  Maddah-Ali and Niesen (MAN) in 2014 showed that coded caching in single
bottleneck-link broadcast networks allows serving an arbitrarily large number
of cache-equipped users with a total link load (bits per unit time) that does
not scale with the number of users. Since then, the general topic of coded
caching has generated enormous interest both from the information theoretic and
(network) coding theoretic viewpoint, and from the viewpoint of applications.
Building on the MAN work, this paper considers a particular network topology
referred to as cache-aided Fog Radio Access Network (Fog-RAN), that includes a
Macro-cell Base Station (MBS) co-located with the content server, several
cache-equipped Small-cell Base Stations (SBSs), and many users without caches.
Some users are served directly by the MBS broadcast downlink, while other users
are served by the SBSs. The SBSs can also exchange data via rounds of direct
communication via a side channel, referred to as "sidelink". For this novel
Fog-RAN model, the fundamental tradeoff among (a) the amount of cache memory at
the SBSs, (b) the load on the downlink (from MBS to directly served users and
SBSs), and (c) the aggregate load on the sidelink is studied, under the
standard worst-case demand scenario. Several existing results are recovered as
special cases of this network model and byproduct results of independent
interest are given. Finally, the role of topology-aware versus
topology-agnostic caching is discussed.
