Several Constructs Of Placement Delivery Arrays

The cent.ralized coded caching scheme is a new scheme,which can solve the wireless network congestion.Its core is to get more caching gains by jointly designing the content placement phase and the content delivery phase.Since the scenario file packets expo-nentially with increasing number of users,it is not feasible in practical web application,when the nu mber of users is large.The Placement Delivery Array（PDA）proposed by Yan et al.corresponds to the two stages of the centralized coded caching scheme.It can significant ly reduce the file packets by sacrificing less coding gains,so designing a class of PDAs is of great significance in practical web application.In this paper,we construct several new PDAs with different methods.Firstly,by establishing the adjacency relationship on K_n·K_m,m and the technique of text substitu-tion,we construct a class of regular PDAs,Secondly,by establishing edge and matching relation of Km.,and the technique of text substitution,we construct a class of regular PDAs,Thirdly,we construct a class of PDAs based on strong edge coloring of circle.Fourthly,we use Hadamard product to construct a class of PDAs,so that under the same complexity F,the transmission rate of PDAs constructed are smaller than that of the original PDAs.Finally,we obtain a class of PDAs by recursive method.