Timely status update: Should ARQ be used in two-hop networks?

Jian FENG, Haoyuan PAN, Tse Tin David CHAN, Jiaxin LIANG

Research output: Chapter in Book/Report/Conference proceedingChapters

2 Citations (Scopus)


This paper investigates the information freshness of two-hop networks. Age of information (AoI) is used as the metric to characterize the information freshness, defined as the time elapsed since the latest received status update was generated. In error-prone wireless networks, prior studies indicated that Automatic Repeat-reQuest (ARQ) does not help improve the average AoI performance of single-hop networks, because sending a new packet always carries the most up-to-date information (i.e., discarding the old packet). We believe that this observation does not apply to two-hop networks. For example, when a packet transmission fails in the second hop, although a new packet has more recent information, it may require more time to be delivered (i.e., the communication has to restart from the first hop), thus leading to a high AoI. This paper analyzes the theoretical average AoI of two-hop networks with and without ARQ. Specifically, we model the two schemes using Markov chains, from which we derive the average AoI. Our theoretical and simulation results confirm that, unlike single-hop networks, ARQ should be used in two-hop networks to achieve lower average AoI. In particular, when ARQ is used, the successful decoding probability of the second hop has a greater impact on the average AoI than that of the first hop. Overall, our findings provide insight into the ARQ design for two-hop timely status update systems. Copyright © 2022 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved.

Original languageEnglish
Title of host publicationProceedings of IEEE International Conference on Communications (ICC 2022)
Place of PublicationUSA
ISBN (Electronic)9781538683477
Publication statusPublished - 2022


Feng, J., Pan, H., Chan, T.-T., & Liang, J. (2022). Timely status update: Should ARQ be used in two-hop networks? In Proceedings of IEEE International Conference on Communications (ICC 2022) (pp. 3514-3519). USA: IEEE.


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