Performance of continuous and blockwise decoded turbo codes

In this letter we define and evaluate the average maximum-likelihood performance of the three ways of co-decoding turbo codes. In all cases the information sequence is split into blocks of N bits (N being the length of the interleaver used by the turbo code), that are encoded by the first constituent encoder and, after interleaving, by the second encoder. In the first operation mode, both constituent encoders work in a continuous fashion, whereas in the second, at the end of each block, a suitably chosen sequence of bits is appended to the information block in order to terminate the trellises of both constituent codes. In the third mode, the operation is similar to the second, but, instead of trellis termination, both constituent encoders are simply reset.