A Cascaded Multi-IRS-assisted Signed Quadrature Spatial Modulation System

A cascaded multi-intelligent reflecting surface (IRS)-assisted signed quadrature spatial modulation (SQSM) system is proposed in this paper with intelligently integrating single and multiple IRS into the SQSM scheme. In this system, the signal is transmitted via the reflection of single or cascaded multiple IRSs. The proposed system models, however, benefit from the spatial multiplexing gain and the signal-to-noise ratio (SNR) gain of SQSM and IRSs, respectively. The bit error rate (BER) performance of the proposed systems is evaluated and compared to the performance of the conventional SQSM system without IRS for the sake of fair comparison. The simulation results show that a considerable performance gain is achieved by the proposed cascaded multi-IRS-assisted SQSM system over the conventional SQSM scheme, and this gain increases with increasing the number of cascaded IRSs and the number of their passive elements. The close match is also noticed between the analytical and simulated BER performances of the proposed systems with high SNR values.