A High Spectral Efficiency Spatial Modulation Technique

A high spectral efficiency multiple-input multipleoutput (MIMO) technique called Quadrature Spatial Modulation (QSM) is proposed in this work. QSM enhances the overall spectral-efficiency of conventional SM systems by using an extra spatial modulation dimension. The conventional SM technique uses only the real part of the spatial modulation constellation and QSM extends this to in-phase and quadrature dimensions. It is shown that significant performance enhancements as compared to conventional SM can be achieved without any extra cost. Also, a closed-form expression for the pair-wise error probability (PEP) of generic QSM system is derived and used to calculate a tight upper bound of the Average Bit Error Probability (ABEP) over Rayleigh fading channels. Additionally, simple and general asymptotic expression is derived and analyzed. Obtained Monte Carlo simulation results corroborate the accuracy of the conducted analysis and demonstrate the significant enhancements of the QSM scheme.