Parallel concatenated code with soft-in soft-out interactive turbo decoder

Abstract

A method for parallel concatenated (Turbo) encoding and decoding. Turbo encoders receive a sequence of input data tuples and encode them. The input sequence may correspond to a sequence of an original data source, or to an already coded data sequence such as provided by a Reed-Solomon encoder. A turbo encoder generally comprises two or more encoders separated by one or more interleavers. The input data tuples may be interleaved using a modulo scheme in which the interleaving is according to some method (such as block or random interleaving) with the added stipulation that the input tuples may be interleaved only to interleaved positions having the same modulo-N (where N is an integer) as they have in the input data sequence. If all the input tuples are encoded by all encoders then output tuples can be chosen sequentially from the encoders and no tuples will be missed. If the input tuples comprise multiple bits, the bits may be interleaved independently to interleaved positions having the same modulo-N and the same bit position. This may improve the robustness of the code. A first encoder may have no interleaver or all encoders may have interleavers, whether the input tuple bits are interleaved independently or not. Modulo type interleaving also allows decoding in parallel.