Title: Some new bounds of placement delivery arrays,
Abstract: Coded caching scheme is a technique which reduce the load during peak traffic
times in a wireless network system. Placement delivery array (PDA in short) was
first introduced by Yan et al.. It can be used to design coded caching scheme.
In this paper, we prove some lower bounds of PDA on the element and some lower
bounds of PDA on the column. We also give some constructions for optimal PDA.