Research Of Caching Scheme For Ultra-Dense Wireless Network

Recently,with the rapidly development of mobile Internet and Internet of things,mobile terminal data traffic has shown an explosive growth trend.In order to satisfy user requests in a better way,ultra-dense network has become the most effective way to improve the capacity of wireless networks by reducing the distance between base station and user.However,since the number of base stations is growing,it may aggravate backhaul stress.Therefore,many researchers proposed that using edge caching could shorten the distance between the file and user,reduce the transmission delay and ease the backhaul pressure.Thus,it is significant to explore the fundamental influence of edge caching on the performance of ultra-dense network.However,due to the large-scale reduction of the distance between the base station and users,the signal propagation model changes,and the statistical characteristics of the interference in the network change essentially,which brings great challenges to the research of network performance.Therefore,it is particularly important to study the performance of wireless cache networks under the premise of considering the characteristics of ultra-dense wireless networks and limited backhaul links.In view of the above reasons,this paper studies spectrum efficiency and user local delay to find the fundamental influence of edge caching on the performance of ultra-dense network.Besides,the cache strategy is optimized based on maximizing the area spectral efficiency.The main contributions of this work can be listed as follows:1.Using the stochastic geometry theory to model the ultra-dense wireless cache network,we consider the characteristics of the ultra-dense network in the network model,and add capacity-limited conditions in the backhaul model.By obtaining the expression of area spectral efficiency and its approximate expression under the multipath loss model,it is revealed that the spectral efficiency of network will no longer show a monotonous increasing trend with the increase of the density of base station,especially when the ratio of base station to user density is certain.In an ultra-dense wireless cache network scenario,excessive cache ratio or backhaul retrieving probability will deteriorate network performance and make area spectrum efficiency decrease to zero.2.To optimize the spectrum efficiency of the network,we optimize the wireless network caching strategy by optimizing the backhaul retrieving probability,and prove that,by our optimization,the performance of the cache network has been obviously improved,especially when the base station is intensively deployed.In particular,area spectrum efficiency could converge to be a constant instead of zero in the dense BS regime when the ratio of base station density to user density is certain.3.We also analyze the user local delay of wireless caching network.Different from other expression of local delay,we consider the impact of cache hit ratio on the definition of average delay.Finally,the closed-form expression of the user's average delay is given,and by analysis,we find that user local delay increases first and then decrease with the increase of base station density,and the critical base station density is given at end.