Extensive Cooperative Content Caching and Delivery Scheme Based on Multicast for D2D-Enabled HetNets

The 5th generation (5G) mobile communication system demands low delay and high user rate of experience for mobile data services, which contradicts with the explosive growth of global mobile data traffic. The explosive growth of data traffic brings serious burden of backhaul links and deteriorates the performance of backhaul delay, and the performance of backhaul delay determines the user rate of experience and average downloading delay of users to a great extent. Cooperative content caching and delivery technique in edge caching entities is an effective method to solve the above problems. This paper proposes an extensive cooperative content caching and delivery scheme based on multicast for device-to-device(D2D)-enabled heterogeneous cellular networks (HetNets). We firstly design an extensive cooperative content caching ( ${E}{C^{3}}$ ) scheme for D2D-enabled HetNets, which does not only consider the cooperative caching among D2D user, small base station (SBS) and macro base station (MBS) levels, but also considers the cooperative caching within each level. Moreover, our proposed ${E}{C^{3}}$ scheme also considers the influence of the backhaul links and remote server caching for cooperative caching. By introducing a content request probability (CRP) for each user predicted by context information, the ${E}{C^{3}}$ is formulated as an integer linear programming (ILP) problem. A hybrid genetic algorithm (HGA) is proposed for solving the problem, which combines genetic algorithm (GA), simulated annealing algorithm (SA) and local content request probability priority algorithm (LCRPPA). Furthermore, we design a scheme of content delivery based on multicast (CDBM), which is solved by a suboptimal edge priority algorithm based on multicast (EPABM). Simulation results show that the proposed extensive cooperative content caching and delivery scheme based on multicast can significantly improve the system performance compared with the existing cooperative content caching and delivery schemes.