Cache Freshness in Information Updating Systems
Cache Freshness in Information Updating Systems
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DOI：
10.1109/ciss50987.2021.9400310
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发表时间：
2021-03
期刊：
影响因子：
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通讯作者：
Melih Bastopcu;S. Ulukus
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文献类型：
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作者：
Melih Bastopcu;S. Ulukus
我们考虑一个具有一个源、$m$个缓存和一个用户的缓存更新系统。有$n$个文件。源保存文件的最新版本，这些文件以已知的速率$\lambda_{i}$进行更新。第一个缓存以速率$c_{1i}$从源下载并保存文件的最新版本，对于$r > 1$，缓存$r$以速率$c_{ri}$从缓存$r - 1$下载并保存文件。用户以速率$u_{i}$从缓存$m$获取更新。当用户获取更新时，它要么从缓存$m$获得新的更新，要么由于源处的文件更新，缓存$m$中的文件变得过时。我们找到了用户处文件平均新鲜度的解析表达式。我们提供了一种基于交替最大化的方法来找到缓存的更新速率$c_{ri}$以及用户的更新速率$u_{i}$，以使文件在用户处的新鲜度最大化。我们注意到，对于用户（相应地，对于缓存）的一组给定更新速率，缓存（相应地，对于用户）的最优速率分配策略是一种阈值策略，其中源处快速变化文件的最优更新速率可能为零。
We consider a cache updating system with a source, $m$ caches and a user. There are $n$ files. The source keeps the freshest version of the files which are updated with known rates $\lambda_{i}$. The first cache downloads and keeps the freshest version of the files from the source with rates $c_{1i}$ and cache $r$ downloads and keeps the files from cache $r-1$ with rates $c_{ri}$ for $r > 1$. The user gets updates from cache $m$ with rates $u_{i}$. When the user gets an update, it either gets a fresh update from cache $m$ or the file at cache $m$ becomes outdated by a file update at the source. We find an analytical expression for the average freshness of the files at the user. We provide an alternating maximization based method to find the update rates for the caches, $c_{ri}$, and for the user, $u_{i}$, to maximize the freshness of the files at the user. We note that for a given set of update rates for the user (resp. for the caches), the optimal rate allocation policy for the caches (resp. for the user) is a threshold policy, where the optimal update rates for rapidly changing files at the source may be equal to zero.