Generalized Quadrature Space-Frequency Index Modulation for MIMO-OFDM Systems.

In this paper, motivated by the framework of diversity-achieving quadrature spatial modulation (DA-QSM), we propose a generalized quadrature space-frequency index modulation (GQSF-IM) transmission scheme for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. The dispersion matrices potentially transmit some combination of each symbol from each antenna at every subcarrier, and their structures lead to desirable coding properties. By setting two well-designed dispersion-matrix sets for both the in-phase (I-) and quadrature (Q-) dimensions, each resource block (RB) of MIMO-OFDM independently selects part of dispersion matrices from each set to modulate the real and imaginary parts of complex symbols, respectively. Thus a simple and systematic method which easily generates dispersion-matrix set with large size is presented. It can be verified that the proposed GQSF-IM scheme subsumes the existing QSF-IM scheme as its special case. Moreover, it can be proved that the GQSF-IM scheme automatically achieves the second order transmit diversity without requiring any parameter or matrix optimization. Owing to obtaining higher transmit diversity order, simulation results of bit error rate (BER) performance show that GQSF-IM outperforms QSF-IM in different channels such as independent and identically distributed (i.i.d.), correlated Rayleigh fading, and Rician channels. Furthermore, GQSF-IM can achieve obvious better BER performance when it combines with interleaving for more diversity gains. [ABSTRACT FROM AUTHOR]