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| 2. |
- Zhu, Min, et al.
(författare)
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Adaptive doping of spatially coupled LDPC codes
- 2021
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Ingår i: 2020 IEEE Information Theory Workshop, ITW 2020. - 9781728159638 - 9781728159621
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Konferensbidrag (refereegranskat)abstract
- In this paper, we study the problem of error propagation in sliding window decoding (SWD) of spatially coupled LDPC (SC-LDPC) codes. A general decoder model that accounts for error propagation is proposed and analyzed, and the decoded block error rate (BLER) is calculated using the model. In order to improve the BLER performance under decoder error propagation conditions, adaptive variable node (VN) doping is proposed, assuming a noiseless binary feedback channel is available. Example calculations using the proposed model, as well as numerical simulation results, are used to show that adaptive VN doping improves the BLER performance compared to the periodic VN doping and to the undoped case.
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| 3. |
- Costello, Daniel J., et al.
(författare)
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Spatially Coupled Generalized LDPC Codes : Introduction and Overview
- 2018
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Ingår i: 2018 IEEE 10th International Symposium on Turbo Codes and Iterative Information Processing, ISTC 2018. - 9781538670484 ; 2018-December
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Konferensbidrag (refereegranskat)abstract
- Generalized low-density parity-check (GLDPC) codes are a class of LDPC codes in which the standard single parity check (SPC) constraints are replaced by more general constraints, viz., constraints defined by a linear block code. These stronger constraints typically result in improved error floor performance, due to better minimum distance and trapping set properties, at a cost of some increased decoding complexity. In this paper, we summarize some recent results on spatially coupled generalized low-density parity-check (SC-GLDPC) codes. Results are compared to GLDPC block codes and the advantages and disadvantages of SC-GLDPC codes are discussed.
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| 4. |
- Devine, K. M., et al.
(författare)
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Analysis of a model for the formation of fold-type oscillation marks in the continuous casting of steel
- 2020
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Ingår i: IMA Journal of Applied Mathematics. - : Oxford University Press (OUP). - 0272-4960 .- 1464-3634. ; 85:3, s. 385-420
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the different possible behaviours of a recent asymptotic model for oscillation-mark formation in the continuous casting of steel, with particular focus on how the results obtained vary when the heat transfer coefficient (R-mf), the thermal resistance (mu(f)) and the dependence of the viscosity of the flux powder as a function of temperature, are changed. It turns out that three different outcomes are possible: (I) the flux remains in molten state and no solid flux ever forms; (II) both molten and solid flux are present, and the profile of the oscillation mark is continuous with respect to the space variable in the casting direction; (III) both molten and solid flux are present, and the profile of the oscillation mark is discontinuous with respect to the space variable in the casting direction. Although (I) gave good agreement with experimental data, it suffered the drawback that solid flux is typically observed during actual continuous casting; this has been rectified in this work via alternative (II). On the other hand, alternative (III) can occur as a result of hysteresis-type phenomenon that is encountered in other flows that involve temperature-dependent viscosity; in the present case, this manifests itself via the possibility of multiple states for the oscillation-mark profile at the instants in time when solid flux begins to form and when it ceases to form.
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| 5. |
- Mitchell, David G.M., et al.
(författare)
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Approximating Decoding Thresholds of Punctured LDPC Code Ensembles on the AWGN Channel
- 2015
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Ingår i: 2015 IEEE International Symposium on Information Theory (ISIT). - 9781467377041 ; , s. 421-425
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Konferensbidrag (refereegranskat)abstract
- In this paper, we provide an efficient way to predict iterative belief propagation (BP) decoding thresholds of randomly punctured low-density parity-check (LDPC) code ensembles on the binary-input additive white Gaussian noise channel (AWGNC), given only the BP threshold of the mother code ensemble on the binary erasure channel (BEC) and the code design rate. We show that the predictions are accurate by comparing them with values calculated by discretized density evolution for a variety of puncturing fractions. We find that the strength and suitability of an LDPC code ensemble for random puncturing over the AWGNC with respect to iterative decoding threshold is completely determined by a single constant, and this behavior is demonstrated using both LDPC block code and spatially coupled LDPC code ensembles. Finally, we present simulation results that confirm the excellent decoding performance promised by the asymptotic results.
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| 6. |
- Mitchell, David G.M., et al.
(författare)
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On the Minimum Distance of Generalized Spatially Coupled LDPC Codes
- 2013
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Ingår i: IEEE International Symposium on Information Theory Proceedings (ISIT), 2013. - 2157-8117 .- 2157-8095. - 9781479904440 ; , s. 1874-1878
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Konferensbidrag (refereegranskat)abstract
- Families of generalized spatially-coupled low-density parity-check (GSC-LDPC) code ensembles can be formed by terminating protograph-based generalized LDPC convolutional (GLDPCC) codes. It has previously been shown that ensembles of GSC-LDPC codes constructed from a protograph have better iterative decoding thresholds than their block code counterparts, and that, for large termination lengths, their thresholds coincide with the maximum a-posteriori (MAP) decoding threshold of the underlying generalized LDPC block code ensemble. Here we show that, in addition to their excellent iterative decoding thresholds, ensembles of GSC-LDPC codes are asymptotically good and have large minimum distance growth rates.
