Perturbation-Enhanced SCL Decoder for Polar Codes.

For polar codes, successive cancellation list (SCL) decoding algorithm significantly improves finite-length performance over SC decoding. SCL-flip decoding can further enhance the performance but the gain diminishes as code length increases, due to the difficulty in locating the first error bit position. In this paper, we propose SCL-perturbation decoding algorithms to address this issue. Specifically, we introduce small random perturbations to the received symbols before each SCL decoding attempt. With the same number of decoding attempts, perturbation yields higher coding gain than flipping at large block length. Extensive simulation results show stable gain under various code rates, lengths, list sizes and numbers of decoding attempts. To our best knowledge, this is the first SCL enhancement with non-diminishing gain as code length increases.