Ring-TCM codes for QAM

Multilevel convolutional codes based on rings of integers modulo-4 suitable for rectangular QAM constellations are presented. Codes performing at similar or better coding gains than binary TCM codes which have similar or less complex decoders than these and which, in addition, are 90 degrees phase rotationally invariant are reported in this paper. This means a significant improvement on channels subject to likely loss of phase synchronisation.<
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