Interleavers For Punctured Turbo Codes

Puncturing is a way of increasing the code rate by deleting one or more parity bits in a code word without an increase in complexity. Puncturing is applied to the Turbo code scheme of Berrou et al. to increase the coding rate from 1/3 to 1/2 or higher rates. Normally, puncturing causes uneven protection due to the process of random interleav-ing. This problem can be solved with a mod-k in-terleaver to ensure even protection. We nd that mod-k interleavers can improve the performance of Turbo codes with pseudo random interleavers. We also introduce a symmetric interleaver which can perform both interleaving and deinterleaving. A symmetric interleaver can usually be found that performs slightly better than non-symmetric inter-leavers at low error rates.