Efficient metric sorting schemes for successive cancellation list decoding of polar codes

Path metric sorting unit of successive cancellation list (SCL) decoders for polar codes is the main concern in this paper. After reviewing existing sorting units in SCL decoders, we propose 2 new sorting schemes namely quick select (QS) based selection algorithm and simplified bitonic sorter (SBT), which exploit the special data dependency of path metrics in log-likelihood ratio based SCL decoding. Theoretical analysis shows that for the list size of L ≤ 8, QS-based selection algorithm has lower delay than existing schemes. FPGA implementation based on Artix7 Family shows that for the list size of L ≥ 16, SBT has the same delay while the hardware reduction is over 40%.