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

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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.