Multi-attempt list decoding of polar codes

Dongsheng Wu, Qingshuang Zhang, Yingxian Zhang

Zhongjun Yang

Soft information perturbation can significantly enhance the successive cancellation list (SCL) decoding performance of polar codes. However, the existing perturbation-based SCL (PSCL) decoding requires a large number of re-decoding attempts, leading to high decoding complexity, and hence limits its application for long polar codes. In this letter, an enhanced PSCL (E-PSCL) decoding is proposed. It utilizes a new biased perturbation strategy that requires a reduced number of redecoding attempts, but yields an advanced decoding performance. To further improve the E-PSCL decoding performance, a reliability metric (RM) is introduced. It can better identify the possibly erroneous positions within the SCL decoding failures. During each decoding attempt, the E-PSCL decoding takes turns to flip these positions. Moreover, for the RM, it is derived from the SCL decoding error probability for which both the frozen bits and the error propagation are considered. Simulation results show that with the same number of decoding attempts, the proposed E-PSCL decoding outperforms the state-of-the-art dynamic SCL flip (D-SCLF) decoding and the conventional PSCL decoding.

Fedor I. Ivanov, Valerii Morishnik, Evgenii A. Krouk

In this paper, an improvement for SC list flip (SCL-Flip) decoding is presented for polar codes. A novel bit-selection metric for critical set (set of information symbols of polar codes being flipped during additional decoding attempts) based on path metric of successive cancellation list (SCL) decoding is suggested. With the proposed metric, the improved SCL scheme based on special nodes (SN) decoders was developed. This decoder will be denoted by GSCLF. The main idea of the proposed decoder is joint using of two approaches: first one is a fast decoding of special nodes in binary tree representation of polar code (e.g., some special nodes in tree representation of polar code that allow efficient list decoding with low complexity) and the second one is an applying of additional decoding attempts (flips) in the case when initial decoding was erroneous. The simultaneous use of these two approaches results in both a significant reduction in spatial complexity and a significant reduction in the number of computations required for decoding whereas keeping excellent performance. Simulation results presented in this paper allow us to conclude that the computational complexity of the proposed GSCLF decoder is from 66% to 80% smaller than the one of SCL-32 decoder.

Grigorii Trofimiuk, Nikolay Iakuba, Stanislav Rets +2 more

A. Çağrı Arlı

Jiangxue Han, Rongke Liu, Runxin Wang

In this paper, we propose a simplified multi-bit successive cancellation list (SMSCL) decoding method for polar codes. In the proposed SMSCL decoding, frozen bits are ignored, and multiple information bits are intermediately decoded at each decision step. In addition, a modified two-stage pruning network is proposed to reduce the complexity of path pruning in SMSCL decoding. Compared to the existing multi-bit SCL decoders, the SMSCL decoder can achieve significant latency and complexity reduction over a wide range of code rates.