Reduced-latency LLR-based SC list decoder for polar codes

Polar codes, as the new generation of channel codes, have potential applications in communication and storage systems. Successive cancellation list (SCL) algorithm is the main decoding approach for improving the error-correcting performance of polar codes. Recently low-complexity SCL decoders in the log-likelihood-ratio (LLR) form were proposed to replace the original ones in the likelihood form. However, these LLR-based SCL decoders can only decode 1 bit in one cycle, which leads to very long latency. This paper, for the first time, presents a reduced-latency LLR-based SCL decoder. With the new decoding scheme that determines 2 bits simultaneously, the proposed (n, k) decoder reduces the entire decoding latency from 3n-2 to 2n-2 clock cycles with the same critical path delay as the prior LLR-based SCL decoders. As a result, the decoding throughput and hardware efficiency are increased by a factor of 1.5. In addition, compared to a prior reduced-latency non LLR-based SCL decoder, the proposed work reduces the area by two times as well.