Trellis coded noncoherent QAM: a new bandwidth and power efficient scheme

The authors introduce the concept of noncoherently detected, multilevel/phase trellis coded schemes. They derive the optimal noncoherent decoding algorithm for trellis coded QAM (quadrative-amplitude-modulated) signals. Further, two reduced complexity decoder structures are proposed and analyzed. The first is based on a reduced state algorithm, whereas the second one uses a novel algorithm that combines both envelope and multiple differential detection. The two decoders have been evaluated for a 16-QAM signalling format by means of computer simulation. The results indicate that the proposed schemes have performance gains of up to 5 dB over equivalent conventionally detected noncoherent systems