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.