  In coded caching system we prefer to design a coded caching scheme with low
subpacketization and small transmission rate (i.e., the low implementation
complexity and the efficient transmission during the peak traffic times).
Placement delivery arrays (PDA) can be used to design code caching schemes. In
this paper we propose a framework of constructing PDAs via Hamming distance. As
an application, two classes of coded caching schemes with linear
subpacketizations and small transmission rates are obtained.
