Fast Successive-Cancellation Decoding of Polar Codes With Sequence Nodes

Due to the sequential nature of the successive-cancellation (SC) algorithm, the decoding of polar codes suffers from significant decoding latencies, which hinders its application in low-latency communication scenarios. Fast SC decoding is able to speed up the SC decoding process, by implementing parallel decoders at the intermediate levels of the SC decoding tree for some special polar constituent subcodes (special nodes) with specific information and frozen bit patterns. To further improve the parallelism of SC decoding, this paper presents a new class of special nodes composed of a sequence of rate one or single-parity-check (SR1/SPC) nodes, which can be easily found especially in high-rate polar code and is able to envelop a wide variety of existing special node types. Then, we analyse the parity constraints caused by the frozen bits in each descendant node, such that the estimated codeword of the SR1/SPC node can keep its validity once the parity constraints are satisfied. Inspired by maximum-likelihood (ML) decoding, a generalized fast decoding algorithm is finally proposed to decode SR1/SPC nodes efficiently, which is able to guarantee that all the parity constraints are satisfied. Simulation results show that some SR1/SPC nodes can be decoded with quasi-ML performance, and the overall decoding latency can be reduced by up to 43.8% with slight performance improvement, as compared to the state-of-the-art fast SC decoder.