Optimization on data offloading ratio of designed caching in heterogeneous mobile wireless networks

Abstract Caching context at small base stations (SBSs) is a prospective approach to relieve backhaul pressure. Numerous prior arts focus on caching strategy by separately considering user mobility and wireless interference, which are two inherent characteristics of heterogeneous mobile wireless networks. Unlike these existing works, we consider the influences of both characteristics together on caching strategy by adopting data offloading ratio (DOR) as a performance metric, which reflects the utilization of resources of SBSs. Here, we will focus on two caching models, namely short length coded caching (SLC) and long length coded caching (LLC), to avoid the repetition of index of file segments in SLC. First, we derive explicit expressions of DOR under LLC and SLC in environments with both characteristics (Scenario-A). The maximization of DORs are then investigated and near optimal solutions are obtained in this NP-hard problem. Second, a degraded environment that only considers user mobility (Scenario-B) is investigated, where the near optimal solutions are obtained by submodular expressions with linear complexity. Finally, simulations firmly support the necessity of combining both characteristics. Specifically, the DORs of our caching strategies under LLC and SLC in Scenario-A are increased by 30 % on average in comparison to the state of the art.