Understanding performance of Reconfigurable Intelligent Surfaces (RIS)

Use of milimeter wave frequency band (mmWave, from 30 to 300 GHz) is one main technological novelties of 5G and 6G mobile data communications. Exploitation of mmWave spectrum enables substantially larger bandwidth and datarates, but such high-frequency bands have a very short range, and propagation is very sensitive to obstacles – transmission in Non Line Of Sight (NLOS) conditions is thus challenging.

Reconfigurable Intelligent Surfaces (RIS, also denominated Large Intelligent Surfaces, LIS, or software-controlled metasurfaces) help to overcome the shortcomings of mmWave propagation, and consequently enhance capacity and coverage of wireless networks. A RIS consists of an array of reflecting elements that can be programmed to dynamically optimize the wireless communicating environment, in particular, by reflecting, redirecting and regenerating incident signals.

Modeling, study and optimization of metasurfaces characteristics is relevant for assessing and improving performance of 5G systems. Research work of Jesús Cumana-Morales (done in collaboration with Marceau Coupechoux and myself) describes a simplified model of metasurfaces, and uses that model to delve into the study of RIS properties, based on model analysis and numerical simulations. In particular, it focuses on the performance impact (in terms of SNR and datarate) of beam misalignement (modeled as an error in the incident angle). Described model is as well used to evaluate numerically different methods for reducing SNR degradation.

This paper started as a student project of Jesús Cumana-Morales, PhD candidate at the Czech Technical University (CTU), for the course “Wireless Networks: from Cellular to Connected Objects” (INF567, from the Ecole Polytechnique 3rd year, coordinated by Marceau Coupechoux and in which I also teach), which is part of the common EuroTeQ catalogue, and can be followed online by students from EuroTeQ partner institutions (such as CTU) across Europe. Jesús’ research work has been accepted and presented in the IEEE International Mediterranean Conference on Communications and Networks (IEEE MeditCom 2023), held in Dubrovnik (Croatia) in September.

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