Placement Delivery Arrays Based on Combinatorial Designs

As an effective technique to reduce network congestion during peak-traffic times, coded caching is being widely studied in wireless network. Yan et al. proved that the problem of designing a coded caching scheme can be converted into constructing a placement delivery array (PDA). It is meaningful to design coded caching schemes with low transmission rate and small packet number. In this letter, from the perspective of combinatorial designs, we construct a class of PDA using (v,k,2)-symmetric balanced incomplete block design which has advantages in transmission rate. Additionally, two classes of PDAs based on t-designs are constructed. Compared with some known schemes, new schemes have advantages in packet number.