Reconfigurable intelligent surfaces vs. relaying: Differences, similarities, and performance comparison

Marco Di Renzo, Konstantinos Ntontin, Jian Song, Fadil H. Danufane, Xuewen Qian, Fotis Lazarakis, Julien De Rosny, Dinh Thuy Phan-Huy, Osvaldo Simeone, Rui Zhang, Meroaune Debbah, Geoffroy Lerosey, Mathias Fink, Sergei Tretyakov, Shlomo Shamai

Research output: Contribution to journalArticlepeer-review

488 Scopus citations


Reconfigurable intelligent surfaces (RISs) have the potential of realizing the emerging concept of smart radio environments by leveraging the unique properties of metamaterials and large arrays of inexpensive antennas. In this article, we discuss the potential applications of RISs in wireless networks that operate at high-frequency bands, e.g., millimeter wave (30-100 GHz) and sub-millimeter wave (greater than 100 GHz) frequencies. When used in wireless networks, RISs may operate in a manner similar to relays. The present paper, therefore, elaborates on the key differences and similarities between RISs that are configured to operate as anomalous reflectors and relays. In particular, we illustrate numerical results that highlight the spectral efficiency gains of RISs when their size is sufficiently large as compared with the wavelength of the radio waves. In addition, we discuss key open issues that need to be addressed for unlocking the potential benefits of RISs for application to wireless communications and networks.

Original languageEnglish (US)
Article number3002955
Pages (from-to)798-807
Number of pages10
JournalIEEE Open Journal of the Communications Society
StatePublished - 2020

All Science Journal Classification (ASJC) codes

  • Computer Networks and Communications


  • 5G
  • 6G
  • Reconfigurable intelligent surfaces
  • Relays
  • Smart radio environments


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