Simultaneous zero-tailing of parallel concatenated codes

In a parallel concatenated convolutional code an information word is encoded by a first convolutional encoder and an interleaved version of the information word is encoded by a second convolutional encoder. We discuss the situation in which we require that both convolutional encoders end in the all zero state. To do so, we have to split the information word in two parts. One part containing information bits, and a second part containing bits, called tail-bits, computed such that both encoders end in the all zero state, which we call simultaneous zero-tailing. Depending on the structure of the interleaver, different numbers of tail-bits are needed. By using a constructive method we characterize all interleavers for a prescribed number of tail-bits. We explain methods of encoding. In addition simulations have been carried out to investigate the performance of simultaneous zero-tailing, This shows that simultaneous zero-tailing is similar in performance compared with previously known zero-tailing methods and that it is better than zero-tailing just one of the encoders