Age of Information: An Introduction and Survey

Roy D. Yates, Yin Sun, D. Richard Brown, Sanjit K. Kaul, Eytan Modiano, Sennur Ulukus

Research output: Contribution to journalReview articlepeer-review

143 Scopus citations


We summarize recent contributions in the broad area of age of information (AoI). In particular, we describe the current state of the art in the design and optimization of low-latency cyberphysical systems and applications in which sources send time-stamped status updates to interested recipients. These applications desire status updates at the recipients to be as timely as possible; however, this is typically constrained by limited system resources. We describe AoI timeliness metrics and present general methods of AoI evaluation analysis that are applicable to a wide variety of sources and systems. Starting from elementary single-server queues, we apply these AoI methods to a range of increasingly complex systems, including energy harvesting sensors transmitting over noisy channels, parallel server systems, queueing networks, and various single-hop and multi-hop wireless networks. We also explore how update age is related to MMSE methods of sampling, estimation and control of stochastic processes. The paper concludes with a review of efforts to employ age optimization in cyberphysical applications.

Original languageEnglish (US)
Article number9380899
Pages (from-to)1183-1210
Number of pages28
JournalIEEE Journal on Selected Areas in Communications
Issue number5
StatePublished - May 2021

All Science Journal Classification (ASJC) codes

  • Computer Networks and Communications
  • Electrical and Electronic Engineering


  • Age of information (AoI)
  • age-delay tradeoff
  • age-energy tradeoff
  • communication networks
  • information freshness
  • information update system
  • non-linear age penalty
  • packet delay
  • queueing systems
  • selective encoding
  • time measurement
  • timely source coding
  • wireless communication


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