Performance Analysis And Optimization Of Caching Enabled 3D Dense Wireless Network

Wireless communication network has undergone several generations of evolution,and has achieved great development in terms of coverage and access capabilities.To achieve wireless coverage in the sky,ocean,desert and remote areas,wireless networks will evolve towards three-dimensional(3D)densification in the future to ensure the integrity and consistency of user services in the whole scene.Specifically,in the 3D dense wireless network(3D-DWN),the infrastructure of wireless networks will extend to the sky.The terrestrial base station(TBS)and unmanned aerial vehicle(UAV)mounted aerial base station(ABS)will simultaneously provide services for users,making full use of spatial resources and expanding network coverage.However,the high dynamic characteristics of the ABSs will cause the instability of communication coverage and information services.On the other hand,due to the limited backhaul resources of wireless communication network,a large number of service requests will cause great pressure on the backhaul link in the process of multiplexing the backhaul resources for coordinated coverage.To solve this problem,edge caching technology can be adopted.In particular,content could be pre-cached on the base station side to relieve the pressure on bandwidth resources from the edge to the network center.However,edge caching will change the statistical characteristics of interference in the 3D-DWN,which makes the interference complex and difficult to control.In consequence,the increase of network capacity is suppressed.In view of this,taking the network spatial throughput(ST)as the performance metric in the caching enabled 3D-DWN,this paper excavates the restriction mechanism of network performance including high dynamics and caching strategy of ABSs.Moreover,the content caching strategy is designed to maximize the network ST and improve the capacity of the 3D-DWN.The main contributions and findings are listed as follows:1.Considering the backhaul limited network scenario,the closed expression of network ST expression in 3D-DWN is given and the performance gain of ABS’s high dynamics in improving the capacity of 3D-DWN is revealed.Furthermore,the condition for the deployment of the ABS is obtained.There is a critical user height hU?.When the user height is met hU≥hU?,the introduction of ABS can increase the network ST and improve the existing network performance.The value of hU? increases linearly with the increase of the flight height hUAP.In particular,hU? can be dynamically adjusted by changing hUAP.In addition,network ST is shown to exponentially decrease with the UAV hovering radius Rh(antenna height difference ΔhUAP).This indicates that increasing Rh(ΔhUAP)will result in a further deterioration of the network ST.2.With the aid of above theoretical analysis results,this paper further proposes a content dynamic caching strategy,which maximizes the network ST of 3D-DWN by optimizing the content cache probability.This strategy dynamically adjusts the content cache probability according to the changes of network parameters.Under the dense deployment of network,the number of active base stations is controlled by reducing the content cache probability,which realizes the effective control of network interference.The optimization results show that the capacity gain brought by the content caching and the complex interference generated by the activated base station can be balanced by dynamically adjusting the caching strategy,thereby maximizing the network ST.In addition,it is found that the capacity of ground dense wireless network can be consistent with that of 3D-DWN through the optimization of caching strategy when base stations are densely deployed.In other words,the caching strategy improves the capacity of fixed network better than that of mobile network.Meanwhile,the optimized air wireless network can eliminate the capacity difference at different flight altitudes.As a result,the ST tends to be stable and maintained within a certain range.