Device to Device Networks With Cache-Enabled and Self-Sustained Mobile Helpers

In this paper, we develop a novel framework to analyze the successful content delivery performance of device-to-device (D2D) networks with cache-enabled and self-sustained mobile helpers (MHs). Particularly, to facilitate the access of multimedia services for user equipments (UEs) under intermittent energy arrivals, an energy-based content delivery strategy, namely the energy-dependent nearest MH transmission (ED-NMT) strategy is considered. Under the proposed ED-NMT strategy, an MH is capable of delivering the content to the requesting UE if sufficient energy is harvested in its battery and it is the nearest MH of the tagged UE. Assuming infinite battery capacity, with ED-NMT strategy, we characterize the energy availability, and thereby, the transmission probability of MHs which cache the <inline-formula> <tex-math notation="LaTeX">$f$ </tex-math></inline-formula>-th file at the local storage. Then, we derive the cache-hit probability and the coverage probability of the <inline-formula> <tex-math notation="LaTeX">$f$ </tex-math></inline-formula>-th file. Finally, with the obtained results, we evaluate the successful content delivery probability (SCDP) of the D2D network with cache-enabled and self-sustained MHs. It is shown through both analytical and numerical results that under certain conditions, there is no performance loss due to stochastic and intermittent energy arrivals.