Composite Multiple-Mode Virtual Spatial Modulation and Its Generalization for Wireless Communication Systems

Virtual spatial modulation (VSM) has shown potential for enhancing the energy efficiency of multiple-input multiple-output (MIMO) systems. However, the use of a limited set of virtual parallel channels in VSM results in lower spectral efficiency compared to traditional MIMO systems. To address this, we propose a composite multiple-mode VSM (C-MM-VSM) scheme, along with its optimized variants, to increase spectral efficiency. The C-MM-VSM extends indexing to multiple domains, mapping input bits to channel activation patterns, energy allocation patterns, and mode activation patterns. As the constellation sets are practically higher than active antennas, we propose a variant scheme, which introduces a new mapping rule between input bits and additional mode activation patterns, increasing the mode bits of the system. We also develop diversity-enhanced schemes using coordinate interleaving for improved average bit error probability (ABEP). Additionally, we propose generalized schemes that optimize all the indexes and the in-phase/quadrature extension which expands indexing to in-phase and quadrature domains, achieving double spectral efficiency. Analytical ABEP results, along with simulations, confirm that the proposed schemes outperform benchmark schemes, providing significant spectral efficiency and ABEP improvements without needing extra resources.