Octopus: A Cooperative Hierarchical Caching Strategy for Radio Access Networks

Recently, implementing Radio Access Network (RAN) functionality on cloud-based computing platform has become an emerging solution that leverages the many advanta ges of cloud infrastructure, such as shared computing resource s and storage capacity, while lowering the operational cost.In this paper, we propose a novel caching framework aimed at fully exploiting the potential of such systems through coop erative hierarchical caching which minimizes the network cos ts of content delivery and improves users’ Quality of Experience (QoE). In particular, we consider the cloud-cache in the cloud processing unit (CPU) as a new layer in the RAN cache hierarch y, bridging the capacity-performance gap between the traditi onal edge-based and core-based caching schemes. A delay cost mod el is introduced to characterize and formulate the cache place ment optimization problem, which is shown to be NP-complete. As such, a low complexity, heuristic cache management strateg y is proposed, constituting of a proactive cache distribution algorithm and a reactive cache replacement algorithm. Extensive nume rical simulations are carried out using both real-world YouTube video requests and synthetic content requests. It is demonstrate d that our proposed Octopus caching strategy significantly outper forms the traditional caching strategies in terms of cache hit rat io, average content access delay and backhaul traffic load.