Enhancing Spatial Modulation System Performance Through Signal Space Diversity

Signal space diversity (SSD) is considered in this letter to enhance the performance of spatial modulation (SM) multiple-input multiple-output systems. SSD implies that the phase of the modulated quadrature amplitude modulation/phase shift keying symbol is rotated such that each incoming bit is represented by both the in-phase (I) and the quadrature (Q) components of the complex symbol. The resultant I and Q components are then interleaved over time to achieve a diversity gain and enhance the system performance. In this letter, SSD technique is applied to SM to achieve a transmit diversity and enhance the error performance without sacrificing spectral efficiency. The novel scheme is called diversity-enhanced SM (DE-SM). An analytical framework for evaluating the proposed DE-SM scheme is conducted, where the average bit error rate is formulated in an upper bound expression. Obtained results reveal the significant enhancement of DE-SM especially in single-receive antenna systems. The impact of the involved different parameters including optimum phase rotation are also investigated and studied.