis of LDPC Codes
5.2.2 Numerical Analysis of Finite-Length LDPC Codes
5.3 Follower Noise Jamming with Fixed Scan Speed
5.4 Anti-Jamming Partially Regular LDPC Codes for Follower Noise Jamming
5.4.1 Simplified Channel Model and Corresponding Density Evolution
5.4.2 Construction of AJ-PR-LDPC Codes Based on DE
5.5 Numerical Analysis of AJ-PR LDPC Codes
6 Conclusion
Abstract (In Korean)Docto
Low-Density Parity-Check Codes From Transversal Designs With Improved Stopping Set Distributions
This paper examines the construction of low-density parity-check (LDPC) codes
from transversal designs based on sets of mutually orthogonal Latin squares
(MOLS). By transferring the concept of configurations in combinatorial designs
to the level of Latin squares, we thoroughly investigate the occurrence and
avoidance of stopping sets for the arising codes. Stopping sets are known to
determine the decoding performance over the binary erasure channel and should
be avoided for small sizes. Based on large sets of simple-structured MOLS, we
derive powerful constraints for the choice of suitable subsets, leading to
improved stopping set distributions for the corresponding codes. We focus on
LDPC codes with column weight 4, but the results are also applicable for the
construction of codes with higher column weights. Finally, we show that a
subclass of the presented codes has quasi-cyclic structure which allows
low-complexity encoding.Comment: 11 pages; to appear in "IEEE Transactions on Communications
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