Quadrature Spatial Modulation OFDM System Performance in the Presence of High Power Amplifier Nonlinearities

This paper proposes a combination between quadrature spatial modulation (QSM) multiple-input multiple-output (MIMO) system and orthogonal frequency division multiplexing (OFDM) aiming to benefit from their superior inherent advantages. The proposed system uses multiple transmit antennas and applies QSM technique on the different OFDM sub-carriers transmitted from the multiple antennas. Therefore, at each frequency sub-carrier, one antenna will be transmitting a real part of the modulated symbol and another or the same antenna will be transmitting the imaginary part of that symbol. As such, many of the transmitted sub-carriers in one OFDM symbol will be un-modulated and transmitting no data, which promises major reduction in the peak to average power ratio (PAPR). Typical OFDM systems generally suffer from high PAPR, which causes major performance degradation in the presence of high power amplifier (HPA) nonlinearities. It is revealed, in this paper, that the proposed system achieves superior performance as compared to it's spatial modulation and spatial multiplexing counterpart systems. Analytical analysis on the overall bit error probability is provided and corroborated through Monte Carlo simulation results.