Abstract
Age of information (AoI) is a metric that quantifies the timeliness of information delivered in a system, which is an emerging requirement for a variety of services like autonomous driving, industrial internet of things, as well as the likes of mobile applications. This monograph presents an overview of AoI from the perspective of wireless networking. It gives a comprehensive introduction to the analytical techniques used in deriving this metric as well as networking strategies that improve the AoI. Extensions to other age-related metrics, applications, and future research directions are also discussed.