Optimum detection of non-orthogonal QAM signals with spectral overlapping

The authors evaluate and propose two approaches for the detection of two non-orthogonal m-QAM signals with spectral overlapping through an AWGN channel. Some previously reported works are revisited and alternative solutions in order to permit their application in practical communication systems are proposed. The subject method is proved to be relevant because it does not obey the Riesz basis condition for performing signal separation. The optimum maximum-likelihood receiver for this detection problem is also derived and the performance analysis is presented, including some analytical and Monte Carlo simulation results.