Double-IRS Assisted Multi-User MIMO: Cooperative Passive Beamforming Design
Simulation results validate the analytical results and show the practical advantages of the proposed double-IRS system with cooperative passive beamforming designs in terms of the maximum signal-to-noise ratio (SNR) and multi-user effective channel rank, respectively.
Abstract
Intelligent reflecting surface (IRS) has emerged as an enabling technology to\nachieve smart and reconfigurable wireless communication environment\ncost-effectively. Prior works on IRS mainly consider its passive beamforming\ndesign and performance optimization without the inter-IRS signal reflection,\nwhich thus do not unveil the full potential of multi-IRS assisted wireless\nnetworks. In this paper, we study a double-IRS assisted multi-user\ncommunication system with the \\emph{cooperative} passive beamforming design\nthat captures the multiplicative beamforming gain from the inter-IRS channel.\nUnder the general channel setup with the co-existence of both double- and\nsingle-reflection links, we jointly optimize the (active) receive beamforming\nat the base station (BS) and the cooperative (passive) reflect beamforming at\nthe two distributed IRSs (deployed near the BS and users, respectively) to\nmaximize the minimum signal-to-interference-plus-noise ratio (SINR) of all\nusers. Moreover, for the single-user and multi-user setups, we analytically\nshow the superior performance of the double-IRS cooperative system over the\nconventional single-IRS system in terms of the maximum signal-to-noise ratio\n(SNR) and multi-user effective channel rank, respectively. Simulation results\nvalidate our analytical results and show the practical advantages of the\nproposed double-IRS system with cooperative passive beamforming designs.\n