关键词: 智能反射面, 认知物联网, 多输入多输出, 波束形成

Abstract: Aiming at the problem of low spectrum efficiency in MIMO(Multiple Input Multiple Output) C-IoT (Cognitive Internet of Things) systems, a block coordinate descent algorithm based on alternating iterative assisted by IRS(Intelligent Reflecting Surface) is proposed. System weighted sum rate is maximized by jointly optimizing active beamforming at secondary transmitter and passive beamforming at IRS, and is constrained by the interference power at the primary receiver, the transmit power at the secondary transmitter, and the unit mode at the IRS. After decomposing the complex non-convex optimization problem into subproblems, the subproblems are processed using the Lagrange Dual method and the Successive Convex Approximation method, respectively. The simulation results show that the proposed algorithm can converge quickly in a multi-antenna user scenario, and the spectrum efficiency of the C-IoT system can be effectively improved by increasing the number of IRS reflective elements or correctly deploying the location of the IRS. 

Key words: intelligent reflecting surface, cognitive internet of things, multiple input multiple output(MIMO), beamforming