Intelligent reflecting surface (IRS) has emerged as a key enabling technology to realize smart and reconfigurable radio environment for wireless communications, by digitally controlling the signal reflection via a large number of passive reflecting elements in real time. Different from conventional wireless communication techniques that only adapt to but have no or limited control over dynamic wireless channels, IRS provides a new and cost-effective means to combat the wireless channel impairments in a proactive manner. However, despite its great potential, IRS faces new and unique challenges in its efficient integration into wireless communication systems, especially its channel estimation and passive beamforming design under various practical hardware constraints. In this paper, we provide a comprehensive survey on the up-to-date research in IRS-aided wireless communications, with an emphasis on the promising solutions to tackle practical design issues. Furthermore, we discuss new and emerging IRS architectures and applications as well as their practical design problems to motivate future research.

中文翻译：

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智能反射表面辅助无线通信的信道估计和实用无源波束形成设计综述


智能反射表面（IRS）已成为通过大量无源反射元件实时数字控制信号反射来实现无线通信的智能和可重构无线电环境的关键使能技术。与仅适应但对动态无线信道没有或有限控制的传统无线通信技术不同，IRS提供了一种新的且具有成本效益的手段来主动地对抗无线信道损伤。然而，尽管IRS具有巨大的潜力，但它在有效集成到无线通信系统中时面临着新的、独特的挑战，特别是在各种实际硬件限制下的信道估计和无源波束形成设计。在本文中，我们对 IRS 辅助无线通信的最新研究进行了全面调查，重点是解决实际设计问题的有前途的解决方案。此外，我们还讨论了新兴的 IRS 架构和应用程序以及它们的实际设计问题，以推动未来的研究。