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10th International Workshop on Signal Design and its Applications in Communications (IWSDA)

作者： Moradi, Mohsen Bilkent Univ Dept Elect & Elect Engn Ankara Turkey

ISBN: (数字)9781665452984

ISBN: (纸本)9781665452984

While sequential decoding of polarization-adjusted convolutional (PAC) codes constructed using polar rate profile has low computational complexity, their error-correction performance falls far short of the theoretical bounds for finite blocklength codes. In this paper, we use the bit-flipping technique in the stack decoding algorithm of PAC codes in order to improve their error-correction performance. This technique maintains the low memory requirements of stack decoding and polar demapper. Additionally, at high SNR values, the number of visits at each level of the decoding tree is almost one. Numerical findings indicate that this approach is capable of outperforming the stack decoding algorithm.

关键词： polarization-adjusted convolutional codes polar codes stack decoding sequential decoding bit flipping

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A Tree Pruning Technique for decoding Complexity Reduction of Polar Codes and PAC Codes

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IEEE TRANSACTIONS ON COMMUNICATIONS 2023年第5期71卷 2576-2586页

作者： Moradi, Mohsen Mozammel, Amir Bilkent Univ Dept Elect & Elect Engn TR-06800 Ankara Turkiye

Sorting operation is one of the main bottlenecks for the successive-cancellation list (SCL) decoding. This paper introduces an improvement to the SCL decoding for polar and pre-transformed polar codes that reduces the number of sorting operations without visible degradation in the code's error-correction performance. In an SCL decoding with an optimum metric function we show that, on average, the correct branch's bit-metric value must be equal to the bit-channel capacity, and on the other hand, the average bit-metric value of a wrong branch can be at most zero. This implies that a wrong path's partial path metric value deviates from the bit-channel capacity's partial summation. For relatively reliable bit-channels, the bit metric for a wrong branch becomes very large negative number, which enables us to detect and prune such paths. We prove that, for a threshold lower than the bit-channel cutoff rate, the probability of pruning the correct path decreases exponentially by the given threshold. Based on these findings, we presented a pruning technique, and the experimental results demonstrate a substantial decrease in the amount of sorting procedures required for SCL decoding. In the stack algorithm, a similar technique is used to significantly reduce the average number of paths in the stack.

关键词： decoding Measurement Polar codes Sorting Picture archiving and communication systems Encoding Indexes PAC codes polar codes SCL decoding sequential decoding polarized channel stack decoding pruning

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Polarization-Adjusted Convolutional (PAC) Codes: Sequential decoding vs List decoding

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2021年第2期70卷 1434-1447页

作者： Rowshan, Mohammad Burg, Andreas Viterbo, Emanuele Monash Univ Dept Elect & Comp Syst Engn ECSE Clayton Vic 3800 Australia Ecole Polytech Fed Lausanne Telecommun Circuits Lab CH-1015 Lausanne Switzerland

In the Shannon lecture at the 2019 International Symposium on Information Theory (ISIT), Arikan proposed to employ a one-to-one convolutional transform as a pre-coding step before the polar transform. The resulting codes of this concatenation are called polarization-adjusted convolutional (PAC) codes. In this scheme, a pair of polar mapper and demapper as pre- and postprocessing devices are deployed around a memoryless channel, which provides polarized information to an outer decoder leading to improved error correction performance of the outer code. In this paper, the list decoding and sequential decoding (including Fano decoding and stack decoding) are first adapted for use to decode PAC codes. Then, to reduce the complexity of sequential decoding of PAC/polar codes, we propose (i) an adaptive heuristic metric, (ii) tree search constraints for backtracking to avoid exploration of unlikely sub-paths, and (iii) tree search strategies consistent with the pattern of error occurrence in polar codes. These contribute to the reduction of the average decoding time complexity from 50% to 80%, trading with 0.05 to 0.3 dB degradation in error correction performance within FER = 10(-3) range, respectively, relative to not applying the corresponding search strategies. Additionally, as an important ingredient in Fano decoding of PAC/polar codes, an efficient computation method for the intermediate LLRs and partial sums is provided. This method is effective in backtracking and avoids storing the intermediate information or restarting the decoding process. Eventually, all three decoding algorithms are compared in terms of performance, complexity, and resource requirements.

