COMBINED TRANSMISSION-SYSTEM OF TCM, BIT-INTERLEAVING AND DECISION-FEEDBACK EQUALIZATION FOR FADING CHANNEL

Bit-interleaving can enhance performance of a trellis coded modulation system over a fading channel. A combined system with decision feedbac k equalization is proposed. In the system, TCM decoded symbols are fed back for equalization. To avoid a bad effect of decoding delay, a dei nterleaver is utilized effectively. Information sequence is divided in to three subsequences and encoded by three encoders. Among the 3 code vectors from the encoders, bits are interleaved and decoding proceeds in parallel. Simulation results show that the proposed system realizes 0.6dB more coding gain than a symbol interleaved system. A calculatio n method of a branch metric for decoding is proposed. Performance with the branch metric is shown to be nearly independent from the desired/ undesired power ratio of a intersymbol interference channel. An approx imate upper bound is analyzed for the proposed system, and the optimum code is searched.