BIT ERROR PROBABILITY OF TRELLIS-CODED QUADRATURE AMPLITUDE MODULATION OVER CROSS-COUPLED MULTIDIMENSIONAL CHANNELS.

Convolutionally encoded M-ary quadrature amplitude modulation (M-QAM) systems operated over multidimensional channels, for example dual-polarized radio systems, are considered. Upper bounds on the average bit-error probability for 4-QAM (QPSK) with conventional convolutional coding have been derived by means of a truncated union bound technique and averaging over the cross-polarization interference using the method of moments. By modifying the technique, approximate upper bounds on the average bit-error probability have been found for bandwidth-efficient trellis-coded QAM systems that offer larger coding gains in an interference environment than in a Gaussian noise channel. A new concept referred to as dual-channel polarization hopping is introduced that can improve the system performance significantly for multidimensional systems with nonsymmetrical cross-coupling interference.