An intelligent reflecting surface (IRS) is a 2D surface of a special electromagnetic material, which is composed of a large array of passive scattering elements. Recently this has attracted attention from both industry and academia, especially in the communication field. Since the IRS-based relay can redirect electromagnetic signals and realize the beamforming, thereby improving the energy efficiency of wireless signals as well as the system performance, IRS is viewed as one of the potential key technologies of 6G communication systems.

The phases of the elements of IRS can be individually tuned, thereby exhibiting sensitivities to signals from different directions. Channel sensing with the aid of IRS will have many applications such as indoor localization, human pose understanding, line-of-sight (LOS) path identification, etc. Additionally, channel estimation as a traditional topic in communications systems is important in data detection, transmission precoder design, interference suppression, etc. Due to the fact that IRS has no radio frequency and baseband processing capabilities, channel estimation in IRS-assisted systems faces new challenges.

Therefore, the objective of this Special Issue is to solicit articles regarding recent advances in channel sensing techniques and channel estimation for IRS-assisted communication systems. We welcome both original research and review articles.

Potential topics include but are not limited to the following:

• Channel modeling in IRS-assisted systems
• Channel sensing techniques in IRS-assisted systems
• Environment sensing based on CSI in IRS-assisted systems
• Indoor localization based on channel sensing in IRS-assisted systems
• Channel estimation in IRS-assisted systems
• Parametric model-based channel estimation in IRS-assisted systems
• Training sequences design in IRS-assisted systems
• Data detection in IRS-assisted systems
• Channel tracking and prediction in IRS-assisted wireless networks
• Deep learning for IRS-assisted systems