Cooperative Hybrid Networks with Active Relays and RISs for B5G: Applications, Challenges, and Research Directions

Zaid Abdullah, Steven Kisseleff, Wallace Alves Martins, Gaojie Chen, Luca Sanguinetti, Konstantinos Ntontin, Anastasios Papazafeiropoulos, Symeon Chatzinotas, Bjorn Ottersten

Research output: Contribution to journalArticlepeer-review


Among the recent advances and innovations in wireless technologies, reconfigurable intelligent surfaces (RISs) have received much attention and are envisioned to be one of the enabling technologies for beyond 5G (B5G) networks. On the other hand, active (or classical) cooperative relays have played a key role in providing reliable and power-efficient communications in previous wireless generations. In this article, we focus on hybrid network architectures that amalgamate both active relays and RISs. The operation concept and protocols of each technology are first discussed. Subsequently, we present multiple use cases of cooperative hybrid networks where both active relays and RISs can coexist harmoniously for enhanced rate performance. Furthermore, a case study is provided which demonstrates the achievable rate performance of a communication network assisted by either an active relay, an RIS, or both, and with different relaying protocols. Finally, we provide the reader with the challenges and key research directions in this area.

Original languageEnglish
Pages (from-to)1-10
Number of pages10
JournalIEEE Wireless Communications
Publication statusPublished - 25 Oct 2022


  • Bandwidth
  • Protocols
  • Relays
  • Signal to noise ratio
  • Spatial diversity
  • Throughput
  • Transmitting antennas


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