Electromagnetic Signal and Information Theory

in this article, we present electromagnetic signal and information theory (ESIT). ESIT is an inter- disciplinary scienti c discipline, which amalgamates electromagnetic theory, signal processing theory, and information theory. ESIT is aimed at conceiving and designing physically consistent communication models and schemes for the transmission and process- ing of information in communication networks. In sim- ple terms, ESIT can be de ned as physics-aware information theory and signal processing for commu- nications. We consider three relevant problems in con- temporary communication theory, and we show how they can be tackled under the lenses of ESIT. Speci - cally, we focus on 1) the theoretical and practical motivations behind antenna designs based on subwa- velength radiating elements and interdistances; 2) the modeling and role played by the electromagnetic mutual coupling, and the appropriateness of multiport network theory for modeling it; and 3) the analytical tools for unveiling the performance limits and realiz- ing spatial multiplexing in near eld, line-of-sight, channels. To exemplify the role played by ESIT and the need for electromagnetic consistency, we consider case studies related to recon gurable intelligent sur- faces and holographic surfaces, and we highlight the inconsistencies of widely utilized communication mod- els, as opposed to communication models that origi- nate from first electromagnetic principles.