Robustness of Clustered D2D Cache Placement Against Mobility

In this study we consider the problem of cache placement in a device-to-device (D2D) enabled cellular network with mobile users. D2D communication occurs between helper users and ordinary users, where helpers are able to cache contents and deliver these contents to ordinary users via D2D transmission upon request. The objective of the cache placement is maximizing the offloaded traffic and lighten the burden of the Base Station. We first formulate a single-shot cache placement problem as a Mixed Integer Linear Program (MILP) and obtain the optimal solution. We also propose three clustering algorithms and a cache placement algorithm. Then we tested the performance of these schemes under user and helper mobility. Cache placement is recomputed at a certain cache update periods, in order to take into account the changing topology. Simulation results show that the optimization framework designed for a single-shot scenario fails at challenging conditions, while the proposed algorithms is more robust to mobility.