Iterative decoding of non-systematic turbo-codes

Parallel concatenated convolutional codes (PCCCs) are usually constructed using systematic recursive convolutional codes (SRCCs) as constituent codes. In this paper, we introduce a new version of parallel concatenation that uses nonsystematic recursive convolutional codes (NSRCCs) as constituent codes. A systematic constituent code then becomes a particular case of this general scheme. The use of this larger class of constituent codes enhances the number of possible codes in the search space, thus allowing the possibility of finding better codes. We also introduce a modified iterative decoding method for this more general form of parallel concatenation. The decoding technique is no more complex than the standard iterative decoding algorithm.