Analysis of an SDN-Based Cooperative Caching Network with Heterogeneous Contents
The Key Laboratory of Universal Wireless Communications, Ministry of Education, Beijing University of Posts and Telecommunications, Beijing 100876, China
Beijing University of Posts and Telecommunications, Beijing 100876, China
Information and Communication Engineering, University of Electronic Science and Technology of China, Chengdu 610054, China
Author to whom correspondence should be addressed.
Electronics 2019, 8(12), 1491; https://doi.org/10.3390/electronics8121491
Received: 15 October 2019 / Revised: 24 November 2019 / Accepted: 4 December 2019 / Published: 6 December 2019
(This article belongs to the Special Issue Cooperative Communications for Future Wireless Systems)
The ubiquity of data-enabled mobile devices and wireless-enabled data applications has fostered the rapid development of wireless content caching, which is an efficient approach to mitigating cellular traffic pressure. Considering the content characteristics and real caching circumstances, a software-defined network (SDN)-based cooperative caching system is presented. First, we define a new file block library with heterogeneous content attributes [file popularity, mobile user (MU) preference, file size]. An SDN-based three-tier caching network is presented in which the base station supplies control coverage for the entire macrocell and cache helpers (CHs), MUs with cache capacities offer data coverage. Using the ‘most popular content’ and ‘largest diversity content’, a distributed cooperative caching strategy is proposed in which the caches of the MUs store the most popular contents of the file block library to mitigate the effect of MU mobility, and those of the CHs store the remaining contents in a probabilistic caching manner to enrich the content diversity and reduce the MU caching pressure. The request meet probability (RMPro) is subsequently proposed, and the optimal caching distribution of the contents in the probabilistic caching strategy is obtained via optimization. Finally, using the result of RMPro optimization, we also analyze the content retrieval delays that occur when a typical MU requests a file block or a whole file. Simulation results demonstrate that the proposed caching system can achieve quasi-optimal revenue performance compared with other contrasting schemes.