Guest Editorial Age of Information

Roy D. Yates, Yin Sun, D. Richard Brown, Sanjit K. Kaul, Eytan Modiano, Sennur Ulukus
2021 IEEE Journal on Selected Areas in Communications  
W ITH the emergence of real-time cyberphysical systems, status updates are becoming an important form of communication. Vehicular messaging, security reports from homes and offices, surveillance video, and video feedback from remote-controlled systems all represent status updates at networked monitors that need to be as timely as possible. However, this is typically constrained by limited network resources. This tension has led to the introduction of new performance metrics based on the Age of
more » ... nformation (AoI) that capture how timely is one's knowledge of an entity or process. Optimization based on AoI metrics of both the networks and the senders' updating policies has yielded new and even surprising results. This Special Issue addresses research in this area. As guest editors, we have contributed a survey that introduces research in data freshness and provides a broad summary of recent work. This survey is followed by twenty contributed papers that reflect the state of the art in AoI research. These twenty contributions were chosen from among 58 submissions that were judged within the scope of this issue. These submissions were reviewed by both external reviewers and the editors. Unfortunately, some worthwhile submissions could not be accepted because of journal page constraints. Papers subject to these difficult editorial decisions received additional scrutiny by the editors. Nevertheless, the editors are hopeful that the relatively timely IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS (JSAC) review process was a constructive process for all submitting authors. In the following, we describe the contributed papers. We have clustered these papers somewhat arbitrarily. For example, energy is a consideration in several papers, but there is no energy cluster. However, it should be apparent that the diversity of these papers is consistent with the likely ubiquity of updating systems in the future. These papers introduce new models employing pricing and games for allocating resources to updating processes. In "Pricing fresh data," Zhang et al. introduce the concept of "trading" fresh data, where users pay the source in order to receive data updates. Users incur a cost that increases with the age-of-information. The key contribution of the work is the design of a pricing mechanism that maximizes the source's profit. The authors explore three different pricing schemes and demonstrate their optimality in different regimes of operation. In particular, they consider: a time-dependent pricing scheme, in which the price for each update depends on when it is requested; a quantity-based pricing scheme, in which the price of each update depends on how many updates have been previously requested; and a simple subscription-based pricing scheme, in which the price per update is constant but the source charges an additional subscription fee. The paper "Optimal and quantized mechanism design for fresh data acquisition," by Zhang et al., considers an information update system in which a destination acquires, and pays for, fresh data updates from multiple sources. An optimal economic mechanism for fresh data acquisition is designed to minimize the sum of the destination's age-related cost and its payment to the sources, while ensuring the sources voluntarily participate and truthfully report their private cost information for collecting fresh data. In addition, the computational complexity is reduced in a quantized version of the mechanism that is shown to be asymptotically optimal. In "Game of ages in a distributed network," Saurav and Vaze consider a distributed IoT network, where each node wants to minimize its own age of information and there is a cost to make any transmission. Nodes cannot coordinate their transmission and can learn about the network only via binary collision information. A simple update strategy is shown to converge to a Nash equilibrium for any number of nodes that are unknown to the update strategy. This paper explores the balance between transmitting too often (resulting in a high probability of collision and a large average transmission cost) and transmitting too seldom (resulting in high average age). This extends prior work in this area by showing that an equilibrium exists independent of the number of network nodes. Cyberphysical Systems and Applications Papers in this area use AoI to evaluate and optimize cyberphysical systems ranging from a UAV update collectors to edge and cloud server allocation.
doi:10.1109/jsac.2021.3066816 fatcat:q25s42txefgy7bph73bcifeqqm