Intelligent reflecting surfaces (IRSs) have been introduced into wireless communications systems due to their great potential to smartly customize and reconfigure radio propagation environments in a cost-effective manner. Despite the promising advantages of IRSs, academic research on IRSs is still in its infancy. In particular, the design and analysis of IRS-assisted wireless communication systems critically depend on an accurate and tractable modeling of the IRS. In this article, we first present and compare three IRS models, namely the conventional independent diffusive scatterer-based model, physics-based model, and impedance network-based model, in terms of their accuracy, tractability, and hardware complexity. Besides, a new framework based on partitioning the IRS into tiles and employing codebooks of transmission modes is introduced to enable scalable IRS optimization. Then, we investigate the impact of the three considered IRS models on system design, where several crucial technical challenges for the efficient design of IRS-assisted wireless systems are identified and the corresponding solutions are unraveled. Furthermore, to illustrate the properties of the considered models and the efficiency of the proposed solution concepts, IRS-assisted secure wireless systems and simultaneous wireless information and power transfer (SWIPT) systems are studied in more detail. Finally, several promising future research directions for IRS-assisted wireless systems are highlighted.
翻译:智能反射表面(IRS)已引入无线通信系统,因为其极有可能以具有成本效益的方式智能定制和重新配置无线电传播环境。尽管IRS具有大的潜力,但关于IRS的学术研究仍处于初级阶段,特别是,IRS辅助无线通信系统的设计和分析严重依赖IRS的准确和可移植模型。在本篇文章中,我们首先提出并比较了三种IRS模型,即传统的独立分散式散射器模型、物理模型和阻碍性网络模型,其准确性、可感应性和硬件复杂性。此外,还引入了一个基于将IRS分成砖块和使用传输模式编码的新框架,以便能够实现可扩展的IRS优化。然后,我们调查三个经过考虑的IRS模型对系统设计的影响,其中确定了对IRS辅助无线系统高效设计的若干关键技术挑战,并打破了相应的解决方案。此外,为了说明所考虑的模型的特性以及无线通信模型在拟议的无线通信系统详细度方面的效率,国际移动通信系统辅助性研究系统最后是有希望的无线信息系统。