Optimized Coded Prefetching Scheme in Hierarchical Cache-Enabled Networks

Caching popular content at small base stations (SBSs) of a wireless edge network is a good choice to reduce user request latency and backhaul load. However, an effective coded caching scheme to solve the challenges in hierarchical cacheenabled networks (HCENs), including the limited SBS cache capacity, rich content amount, especially the deployment of coded prefetching, has not yet been fully studied. In this paper, we propose a caching scheme based on coded prefetching and coded transmission in HCENs. In particular, considering the impact of preference of users, the SBSs cache capacity, and the number of contents of coded linear combination, we design a cache probability matrix, where contents is stored at each SBS by linear combination with caching probability. Furthermore, the proposed algorithm including prefetching and transmission is analyzed, the expression of the system average delay is derived, and an optimization problem of minimizing the average delay is established to obtain the optimal cache probability matrix. Finally, the simulation results verify the effectiveness of our coded prefetching caching scheme, which can achieve lower average delay than other caching schemes with uncoded prefetching and coded transmission in HCENs.