Systematic feed-forward convolutional encoders are better than other encoders with an M-algorithm decoder
Consider nonbacktracking convolutional decoders that keep a fixed number of trellis survivors. It is shown that the error performance of these depends on the early part of the distance profile and on the number of survivors kept, and not on the free distance or the details of the code generators. Particularly, the encoder may be feedforward systematic without loss. Furthermore, this kind of encode