Improved list decoding of polar codes by shifted-pruning

Mohammad Rowshan, Emanuele Viterbo

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6 Citations (Scopus)


In successive cancellation list (SCL) decoding, the list pruning operation retains the L paths with highest likelihoods. However, the correct path might be among the paths with low likelihoods due to channel noise. In this case, the correct path is eliminated from the list. In this work, we study the event of elimination of the correct path and we analyze where and how this event occurs. A modified pruning scheme named shifted-pruning over a set of low-reliability bit-channels named critical bits is proposed aiming to avoid the elimination of the correct path in additional decoding attempts after a decoding failure occurs. Shifted-pruning is realized by selecting the paths k + 1 to k + L out of the 2L ordered paths instead of the paths 1 to L. The numerical results for polar codes of length 512 and code rates 0.5 and 0.8 and list sizes L = 2, 8 and 32 show that the shifted-pruning scheme is a low-complexity equivalent to the bit-flipping scheme while it can outperform the bit-flipping method by providing 0. 25-0.5dB gain.

Original languageEnglish
Title of host publication2019 IEEE Information Theory Workshop (ITW)
EditorsMichael Lentmaier, Sennur Ulukus, Serdar Yüksel
Place of PublicationPiscataway NJ USA
PublisherIEEE, Institute of Electrical and Electronics Engineers
Number of pages5
ISBN (Electronic)9781538669006, 9781538668993
ISBN (Print)9781538669013
Publication statusPublished - 2019
EventInformation Theory Workshop 2019 - Visby, Sweden
Duration: 25 Aug 201928 Aug 2019 (Proceedings)


ConferenceInformation Theory Workshop 2019
Abbreviated titleITW 2019
Internet address


  • list decoding
  • Polar codes
  • successive cancellation
  • tree pruning

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