Modeling, Optimization, and Hardware Design of Intelligent Reflecting Surface Assisted Wireless Communication Systems

在过去的几十年中，已经开发了各种技术来提高无线通信系统的频谱和功率效率。这些技术包括（大规模）多输入多输出（MIMO）、全双工通信和非正交多址。尽管这些方案和其他类似的方法具有显著的优点，但它们也具有局限性。特别是，它们的有效性关键取决于无线信道。如果信道具有很少的散射体或/和在发射器和接收器之间没有视线（LoS），则性能可能严重降低。然而，到目前为止，实际上所有提高无线通信系统性能的尝试都集中在发射机和/或接收机上。无线信道本身一直被视为“天赐的”。为了克服这种限制，最近，提出了将大反射表面引入无线系统的想法，该反射表面的电磁（EM）特性可以外部控制。这些智能反射表面（IRS）可以部署在室外建筑物的正面上或室内墙壁上，以辅助发射器和接收器之间的通信。从通信系统设计的角度来看，IRS构成了一个完整的范式转变，因为它们第一次允许操纵无线信道的属性。然而，IRS辅助无线通信系统的研究还处于起步阶段，为了充分评估和挖掘其巨大的潜力，需要一个涵盖IRS辅助无线通信系统建模、优化和实现的整体设计方法。为了实现这一目标，我们组建了一个研究团队，他们在信号处理和通信（斯科贝尔，数字通信研究所），EM建模和天线设计（Vossiek，微波和光子学研究所）以及收发器设计和实施（Weigel，电子工程研究所）方面具有重要的专业知识。拟议项目的具体目标包括：1）基于控制EM波传播及其与IRS相互作用的物理定律，开发用于IRS辅助的无线系统的通用通信理论模型。2）设计和优化IRS辅助的无线系统，包括波束成形、资源分配和信道估计。3）设计和实现完全模块化和灵活的IRS，其具有耦合和孔径效率优化的单元和能够进行大规模测量的阵列设计。4）基于实验验证和改进所提出的理论模型以及单元、阵列、天线和天线。该项目的预期成果包括经实验验证的IRS辅助无线通信的分析模型和设计框架，以及一个全面运行的IRS测试平台。

Over the past decades, various techniques have been developed to improve the spectral and power efficiency of wireless communication systems. These techniques include (massive) multiple-input multiple-output (MIMO), full duplex communication, and non-orthogonal multiple access. Despite their significant advantages, these schemes and other similar approaches also have limitations. In particular, their effectiveness crucially depends on the wireless channel. If the channel has few scatterers or/and there is no line-of-sight (LoS) between transmitter and receiver, performance may severely degrade. However, so far, practically all attempts to improve the performance of wireless communication systems have focused on the transmitter and/or the receiver. The wireless channel itself has always been viewed as "God-given". To overcome this limitation, very recently, the idea of introducing large reflecting surfaces, whose electromagnetic (EM) properties can be externally controlled, into wireless systems was presented. These intelligent reflecting surfaces (IRSs) may be deployed outdoors on the facades of buildings or indoors on walls to assist the communication between the transmitters and receivers. From a communication system design point of view, IRS constitute a complete paradigm shift as they allow, for the first time, the manipulation of the properties of the wireless channel. However, the research on IRS-assisted wireless communication systems is still in its infancy.To fully evaluate and exploit their tremendous potential, a holistic design approach covering the modeling, optimization, and implementation of IRS-assisted wireless communication systems is needed. To accomplish this, we have assembled a team of researchers with significant expertise in signal processing and communications (Schober, Institute for Digital Communications), EM modelling and antenna design (Vossiek, Institute of Microwaves and Photonics), and transceiver design and implementation (Weigel, Institute for Electronics Engineering). The specific objectives of the proposed project include:1) Development of a general communication-theoretical model for IRS-assisted wireless systems based on the laws of physics governing the propagation of EM waves and their interaction with the IRS.2) Design and optimization of IRS-assisted wireless systems including beamforming, resource allocation, and channel estimation.3) Design and implementation of a fully modularized and flexible IRS with coupling and aperture efficiency optimized unit cells and an array design enabling large-scale measurements.4) Experiment based verification and refinement of the proposed theoretical models as well as the unit cell, array, and signal designs.The expected outcomes of this project include experimentally verified analytical model and design frameworks for IRS-assisted wireless communications as well as a fully operational IRS testbed.