The Study on the early Stopping Criteria for Polar Belief-Propagation Decoders

To reduce decoding latency, the research on early stopping criteria for polar Belief Propagation (BP) algorithm has practical significance. In this paper, we propose an early stopping criteria for polar BP algorithm using cyclic redundancy check (BP-CRC for short), a CRC checking is performed on the source estimated value if the number of iterations is larger than a threshold value. If the checking is passed, BP algorithm is stopped. Otherwise, BP algorithm is not stopped until a fixed number of iterations reached. For (1024,512）Polar codes over binary-input additive white Gaussian noise channels, the simulation between BP-CRC and G-matrix stopping criterion (BP-Gmatrix for short) show the performance using the proposed algorithm is equal to that using the original BP algorithm, but the average number of iterations is significantly reduced. It was found that the reduced number of average iterations is the same both for BP-CRC and G-matrix. As the SNR increases, the reduced number of average iterations is larger. Compared to the operation of the generator matrix G, CRC has advantages of computing complexity. Moreover, the latency and energy dissipation of BP decoder can be greatly reduced with less average iterations. In summary, CRC is an effective lowpower and low complexity of early stopping criteria for polar BP algorithm.