Propagation Modeling and Analysis of Reconfigurable Intelligent Surfaces for Indoor and Outdoor Applications in 6G Wireless Systems
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In 5G networks, the enhanced mobile broadband, massive Internet-of-things, and ultra-reliable and low latency communications are defined as three use-cases with diverse requirements. To cope with these objectives, more radical physical layer concepts are needed to comprehend the potential requirements in future wireless systems. This has pushed researchers to look into new paradigms beyond 5G and 6G wireless systems are conceptualized in recent years. One of the promising technologies is the so-called reconfigurable intelligent surfaces (RISs) which convert the wireless channel into a transmit entity by manipulating the impinging waves using artificial elements. In this paper, the potential benefits of using RISs are investigated for indoor/outdoor setups and various frequency bands. Many RIS-assisted communication scenarios are studied to ensure reliable transmission in deteriorated channels. First, a general propagation model with a single RIS is considered and the effect of the total number of reflecting elements on the distribution of the received SNR and error performance is investigated. Also, the path loss exponent is derived for below and above 6 GHz by considering empirical path loss models. Furthermore, propagation models with multiple RISs are developed and analyzed for indoor and outdoor NLOS scenarios. The bit error performance is evaluated and the relation between error performance and the number of reflecting elements of RISs is determined. RIS selection strategies are also investigated for systems equipped with multiple RISs. Through extensive simulations, it is demonstrated that the RIS-assisted systems provide promising solutions for indoor/outdoor scenarios and exhibit significant results in error performance and achievable data rates even in the presence of system imperfections such as limited range phase adjustment and imperfect channel phase estimation at RISs.
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