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.
翻译:智能反射表面(IRS)已成为通过数字控制信号反射,通过大量实时被动反射元素,实现无线通信智能和可调整的无线电环境的关键赋能技术。与传统的无线通信技术不同,这些技术仅适应动态无线频道,但对动态无线频道没有或有限的控制。IRS提供了一种新的、成本效益高的手段,以积极主动的方式消除无线频道缺陷。然而,尽管具有巨大潜力,IRS在有效融入无线通信系统方面面临着新的和独特的挑战,特别是在各种实用硬件限制下,其频道估计和被动波形设计。我们在本文件中对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希望的解决办法。此外,我们讨论了新的和新出现的IRS结构和应用及其实际设计问题,以激发未来的研究。