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How Much Can D2D Communication Reduce Content Delivery Latency in Fog Networks with Edge Caching?

Research output: Contribution to journalArticle

Roy Karasik, Osvaldo Simeone, Shlomo Shamai

Original languageEnglish
Early online date27 Dec 2019
Publication statusE-pub ahead of print - 27 Dec 2019

King's Authors


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.

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