  Integrating unmanned aerial vehicles (UAVs) as user equipment (UE) and
base-stations (BSs) into an existing LTE-Advanced heterogeneous network
(HetNet) can further enhance wireless connectivity and support emerging
services. However, this would require effective configuration of system-level
design parameters for interference management. This paper provides system-level
insights into a three-tier LTEAdvanced air/ground HetNet, wherein the UAVs are
deployed both as BSs and UEs, and co-exist with existing terrestrial nodes.
Moreover, this HetNet leverages on cell range expansion (CRE), intercell
interference coordination (ICIC), 3D beamforming, and enhanced support for
UAVs. Through Monte-Carlo simulations, we compare system-wide fifth percentile
spectral efficiency (5pSE) and coverage probability for different ICIC
techniques, while jointly optimizing the ICIC and CRE parameters. Our results
show that reduced power subframes defined in 3GPP Rel-11 can provide
considerably better 5pSE and coverage probability than the 3GPP Rel-10 with
almost blank subframes.
