Age of Information Aware Cache Updating with File- and Age-Dependent Update Durations
Age of Information Aware Cache Updating with File- and Age-Dependent Update Durations
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发表时间：
2019-09
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通讯作者：
Haoyue Tang;P. Ciblat;Jintao Wang;Michèle A. Wigger;R. Yates
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作者：
Haoyue Tang;P. Ciblat;Jintao Wang;Michèle A. Wigger;R. Yates
我们考虑一个系统，包括一个随时间变化的文件库，一个服务器，在任何时候都观察当前版本的所有文件，和一个缓存，在开始时存储的所有文件的当前版本，但后来必须从服务器更新这些文件。与以前的作品不同，更新持续时间不是恒定的，而是取决于文件及其信息年龄（AoI），即，自上次更新以来所经过的时间。这项工作的目标是设计一个更新策略，最大限度地减少相对于一个给定的流行度分布的所有文件的平均AoI。实际上，一个放松的问题，接近原来的优化问题，得到了一个实用的更新策略。更新策略依赖于文件流行度和根据其AoI表征文件更新持续时间的函数。数值模拟表明，这种新的更新策略相比，所谓的平方根的政策，是最佳的文件独立和恒定的更新持续时间的显着改善。
We consider a system consisting of a library of time-varying files, a server that at all times observes the current version of all files, and a cache that at the beginning stores the current versions of all files but afterwards has to update these files from the server. Unlike previous works, the update duration is not constant but depends on the file and its Age of Information (AoI), i.e., of the time elapsed since it was last updated. The goal of this work is to design an update policy that minimizes the average AoI of all files with respect to a given popularity distribution. Actually a relaxed problem, close to the original optimization problem, is solved and a practical update policy is derived. The update policy relies on the file popularity and on the functions that characterize the update durations of the files depending on their AoI. Numerical simulations show a significant improvement of this new update policy compared to the so-called square-root policy that is optimal under file-independent and constant update durations.