Exploiting user mobility for D2D assisted wireless caching networks

Caching popular contents at helpers and users can offload the traffic from base stations by the helper transmission or device-to-device (D2D) transmission. In this paper, we investigate the effect of user mobility on the offloading probability for D2D assisted wireless caching systems. Specifically, we model the mobility pattern of users as the contact time and connect frequency between different users, and the offloading probability of both entire caching scheme and coded caching scheme are then derived. In order to maximize the offloading probability, the optimal caching placement problem for helpers and users is formulated and the corresponding solutions are proposed for both entire caching and coded caching schemes. We show the proposed scheme achieves both mobility gain and computation gain, in addition to the traditional caching gain, by increasing caching efficiency and distributing content across users caches. Finally, we find that the mobility of user not only provides mobility gain, but also improves computation gain.