Capacity Characterization for Intelligent Reflecting Surface Aided MIMO Communication

Shuowen Zhang, Rui Zhang

Research output: Journal article publicationJournal articleAcademic researchpeer-review

96 Citations (Scopus)


Intelligent reflecting surface (IRS) is a promising solution to enhance the wireless communication capacity both cost-effectively and energy-efficiently, by properly altering the signal propagation via tuning a large number of passive reflecting units. In this paper, we aim to characterize the fundamental capacity limit of IRS-aided point-to-point multiple-input multipleoutput (MIMO) communication systems with multi-antenna transmitter and receiver in general, by jointly optimizing the IRS reflection coefficients and the MIMO transmit covariance matrix. First, we consider narrowband transmission under frequency-flat fading channels, and develop an efficient alternating optimization algorithm to find a locally optimal solution by iteratively optimizing the transmit covariance matrix or one of the reflection coefficients with the others being fixed. Next, we consider capacity maximization for broadband transmission in a general MIMO orthogonal frequency division multiplexing (OFDM) system under frequency-selective fading channels, where transmit covariance matrices are optimized for different subcarriers while only one common set of IRS reflection coefficients is designed to cater to all the subcarriers. To tackle this more challenging problem, we propose a new alternating optimization algorithm based on convex relaxation to find a high-quality suboptimal solution. Numerical results show that our proposed algorithms achieve substantially increased capacity compared to traditional MIMO channels without the IRS, and also outperform various benchmark schemes. In particular, it is shown that with the proposed algorithms, various key parameters of the IRS-aided MIMO channel such as channel total power, rank, and condition number can be significantly improved for capacity enhancement.

Original languageEnglish
Article number9110912
Pages (from-to)1823-1838
Number of pages16
JournalIEEE Journal on Selected Areas in Communications
Issue number8
Publication statusPublished - Aug 2020


  • alternating optimization
  • capacity
  • Covariance matrices
  • Intelligent reflecting surface (IRS)
  • MIMO communication
  • multiple-input multiple-output (MIMO)
  • Narrowband
  • OFDM
  • Optimization
  • passive reflection
  • Receivers
  • Transmitters

ASJC Scopus subject areas

  • Computer Networks and Communications
  • Electrical and Electronic Engineering

Cite this