Opportunistic Beamforming Using an Intelligent Reflecting Surface without Instantaneous CSI

Qurrat Ul Ain Nadeem, Anas Chaaban, Merouane Debbah

Research output: Contribution to journalArticlepeer-review


While intelligent reflecting surface (IRS) assisted wireless communication has emerged as an important research paradigm, channel state information (CSI) acquisition remains a critical challenge to design the IRS phase-shifts and yield the promised coherent beamforming gains. In this letter, we propose an IRS-assisted opportunistic beamforming (OBF) scheme under proportional fair scheduling, which does not require instantaneous CSI to design the IRS parameters. In a slow-fading environment, we show that with only random rotations at the IRS, the proposed scheme can capitalize on the multi-user (MU)-diversity effect to approach the performance of coherent beamforming as the number of users grows large. Next we study the sum-rate scaling of IRS-assisted OBF in the correlated Rayleigh fast fading environment under a deterministic beamforming scheme that results in a considerable sum-rate improvement.

Original languageEnglish (US)
Article number9194749
Pages (from-to)146-150
Number of pages5
JournalIEEE Wireless Communications Letters
Issue number1
StatePublished - Jan 2021


  • broadcast channel (BC)
  • Intelligent reflecting surface (IRS)
  • multi-user (MU) diversity
  • scheduling
  • sum-rate

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Electrical and Electronic Engineering


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