Research On Key Technologies Of Content Distribution Optimization In Mobile Network

Recently,with the proliferation of powerful mobile devices,such as smart phones and tablets,data traffic on mobile networks is growing explosively.In the data traffic on mobile networks,the content-related traffic occupies a domi-nant position,which has the characteristics of large traffic,high duplicate trans-mission rate and slow change in contents'popularity.How to optimize the con-tent transmission and distribute large mobile data traffic effectively over limited network capacity while considering these characteristics of content services,has become a hot research field in recent years.Content caching and distribution technology is a promising solution to optimize mobile content transmission and improve content distribution efficiency,which has attracted a lot of attention.By deploying caching in mobile network nodes and storing popular content ob-jects closer to the mobile users,most content requests can be served from the mobile network caches,thereby alleviating the load of origin content servers,improving network bandwidth utilization,decreasing duplicate transmission,reducing content delivery delay,and providing users with better content ser-vice experience.In mobile cellular network,according to the deployment locations of caching resources,the content distribution technology can be classified into mobile core network caching technology,radio access network caching technology,and user equipment caching technology.The research work of this thesis mainly fo-cuses on the mobile core network caching technology and radio access network caching technology.For the mobile core network,it studies the content distri-bution optimization mechanism that is compatible with the current 4G Evolved Packet Core(EPC).For the radio access network,on the one hand,the problem of caching resource allocation for multiple content providers is studied.On the other hand,the content caching technology and adaptive video streaming technology are jointly considered to study the energy-efficient content caching mechanism for adaptive video streaming.The main contributions are as fol-lows:1.A content distribution optimization mechanism for mobile core net-workIn order to improve the content distribution efficiency of the current 4G EPC,this thesis proposes a content distribution optimization architecture called ICICD(ISP-Controlled In-network Content Distribution)to distribute content effectively through the information sharing between Mobile Network Opera-tor(MNO)and content providers.Based on centralized information collection and maintenance strategy and distributed user requests processing strategy,the ICICD can efficiently process user requests and distribute content.This thesis gives a detailed description of the main ICICD components,i.e.,proxy,cache server,Tracker and origin content server.Furthermore,a content pre-caching mechanism based on bipartite graph is proposed,which considers not only the content request information,but also the link state information to select the op-timal cache servers to pre-cache the new content.2.A caching resource allocation mechanism for multiple content providers in radio access networkExisting studies on content caching in radio access network mainly focus on performance optimization and energy efficiency for content caching.To the best of our knowledge,the problem of caching resource allocation for multiple content providers has been largely ignored.This thesis uses game theory model to solve the caching resource allocation problem in the scenario of one base station and multiple content providers.The system is modeled as an oligopoly market,in which the product is the caching resource,the product provider is the base station,the product demanders are content providers,and the cost of the caching resource is defined by a price function.The caching resource al-location problem is formulated as a dynamic non-cooperative Cournot game,the Cournot equilibrium solution of which can be obtained by the proposed Newton-Raphson method based iterative algorithm.3.An energy-efficient content caching mechanism for adaptive video streaming in radio access networkHTTP Adaptive Bit Rate(ABR)streaming and Scalable Video Coding(SVC)are two common adaptive video streaming technologies,which can adap-tively provide users with different quality's video content according to their varying wireless network conditions.This thesis jointly considers the con-tent caching technology and adaptive video streaming technology to study the energy-efficient content caching m echanism for adaptive video streaming.Based on the video popularity model,content caching model,energy cost saving model and QoE model,the content caching problem for HTTP ABR streaming is for-mulated as two sub-optimization problems,i.e.,QoE optimization sub-problem and energy-efficient content caching optimization sub-problem.By solving the two sub-optimization problems,the optimal solutions(i.e.,the set of playback rates selected by users and the MNO's caching policy for each individual con-tent)can be obtained.In addition,the content caching problem for SVC is for-mulated as a convex optimization problem.By solving the optimization prob-lem,the optimal set of content caching parameters for the MNO to design an optimal caching policy for layered video contents can be obtained.