Rate-Compatible Punctured Polar Codes
Seokju Han, Bonghoe Kim, Jeongseok Ha
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 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">direct paths</i> 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 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">reliability score</i> 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.