Constellation Design for Quadrature Spatial Modulation

Abstract

This paper considers constellation design for quadrature spatial modulation (QSM) to minimize the average probability of error. Different than the constellation design previously obtained for spatial modulation (SM), it is shown that, the error performance of QSM not only depends on the Euclidean distances between the amplitude-phase modulation (APM) symbols and the energies of APM symbols, but also on the in-phase and quadrature components of the QSM symbols. The analysis of the union bound of the average error probability reveals that at a very large number of transmit antennas, the optimal constellations for QSM converge to a quadrature phase-shift keying (QPSK) constellation. Simulation results demonstrate the performance superiority of the obtained constellations over the standard PSK and QAM constellations, as well as the constellations specifically designed for SM.