Fast simplified successive cancellation list (FSSCL) decoding algorithms for polar codes have been proposed to achieve low latency and high error correction performance. However, the size of the metric sorters for FSSCL-single parity check (SPC) decoders significantly expands as the list size L increases. This paper proposes a partitioned sorting network (PSN) that reduces the complexity of metric sorter for FSSCL-SPC. The proposed PSN consists of two sorting networks. For the first sorting network, we analyze the order of the path metrics (PMs) and reduce the number of input candidate paths. Furthermore, for the second sorting network, the number of compare-and-swap units (CASUs) was reduced by identifying candidates that do not need comparison among the sorted candidates from the first sorting network. The FSSCL-SPC with the proposed PSN does not show any degradation in error correction performance compared to the existing FSSCL-SPC. The proposed PSN have up to 77% fewer CASUs and up to 102% higher operating frequencies than existing FSSCL-SPC sorting networks for L=8.
