Transmission Energy Cost Optimization Based Caching And Delivery Scheme In Cellular And D2D Networks

With the continuous growth of mobile user devices,the demand for data traffic increase explosively,and traditional cellular networks have been unable to meet the needs of users.The introduction of D2D communication technology in the traditional cellular networks can effectively alleviate the problems of insufficient network capacity,tight spectrum resources and poor communication quality of edge users in the current network.In addition,since users' requests for content are usually asynchronous and duplicate,which will result in low utilization of network resources and increase the traffic load of the base station.The content caching mechanism i's introduced in the cellular and D2D networks,that is,user devices cache the contents and share them through D2D communication,which can effectively solve the problem of content redundancy in the network and poor communication quality of the network edge users.At the same time,users share content through D2D communication,which can offload base station traffic to the edge of the network,thereby reducing the load pressure on the base station.However,during content caching and content delivery,the user's energy is inevitably consumed,and users have the limited battery capacity.Therefore,it is critical to design a suitable content caching and delivery scheme,which can reduce the user's energy consumption and ensure successful content transmission and the fairness of the user's access to the content.This thesis has studied the above problems and the main contributions are as follows:Firstly,a content caching strategy based on optimized transmission energy consumption is proposed to reduce the total transmission energy cost of content delivery in the cellular and D2D networks.In the first,users are divided into different clusters according to their physical locations,and the system model of the content caching in the cluster is described,including content popularity,probability caching policy,energy consumption analysis and channel model.Secondly,an optimization problem based on minimizing transmission energy consumption is established.The problem takes into account the topological relationship between users in the cluster and users' remaining battery power.To obtain the minimum transmission energy consumption,we calculating the probability caching strategy by convex optimization theory.Finally,simulation results show that the proposed algorithm can reduce the energy cost for content delivery while ensuring cache hit ratio.Secondly,a content delivery strategy based on user fairness is proposed,aiming at improving the fairness of users'content acquisition and maximizing offloading traffic.First of all,the system model of the content delivery in cellular and D2D networks is described.The bidirectional selection between the requesting user and the caching user in content delivery is constructed as the best matching problem in the bipartite graph.Then,for the matching problem between the requesting user and the caching user,a optimization problem of maximizing weight in bipartite graph are established,in which the weight is the probability of successful content transmission.Next,a matching algorithm based on user fairness is proposed to solve the proposed problem.Finally,simulation results show that the proposed algorithm can reduce the transmission energy consumption while considering the fairness of users.