# Aerial Coverage Analysis of Cellular Systems at LTE and mmWave Frequencies Using 3D City Models
## 3 Simulation Results
### Interference Management  
In the previous section, we present the analyses of a system operating in full-load, i.e. all base stations were simultaneously transmitting data on all three of their sectors. However, in reality, most of the time base stations would only transmit on a certain sector when communication is requested by an active user in that sector's area. In the next simulation, we assumed a partial load and we increased the number of sectors per base station, as explained in Section 2.2, only for the mmWave frequency band. Increasing the number of sectors and keeping the active ground user density \(\rho\) (Table 1) constant would decrease the probability that an interfering base station, with sectors oriented towards an AUE location, is transmitting on those sectors, thus decreasing the amount of interference and increasing the SINR for that specific AUE location. Note that the maximum transmit power is decreased with increasing number of sectors due to RF exposure regulations (as explained in Section 2.1.2), thus not resulting in a better link budget. Figure 9 shows the SINR distributions at different heights when varying the number of sectors per base station. Note that the results for the 20 MHz bandwidth are demonstrated here and only for the mmWave scenario. Increasing the number of sectors improves the SINR values. For ground users, the increase in SINR is negligible, while, for AUEs at high altitudes, it is approximately 5 dB when increasing the number of sectors from 3 to 45. Figure 8: Coverage probability for specific heights in a full-load scenario, representing the probability of having an SINR of \(-6\) dB or higher at a certain altitude. When looking at the results of coverage probability (see Figure 10), we can conclude that a significant improvement can be achieved when using a high number of sectors. For example when using 45 sectors, a coverage probability of 90% is present up to approximately 140 m AGL, which is a reasonable maximum height for UAV deployment. Figure 10 shows that increasing the bandwidth to 400 MHz does not have a significant effect for high altitudes, which indicates that AUE are in fact still interference limited instead of being noise limited, even when using mmWave communications. Nonetheless, the statement of noise limited mmWave communications does still hold for ground users up to rooftop height. Improvements however saturate, as Figure 11 indicates, and, at some point, increasing the number of sectors will only give a minimal increase in SINR and will not outweigh the extra cost of more expensive mmWave equipment. Figure 11 also gives a clear indication at which altitudes the mmWave system is noise-limited and at which altitudes it is interference-limited. The lines indicating the increase in SINR at altitudes of 35 m and 150 m at 20 MHz are almost equal to their 400 MHz counterparts, indicating that at these altitudes an increase in bandwidth, resulting in an increase in noise power, does not significantly affect the SINR. One can conclude that at these altitudes the mmWave system is indeed interference limited. When looking at the lines for ground and rooftop users, one can see that there exists a clear difference between the 20 MHz and 400 MHz line, especially for ground users; it is  
Figure 10: Coverage probability for specific heights in a partial load scenario (mmWave only), representing the probability of having an SINR of \(-6\) dB or higher at a certain altitude. Different symbols represent different number of sectors per base station. Figure 9: Cumulative distribution of SINR in partial load at different AUE altitudes comparing different numbers of sectors per base station for the mmWave scenario. clear that, when considering a large bandwidth, the increase of number of sectors does not result in any improvement of the mean SINR. This result is a clear indication that increasing the bandwidth and thus the noise does affect the SINR at low altitudes, resulting in a noise-limited system for ground users.