In this paper, a novel reconfigurable intelligent surface (RIS)-assisted multiple-input multiple-output (MIMO) symbiotic radio (SR) system is proposed, in which an RIS, operating as a secondary transmitter (STx), sends messages to a multi-antenna secondary receiver (SRx) by using cognitive backscattering communication, and simultaneously, it enhances the primary transmission from a multi-antenna primary transmitter (PTx) to a multi-antenna primary receiver (PRx) by intelligently reconfiguring the wireless environment. We are interested in the joint design of active transmit beamformer at the PTx and passive reflecting beamformer at the STx to minimize the total transmit power at the PTx, subject to the signal-to-noise-ratio (SNR) constraint for the secondary transmission and the rate constraint for the primary transmission. Due to the non-convexity of the formulated problem, we decouple the original problem into a series of subproblems using the alternating optimization method and then iteratively solve them. The convergence performance and computational complexity of the proposed algorithm are analyzed. Furthermore, we develop a low-complexity algorithm to design the reflecting beamformer by solving a backscatter link enhancement problem through the semi-definite relaxation (SDR) technique. Then, theoretical analysis is performed to reveal the insights of the proposed system. Finally, simulation results are presented to validate the effectiveness of the proposed algorithms and the superiority of the proposed system.

中文翻译：

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可重构智能表面辅助 MIMO 共生无线电网络


本文提出了一种新型可重构智能表面（RIS）辅助的多输入多输出（MIMO）共生无线电（SR）系统，其中RIS作为辅助发射器（STx），将消息发送到它通过使用认知反向散射通信来增强多天线辅助接收器（SRx），同时通过智能地重新配置无线环境来增强从多天线主发射器（PTx）到多天线主接收器（PRx）的主传输。我们对 PTx 处的有源发射波束形成器和 STx 处的无源反射波束形成器的联合设计感兴趣，以最大限度地减少 PTx 处的总发射功率，并受到二次传输和信噪比 (SNR) 的约束。主传输的速率限制。由于问题的非凸性，我们使用交替优化方法将原始问题解耦为一系列子问题，然后迭代求解它们。分析了该算法的收敛性能和计算复杂度。此外，我们开发了一种低复杂度算法来设计反射波束形成器，通过半定松弛（SDR）技术解决反向散射链路增强问题。然后，进行理论分析以揭示所提出系统的见解。最后给出仿真结果来验证所提算法的有效性和所提系统的优越性。