A simple interleaver design for variable-length turbo codes

Performance of short-length turbo code is largely determined by the interleaver structure. This paper proposes a new interleaver design based on an extension of S-random interleavers. The proposed interleaver makes use of several short length S-random interleavers to construct an interleaver of longer length. Since S-random interleavers of short length are easily found by computer search, the overall complexity of constructing longer-length interleaver is relatively low while retaining comparable performance with regular S-random interleavers of full length. The major advantage of the proposed interleaver is its robustness against pruning of the interleaver length and thus suitable for the system that requires variable-length turbo codes.