Design of rate-compatible punctured turbo (RCPT) codes

We propose and compare some design criteria for the search of good rate-compatible punctured turbo (RCPT) code families. The considerations presented by S. Benedetto et al. (see IEEE Trans. on Commun., vol.46, no.9, p.1101-5, 1998) to find "best" component encoders for turbo code construction are extended to find the "best" rate-compatible puncturing patterns for a given interleaver length k. This approach is shown to be the optimal one, both in the maximum-likelihood sense (using transfer function bounds) and in the iterative decoding sense (through simulation results). A rate-compatibility restriction to the puncturing rule is used, implying that all the code bits of a high-rate punctured code are used by the lower rate codes. The two main applications of this technique are its use in modified type II ARQ/FEC schemes and to achieve unequal error protection of an information sequence.