Abstract
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.
Highlights
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
With consideration of the content heterogeneity, we model the content attributes as [file popularity, mobile user (MU) preference, file size], where file popularity denotes the global probability that the file will be requested in the network, the MU preference for file category is the local probability for which category the MU prefers, and the file size represents the scale heterogeneity
Two schemes are compared with the proposed caching system: one is the popularity-based caching policy (PBCP) [4] in which each MU or cache helpers (CHs) stores file blocks according to the popularity distribution, and the other is the uniform caching policy (UNCP) in which each MU or CH stores file blocks from the library uniformly
Summary
As the numbers of mobile users (MUs) have increased in recent years, mobile multimedia data transmitted by wireless networks have increased exponentially. Cisco’s most recent report estimates that global multimedia data are predicted to increase nearly eightfold between 2015 and. Wireless multimedia data are primarily delivered through cellular networks (e.g., 3G, 4G and 5G). Recent studies have shown that fast-growing data traffic will soon become a significant burden on the cellular network [1]. Electronics 2019, 8, 1491 the traffic burden. Despite benefits from these techniques, the deployment costs of radio frequency chains or high-speed backhaul installations are prohibitively high, and backhaul availability and capacity create performance bottlenecks [2].
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