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| 7. |
- Mitchell, David G.M., et al.
(författare)
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Randomly Punctured LDPC Codes
- 2016
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Ingår i: IEEE Journal on Selected Areas in Communications. - 1558-0008. ; 34:2, s. 408-421
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present a random puncturing analysis of low-density parity-check (LDPC) code ensembles. We derive a simple analytic expression for the iterative belief propagation (BP) decoding threshold of a randomly punctured LDPC code ensemble on the binary erasure channel (BEC) and show that, with respect to the BP threshold, the strength and suitability of an LDPC code ensemble for random puncturing is completely determined by a single constant that depends only on the rate and the BP threshold of the mother code ensemble. We then provide an efficient way to accurately predict BP thresholds of randomly punctured LDPC code ensembles on the binary- input additive white Gaussian noise channel (BI-AWGNC), given only the BP threshold of the mother code ensemble on the BEC and the design rate, and we show how the prediction can be improved with knowledge of the BI-AWGNC threshold. We also perform an asymptotic minimum distance analysis of randomly punctured code ensembles and present simulation results that confirm the robust decoding performance promised by the asymptotic results. Protograph-based LDPC block code and spatially coupled LDPC code ensembles are used throughout as examples to demonstrate the results.
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| 8. |
- Mitchell, David G.M., et al.
(författare)
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Randomly Punctured Spatially Coupled LDPC Codes
- 2014
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Ingår i: [Host publication title missing].
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Konferensbidrag (refereegranskat)abstract
- In this paper, we study random puncturing of protograph-based spatially coupled low-density parity-check (SC- LDPC) code ensembles. We show that, with respect to iterative decoding threshold, the strength and suitability of an LDPC code ensemble for random puncturing over the binary erasure channel (BEC) is completely determined by a single constant that depends only on the rate and iterative decoding threshold of the mother code ensemble. We then use this analysis to show that randomly punctured SC-LDPC code ensembles display near capacity thresholds for a wide range of rates. We also perform an asymptotic minimum distance analysis and show that, like the SC-LDPC mother code ensemble, the punctured SC-LDPC code ensembles are also asymptotically good. Finally, we present some simulation results that confirm the excellent decoding performance promised by the asymptotic results.
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| 9. |
- Mitchell, David G.M., et al.
(författare)
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Spatially Coupled LDPC Codes Constructed From Protographs
- 2015
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Ingår i: IEEE Transactions on Information Theory. - 0018-9448. ; 61:9, s. 4866-4889
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we construct protograph-based spatially coupled low-density parity-check (LDPC) codes by coupling together a series of L disjoint, or uncoupled, LDPC code Tanner graphs into a single coupled chain. By varying L, we obtain a flexible family of code ensembles with varying rates and frame lengths that can share the same encoding and decoding architecture for arbitrary L. We demonstrate that the resulting codes combine the best features of optimized irregular and regular codes in one design: capacity approaching iterative belief propagation (BP) decoding thresholds and linear growth of minimum distance with block length. In particular, we show that, for sufficiently large L, the BP thresholds on both the binary erasure channel and the binary-input additive white Gaussian noise channel saturate to a particular value significantly better than the BP decoding threshold and numerically indistinguishable from the optimal maximum a posteriori decoding threshold of the uncoupled LDPC code. When all variable nodes in the coupled chain have degree greater than two, asymptotically the error probability converges at least doubly exponentially with decoding iterations and we obtain sequences of asymptotically good LDPC codes with fast convergence rates and BP thresholds close to the Shannon limit. Further, the gap to capacity decreases as the density of the graph increases, opening up a new way to construct capacity achieving codes on memoryless binary-input symmetric-output channels with low-complexity BP decoding.
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| 10. |
- Zhu, Min, et al.
(författare)
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Window Decoding of Braided Convolutional Codes
- 2015
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Ingår i: 2015 IEEE Information Theory Workshop - Fall (ITW). - 9781467378529
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Konferensbidrag (refereegranskat)abstract
- We consider a window decoding scheme for Braided Convolutional Codes (BCCs) based on the BCJR algorithm. We describe the principle of this decoding scheme and show that BCCs with window decoding exhibit excellent performance. The tradeoff between performance and decoding latency is examined and, to reduce decoding complexity, both uniform and nonuniform message passing schedules within the decoding window are considered. Finally, puncturing is employed to obtain rate-compatible code rates of 1/2 and 2/3 starting from a rate 1/3 example mother code. Simulation results show that, with nonuniform message passing and puncturing, near capacity performance can be maintained throughout the rate range considered with reasonable decoding complexity and no visible error floors.
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