Joint interleaver and trellis code design

Trellis coded modulation is often combined with some form of interleaving to mitigate correlation between the attenuation (fading) suffered by adjacent symbols. A common assumption has the interleaver producing a sequence of symbols with essentially independent fading. In fact, the dependence originally present in the fading is merely permuted by the interleaver. This paper presents a trellis code design technique that includes the post-interleaver correlation in the design metrics. Bit error rate simulations demonstrate that the new design technique provides a dramatic performance improvement when fading or interference is severe and strongly correlated.