A Fog-Radio Access Network (F-RAN) is studied in which cache-enabled Edge Nodes (ENs) with dedicated fronthaul connections to the cloud aim at delivering contents to mobile users. Using an information-theoretic approach, this work tackles the problem of quantifying the potential latency reduction that can be obtained by enabling Device-to-Device (D2D) communication over out-of-band broadcast links. Following prior work, the Normalized Delivery Time (NDT) — a metric that captures the high signal-to-noise ratio worst-case latency — is adopted as the performance criterion of interest. Joint edge caching, downlink transmission, and D2D communication policies based on compress-and-forward are proposed that are shown to be information-theoretically optimal to within a constant multiplicative factor of two for all values of the problem parameters, and to achieve the minimum NDT for a number of special cases. The analysis provides insights on the role of D2D cooperation in improving the delivery latency.

中文翻译：

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D2D 通信在具有边缘缓存的雾网络中可以减少多少内容交付延迟？

研究了雾无线电接入网络 (F-RAN)，其中启用缓存的边缘节点 (EN) 与云的专用前传连接旨在向移动用户提供内容。使用信息论方法，这项工作解决了量化潜在延迟减少的问题，该问题可以通过在带外广播链路上启用设备到设备 (D2D) 通信来获得。在先前的工作之后，标准化交付时间 (NDT)——一种捕捉高信噪比最坏情况延迟的指标——被用作感兴趣的性能标准。提出了基于压缩和转发的联合边缘缓存、下行链路传输和 D2D 通信策略，这些策略被证明是信息理论上最优的，对于问题参数的所有值，在常数乘法因子 2 内，并在一些特殊情况下实现最低无损检测。该分析提供了关于 D2D 合作在改善交付延迟方面的作用的见解。