Base Station Caching Based Wireless Resource Allocation In Cellular Network

With the continuous development of mobile Internet,the demand for new data services is becoming higher and higher.At the same time,because of the large-scale popularization of intelligent terminals and more and more network connection devices,the mobile data traffic is increasing exponentially.In response to the demand for massive data surge in mobile communications in 2020,the fifth generation mobile communication system(Fifth-Generation Mobile Communication System,5G)proposed a goal to achieve 1000 times growth in system capacity.New multiple access and ultra dense network technologies are regarded as the enabling technology for system capacity growth.Because of the large deployment of small base stations in dense networking technology,the capacity of backhaul links have become a bottleneck for cellular system to improve system performance,which makes the wireless caching become a hot research topic.Therefore,based on different caching schemes,designing resource allocation strategies is of great significance in cellular network.In cellular networks,according to different caching models,it can be divided into caching the complete file,which includes most popular caching and random caching etc,and caching part of file,containing prefix caching and proportional partial caching and so on.Different caching models will bring different changes to the resource allocation of cellular networks.Therefore,based on different caching models,this dissertation will focus on the resource allocation strategy in cellular networks,and carry out in-depth study around different optimization objectives.For the partial caching scheme,which caches the front part of the popular file at the base station,if the user' request file cache hit,the base station only needs to get the rest part of the file from the core network through backhaul links,otherwise the base station needs to get the complete file from the core network.As the backhaul links' capacity of base stations is limited and the cache is added,the data rate of users is not only related to the state of the physical channel,but also by the hit rate of user's request file and the capacity constraint of backhaul.In this dissertation,we propose a radio resource allocation strategy that minimizes file transmission delay under backhaul constraint based on the partial caching in base stations.Due to the user assignment and subcarrier allocation optimization variables are Boolean variables,the original problem is non convex and it is difficult to solve directly.Therefore,this dissertation decomposes the the original problem into two sub problems.First,the subcarrier allocation is optimized under the condition of fixed user assignment,and then a heuristic algorithm is proposed to solve the problem of user assignment.Simulation results show that the optimized resource allocation can reduce the transmission delay significantly based on the partial caching scheme.For the joint caching scheme,because of the advantages and disadvantages of different caching schemes and a single caching scheme can only taking advantage of its own advantages,we consider a joint caching strategy combining the most popular caching and prefix caching.Based on this joint caching scheme on base stations,this dissertation forms a resource allocation optimization problem to minimize video playback latency.Due to the constraint of backhaul links' capacity,the optimization problem is not convex and difficult to solve directly.Therefore,we solve the original problem by transforming it into a convex problem.Since the rate of third types of users is not constrained by the capacity of backhaul links,the original problem is transformed into minimizing the power consumption problem.By increasing the third type of users' rate,the solution of minimizing the power consumption problem approaches the maximum transmit power of base stations.As the minimization power problem is still not a convex problem,it can be transformed into a convex problem through the relaxation and substitution of variables.According to the optimal solution of the convex problem,we get the solution of the original problem.Simulation results show that the proposed radio resource allocation based on this joint caching model can effectively reduce the delay of video playback.