Improved segmented belief propagation list decoding for polar codes with bit-flipping

Belief propagation list (BPL) decoding for polar codes has attracted more attention due to its inherent parallel nature. However, a large gap still exists with CRC-aided SCL (CA-SCL) decoding. In this work, an improved segmented belief propagation list decoding based on bit flipping (SBPL-BF) is proposed. On the one hand, the proposed algorithm makes use of the cooperative characteristic in BPL decoding such that the codeword is decoded in different BP decoders. Based on this characteristic, the unreliable bits for flipping could be split into multiple subblocks and could be flipped in different decoders simultaneously. On the other hand, a more flexible and effective processing strategy for the priori information of the unfrozen bits that do not need to be flipped is designed to improve the decoding convergence. In addition, this is the first proposal in BPL decoding which jointly optimizes the bit flipping of the information bits and the code bits. In particular, for bit flipping of the code bits, a H-matrix aided bit-flipping algorithm is designed to enhance the accuracy in identifying erroneous code bits. The simulation results show that the proposed algorithm significantly improves the error-correction performance of BPL decoding for medium and long codes. It is more than 0.25 dB better than the state-of-the-art BPL decoding at a block error rate (BLER) of 10
⁻⁵
, and outperforms CA-SCL decoding in the low signal-to-noise (SNR) region for (1024,0.5) polar codes.