Research For Distributed Caching Scheme In Dense Small Cell Network

Due to the explosive growth of network data traffic and the shortage of spectrum resources in cellular networks,how to improve network throughput and capacity has become a hot research topic.In order to further improve the area spectrum efficiency of data transmission in the next generation cellular system(5G),the technology of densely deploying small cell networks is proposed.By deploying more small base stations(SBS)under the macro base station(MBS),spectrum effectiveness can be improved;on the other hand,caching contents at SBS can further improve the link quality and reduce download delay,thereby enhancing the network capacity.However,as the density of SBS increasing,there is bound to be a shortage of backhaul resources.By caching contents at SBS,the consumption of backhaul resources can be reduced,users can download the contents they need from the nearest SBS;If the SBS does not cache the required data,it needs to access the MBS to download data from the core network,which consumes more backhaul resources.On the other hand,wireless access resources are also scarce,and cooperative transmission among multiple SBSs is an effective way to improve the utilization rate of wireless resources.However,the caching scheme can affect the current collaboration opportunities between the cells.Therefore,the distributed caching strategy is a key issues deserving to be studied in dense small cell networks.In this thesis,the distributed caching strategy of joint multi-point cooperative transmission(Co MP-JT)and interference,as well as the caching strategy of considering SBS access load balance are studied.The main contents are as follows:Firstly,considering the limited access resource,backhaul resource and limited SBS cache capacity in the dense small cell networks,a distributed caching strategy based on Co MP-JT and interference is proposed for the radio spectrum resource consumption.The proposed caching strategy considers the impact of Co MP-JT on system access,backhaul resource consumption,and the probability of user's successful download,further influencing the system's caching strategy and efficiency of content delivery.On the premise of guaranteeing the user download rate,the cache strategy is formulated by converting it into the submodular optimization problem that meets the simulation constraints.Then we calculate the optimal caching strategy using the proposed algorithm.Through the simulation results,compared with the traditional caching strategy based on maximum popularity and without considering Co MP-JT,the proposed distributed caching strategy with Co MP-JT and interference can effectively reduce the system access and backhaul resource consumption,and guarantee the user's download rate and delay requirements.Then,from the point of improving the system capacity and reducing the consumption of resources,especially when the number of users in the cell increase significantly,caching strategy with SBS access load optimization is introduced under the premise of joint Co MPJT and interference.Considering that the SBS access capacity is limited,SBS access load is balanced through access selection factor,increasing the system capacity.Through the performance simulation analysis about consumption of system resources,the average download rate and the average number of users served by SBS,the proposed cache strategy based on SBS load optimization combined with Co MP-JT and SBS interference can increase the system spectrum resource utilization and system capacity effectively.