D2D-Aware Device Caching in MmWave-Cellular Networks

In this paper, we propose a novel device caching policy that facilitates popular content exchange through high-rate device-to-device (D2D) millimeter-wave (mmWave) communication. The proposed policy, which is termed D2D-aware caching (DAC) policy, splits the cacheable content into two content groups and distributes it evenly at the paired devices. By exploiting the high-bandwidth availability and the directionality of mmWaves, we ensure high rates for the D2D transmissions, while mitigating the co-channel interference that limits the D2D-communication potentials in the sub-6 GHz bands. Furthermore, based on a stochastic-geometry approach for the modeling of the location and number of the base stations (BSs) and users (UEs) in the network, we analytically derive the offloading gain that the proposed policy achieves and the distribution of the content retrieval delay for both half- and full-duplex D2D communication. The accuracy of the proposed analytical framework is validated against Monte-Carlo simulations. In addition, for a wide range of content-popularity indicator the results show that the proposed policy achieves better offloading and smaller content-retrieval delays than a widely considered state-of-the-art policy that caches the same content at every UE.