Intelligent Reflecting Surfaces (IRS) show a revolutionary potential for wireless communications. In this paper, a single IRS is used to achieve distributed multi-user beamforming and interference-free transmission. We first establish the IRS assisted multi-user system model and formulate an optimization problem called multi-user linearly constrained minimum variance (MU-LCMV) beamformer, under the criterion of minimizing the overall received signal power subject to a certain level of power response (e.g., unit power response) at desired signal directions and arbitrary low power response (e.g., zero power response) at the interference directions. A closed-form amplitude-unconstrained phase-continuous (AUPC) solution is derived first, then an amplitude-constrained phase-continuous (ACPC) solution is obtained by using sequential quadratic programming (SQP). Given the solutions, the IRS beam pattern shows that to achieve multi-user ( NN pairs of transceivers, N>1N > 1 ) transmission through a single surface, up to N−1N-1 redundant beams are generated, significantly affecting power efficiency. The directions of the redundant beams are mathematically derived. The effect of mutual coupling on IRS is also analyzed to show the characteristic of side lobes. Simulation results verify the existence and accuracy of the redundant beam directions. This work can potentially enhance state-of-the-art wireless communication systems ranging from transceiver design, system and architecture design, network deployment and self-organizing-network operations.

中文翻译：

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基于智能反射面的多用户波束形成与传输


智能反射表面（IRS）显示出无线通信的革命性潜力。本文采用单个IRS来实现分布式多用户波束赋形和无干扰传输。我们首先建立IRS辅助多用户系统模型，并在一定功率响应水平下最小化总接收信号功率的标准下，制定称为多用户线性约束最小方差（MU-LCMV）波束形成器的优化问题（在期望信号方向上的任意低功率响应（例如，单位功率响应）和在干扰方向上的任意低功率响应（例如，零功率响应）。首先导出闭合形式的幅度无约束相位连续（AUPC）解，然后使用顺序二次规划（SQP）获得幅度约束相位连续（ACPC）解。根据这些解决方案，IRS 波束方向图表明，要通过单个表面实现多用户（NN 对收发器，N>1N > 1 ）传输，会生成多达 N−1N-1 个冗余波束，从而显着影响功率效率。冗余光束的方向是通过数学推导得出的。还分析了互耦合对IRS的影响，以显示旁瓣的特性。仿真结果验证了冗余波束方向的存在性和准确性。这项工作可以潜在地增强最先进的无线通信系统，包括收发器设计、系统和架构设计、网络部署和自组织网络操作。