Interference Coordination for Aerial and Terrestrial Nodes in Three-Tier LTE-Advanced HetNet

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 LTE-Advanced 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 Re1-10 with almost blank subframes.