Caching is a technique to reduce the communication load in peak hours by prefetching contents during off-peak hours. An information-theoretic framework for coded caching was introduced by Maddah-Ali and Niesen in a recent work, where it was shown that significant improvement can be obtained compared to uncoded caching. Considerable efforts have been devoted to identify the precise information-theoretic fundamental limits of the coded caching systems, however the difficulty of this task has also become clear. One of the reasons for this difficulty is that the original coded caching setting allows all possible multiple demand types during delivery, which in fact introduces tension in the coding strategy. In this paper, we seek to develop a better understanding of the fundamental limits of coded caching by investigating systems with certain demand type restrictions. We first consider the canonical three-user three-file system, and show that, contrary to popular beliefs, the worst demand type is not the one in which all three files are requested. Motivated by these findings, we focus on coded caching systems where every file must be requested by at least one user. A novel coding scheme is proposed, which can provide new operating points that are not covered by any previously known schemes.

中文翻译：

---

关于具有受限需求类型的编码缓存系统的基本限制

缓存是一种通过在非高峰时段预取内容来减少高峰时段的通信负载的技术。Maddah-Ali 和 Niesen 在最近的一项工作中引入了一种用于编码缓存的信息理论框架，其中表明与未编码缓存相比可以获得显着的改进。已经付出了相当大的努力来确定编码缓存系统的精确信息理论基本限制，但是这项任务的难度也变得很明显。造成这种困难的原因之一是，原始编码缓存设置在交付期间允许所有可能的多种需求类型，这实际上在编码策略中引入了张力。在本文中，我们试图通过调查具有某些需求类型限制的系统来更好地理解编码缓存的基本限制。我们首先考虑规范的三用户三文件系统，并表明，与流行的看法相反，最差的需求类型并不是请求所有三个文件的那种。受这些发现的启发，我们专注于编码缓存系统，其中每个文件必须至少由一个用户请求。提出了一种新颖的编码方案，该方案可以提供任何先前已知方案未涵盖的新操作点。我们专注于编码缓存系统，其中每个文件必须至少由一个用户请求。提出了一种新颖的编码方案，该方案可以提供任何先前已知方案未涵盖的新操作点。我们专注于编码缓存系统，其中每个文件必须至少由一个用户请求。提出了一种新颖的编码方案，该方案可以提供任何先前已知方案未涵盖的新操作点。