Intelligent Reflecting Surface
Intelligent reflecting surface (IRS) is a large 2D surface of metamaterial, which is composed of passive scattering elements. Each element can be controlled to change the electromagnetic properties such as phase shift of the reflection of incident signals to make better communication channels. As millimeter wave (mmWave) communication systems are becoming the standard in 5G and future wireless communications, the role of IRS is expected to grow even more as mmWave communications suffers from high propagation path loss and blockage.
IRS is a promising technology for future wireless communication systems due to its energy efficiency and various applications. In contrast to the conventional systems, however, IRS-assisted systems pose various implementational issues as the transmitter-IRS-receiver cascade channel complicates the system design. Research about the IRS-assisted wireless communication system includes joint active (at base stations) and passive (at IRS) beamforming, channel estimation of reflected signals, deploying multiple IRSs, etc.