Flexible Restart Mechanism for Successive Cancellation Flip Decoding of Polar Codes

Polar codes can achieve near-capacity performance under low-complexity successive cancellation (SC) decoding. However, short to medium-length block codes exhibit insufficient error-correction performance with the SC algorithm, which limits their practical applications. Although the successive cancellation flip (SCF) decoder improves SC performance, its variable execution time poses challenges in certain scenarios. The simplified restart mechanism (SRM) reduces the execution time of SCF decoders through conditional restart of the additional trials from the second half of the codeword. However, regardless of the position of the flipped bit on the RHS, additional decoding trials can only start from a fixed restart position, which limits efficiency improvements. This letter proposes a flexible restart mechanism (FRM), introducing multiple optional restart positions to further optimize the simplified restart mechanism, reducing both execution time and its variability. In simulations, we used P(1024, 128) and P(2048, 256) polar codes to compare the performance of SCF decoders embedding with FRM and SRM. The results indicate that, compared to the SCF decoder, the SCF decoder with FRM reduces average execution time, average additional execution time, execution time variance, and median additional execution time by 14.95%, 63.42%, 86.55%, and 58.20%, respectively. Compared to the SCF decoder embedding with SRM, FRM achieves improvements in these metrics by 5.15%, 23.14%, 20.24%, and 29.71%, respectively.