Optimized sorting network for successive cancellation list decoding of polar codes

Abstract

In this paper, we propose an optimized bitonic sorting architecture and a hybrid sorting architecture for addressing the sorting problem of successive cancellation list decoders for polar codes. Since half of the 2L metrics are already sorted, lots of redundant sorting operations can be deleted. According to this property and the characteristics of the sorting network, we put forward several optimization strategies to reduce the compare-and-exchange units and the pipeline depths. For the list size L ≤ 32, the synthesis results show that the area of proposed hybrid sorter is at least 22% smaller than existing sorters, and the latency is at least 25% smaller.

An implementation of fast polar codes decoder with reducing internal memory and supporting flexible code rate

“…Fig. (6) shows the internal memory structure that requires to be rearranged using across the one-layer calculation scheme. This calculation scheme directly calculates from the 8th layer to the 6th layer, and does not need to store the value of the LLRs of the 7th layer.…”

“…In order to address this issue, simplified SC (SSC), Fast-SSC, SSC with maximum-likelihood decoding (ML-SSC) and belief propagation (BP) algorithm were proposed in [7,8,9,10,11,12,13,14,15]. To improve the errorcorrection performance of polar codes with the short and moderate code length, SC-list (SCL), Cyclic redundancy check aided successive cancellation list (CA-SCL) and BPlist (BPL) were proposed to improve the error-correction performance shown in [4,6,16,17,18,19,20,21,22]. In order to reduce the number of nodes traversing the polar decoding tree, [8,9] proposed four special nodes to improve the throughput, collectively referred to as Fast-SSC decoder.…”