Joint Route Selection and Radio Resources Allocation for Caching in Multi-Hop Networks

In this paper, we focus on a cache-enabled networks, where a content requested by user equipments (UEs) can be delivered by means of multi-hop relaying via unmanned aerial vehicles (UAVs) and/or via other UEs exploiting device-to-device (D2D) communication. For such scenario, we optimize transmission power allocation, bandwidth allocation, and route selection to minimize the content delivery duration. The formulated problem is a mixed-integer nonlinear programming (MINLP) problem and, thus, it is hard to solve. Hence, we first solve the power and bandwidth allocation by a cooperative game among all transmitting nodes involved in the content delivery process and we prove that this game is a potential game. Then, we introduce a fast-converging iterative algorithm employing an approximate better-response mechanism for the resource allocation (i.e., power and bandwidth). After that, we design a low-complexity greedy algorithm jointly handling route selection and power and bandwidth allocation. The algorithm selects transmission routes to deliver the requested contents to the UEs and, after each selection, the resource allocation at the transmitting nodes involved in the content delivery process (i.e., GBS, UAVs, and relaying UEs) is updated. The simulation results demonstrate that the proposed scheme reduces the average content delivery duration by up to 23.2% compared to the best-performing benchmark algorithm.