Exploiting Mobility to Content Placement in D2D Caching Systems

Mobility-aware content placement is studied for D2D caching system. In this work, user mobility is modeled in terms of relative motion of other users with respect to a typical user of interest. Due to mobility and wireless fading, the typical user may not receive all parts of the content requested. Hence, a base station (BS) is required to serve the rest parts of the content. Correspondingly, analyzing incoming and outgoing user in the D2D communication area of the typical user, we formulate a minimization problem for the average data load of a BS and then transform it to a maximization problem for a submodular function over a matroid constraint. Using submodularity, we propose a greedy algorithm which reduces the average data load of a BS near optimally.