We consider a cache-aided wireless device-to-device (D2D) network of the type introduced by Ji et al., where the placement phase is orchestrated by a central server. We assume that the devices’ caches are filled with uncoded data, and the whole content database is contained in the collection of caches. After the cache placement phase, the files requested by the users are serviced by inter-device multicast communication. For such a system setting, we provide the exact characterization of the optimal load-memory trade-off under the assumptions of uncoded placement and one-shot delivery. In particular, we derive both the minimum average (under uniformly distributed demands) and the minimum worst-case sum-load of the D2D transmissions, for given individual cache memory size at disposal of each user. Furthermore, we show that the performance of the proposed scheme is within factor 4 of the information-theoretic optimum. Capitalizing on the one-shot delivery property, we also propose an extension of the presented scheme that provides robustness against random user inactivity.

中文翻译：

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具有未编码缓存放置和一次性交付的D2D编码缓存的最优性

我们考虑由 Ji 等人介绍的缓存辅助无线设备到设备 (D2D) 网络，其中放置阶段由中央服务器协调。我们假设设备的缓存中充满了未编码的数据，并且整个内容数据库都包含在缓存集合中。在缓存放置阶段之后，用户请求的文件由设备间多播通信提供服务。对于这样的系统设置，我们在未编码放置和一次性交付的假设下提供了最佳负载-内存权衡的精确特征。特别是，对于每个用户可处置的给定单独缓存大小，我们推导出 D2D 传输的最小平均值（在均匀分布的需求下）和最小最坏情况总负载。此外，我们表明，所提出方案的性能在信息理论最优值的 4 倍以内。利用一次性交付特性，我们还提出了对所提出方案的扩展，该方案提供了针对随机用户不活动的鲁棒性。