This paper presents a literature review on recent applications and design aspects of the intelligent reflecting surface (IRS) in the future wireless networks. Conventionally, the network optimization has been limited to transmission control at two endpoints, i.e., end users and network controller. The fading wireless channel is uncontrollable and becomes one of the main limiting factors for performance improvement. The IRS is composed of a large array of scattering elements, which can be individually configured to generate additional phase shifts to the signal reflections. Hence, it can actively control the signal propagation properties in favor of signal reception, and thus realize the notion of a smart radio environment. As such, the IRS’s phase control, combined with the conventional transmission control, can potentially bring performance gain compared to wireless networks without IRS. In this survey, we first introduce basic concepts of the IRS and the realizations of its reconfigurability. Then, we focus on applications of the IRS in wireless communications. We overview different performance metrics and analytical approaches to characterize the performance improvement of IRS-assisted wireless networks. To exploit the performance gain, we discuss the joint optimization of the IRS’s phase control and the transceivers’ transmission control in different network design problems, e.g., rate maximization and power minimization problems. Furthermore, we extend the discussion of IRS-assisted wireless networks to some emerging use cases. Finally, we highlight important practical challenges and future research directions for realizing IRS-assisted wireless networks in beyond 5G communications.

中文翻译：

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通过智能反射面实现智能无线通信：当代调查

本文对智能反射面 (IRS) 在未来无线网络中的最新应用和设计方面进行了文献综述。传统上，网络优化仅限于两个端点的传输控制，即终端用户和网络控制器。衰落无线信道不可控，成为性能提升的主要限制因素之一。IRS 由大量散射元件组成，它们可以单独配置以产生额外的信号反射相移。因此，它可以主动控制信号传播特性，有利于信号接收，从而实现智能无线电环境的概念。因此，IRS 的相位控制与传统的传输控制相结合，与没有 IRS 的无线网络相比，可以潜在地带来性能提升。在本次调查中，我们首先介绍了 IRS 的基本概念及其可重构性的实现。然后，我们专注于 IRS 在无线通信中的应用。我们概述了不同的性能指标和分析方法，以表征 IRS 辅助无线网络的性能改进。为了利用性能增益，我们讨论了 IRS 相位控制和收发器传输控制在不同网络设计问题中的联合优化，例如速率最大化和功率最小化问题。此外，我们将 IRS 辅助无线网络的讨论扩展到一些新兴用例。最后，