  Caching at the edge of wireless networks is a keytechnology to reduce traffic
in the backhaul link. However, aconcentrated amount of requests during
peak-periods may causethe outage of the system, meaning that the network is not
ableto serve the whole set of demands. The outage probability is afundamental
metric to take into account during the networkdesign. In this paper, we derive
the analytical expression ofthe outage probability as a function of the total
amount ofusers requests, library size, requests distribution, cache size
andcapacity constraints on the backhaul resources. In particular, wefocus on a
scenario where end-users have no direct connectionto the master node which
holds the complete library of contentthat can be requested. A general
formulation of the outage isderived and studied for two relevant caching
schemes, i.e. therandom caching scheme and the most popular caching schemes.The
exact closed form expressions presented in this paper provideuseful insights on
how requests, memory and resources can bebalanced when the parameters of a
cache-enabled network haveto designed
