Generalized Constellation Rearrangement in Cooperative Relaying

In Constellation Rearrangement (CoRe), the basestation and the relay use different constellations, with the same number of signal points, to communicate with the user terminal. In contrast to the existing CoRe techniques, which restrict the possible constellations, the authors propose generalized Quadrature Amplitude Modulation (QAM) constellations. Since generalized CoRe schemes do not restrict constellations, they have the potential of outperforming all other CoRe schemes, with a complexity penalty in decoding. They pose an optimization to find the generalized QAM constellations, which minimize an upper bound on the uncoded Symbol Error Rate (SER).