A tree pruning technique for decoding complexity reduction of polar codes and PAC codes

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Bibliographic Details
Title: A tree pruning technique for decoding complexity reduction of polar codes and PAC codes
Authors: Moradi, Mohsen, Mozammel, Amir
Source: IEEE Transactions on Communications
Publisher Information: Institute of Electrical and Electronics Engineers
Publication Year: 2023
Collection: Bilkent University: Institutional Repository
Subject Terms: PAC codes, Polar codes, SCL decoding, Sequential decoding, Polarized channel, Stack decoding, Pruning
Description: 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.
Document Type: article in journal/newspaper
File Description: application/pdf
Language: English
Relation: https://dx.doi.org/10.1109/TCOMM.2023.3255254; https://hdl.handle.net/11693/114892
DOI: 10.1109/TCOMM.2023.3255254
Availability: https://hdl.handle.net/11693/114892
https://doi.org/10.1109/TCOMM.2023.3255254
Accession Number: edsbas.F0C04F15
Database: BASE
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