AI for CSI Feedback Enhancement in 5G-Advanced and 6G

The 3rd Generation Partnership Project has started the study of Release 18 in 2021. Artificial intelligence (AI)-native air interface is one of the key features of Release 18, where AI for channel state information (CSI) feedback enhancement is selected as the representative use case. This article provides a comprehensive overview of AI for CSI feedback enhancement in 5G-Advanced and 6G. The scope of the AI for CSI feedback enhancement in 5G-Advanced, including overhead reduction, accuracy improvement, and channel prediction, is first presented and discussed. Then, three representative frameworks of AI-enabled CSI feedback, including one-sided implicit feedback, two-sided autoencoder-based implicit feedback, and two-sided explicit feedback, are introduced and compared. Finally, the considerations in the standardization of AI for CSI feedback enhancement, especially focusing on evaluation, complexity, collaboration, generalization, information sharing, joint design with channel prediction, and reciprocity, have been identified and discussed. This article provides a guideline for the standardization study of the AI-based CSI feedback enhancement.