Secrecy Rate of Relay and Intelligent Reflecting Surface Antenna-Assisted MIMO

This paper proposes the use of an amplify-and-forward (AF) relay in addition to intelligent reflecting surface (IRS) antennas to ensure higher secrecy rates compared to IRS-only multiple-input multiple-output (MIMO) communication systems. An optimization algorithm is used to maximize the secrecy rate with respect to the transmit signal covariance matrix and then compared it to both IRS-assisted MIMO and a no-IRS case. The results are discussed as to whether or not relays may be useful in increasing the secrecy and channel capacity of MIMO channels when used in addition to IRS antennas.