关键词： Polarization-adjusted convolutional codes polar codes convolutional codes list decoding sequential decoding Fano algorithm tree search path metric stack decoding

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On the improvements of successive cancellation Creeper decoding for polar codes

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DIGITAL SIGNAL PROCESSING 2023年 137卷

作者： Timokhin, Ilya Ivanov, Fedor Natl Res Univ Higher Sch Econ Moscow Russia

In this paper, an improvement for successive cancellation (SC) decoding is presented for polar codes. This improvement is based on applying Creeper approach that was used to decode convolutional codes. The proposed decoder combines a stack and a Fano approaches, allowing to significantly decrease complexity of Successive Cancellation Fano decoder at the cost of a slight increase in space complexity. We also show how to combine the SC-Creeper decoding with a bit-flipping approach to further improve the performance of SC-Creeper due to introducing additional decoding attempts. Simulation results show that the proposed SC-Creeper and SC-Creeper Flip decoders with carefully selected parameters have the same performance as both CRC-aided Successive Cancellation List decoder with list size 8 and Fano decoder, while having much smaller complexity. (c) 2023 Elsevier Inc. All rights reserved.

关键词： Polar codes Successive cancellation decoding Fano decoding stack decoding Creeper algorithm

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Polar Codes Sequential Decoder Hardware Architecture 42

Polar Codes Sequential Decoder Hardware Architecture

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42nd International Conference on Telecommunications and Signal Processing (TSP)

作者： Krylov, Aleksei Rashich, Andrey Gelgor, Aleksandr Fadeev, Dmitrii Peter Great St Petersburg Polytech Univ Higher Sch Appl Phys & Space Technol St Petersburg Russia

ISBN: (纸本)9781728118642

Polar codes show potential benefits in modern telecommunication systems, they are already adopted for 5G. The efficiency of polar codes are provided by list successive cancellation decoder which complexity is extremely high for large list sizes. To overcome this problem keeping the decoding performance on the same level the sequential decoder of polar codes was proposed. Although there is no hardware implementations and resources estimations of this decoder. In this paper, hardware architecture of high performance sequential decoder of polar codes is proposed.

关键词： 5G ASIC polar codes sequential decoding stack decoding successive cancellation decoding

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Low-Complexity Segmented CRC-Aided SC stack Decoder for Polar Codes 50

Low-Complexity Segmented CRC-Aided SC Stack Decoder for Pola...

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50th IEEE Asilomar Conference on Signals, Systems, and Computers (ASILOMARSSC)

作者： Song, Wenqing Zhou, Huayi Zhao, Yi Zhang, Shunqing You, Xiaohu Zhang, Chuan Southeast Univ Natl Mobile Commun Res Lab Nanjing Jiangsu Peoples R China Intel Labs Intel Collaborat Res Inst Mobile Networking & Com Shanghai Peoples R China

ISBN: (纸本)9781538639542

In order to improve the decoding performance of successive cancellation (SC) decoder for polar code, SC stack (SCS) polar decoder has been proposed by existing literatures. Compared with SCL decoder, SCS decoder successfully reduces the decoding complexity especially at high SNR while keeping the same decoding performance. However in correlated channels at low SNR, SCS decoder suffers a lot from the overwhelming complexity due to frequent backtracking operations. Aim to lower such complexity as well as the required storage resources of SCS decoder, this paper proposes a low complexity SCS polar decoder based on segmented CRC scheme. Employing the segmented CRC as an early termination scheme, the proposed SCS decoder can successfully reduce the complexity especially at low SNR without any performance degradation. Numerical results have shown that for (1024, 512) polar code, the proposed approach achieves more than 34.4% complexity reduction and 29.7% resource occupation reduction compared to the conventional CRC-aided SCS (CA-SCS) decoder at SNR of 1.5 dB.

