Trellis code design for periodic interleavers

A standard technique for correlated fading combines trellis codes designed for independent fading with interleaving that makes correlated fading appea r to be independent for symbols within the Viterbi traceback depth. When th e fading correlation is persistent and delay constraints preclude deep inte rleaving, some correlation remains among symbols within the traceback depth . Incorporating this post-interleaver correlation improves the trellis code design. This letter presents such a trellis code design technique for peri odic interleavers. Bit error rate simulations demonstrate that the new desi gn technique can provide a dramatic performance improvement when fading or interference is severe and persistent.