Investigation of Transmit Antenna Selection for MU-VASM Systems over Correlated Channels

In a variable active antenna spatial modulation (VASM) system, the number of activated antennas adjusts dynamically according to the input spatial bitstream. Thus, it is a typical variation of spatial modulation techniques, known for its high flexibility and outstanding spectral efficiency. In this paper, the operation of the multi-user (MU) VASM system is investigated under correlated channel conditions. Furthermore, three transmit antenna selection (TAS) methods, including channel gain-based TAS (CG-TAS), Euclidean distance-based TAS (ED-TAS), and hierarchical combination-based TAS (HC-TAS), are applied to enhance the quality of the MU-VASM system. The effect of the correlated channel on the bit error rate (BER) performance of every user as well as the average BER (ABER) performance of the whole system is investigated for three TAS methods. The simulation results indicate that correlated channels degrade the system’s performance. Nevertheless, the application of these TAS methods has noticeably improved the system’s quality. In particular, HC-TAS with low computational complexity consistently delivers superior ABER improvement for the system compared to other TAS methods, even in scenarios with correlated channels.