Successive Cancellation List Bit-flip Decoder for Polar Codes

Polar codes asymptotically achieve the capacity of binary-input memoryless symmetric channels under successive cancellation (SC) decoder. However, for finite code length, the block error rate (BLER) performance of SC decoder is mediocre. SC-flip decoder, in recent literatures, has been proposed to improve the BLER performance of SC decoder with the help of additional SC decoding attempts with unreliable bits being flipped. It is natural to ask whether the bit flip method can be employed in SC-list (SCL) decoder for polar codes. In this paper, the idea of bit-flip is introduced into cyclic redundancy check aided SCL (CA-SCL) decoder, and SCL bit-flip (SCLF) decoder is proposed. The BLER of CA-SCL decoder is improved through flipping the unreliable bit decisions. Simulation results show that for various configurations, the BLER of SCLF outperforms traditional CA-SCL decoder around 0.12-0.25dB with negligible extra complexity in mediate and high signal-to-noise ratio region.