A double byte interleaving scheme for ADSL modems

We present a new way of operation for the convolutional interleaver of an asynchronous digital subscriber line (ADSL) modem, exploiting the single latency path through the modem. A combined buffer is added after the Reed-Solomon (RS) coders in order to support the parallel way of operation. On the other hand, the combined buffer increases the correcting capabilities of the structure in case the fast path through the modem used, as it serves as an interleaver with a depth of two. The interleaving process is of the double byte kind. The proposed structure offers a performance equivalent to that achieved by a conventional interleaver with a depth of interleaving of double size, reducing thus significantly the delay caused by the interleaver. The gains achieved range from 50% to even a 100%.