  We propose a new caching concept in which wireless nodes in Device-to-Device
(D2D) network can cache the initial-segments of the popular video files and may
share to users in their proximity upon request. We term this approach as
Bootstrapping- D2D (B-D2D) system. Our findings suggest that caching only
initial-segments creates a large pool of popular files, thus improving the
probability of availability of initial-segments within the vicinity of the
requesting users. Our proposed B-D2D system is based on a popular clustering
algorithm called density-based spatial clustering of applications with noise
(DBSCAN), that groups the users into dense and arbitrary shape clusters based
on two predefined thresholds. We then formulate an optimization problem to
maximize the probability of availability of initial-segments within the
transmission range of requesting wireless devices. The simulation results
demonstrate that, caching the initial video segments could substantially
improve the availability of segments within the proximity of users without
requiring any extra hardware infrastructure cost, and D2D services could be
utilized to deliver the video contents with lower startup delays in cellular
networks.
