  Caching of video files on user devices, combined with file exchange through
device-to-device (D2D) communications is a promising method for increasing the
throughput of wireless networks. Previous theoretical investigations showed
that throughput can be increased by orders of magnitude, but assumed a Zipf
distribution for modeling the popularity distribution, which was based on
observations in {\em wired} networks. Thus the question whether cache-aided D2D
video distribution can provide in practice the benefits promised by existing
theoretical literature remains open. To answer this question, we provide new
results specifically for popularity distributions of video requests of mobile
users. Based on an extensive real-world dataset, we adopt a generalized
distribution, known as Mandelbrot-Zipf (MZipf) distribution. We first show that
this popularity distribution can fit the practical data well. Using this
distribution, we analyze the throughput--outage tradeoff of the cache-aided D2D
network and show that the scaling law is identical to the case of Zipf
popularity distribution when the MZipf distribution is sufficiently skewed,
implying that the benefits previously promised in the literature could indeed
be realized in practice. To support the theory, practical evaluations using
numerical experiments are provided, and show that the cache-aided D2D can
outperform the conventional unicasting from base stations.
