The development of metasurfaces has unlocked various use cases in wireless communication networks to improve performance by manipulating the propagation environment. Intelligent omni-surface (IOS), an innovative technique in this category, is proposed for coverage extension. In contrast to the widely studied reflective metasurfaces, i.e., intelligent reflecting surfaces (IRSs), which can only serve receivers located on the same side of the transmitter, the IOS can achieve full-dimensional wireless communications by enabling the simultaneous reflection and refraction of the surface, and thus users on both sides can be served. In this paper, we provide a comprehensive overview of the state-of-the-art in IOS from the perspective of wireless communications, with the emphasis on their design principles, channel modeling, beamforming design, experimental implementation and measurements, as well as possible applications in future cellular networks. We first describe the basic concepts of metasurfaces, and introduce the corresponding design principles for different types of metasurfaces. Moreover, we elaborate on the reflective-refractive model for each IOS element and the channel model for IOS-aided wireless communication systems. Furthermore, we show how to achieve full-dimensional wireless communications with the IOS for three different scenarios. In particular, we present the implementation of an IOS-aided wireless communication prototype and report its experimental measurement results. Finally, we outline some potential future directions and challenges in this area.
翻译:与广泛研究的反映式表面(即智能反射表面(IRS),它只能为发射机同一侧的接收器服务)相比,光学表面(IOS)可以通过同步反射和折射表面来实现全天无线通信,从而为双方用户提供服务。在本文中,我们从无线通信的角度全面概述了IOS的最新状态,强调其设计原则、频道建模、束式设计、实验性实施和测量以及未来蜂窝网络的可能应用。我们首先描述光学表面的基本概念,为不同种类的元表层引入相应的设计原则。此外,我们从无线通信的角度全面介绍IOS的每个元素的反射式模型和IOS辅助无线通信的频道模型。我们展示了当前无线通信领域和目前无线通信领域的一些无线通信模式,我们最终在无线通信领域实现一个完整的模型。