Improved belief propagation decoder for LDPC-CRC-polar codes with bit-freezing

Though belief propagation bit-flip (BPBF) decoding improves the error correction performance of polar codes, it uses the exhaustive flips method to achieve the error correction performance of CA-SCL decoding, thus resulting in high decoding complexity and latency. To alleviate this issue, we incorporate the LDPC-CRC-Polar coding scheme with BPBF and propose an improved belief propagation decoder for LDPC-CRC-Polar codes with bit-freezing (LDPC-CRC-Polar codes BPBFz). The proposed LDPC-CRC-Polar codes BPBFz employs the LDPC code to ensure the reliability of the flipping set, i.e., critical set (CS), and dynamically update it. The modified CS is further utilized for the identification of error-prone bits. The proposed LDPC-CRC-Polar codes BPBFz obtains remarkable error correction performance and is comparable to that of the CA-SCL (L = 16) decoder under medium-to-high signal-to-noise ratio (SNR) regions. It gains up to 1.2dB and 0.9dB at a fixed BLER = 10
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compared with BP and BPBF (CS-1), respectively. In addition, the proposed LDPC-CRC-Polar codes BPBFz has lower decoding latency compared with CA-SCL and BPBF, i.e., it is 15 times faster than CA-SCL (L = 16) at high SNR regions.