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 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 implementation simplicity. Furthermore, 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 systems are studied in more detail. Finally, several promising future research directions for IRS-assisted wireless systems are highlighted.

中文翻译：

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智能且可重新配置的无线通信：从 IRS 建模到算法设计


智能反射面 (IRS) 已被引入无线通信系统，因为它们具有以经济高效的方式智能定制和重新配置无线电传播环境的巨大潜力。尽管 IRS 具有令人鼓舞的优势，但 IRS 的学术研究仍处于起步阶段。特别是，IRS 辅助无线通信系统的设计和分析关键取决于 IRS 的准确且易于处理的建模。在本文中，我们首先介绍并比较了三种 IRS 模型，即传统的基于扩散散射体的模型、基于物理的模型和基于阻抗网络的模型，它们的准确性、易处理性和实现简单性。此外，引入了一种基于将 IRS 划分为图块并采用传输模式码本的新框架，以实现可扩展的 IRS 优化。然后，我们研究了三种考虑的 IRS 模型对系统设计的影响，其中确定了 IRS 辅助无线系统有效设计的几个关键技术挑战，并阐明了相应的解决方案。此外，为了说明所考虑的模型的属性和所提出的解决方案概念的效率，对IRS辅助的安全无线系统以及同步无线信息和电力传输系统进行了更详细的研究。最后，强调了 IRS 辅助无线系统的几个有前途的未来研究方向。