Efficient Soft-Cancellation Flip Decoding of Polar Codes

The soft-cancellation (SCAN) is a low-complexity soft-output decoding algorithm of polar codes. However, the performance of the SCAN is inferior for short to medium codes. To address this issue, an efficient SCAN Flip decoding algorithm devoted to correct the first erroneous bit in the SCAN is proposed in this letter. The minimum dissemination characteristic of the SCAN decoding is found and analyzed. Besides, an on-the-fly critical set method is proposed to narrow down the range of flip locations. Moreover, before each flipping trial, cleaning of some internal messages is performed to avoid the negative impact of previous wrong message propagation. Numerical results show that the proposed algorithm has better error-correction performance and lower average number of iterations than state-of-the-art SCAN Flip decoding algorithms.