  We introduce the concept of using unmanned aerial vehicles (UAVs) as drone
base stations for in-band Integrated Access and Backhaul (IB-IAB) scenarios for
5G networks. We first present a system model for forward link transmissions in
an IB-IAB multi-tier drone cellular network. We then investigate the key
challenges of this scenario and propose a framework that utilizes the flying
capabilities of the UAVs as the main degree of freedom to find the optimal
precoder design for the backhaul links, user-base station association, UAV 3D
hovering locations, and power allocations. We discuss how the proposed
algorithm can be utilized to optimize the network performance in both large and
small scales. Finally, we use an exhaustive search-based solution to
demonstrate the performance gains that can be achieved from the presented
algorithm in terms of the received signal to interference plus noise ratio
(SINR) and overall network sum-rate.
