Joint Beamforming and Location Optimization for Cooperative Content-Aware UAVs

In this paper, we study the downlink transmission in a multi-UAV enabled wireless communication system where different types of contents are requested by ground users. Particularly, in the system, we consider a number of UAVs each equipped with a cache that is refreshed during off-peak hour to store some contents to be requested by ground users. To harness their full potential, a novel cooperative communication for the cache-enabled UAVs is presented, and we formulate an optimization problem that jointly decides the UAV placement as well as the transmit beamforming to maximize the number of users admitted to the system. Since the formulated problem is a mixed-integer non-convex program, which is generally known to be NP-hard, we resort to an appealing framework developed from the conventional difference-of-convex (DC) programming. Numerical results reveal the superiority of employing cooperative UAVs over non-cooperative ones and offer some insights into how the flexible deployment of cooperative UAVs benefits the system performance.