This paper surveys the optimization frameworks and performance analysis methods for large intelligent surfaces (LIS), which have been emerging as strong candidates to support the sixth-generation wireless physical platforms (6G). Due to their ability to adjust the behavior of interacting electromagnetic (EM) waves through intelligent manipulations of the reflections phase shifts, LIS have shown promising merits at improving the spectral efficiency of wireless networks. In this context, researchers have been recently exploring LIS technology in depth as a means to achieve programmable, virtualized, and distributed wireless network infrastructures. From a system level perspective, LIS have also been proven to be a low-cost, green, sustainable, and energy-efficient solution for 6G systems. This paper provides a unique blend that surveys the principles of operation of LIS, together with their optimization and performance analysis frameworks. The paper first introduces the LIS technology and its physical working principle. Then, it presents various optimization frameworks that aim to optimize specific objectives, namely, maximizing energy efficiency, sum-rate, secrecy-rate, and coverage. The paper afterwards discusses various relevant performance analysis works including capacity analysis, the impact of hardware impairments on capacity, uplink/downlink data rate analysis, and outage probability. The paper further presents the impact of adopting the LIS technology for positioning applications. Finally, we identify numerous exciting open challenges for LIS-aided 6G wireless networks, including resource allocation problems, hybrid radio frequency/visible light communication (RF-VLC) systems, health considerations, and localization.

中文翻译：

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6G 无线网络的智能表面：优化和性能分析技术综述

本文调查了大型智能表面 (LIS) 的优化框架和性能分析方法，它们已成为支持第六代无线物理平台 (6G) 的有力候选者。由于它们能够通过对反射相移的智能操纵来调整相互作用的电磁 (EM) 波的行为，因此 LIS 在提高无线网络的频谱效率方面显示出有前景的优点。在此背景下，研究人员最近一直在深入探索 LIS 技术，将其作为实现可编程、虚拟化和分布式无线网络基础设施的一种手段。从系统层面来看，LIS 也被证明是一种低成本、绿色、可持续和节能的 6G 系统解决方案。本文提供了一个独特的组合，调查了 LIS 的操作原理，以及它们的优化和性能分析框架。本文首先介绍了LIS技术及其物理工作原理。然后，它提出了各种优化框架，旨在优化特定目标，即最大化能源效率、总和率、保密率和覆盖率。论文随后讨论了各种相关的性能分析工作，包括容量分析、硬件损伤对容量的影响、上下行数据速率分析和中断概率。本文进一步介绍了采用 LIS 技术进行定位应用的影响。最后，我们确定了 LIS 辅助 6G 无线网络的众多令人兴奋的开放挑战，包括资源分配问题、