Research On Optimization Algorithms Of Cache Placement Probability Based On Interference Management

With the development of wireless communication network,the communication services is becoming more and more diversified,and the traffic demand of users is also increasing.The exponential growth of traffic demand aggravates the backhaul link burden and the core network pressure.By deploying cache-enabled base stations(BS)in wireless communication networks,a file can be cached with a certain cache placement probability in the off-peak period,and then the cached file is delivered in the peak period,which can effectively reduce the backhaul link burden and core network pressure.When a user requests a file,if the cache-enabled BS caches the requested file,this BS can directly obtain the requested file and deliver it to the user through wireless link.Therefore,in order to reduce the burden of backhaul link and the pressure of the core network,it is necessary to optimize the cache placement probabilities.On the other hand,the wireless communication network is evolving towards the direction of dense,the cell radius is decreasing,and the spectrum reuse is increasing,which leads to the increased interference in the communication network and seriously affects the file delivery.In delivery phase,it is very important to eliminate interference by interference management,which can reduce the strength of interference signal and then improve the signal-tointerference ratio(SIR)at user.Hence,the requested file can be successfully deliver to the user.Therefore,this these proposes an optimization algorithm of cache placement probabilities based on interference management to improve the file hit probability.In this thesis,we consider a multiple input multiple output(MIMO)heterogeneous network.Using tools from stochastic geometry,the location distribution of cache-enabled small BS and user are modeled by homogeneous Poisson point process(HPPP)and one macro BS.For this network,K-th order Voronoi cells is constructed to form clusters,so that each cluster include K SBS.Within each cluster,interference alignment(IA)is used to eliminate the interference signal caused by other small BS in the cluster.Then,we derive the approximate expressions of coverage probability and hit probability.The optimization probability with the goal of maximizing hit probability is established by adjusting cache placement probabilities.Then,it is proved that the optimization problem is convex,and the Lagrange function method is used to solve the optimization problem.Hence,the optimal cache placement probabilities can be obtained.Finally,the performance of the proposed algorithm is analyzed by simulation.Because the interference alignment can make full use of the advantages of multiple antennas at user,it can eliminate more interference signals.Therefore,the optimization algorithm of cache placement probabilities based on interference alignment can obtain higher coverage probabilities.Furthermore,the higher hit probability can be obtained.