Electromagnetic Interference in RIS-Aided Communications

The prospects of using a reconfigurable intelligent surface (RIS) to aid wireless communication systems have recently received much attention. Among the different use cases, most popular one is where each element RIS scatters incoming signal with controllable phase-shift, without increasing its power. In prior literature, this setup has been analyzed by neglecting electromagnetic interference, consisting inevitable waves from external sources. letter, we provide physically meaningful model for interference that can be used as baseline when evaluating RIS-aided communications. show non-negligible impact on performance, especially size grows large. When direct link present (though relatively weak gain), even reduce performance. Importantly, it turns out SNR quadratically number elements only spatial correlation matrix asymptotically orthogonal effective channel (including phase-shifts) towards intended receiver. Otherwise, increases linearly.