论文标题
缓存更新系统中的信息新鲜度
Information Freshness in Cache Updating Systems
论文作者
论文摘要
我们考虑使用源，缓存和用户的缓存更新系统。有$ n $文件。来源保留了最新版本的文件，并以已知价格$λ_i$更新。缓存下载，并保留最新版本的文件，并以$ c_i $的价格从源中。用户从缓存中获得更新，并使用价格$ u_i $。当用户获取更新后，它要么从缓存中获取新的更新，要么在缓存处的文件在源上的文件更新过时，在这种情况下，用户会获得过时的更新。我们找到了用户文件平均新鲜度的分析表达式。接下来，我们将设置概括为源和用户之间有多个缓存的情况，并在用户找到平均新鲜度。我们提供了一种基于最大化的方法，以查找缓存，$ c_i $以及用户$ u_i $的更新速率，以最大程度地提高用户文件的新鲜度。我们观察到，对于用户的一组给定更新率（缓存的分别为。最后，我们考虑了一个系统，其中多个用户连接到一个缓存，并找到缓存的更新率和用户，以最大程度地提高所有用户的总新鲜度。
We consider a cache updating system with a source, a cache and a user. There are $n$ files. The source keeps the freshest version of the files which are updated with known rates $λ_i$. The cache downloads and keeps the freshest version of the files from the source with rates $c_i$. The user gets updates from the cache with rates $u_i$. When the user gets an update, it either gets a fresh update from the cache or the file at the cache becomes outdated by a file update at the source in which case the user gets an outdated update. We find an analytical expression for the average freshness of the files at the user. Next, we generalize our setting to the case where there are multiple caches in between the source and the user, and find the average freshness at the user. We provide an alternating maximization based method to find the update rates for the cache(s), $c_i$, and for the user, $u_i$, to maximize the freshness of the files at the user. We observe that for a given set of update rates for the user (resp. for the cache), the optimal rate allocation policy for the cache (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. Finally, we consider a system where multiple users are connected to a single cache and find update rates for the cache and the users to maximize the total freshness over all users.
