A Cross-Layer Cooperative Caching for Software-Defined Radio Access Networks

To ease the contradiction between the explosive growth of mobile data traffic and the capacity-limited backhaul networks, content caching is considered in a software-defined radio access network (SD-RAN) in this paper. Equipped with low-cost storage units, popular contents that are frequently requested by users can be cached at both the centralized macro cell base station (MBS) at which the main control logics are installed, and the distributed small-cell base stations (SBSs) that are mainly responsible for data transmissions. With an objective of minimizing the average content provisioning cost of SD-RAN, a storage allocation is formulated between the MBS and SBSs subjected to a sum storage constraint. Firstly, a non-cooperative caching strategy is proposed, where the MBS and SBSs cache popular contents independently. In order to better utilize the available storage for achieving more efficient caching, a cross layer cooperative caching strategy is then proposed by leveraging the cooperation and coordination between the MBS and SBSs. Results demonstrate that the average content provisioning cost of SD-RAN can be significantly reduced by using the analytically obtained optimal storage allocation factor, and the proposed cross-layer cooperative caching always outperforms the non-cooperative caching.