A Rate-Compatible Puncturing Scheme for Finite-Length LDPC Codes

In this paper, we propose a rate-compatible puncturing scheme for finite-length low-density parity-check (LDPC) codes over the additive white Gaussian noise (AWGN) channel. The proposed method is applicable to any LDPC mother code, both regular and irregular, and constructs punctured codes which perform well in both the waterfall and the error floor regions for a wide range of code rates. The scheme selects code bits to be punctured one at a time and based on a sequence of criteria. An important selection criterion is the number of short cycles with low approximate cycle extrinsic message degree (ACE) in which a candidate bit node participates. Simulation results demonstrate that the ACE measure, which is most often the determining criterion in the final selection of the puncturing candidates, plays an important role in improving the performance of the codes in both the waterfall and the error-floor regions. These results also demonstrate that the proposed scheme is superior to the existing puncturing methods, particularly when a wide range of code rates is desirable.