Research On Content Cache Technology Under Cellular Network

With the popularization of terminal devices such as smart phones,network traffic has shown an explosive growth trend,which is putting unprecedented pressure on mobile networks.Content caching technology is a potential solution to deal with the surge of wireless data traffic and provides a new direction for the future development of wireless communication.At present,scholars at home and abroad have proposed some caching strategies that can improve system performance.However,these caching strategies have their own limitations in terms of cache architecture or storage space utilization.Aiming at the above problems,two content caching strategies for different network scenarios are proposed.Most existing studies lack consideration of cooperation between base stations,which may lead to problems such as content duplication and unbalanced backhaul load between base stations.In this thesis,a collaborative hierarchical caching strategy in D2D-enabled heterogeneous networks is proposed,in which not only users can share files locally by D2 D connections but also nearby SBSs can cooperate with each other.This hierarchical cooperative caching scheme aims at minimizing the system cost,making full use of local storage space,and effectively improving the cache hit probability.Simulation results show that the proposed strategy can greatly reduce the system cost and maintain a 90% cache hit probability compared to the exiting proactive caching strategy.Existing researches focus on designing cache placement strategies for specific network structures,but few studies focus on the transmission scheme applied to content delivery.In Fog-RAN,different users may be connected to the network in different ways and with different transmission opportunities.Therefore,a centralized cache strategy based on different transmission mechanisms is proposed.The scheme minimizes the average download latency of users under storage capacity constraints by considering flexible physical-layer transmission schemes and diverse content preferences of different users.The simulation results show that the proposed strategy can not only improve the cache hit probability,reduce the average download latency of about 20%,but also provide more flexible cooperative transmission mechanism for users.