Polar Code Construction for BP Decoder

Belief propagation (BP) is a high-throughput decoding algorithm for polar codes, but the performance under BP decoder is not satisfactory due to the mismatch between the virtual channels seen by the BP decoder and bit-channel in the conventional construction method. In this letter, we record the required number of iteration of unfrozen bits to reach a specific log-likelihood ratio (LLR), which can identify weak bit-channels. Moreover, we modify the conventional polar code construction by swapping these bit-channels with strong frozen bit-channels. Simulation results show that the proposed method achieves better performance than that of the conventional construction.