  Caching contents at the network edge is an efficient mean for offloading
traffic, reducing latency and improving users' quality-of-experience. In this
letter, we focus on aspects of storage-bandwidth tradeoffs in which small cell
base stations are distributed according to a homogeneous Poisson point process
and cache contents according to a given content popularity distribution,
subject to storage constraints. We provide a closed-form expression of the
cache-miss probability, defined as the probability of not satisfying users'
requests over a given coverage area, as a function of signal-to-interference
ratio, cache size, base stations density and content popularity. In particular,
it is shown that for a given minimum cache size, the popularity based caching
strategy achieves lower outage probability for a given base station density
compared to uniform caching. Furthermore, we show that popularity based caching
attains better performance in terms of cache-miss probability for the same
amount of spectrum.
