low complexity [@leroux; @Gal_SW], however its error-correction performance is mediocre at practical code lengths. Thus, many attempts have been made to overcome this issue [@SCFlip14; @SCF-WCNC18].

Eventually, a list-based decoding approach to polar codes (SCL) was introduced in [@tal_list]. The idea is to let a group of SC decoders work in parallel, maintaining different codeword candidates, or paths, at the same time. Every time a leaf node is reached, the bit is estimated as both 1 and 0, doubling the number of codeword candidates; a path metric for each candidate is then calculated to discard less likely candidates, hence limiting the number of paths. SCL substantially improves the error-correction performance of SC at moderate code lengths, especially when the code is concatenated to an outer code acting as a genie, e.g. a cyclic redundancy check (CRC), at the cost of an augmented complexity. CRC-assisted (CA) SCL has been used as a baseline in 5G error-correction performance evaluations, in particular with a list size equal to 8 [@RGPP_AH1].

While the effectiveness of SCL improves as the list size increases, its implementation complexity increases as well. To limit the rise in complexity, various approaches have been proposed for software and hardware decoders 