LLR-based Successive-Cancellation List Decoder for Polar Codes with Multi-bit Decision

Due to their capacity-achieving property, polar codes have become one of the most attractive channel codes. To date, the successive cancellation list (SCL) decoding algorithm is the primary approach that can guarantee outstanding error-correcting performance of polar codes. However, the hardware designs of the original SCL decoder have large silicon area and long decoding latency. Although some recent efforts can reduce either the area or latency of SCL decoders, these two metrics still cannot be optimized at the same time. This paper, for the first time, proposes a general log-likelihood-ratio (LLR)-based SCL decoding algorithm with multi-bit decision. This new algorithm, referred as LLR-2Kb-SCL, can determine 2K bits simultaneously for arbitrary K with the use of LLR messages. In addition, a reduced-data-width scheme is presented to reduce the critical path of the sorting block. Then, based on the proposed algorithm, a VLSI architecture of the new SCL decoder is developed. Synthesis results show that for an example (1024, 512) polar code with list size 4, the proposed LLR-2Kb-SCL decoders achieve significant reduction in both area and latency as compared to prior works. As a result, the hardware efficiency of the proposed designs with K=2 and 3 are 2.33 times and 3.32 times of that of the state-of-the-art works, respectively.