  Channel charting is a recently proposed framework that applies dimensionality
reduction to channel state information (CSI) in wireless systems with the goal
of associating a pseudo-position to each mobile user in a low-dimensional
space: the channel chart. Channel charting summarizes the entire CSI dataset in
a self-supervised manner, which opens up a range of applications that are tied
to user location. In this article, we introduce the theoretical underpinnings
of channel charting and present an overview of recent algorithmic developments
and experimental results obtained in the field. We furthermore discuss concrete
application examples of channel charting to network- and user-related
applications, and we provide a perspective on future developments and
challenges as well as the role of channel charting in next-generation wireless
networks.
