Generalized Quadrature Index Modulation With Multi-Index and Dimension-Extended Constellation

In this paper, in pursuit of enhancing the spectral efficiency and reliability of transmission in multiple-input multiple-output (MIMO) communication system, a new design method, named as the generalization of quadrature index modulation (GQIM), is proposed. In GQIM system, the key and vector indications are exploited by the design of the transmitted spatial vector (TSV). Also, the transmit diversity gain by transmitting two versions produced by a three dimension (3D) symbol is achieved. More specifically, in our proposed GQIM system, an extended dimension signal constellation, so called extended 3D constellation (E3DC), is designed for the employment in the GQIM framework. Then, for achieving the transmit diversity gain, combing with the antenna indexes, the $X$ -axis, $Y$ -axis, $Z$ -axis components of two versions of the E3D symbol are constructed into four spatial vectors that are considered as candidates of the real/imaginary part of a complex TSV. Furthermore, two possible TSVs are obtained by using two adders and two key controllers with two states of 1 and $j$ . With the aid of the vector indication, one out of two possible TSVs is selected for transmission. Finally, the spectral efficiency and squared MED, the spatial index bits and computational complexity, the upper bound on the average bit error probability are analyzed. The analytical and simulation results demonstrate the correctness of GQIM and show that GQIM achieves a higher data rate and the reliability of transmission in comparison to the existing classic systems.