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

TL;DR

This paper reviews the fundamentals, challenges, and future directions of channel estimation in RIS-assisted wireless systems, emphasizing the importance of accurate CSI for joint beamforming in 6G networks.

Contribution

It provides a comprehensive overview of existing channel estimation techniques and discusses future research opportunities in RIS-assisted wireless communications.

Findings

Highlights the importance of low-overhead channel estimation methods.

Identifies key challenges in estimating channels with passive RIS elements.

Outlines potential future research directions in the field.

Abstract

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 paper.