INTEGRATION OF ADAPTIVE EQUALIZATION AND TRELLIS-CODED MODULATION WITH INTERLEAVING FOR LAND MOBILE COMMUNICATIONS

Future digital land mobile communication, for a moving picture, requir es more transmission speed and less bit error rate than the existing s ystem does for speech. In the system, the intersymbol interference may not be ignored, because of higher transmission speed. An adaptive equ alizer is necessary to cancel intersymbol interference. To achieve low bit error rate performance on the mobile radio channel, trellis-coded modulation with interleaving is necessary, This paper proposes an int erleaved trellis-coded modulation scheme combined with a decision feed back type adaptive equalizer of high performance. The reliable symbol reconstructed in the trellis decoder is used as the feedback signal. T o make equalizer be free from decoding delay, deinterleaving is effect ively utilized. The branch metric, for trellis-coded modulation decodi ng, is calculated as terms of squared errors between a received signal and an expected signal by taking the reconstructed symbol and the imp ulse response estimated by the recursive least squares algorithm into account. The metric is constructed to have good discrimination perform ance to incorrect symbols even in non-minimum phase and to realize pat h diversity effect in a frequency selective fading channel. Computer s imulation results are shown for several channel models. On a frequency selective fading channel, average bit error rate is less than 1/100 o f that of the RLS-MLSE equalizer for f(d)T(s) = 1/1000 at average E(b) /N-o beyond 15 dB. Performance degradation due to equalization error i s less than 1.8 dB. Performance is greatly improved by the effect of t he reconstructed symbol feedback.