Multicarrier trellis-coded modulation over nonuniformly distorted channels

Past research on trellis-coded modulation (TCM) mostly deals with additive white Gaussian noise (AWGN) or homogeneous fading statistics. A multicarrier scheme over TCM is proposed over nonuniformly distorted (ND) channels. We consider quadrature amplitude modulation (QAM) to analyze the proposed TCM, and show the effectiveness of the proposed scheme. The multicarrier approach effectively mitigates nonuniform distortion problem by dividing the entire band into groups of labeled carriers (subchannels with quality indexes) and weights the metrics separately according to the frequency response of the individual carrier. The optimum weight taps are shown to be inversely proportional to the noise level of the respective carrier. Furthermore, the weights are given to make the uneven noise response “flat” so that the weighting function results in a “whitening filter”