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Caching strategies in heterogeneous networks with D2D, small BS and macro BS communications

The increase in wireless data traffic is encouraging a shift from standard cellular networks, with one base station providing wireless connectivity to all the users in the cell, to heterogeneous networks, where several small base stations can assist the macro base station in providing service. Furthermore, with device-to-device communications the users can also share local content without multiple requests to the base station. In this complex network scenario, we propose a proactive caching policy to exploit all these communication opportunities and reduce congestion at the backhaul link. The goal is to minimize the system cost, in terms of energy or bandwidth wastage. We provide a closed form expression for the average system cost in the case in which we consider user mobility and different classes of user's interests. We present a robust optimization framework, and we show significant performance gains compared to a static caching policy.