# Aerial Coverage Analysis of Cellular Systems at LTE and mmWave Frequencies Using 3D City Models
## 4 Conclusions and Further Work  
In this article, we estimated the performance of LTE and future mmWave cellular networks for serving flying UAVs using realistic 3D maps of a typical European middle-sized city and semi-deterministic channel models. Using a mmWave network deployed in the same manner as the current LTE cellular network, a comparison between LTE and mmWave was made and the results showed that inter-cell interference remains the main problem for ground to air communication at high altitudes, as described in the existing literature [4; 5; 6; 7; 26]. Contrary to Qualcomm [3], our results indicate that deploying UAVs at high altitudes will result in their coverage probability dropping below 90% at altitudes above 50 m AGL, when using the existing LTE cellular network. The results showed that an optimal deployment altitude for AEUs does exist, as analytically derived in [7], both for an LTE network and a mmWave network, albeit not at the same altitude due to different blockage effects at these frequencies. For a full-load scenario, LTE outperforms a mmWave cellular network at providing coverage at high altitudes when using the same BS locations. Using a mmWave communication link, ground UEs experience too much blockage by buildings to have good coverage. AUEs at high altitudes have a lower SINR using a simulated mmWave system than when they would using the existing LTE system. The results show that mmWave reaches a coverage probability of 0% at an altitude approximately 50 m lower than LTE. When operating in high-load, both an LTE and a mmWave system fail to provide coverage of to AUEs at altitudes higher than 50 m. However, for a partial load scenario, increasing of the SINR levels at higher altitude is possible when a mmWave system is used, especially when the number of sectors per base station is increased, using mmWave phased antenna array techniques. For mmWave networks, the mean SINR level at higher altitudes can be improved by 1-7 dB compared to the standard three-sector case. The largest improvement of SINR can be seen around the height of 35 m. Simultaneously, this increase of SINR allows 100% coverage probability at high altitudes: up to 50 m for the standard three-sector per BS case, reaching up to 100 m for a case with 42-45 sectors per BS using mmWave. Figure 11: Improvement of mean SINR in partial load over the three-sector case at different heights for a mmWave network. We demonstrated that a significant improvement of the coverage of AUEs at high altitudes is possible using mmWave, even when only a basic form of beamforming is applied. We can expect that the research community will concentrate its future work at mmWave and beamforming techniques when exploring ways to provide coverage for high-altitude UAVs. It is a promising direction towards the 3D cellular networks for urban environments. The contributions of the respective authors are as follows: conceptualization, E.V. and S.P. ; methodology, A.C. and E.V. ; software, A.C.; formal analysis, A.C.; data curation, A.C.; writing-original draft preparaton, A.C.; writing-review and editing, E.V. and S.P. ; visualization, A.C.; supervision, S.P. ; project-administration, E.V. and S.P. ; funding acquisition, S.P. This research and APC was funded by the Research Foundation Flanders (FWO), project no. S003817N \"OmniDrone\". Authors are grateful to [PERSON] for valuable discussions during the preparatory stage. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results. The following abbreviations are used in this manuscript: