On the Free Distance of Convolutional Turbo Codes

The free distance of convolutional codes is the most important parameter determining their performance under good channel conditions. In this paper, we investigate the free distance properties of turbo-like codes generated by non-terminated convolutional encoders and convolutional permutors. In particular, we prove the existence of such codes whose free distance exhibits the same asymptotic growth rate in the permuter memory as block turbo codes in the permuter size