  Cache-enabled device-to-device (D2D) networks turn memory of the devices at
the network edge, such as smart phones and tablets, into bandwidth by enabling
asynchronous content sharing directly between proximate devices. Limited
storage capacity of the mobile devices necessitates the determination of
optimal set of contents to be cached on each device. In order to study the
problem of optimal cache placement, we model the locations of devices in a
finite region (e.g., coffee shop, sports bar, library) as a uniform binomial
point process (BPP). For this setup, we first develop a generic framework to
analyze the coverage probability of the target receiver (target-Rx) when the
requested content is available at the $k^{th}$ closest device to it. Using this
coverage probability result, we evaluate optimal caching probability of the
popular content to maximize the total hit probability. Our analysis concretely
demonstrates that optimal caching probability strongly depends on the number of
simultaneously active devices in the network.
