An Efficient Construction of Rate-Compatible Punctured Polar (RCPP) Codes Using Hierarchical Puncturing

In this paper, we present an efficient method to construct a good rate-compatible punctured polar (RCPP) code. One of the major challenges on the construction of a RCPP code is to design a common information set which is good for all the codes in the family. In the proposed construction, a common information set is simply optimized for the highest-rate punctured polar code in the family and then, this set is updated for each other code by satisfying the condition that information bits are unchanged during retransmissions. This is enabled by presenting a novel hierarchical puncturing and information-copy technique. To be specific, some information bits are copied to frozen-bit channels, which yields an information-dependent frozen vector. Then, the updated information sets are obtained by appropriately combining the common information set and an information-dependent frozen vector. Moreover, the impact of unknown frozen bits are resolved using the proposed hierarchical puncturing. Simulation results demonstrate that the proposed RCPP code attains a significant performance gain (about 2dB) over a benchmark RCPP code where both codes use the same puncturing patterns but the latter uses the conventional all-zero frozen vector. Therefore, the proposed method would be crucial to construct a good RCPP code.