Downlink Resource Sharing and Multi-tier Caching Selection Maximized Multicast Video Delivery Capacity in 5G Ultra-Dense Networks

In this paper, we propose a downlink resource sharing and multi-tier caching selection (DRS-MCS) solution for video streaming applications and services (VASs) in 5G ultra-dense networks (UDNs). The DRS-MCS allows mobile users (MUs) to experience the VASs by multicasting from three-tier caching placements, i.e., macro base station (MBS), femtocell base stations (FBSs), and mobile devices. To do so, the MUs are categorized into three types including 1) sharing users (SUs) that own downlink resources being shared for device-to-device (D2D) communications, 2) caching helpers (CHs) that cache the requested videos for multicasting over D2D communications, and 3) requesting users (RUs) that request the videos. The CHs and the RUs are grouped into different clusters, each cluster has a number of CHs and RUs in close vicinity for D2D multicast communications. We then formulate the DRS-MCS optimization problem. By solving the problem, the DRS-MCS solution can select not only the best pairs of SUs and CHs for D2D multicast communications but also the best caching placements for multicasting in each cluster, so as to maximize the total video capacity delivered to the RUs. Simulation results are shown to demonstrate the benefits of the proposed DRS-MCS solution compared to other conventional multicasting schemes.