Channel Estimation for RIS Assisted Wireless Communications-Part I: Fundamentals, Solutions, and Future Opportunities

The reconfigurable intelligent surface (RIS) with low hardware cost and energy consumption has been recognized as a potential technique for future 6G communications to enhance coverage and capacity. To achieve this goal, accurate channel state information (CSI) in RIS assisted wireless communication system is essential for the joint beamforming at the base station (BS) and the RIS. However, channel estimation is challenging, since a large number of passive RIS elements cannot transmit, receive, or process signals. In the first part of this invited paper, we provide an overview of the fundamentals, solutions, and future opportunities of channel estimation in the RIS assisted wireless communication system. It is noted that a new channel estimation scheme with low pilot overhead will be provided in the second part of this letter.

Automated summary

The reconfigurable intelligent surface (RIS) technology is seen as a promising technique for future 6G communications due to its low hardware cost and energy consumption. Accurate channel state information (CSI) is vital for joint beamforming at the base station (BS) and the RIS in RIS-assisted wireless communication systems. This paper provides an overview of the fundamentals and solutions for channel estimation in such systems, with a new low pilot overhead channel estimation scheme to be introduced in the second part of the letter.