Comparison of QPSK and TCM schemes in frequency-selective fading channels

This paper investigates the average bit error rate of a TDMA digital mobile radio system which employs an adaptive decision feedback equalization (DFE), interleaving, space diversity and trellis-coded modulation (TCM). The feedback filter of the DFE uses the tentative or final decision symbols of the Viterbi decoding of the TCM to cancel tail ISI with a square root Kalman algorithm. A lower bound on the average pairwise error probability for TCM under perfect interleaving and equalization is obtained by analysis. We also present some simulation results for three TCM schemes and QPSK. The results show that TCM with finite interleaving can outperform QPSK if an appropriate equalizer structure is employed