## 5 Conclusions  
This paper, inserted in the context of the project \"Implementing TV White Spaces for Internet Access in Brazil\", provided essential information to support the implementation of TVWS technology in Brazil. This included evaluating the harmonious coexistence between DTV and TVWS systems, as well as investigating operational limits to enable the effective development of new TVWS services. Additionally, it consolidated and compared the results of practical tests examining the coexistence between DTV and TVWS signals used as interference and allocated on channels \(n-1\), \(n+1\), \(n-2\), and \(n+2\) conducted in laboratory and field environments, covering different distances. Laboratory tests involved assessments on the bench and in a controlled environment, analyzing power curves of DTV versus PRavg. The results evidenced that the PR varies according to the interfering technology and the spectral positioning of the TVWS signal to the DTV. The lowest PR recorded was \(-33.24\) dB for 5G-RANGE in GERDM on channel \(n+1\), indicating low OOBE and less impact on DTV reception. The highest PR observed was \(-25.85\) dB for 5G NR on channel \(n+1\), demonstrating a greater potential for interference. In addition, it was found that the simultaneous presence of interferers on channels \(n-1\) and \(n+1\) resulted in an average increase of 3 dB in PR, reinforcing that multiple sources of interference can significantly affect DTV reception. Overall, the results demonstrated that the TVWS signal power could be significantly higher than that of DTV without causing perceptual and visible artifacts or errors on decoded video. Field tests at short distances confirmed these conclusions, highlighting the effective transmission capability of TVWS and that the spectral position of the interference and the receiver model significantly influence the PR. In these tests, it was evident that the performance of the receivers also varied significantly when analyzing the interference on channels \(n+2\) and \(n-2\). STB 1 presented a PR approximately 10 dB higher than the other models, indicating a lower capacity to reject interference. In other words, STBs 2 and 3 demonstrated greater resilience, supporting interfering signals with up to 10 times higher power in \(n+2\) and \(n-2\). Furthermore, long-distance tests revealed that increasing the TVWS power to up to four times the regulated level (6 dB above the regulatory limit) did not disrupt DTV signals. This result indicates that adjustments in the regulation could allow greater flexibility without compromising digital television reception. The results highlighted that the current  
Figure 14: Reception spectrum and constellation of 5G-RANGE for the BS configured for 1 Wp at the locations: (**a**) MS_DeltaBlack. (**b**) MS_CafezalManoeola. (**c**) MS_Pedralva. (**d**) Mobile station in MS_Pedralva during the field tests. regulatory power limitation, set at 1 Wp, compromises the coverage range, particularly in applications that require long distances. Compared to previous tests, which aimed to verify long-range coverage while maintaining support for a throughput of 100 Mbps and in which there were no power restrictions, the system was able to achieve 102 Mbps at 50 km distance with 120.2 Wp, demonstrating that with higher power, it is possible to provide reliable connectivity for large regions. In contrast, the current tests showed that with 1 Wp, the maximum throughput was 96 Mbps at 14.7 km from the base station, while increases to 2 Wp and 4 Wp made it possible to reach 120 Mbps. In the most extreme scenario, at MS_Pedralva (38.34 km from the BS), the system operated at its limit with 1 Wp, reaching a throughput of only 16 Mbps for a 24 MHz BW. However, increasing the power to 8 Wp allowed for a tripling of the throughput. It is important to highlight that the long-distance tests were conducted considering LOS communication to highlight the impact of transmission power limitation on the maximum coverage of the system.