Simplified Metric Sorting for Multi-Bit Successive Cancellation List Decoding of Polar Codes

Abstract

This letter focuses on the metric sorting step for multi-bit successive cancellation list (SCL) decoders of polar codes, which is an important part of the whole decoder. We propose a primary-secondary exchange sorting (PSES) method. In the primary sorting, most of the survivals, {L} paths are selected from the first minor 2L candidates. In the secondary sorting, a small number of {N} paths are extracted from the other huge number of candidates to remedy the missing survivals. The {N} paths in the secondary stage are exchanged with the largest {N} elements in the first {L} paths. Due to the minor candidates in the primary stage and the few survivals in the secondary stage, this method reduces the complexity with negligible performance loss. Additionally, a sorting network based on compare-And-swap unit (CASU) PSES (CPSES) and a sorting network based on Radix-2L PSES (RPSES) are proposed to improve secondary sorting. The evaluation results show that compared with state-of-The-Art metric sorting methods, the proposed CPSES architecture significantly reduces hardware resources, and the proposed RPSES architecture significantly reduces the latency.