  Unmanned Aerial Vehicles (UAVs) enabled communications is a novel and
attractive area of research in cellular communications. It provides several
degrees of freedom in time, space and it can be used for multiple purposes.
This is why wide deployment of UAVs has the potential to be integrated in the
upcoming 5G standard. In this paper, we present a novel cell outage
compensation (COC) framework to mitigate the effect of the failure of any
outdoor Base Station (BS) in 5G networks. Within our framework, the outage
compensation is done with the assistance of sky BSs (UAVs) and Ground BSs
(GBSs). An optimization problem is formulated to jointly minimize the energy of
the Drone BSs (DBSs) and GBSs involved in the healing process which accordingly
will minimize the number of DBSs and determine their optimal 2D positions. In
addition, the DBSs will mainly heal the users that the GBS cannot heal due to
capacity issues. Simulation results show that the proposed hybrid approach
outperforms the conventional COC approach. Moreover, all users receive the
minimum quality of service in addition to minimizing the UAVs' consumed energy.
