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Content Delivery in Fog-Aided Small-Cell Systems with Offline and Online Caching: An Information—Theoretic Analysis

CWiP, Department of Electrical and Computer Engineering, New Jersey Institute of Technology, Newark, NJ 07102, USA
Centre for Telecommunications Research, Department of Informatics, King’s College London, London WC2R 2LS, UK
Department of Electrical and Computer Engineering, The University of Arizona, Tucson, AZ 85721, USA
Author to whom correspondence should be addressed.
Entropy 2017, 19(7), 366;
Received: 28 May 2017 / Revised: 2 July 2017 / Accepted: 14 July 2017 / Published: 18 July 2017
(This article belongs to the Special Issue Network Information Theory)
PDF [397 KB, uploaded 18 July 2017]


The storage of frequently requested multimedia content at small-cell base stations (BSs) can reduce the load of macro-BSs without relying on high-speed backhaul links. In this work, the optimal operation of a system consisting of a cache-aided small-cell BS and a macro-BS is investigated for both offline and online caching settings. In particular, a binary fading one-sided interference channel is considered in which the small-cell BS, whose transmission is interfered by the macro-BS, has a limited-capacity cache. The delivery time per bit (DTB) is adopted as a measure of the coding latency, that is, the duration of the transmission block, required for reliable delivery. For offline caching, assuming a static set of popular contents, the minimum achievable DTB is characterized through information-theoretic achievability and converse arguments as a function of the cache capacity and of the capacity of the backhaul link connecting cloud and small-cell BS. For online caching, under a time-varying set of popular contents, the long-term (average) DTB is evaluated for both proactive and reactive caching policies. Furthermore, a converse argument is developed to characterize the minimum achievable long-term DTB for online caching in terms of the minimum achievable DTB for offline caching. The performance of both online and offline caching is finally compared using numerical results. View Full-Text
Keywords: edge caching; interference channel; information theory; latency; cloud RAN edge caching; interference channel; information theory; latency; cloud RAN

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Azimi, S.M.; Simeone, O.; Tandon, R. Content Delivery in Fog-Aided Small-Cell Systems with Offline and Online Caching: An Information—Theoretic Analysis. Entropy 2017, 19, 366.

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