Coded Caching For Shared-link Networks And Multiaccess Combination Networks

Caching is recognized as one of the methods to solve the problem of data transmission delay,which can transfer the data transmission from the peak-traffic times to the off-peak times and effectively relieve the network communication pressure during the peak-traffic times.During off-peak times,each user caches some multimedia content in advance.During the peaktraffic times,the server only needs to transfer the remaining files in the requested files that are not cached by the user,thus reducing the transmission pressure during the peak-traffic times.However,caching can only bring users the local gain of their own cache content,and when the user's local cache is small,the role of caching is insignificant.Coded caching can make use of the user's local cache content,so that the coded broadcast information generated by the server can create new multicast opportunities,and satisfy multiple users' requests at the same time,thus further reducing the amount of data transmission in the peak-traffic times.However,when the coded caching scheme is implemented,the file must be divided into subfiles.The larger subpacketizations,the higher the complexity of the scheme.Therefore,the current research in the field of coded caching focuses on the design of coding caching scheme with low subpacketizations under the premise of ensuring transmission load.In this thesis,the classical shared-link network model and the more practical multiaccess combination network model are studied respectively,and the main results are as follows.In the studied of the shared-link network model,this thesis constructs a novel coded caching scheme for shared-link networks with low subpacketizations according to the partition idea of combinatorial design and the Hamming Distance relation of row and column vectors of matrix.However,the local cache of users in this scheme contains some redundant content,which wastes the local cache space of users.By removing redundant content from the user's local cache and using Maximum Distance Separated(MDS)code,the user's local cache capacity is reduced and the subpacketizations for the scheme is further reduced.Theoretical proof and numerical simulation show that the proposed scheme is better than that in the existing coded caching scheme under most parameters.In the studied of the multiaccess combination network model,based on the ideas of Zewail and Yener(ZY),this thesis proposes a coded caching scheme for multiaccess combination networks,called ZY scheme.However,the subpacketizations of the ZY scheme grows exponentially with the number of users,resulting in a higher implementation complexity.Secondly,based on the Combination Design Theory,this thesis proposes a direct construction of multiaccess combination network coded caching scheme.This scheme greatly reduces subpacketizations,but the number of users in the scheme must be a combined number.Finally,in order to achieve the universality of the number of users,based on the direct construction scheme,this thesis proposes a hybrid construction of multiaccess combination network coded caching scheme.Theoretical proof and numerical simulation show that the two construction schemes proposed in this thesis have lower subpacketizations than the ZY scheme.