Research On Caching Algorithm Based On User Preference For Cellular Device-to-Device Networhing

Today’s Internet traffic is dominated by content distribution and retrieval.With the rapid explosion of the data volume and content diversity,it becomes challenging to deliver high quality service to the end user efficiently and securely.Content caching,a widely adopted content delivery technique in Internet for reducing network traffic load,has been.exploited in fifth generation(5G)mobile networks.It has been proven that caching of popular content and pushing them close to consumers can significantly reduce the mobile traffic.Apart from caching,device-to-device(D2D)communication has been regarded as another one driving force behind the evolution into 5G,considering D2D communication is able to effectively utilize the air interface resources and offload the cellular network traffic.In the conventional cellular network,a mobile terminal(MT)can only rely on a base station(BS)in the cellular network to acquire the desired content.In the cellular network with D2D,the prospect of cellular communication applications can be extended with direct communication capabilities between devices.For example,if the neighbor MTs have the same content,the content can be directly delivered from his neighbor devices.The work is supported by the National Natural Science Foundation"The Research of Caching for Content Centric Mobile Social Networking",and the Open Foundation of Beijing Key Laboratory of Network System Architecture and Convergence "The Research of Caching based on User Preferences for Content Centric Wireless Networks".This thesis investigates a user preference aware caching deployment algorithm proposed for D2D caching networks.Firstly,the paper introduces the content caching technology of communication network,classifies the existing caching system,points out the main challenges of the current caching system,and analyzes the requirements of future network and the characteristics of content caching.What’ more,the paper summarizes and analyzes the research status of the existing Cellular Network and Cellular D2D Network caching technology and finds out the existing problems in the content caching algorithm.This thesis investigates a user preference aware caching deployment algorithm proposed for D2D caching networks by considering the weakness of the existing caching algorithms.Firstly,the definition of user interest similarity is given based on the user preference.Then a content cache utility of a mobile terminal is defined by taking the transmission coverage region of this mobile terminal and the user interest similarity of its adjacent mobile terminals into consideration.A general cache utility maximization problem with joint caching deployment and cache space allocation is formulated,where the special logarithmic utility function is integrated.In doing so,the caching deployment and the cache space allocation can be decoupled by equal cache space allocation.Subsequently,we relax the logarithmic utility maximization problem,and obtain a low complexity near-optimal solution via dual decomposition method.Compared with the existing caching placement methods,the proposed algorithm can achieve significant improvement on cache hit ratio,content access delay and traffic offloading gain.This thesis formulates a caching problem based on social distance to incentive nodes to cache data for others by using cooperative game to overcome the selfish of users,and then maximize the total cache utility by allocating cache space.In the proposed game,we consider the user social relationship,placement cost and cache space allocation as the factors to formulate the cache utility maximization problem.We divide the game as the two sub-games,caching decision sub-game and cache space allocation sub-game.In the caching decision sub-game,we obtain the Nash equilibrium solution by a social distance-aware caching decision method to minimize the total cost of getting object data in the network.In the cache space allocation sub-game,we solve the cache space allocation problem by using lagrange method to finally maximize the total cache utility of the whole network.The convergence of the proposed algorithm is validated by simulation results.Compared with the existing caching placement algorithms,the proposed algorithm can achieve significant improvement on cache hit ratio,content access delay and traffic offloading ratio gain.