Efficient Sorting Architecture for List-Fast-SSC Decoding of Polar Codes

Polar codes have been proven to achieve the symmetric capacity of memoryless channel. Compared with a successive cancellation list decoder, list-Fast simplified-successive cancellation generates more candidate paths, which leads to more resource costs and higher decoding latency. To remedy this drawback, we present a simplified sorting architecture. An M*L ordered candidate path matrix is constructed by preliminary sorter, where M and L denote the number of candidate path expanded by one constituent code and the list size of the decoder, respectively. Then, we eliminate the candidate paths that are definitely not in the L best paths by the proposed lossless pruning algorithm. Finally, a compatible sorting network combining the advantages of bitonic sorter and odd-even sorter is proposed. Numerical results show that for L = 32 and M = 8, the proposed architecture can reduce 66.7% of candidate paths and save 52.3% of compare and swap units (CASUs) and 25% of CASU stages compared with the odd-even sorter.