  A major practical limitation of the Maddah-Ali-Niesen coded caching
techniques is their high subpacketization level. For the simple network with a
single server and multiple users, Yan \emph{et al.} proposed an alternative
scheme with the so-called placement delivery arrays (PDA). Such a scheme
requires slightly higher transmission rates but significantly reduces the
subpacketization level. In this paper, we extend the PDA framework and propose
three low-subpacketization schemes for combination networks, i.e., networks
with a single server, multiple relays, and multiple cache-aided users that are
connected to subsets of relays. One of the schemes achieves the cutset lower
bound on the link rate when the cache memories are sufficiently large. Our
other two schemes apply only to \emph{resolvable} combination networks. For
these networks and for a wide range of cache sizes, the new schemes perform
closely to the coded caching schemes that directly apply Maddah-Ali-Niesen
scheme while having significantly reduced subpacketization levels.
