Dynamic SCL Decoder With Path-Flipping for 5G Polar Codes

Since polar were ratified as part of the 5G standard, low-complexity polar decoders with close-to-optimum error-rate performance have received significant attention. Compared to successive cancellation (SC) decoding, both SC list and SC flip decoding can improve the error rate performance by increasing the number of considered candidate solutions. The combination of both strategies leads to SC list flip (SCLF) decoding, which can provide a tradeoff between error rate performance and area as well as energy. In this letter, we derive a new flip metric for the SCLF decoding process, based on which we propose the dynamic SCLF (D-SCLF) decoding algorithm. Moreover, we exploit the distributed CRC defined in the 5G standard to further optimize the D-SCLF decoding. Numerical results show that for the downlink control channel, our D-SCLF decoder with a list size of only four and only three additional attempts can achieve the performance of a regular list decoder with a list size of eight, leading to an overall memory and average complexity (energy) reduction.