关键词： Polar codes segmented CRC stack decoding

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CRC-Aided decoding of Polar Codes

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IEEE COMMUNICATIONS LETTERS 2012年第10期16卷 1668-1671页

作者： Niu, Kai Chen, Kai Beijing Univ Posts & Telecommun Minist Educ Key Lab Universal Wireless Commun Beijing 100876 Peoples R China

CRC (cyclic redundancy check)-aided decoding schemes are proposed to improve the performance of polar codes. A unified description of successive cancellation decoding and its improved version with list or stack is provided and the CRC-aided successive cancellation list/stack (CA-SCL/SCS) decoding schemes are proposed. Simulation results in binary-input additive white Gaussian noise channel (BI-AWGNC) show that CA-SCL/SCS can provide significant gain of 0.5 dB over the turbo codes used in 3GPP standard with code rate 1/2 and code length 1024 at the block error probability (BLER) of 10(-4). Moreover, the time complexity of CA-SCS decoder is much lower than that of turbo decoder and can be close to that of successive cancellation (SC) decoder in the high SNR regime.

关键词： Polar codes CRC successive cancellation decoding stack decoding list decoding

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Speech recognition using linear dynamic models

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IEEE TRANSACTIONS ON AUDIO SPEECH AND LANGUAGE PROCESSING 2007年第1期15卷 246-256页

作者： Frankel, Joe King, Simon Univ Edinburgh Ctr Speech Technol Res Edinburgh EH8 9LW Midlothian Scotland

The majority of automatic speech recognition systems rely on hidden Markov models, in which Gaussian mixtures model the output distributions associated with sub-phone states. This approach, whilst successful, models consecutive feature vectors (augmented to include derivative information) as statistically independent. Furthermore, spatial correlations present in speech parameters are frequently ignored through the use of diagonal covariance matrices. This paper continues the work of Digalakis and others who proposed instead a first-order linear state-space model which has the capacity to model underlying dynamics, and furthermore give a model of spatial correlations. This paper examines the assumptions made in applying such a model and shows that the addition of a hidden dynamic state leads to increases in accuracy over otherwise equivalent static models. We also propose a time-asynchronous decoding strategy suited to recognition with segment models. We describe implementation of decoding for linear dynamic models and present TIMIT phone recognition results.

关键词： automatic speech recognition (ASR) linear dynamic models (LDMs) stack decoding

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Various robust search methods in a Hungarian speech recognition system

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Acta Cybernetica 2003年第2期16卷 229-240页

作者： Gosztolya, Gábor Kocsor, András Tóth, László Felföldi, László Research Group on Artificial Intell. Hungarian Academy of Sciences University of Szeged Aradi Vértanúk tere 1. H-6720 Szeged Hungary Department of Informatics University of Szeged Arpád tér 2. H-6720 Szeged Hungary

This work focuses on the search aspect of speech recognition. We describe some standard algorithms such as stack decoding, multi-stack decoding, the Viterbi beam search and an A* heuristic, then present improvements on these search methods. Finally we compare the performance of each algorithm, grading them according to their performance. We will show that our improvements can outperform the standard methods.

关键词： Multi-stack decoding Search methods stack decoding Viterbi beam search

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Start-synchronous search for large vocabulary continuous speech recognition

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IEEE TRANSACTIONS ON SPEECH AND AUDIO PROCESSING 1999年第5期7卷 542-553页

作者： Renals, S Hochberg, MM Univ Sheffield Dept Comp Sci Sheffield S1 4DP S Yorkshire England

In this paper, we present a novel, efficient search strategy for large vocabulary continuous speech recognition. The search algorithm, based on a stack decoder framework, utilizes phone-level posterior probability estimates (produced by a connectionist/hidden Markov model acoustic model) as a basis for phone deactivation pruning-a highly efficient method of reducing the required computation. The single-pass algorithm is naturally factored into the time-asynchronous processing of the word sequence and the time-synchronous processing of the hidden Markov model state sequence. This enables the search to be decoupled from the language model while still maintaining the computational benefits of time-synchronous processing. The incorporation of the language model in the search is discussed and computationally cheap approximations to the full language model are introduced. Experiments mere performed on the North American Business News task using a 60 000 word vocabulary and a trigram language model. Results indicate that the computational cost of the search may be reduced by more than a factor of 40 with a relative search error of less than 2% using the techniques discussed in the paper.

关键词： hidden Markov model large vocabulary continuous speech recognition phone deactivation pruning search stack decoding

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