Rate-Compatible Punctured Polar Codes

Abstract

In this work, we propose a novel puncturing scheme for rate-compatible polar codes of finite lengths. By analyzing the log-likelihood ratio (LLR) message propagation from the channel outputs to the information bits, we show that there exist certain paths, called direct paths through which the reliabilities of LLR values at the information bits are strongly influenced by the channel outputs. For each information bit, we define a metric called reliability score which measures the reliability of LLR value at the information bit built up through the direct paths. Then, we propose a rate-compatible puncturing scheme which decides punctured bits in such a way as to maximize the minimum reliability score. Simulation results show that the proposed puncturing scheme significantly outperforms existing schemes in terms of error-rate performance.