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Optimization Design Of Fog Radio Access Network For Content-Centric Services

Posted on:2019-12-22Degree:MasterType:Thesis
Country:ChinaCandidate:X WeiFull Text:PDF
GTID:2428330545965739Subject:Communication and Information System
Abstract/Summary:PDF Full Text Request
The fog wireless access network(F-RAN)is one of the 5G oriented mobile network architectures.It makes full use of the computing and storage capacity of the fog layer network equipment to achieve better network performance gain.Yet,in recent years,content-centric mobile services show an exponential growth trend,which has caused tremendous burden on the fronthaul link of F-RAN,and made it become the bottleneck of the whole F-RAN.Video on demand(VoD)and content download services,as the main types of content-centric services,generate the maximum load on fronthaul link.However,fog layer cache or fronthaul multicast is individually adopted to reduce the load on fronthual link in most of the existing works.It overlooks fully exploiting the potential of the two joint optimization and does not have a system optimization scheme for the aforementioned two types of services.Therefore,under the F-RAN architecture,we study the joint optimization of fog layer caching and fronthaul multicasting for content download and VoD services,to reduce the load on fronthaul while ensuring user experience.The main work of this thesis is as follows:For the content download service,due to the short delay requirement and the short duration of the transmission,the fronthaul load is characterized as the average transmission delay.With satisfying the users' worst delay requests,the multicast link rate constraint with caching and the cache space constraint,to minimize the average transmission delay on fronthaul link via jointly optimizing the fronthaul multicast and fog layer cache strategy.The optimization problem boils down to a mixed integer nonlinear programming problem(MINLP).We transform and solve the MINLP problem by using integer relaxation,introducing auxiliary variables,epigraph reformulation and continuous convex approximation methods.Then the joint caching and multicasting optimization algorithm is proposed.The joint optimization algorithm utilizes the interaction between caching and fronthaul multicasting,and gets the inner relationship that the cache at the fog layer makes multicasting strategy have no need considering the rate of the link channel,so that it can better reduce the load of the fronthaul link.The simulation results also show that the joint optimization strategy can reduce the average transmission delay on fronthaul link more efficiently compared with the individual caching and multicasting strategy.For VoD service,due to the duration of transmission is longer and the specific requirement for the transmission rate,the fronthaul load is characterized as average transmission rate.According to the characteristic that the request for the same content does not occur at the same time,the buffer space is introduced in the small base station of the fog layer.Considering the effect of cache and buffer space on reducing the transmission of fronthaul link,the Caching and Buffering Enabled Multicast Patching(CBE-MP)strategy is proposed,and we prove its optimality for minimizing fronthaul rate.Then,based on the CBE-MP strategy,the average fronthaul transmission rate is minimized by the optimization of the cache strategy.The optimal caching strategy is obtained by solving the above convex optimization problem.The caching strategy taps the potential of the beginning of cache video for enriching asynchronous demand,thus can consume less multicast times.In this way it can reduce more overhead of the fronthaul.The simulation results also validate the caching strategy can reduce the average rate of fronthual link more efficiently compared with popularity-based strategy and average strategy,and have good performance in the different cache space,content popularity and content request rate.
Keywords/Search Tags:F-RAN, content-centric wireless network, video-on-demand, content download, wireless multicast, cache
PDF Full Text Request
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