Improving Belief Propagation Decoding of Polar Codes using Bi-Directional Bit-Flipping Strategy

Abstract

It is difficult to achieve high throughput and low latency from the cyclic redundancy check (CRC-) aided successive cancellation list (CA-SCL) polar decoder employed in 5G new radio systems. To tackle this problem, the hardware-efficient belief propagation (BP) decoder has been extensively studied. Unfortunately, the performance of the BP decoding for polar codes is quite poor. To improve the performance of this decoder, a novel bi-directional bit-flipping (BF) strategy is proposed. The rule of generating the flip set based on the post log-likelihood ratio (LLR) is combined with the possibility of the two-way flipping. With the help of this idea, the decoding performance of BP decoder is identical to that of the CA-SCL decoder. Moreover, with the same complexity, our proposed BF strategy outperforms both the best known one-directional BF strategy and the previously found bi-directional BF strategy at BLER of 10-4.