Abstract
Quadrature spatial modulation (QSM) is a recent digital multiple-input multiple-output (MIMO) transmission technique. Combined with cooperative relaying, QSM improves the overall spectral efficiency and enhances the communication reliability. This letter studies the performance of QSM amplify-and forward cooperative relaying systems. In particular, a closed-form expression for the average pair-wise error probability of the cooperative system is derived, which is used to calculate a tight upper bound of the average bit error probability (ABEP) over Rayleigh fading. In addition, a simple approximate, yet accurate expression is derived and analyzed asymptotically. Simulation results, which corroborate the numerical ones, show the effectiveness of combined QSM and cooperative relaying in improving the overall system performance.