Improving the performance of multi-IRS aided millimeter-wave communication systems by transmit antenna selection

Abstract

In this article, we propose applying multiple intelligent reflecting surfaces (IRSs) and transmit antenna selection (TAS) in millimeter-wave (MW) communication systems. Specifically, multiple IRSs are deployed to assist communications between a base station and a mobile user using high carrier frequencies of MW bands. To improve the performance and reduce the computational complexity in signal processing at the user, TAS is applied at the base station. We successfully obtain the mathematical formulas of outage probability (OP) and throughput of the proposed multi-IRS-aided MW communication systems with TAS (referred to as multi-IRS-MW systems) over Nakagami-m channels. Then, the performance metrics of the multi-IRS-MW systems with TAS are compared with those of the multi-IRS-MW systems without TAS to confirm the huge benefits of TAS. Additionally, the performance metrics of the multi-IRS-MW systems with and without TAS are also compared with those of MW systems without IRSs, i.e., point-to-point (P2P) MW communication systems (referred to as P2P-MW systems) with and without TAS to verify the big advantages of utilizing IRSs. It is clarified that the performance of the proposed multi-IRS-MW systems with TAS is greatly improved in comparison with that of multi-IRS-MW systems without TAS and P2P-MW systems with and without TAS. Many solutions such as choosing suitable positions of IRSs, increasing the number of transmit antennas, and using appropriate transmit power and carrier frequency are also provided to considerably enhance the performance of the multi-IRS-MW systems with TAS. Finally, we verify the derived formulas via Monte-Carlo simulations.