## 3 TVWS-DTV Coexistence: Field Measurements
### Field Tests Considering Long Distances
#### 3.2.2 Transmission Power of the TVWS BS and Definition of Locations  
In accordance with current regulations, it is established that the BS TVWS primarily operates with a power of 1 Wp (30 dBm) per 6 MHz channel [33]. The total average power in the transmission channel, in this configuration, is 20 dBm, considering the typical PAPR of the GFDM signal in the configurations used by the 5G-RANGE BS is 10 dB. In addition to the power of 1 Wp, power amplifiers were linearized for powers of 2 Wp and 4 Wp. These different powers were defined to expand the conditions of the interfering signal power in the DTV system and to allow the evaluation of the impact of transmission power on coverage and TVWS service quality. The linearization is crucial because increasing the transmission power implies an increase in the OOBE, and consequently, an increase in the values of ACLR or ACPR ratios. These ratios establish the relationship between the transmission channel power and the power of adjacent channels. If the OOBE level is above acceptable levels, techniques such as Digital Pre-Distortion (DPD) are employed, which requires parameterization and adjustment based on the operating frequency, transmission power, and characteristics of the amplifier used in each antenna. Table 7 shows the power delivered to each transmission antenna of the BS for each of the mentioned configurations. Unlike changing channels, adjusting the power in the BS can be achieved through remote access to the equipment, made possible by installing a network between Inatel and _Serra do Paredao_ using a pair of radios that operate Wi-Fi in the 5 GHz range. The Inatel internal network was accessed through a Virtual Private Network (VPN) via a mobile device. From the definition of the average transmission power of the 5G-RANGE system, coverage predictions were made using the Radio Mobile software to define candidate locations for field measurements [49]. The 1 Wp condition was considered for coverage \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Total \(P_{\text{peak}}\) [Wp]** & **Total \(P_{\text{peak}}\) [dBm]** & **PAPR [dB]** & **Total \(P_{\text{avg}}\) [dBm]** & \(P_{\text{avg}}\) **to Each Antenna (MIMO \(2\times 2\)) [dBm]** \\ \hline
1 & 30 & 10 & 20 & 17 \\ \hline
2 & 33 & 10 & 23 & 20 \\ \hline
4 & 36 & 10 & 26 & 23 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Predicted powers for the TVWS BS. prediction, with the BS positioned in _Serra do Paredao_, whose latitude and longitude are \(-\)22.19764 and \(-\)45.74194, respectively, at an altitude of 1.385 m. A directional antenna with a gain of 9.5 dBd was positioned at a height of 12 m from the ground, pointing towards the Vintem neighborhood in the rural area of the city of Santa Rita do Sapucai. The coverage prediction performed using the Radio Mobile tool was used as a starting point for defining candidate locations for field measurements. The coverage prediction made did not consider the terrain morphology and practical issues such as the actual direction of the transmission antenna and the occurrence of multipaths and reflections, among other phenomena, which can lead to discrepancies between predicted and measured values in the field. Therefore, the definition of locations for field measurements met the following criteria:  
* Prediction of a minimum reception level of the 5G-RANGE signal of \(-\)80 dBm;
* Accessibility of the location;
* Availability of a safe area for parking the MS and installing reception antennas;
* Absence of obstructions for LOS communication with the BS;
* Availability of a cellular network signal to enable remote access to the BS and facilitate parameter changes in the system;
* Selection of at least one location that allows identifying the coverage limit of the 5G-RANGE system;
* Selection of at least one location that allows establishing communication links with a throughput close to 100 Mbps for the 5G-RANGE system.