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arXiv 2109.06016cs.ITmath.IT
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基于位置的内容编码缓存的最优内存负载权衡

On the Optimal Memory-Load Tradeoff of Coded Caching for Location-Based Content

Kai Wan, Minquan Cheng, Mari Kobayashi, Giuseppe Caire

摘要:

在无线边缘节点进行缓存是提高空间和频谱效率的一种有效方法,可以减轻网络中与内容相关的流量。最初由Maddah-Ali和Niesen引入的编码缓存通过同时传输对多个用户有用的多播消息来显著加快通信效率。大多数编码缓存的工作都是基于这样的假设,即每个用户都可以请求库中的所有内容。然而,在许多应用中,用户仅对取决于其位置的有限的内容集感兴趣。出于这些考虑,本文阐述了具有边缘缓存节点的基于位置的内容的编码缓存问题。所考虑的问题包括具有对基于$N$位置的文件(例如,高清地图)、位于不同区域的$K$边缘缓存节点和$K$用户(即,车辆),其中每一个都在一个高速缓存节点的服务区域中,并且可以以可忽略的成本检索该高速缓存节点的高速缓存内容。根据位置的不同,每个用户仅从库的位置相关子集中请求文件。目的是最大限度地减少最差情况下的载荷。对于这种新的编码缓存问题,我们提出了一个高度非平凡的逆约束下未编码的缓存放置,这表明一个简单的可实现的计划是最佳的未编码的缓存放置。此外,还证明了该方案在$3$因子内是一般阶最优的.最后,我们将基于位置的内容的编码缓存问题扩展到最初由Hachem等人提出的多路访问编码缓存拓扑,其中每个用户连接到最近的高速缓存节点$L$。当$L \geq 2$时,我们描述了最坏情况下负载的精确最优性。

英文摘要:

Caching at the wireless edge nodes is a promising way to boost the spatial and spectral efficiency, for the sake of alleviating networks from content-related traffic. Coded caching originally introduced by Maddah-Ali and Niesen significantly speeds up communication efficiency by transmitting multicast messages simultaneously useful to multiple users. Most prior works on coded caching are based on the assumption that each user may request all content in the library. However, in many applications the users are interested only in a limited set of content that depends on their location. Motivated by these considerations, this paper formulates the coded caching problem for location-based content with edge cache nodes. The considered problem includes a content server with access to $N$ location-based files (e.g., High-Definition maps), $K$ edge cache nodes located at different regions, and $K$ users (i.e., vehicles) each of which is in the serving region of one cache node and can retrieve the cached content of this cache node with negligible cost. Depending on the location, each user only requests a file from a location-dependent subset of the library. The objective is to minimize the worst-case load. For this novel coded caching problem, we propose a highly non-trivial converse bound under uncoded cache placement, which shows that a simple achievable scheme is optimal under uncoded cache placement. In addition, this achievable scheme is also proved to be generally order optimal within a factor of $3$. Finally, we extend the coded caching problem for location-based content to the multiaccess coded caching topology originally proposed by Hachem et al., where each user is connected to $L$ nearest cache nodes. When $L \geq 2$, we characterize the exact optimality on the worst-case load.

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