  The coded caching scheme originally proposed by Maddah-Ali and Niesen (MAN)
transmits coded multicast messages from a server to users equipped with caches
via a capacitated shared-link and was shown to be information theoretically
optimal within a constant multiplicative factor. This work extends the MAN
scheme to a class of two-hop wired-wireless networks including one server
connected via fronthaul links to a layer of $H$ helper nodes (access
points/base stations), which in turns communicate via a wireless access network
to $K$ users, each equipped with its own cache. Two variants are considered,
which differ in the modeling of the access segment. Both models should be
regarded as abstractions at the network layer for physical scenarios such as
local area networks and cellular networks, spatially distributed over a certain
coverage area. The key focus of our approach consists of routing MAN-type
multicast messages through the network and formulating the optimal routing
scheme as an optimization problem that can be solved exactly or for which we
give powerful heuristic algorithms. Our approach solves at once many of the
open practical problems identified as stumbling blocks for the application of
coded caching in practical scenarios, namely: asynchronous streaming sessions,
finite file size, scalability of the scheme to large and spatially distributed
networks, user mobility and random activity (users joining and leaving the
system at arbitrary times), decentralized prefetching of the cache contents,
end-to-end encryption of HTTPS requests, which renders the helper nodes
oblivious of the user demands.
