Constructive codes for arbitrary discrete memoryless channels

In 1982, Delsarte and Piret constructed a concatenated code for which the error probability decreases exponentially with the block length for a subclass of symmetric channels called regular channels. In the case of arbitrary discrete memoryless channels, they were not able to prove an exponential bound, but one for which the error probability decreases as (log N/N)^α where α is related to the random coding exponent and N is the block length. The present author shows that indeed, the codes also satisfy the much stronger exponential bound for arbitrary discrete memoryless channels and hence are good in this sense. It is also indicated that the codes are valid for the bandlimited additive Gaussian noise channel