## 3 TVWS-DTV Coexistence: Field Measurements
### Field Tests Considering Short Distances
#### 3.1.1 Field Test Setup and Methodology Used  
The 5G-RANGE base station (BS) was configured to use the GFDM technique with a BW of 5.571 MHz, transmitting on channel 28 in the UHF band. Figure 4 shows measurements made by the spectrum analyzer, model MTs222B, manufactured by Anritsu, specifically the power measurement of the center channel at a frequency of 557.143 MHz with a bandwidth of 5.571 MHz, as well as the ACLR measurements for the adjacent channels. The graphs show the received signal power level and the frequency on the \(y\) and \(x\) axes, respectively. The measurement parameters include an RBW of 10 kHz, a VBW of 300 Hz, and a span of 30 MHz. Figure 4a shows the characterization of the RF signal delivered to one of the antennas for a transmission power of around 1 dBm root mean square (RMS) per antenna. As 5G-RANGE uses multiple-input and multiple-output (MIMO) \(2\times 2\), the total power transmitted by the BS is 4 dBm RMS or 2.51 mW RMS. Considering a PAPR margin of 10 dB, the total peak power transmitted (\(P_{\text{TX}_{\text{total}}}\) TVWS) in this condition is about 14 dBm or 0.03 Wp. The adjacent channel power ratio (ACPR), which, like the ACLR, establishes the relationship between the transmission channel power and adjacent channels, for the lower and upper channels in this condition is \(-49.5\) dB and \(-51.3\) dB, respectively. The short-distance tests, which allowed reaching the operational limit of DTV STBs, considered powers close to this description, i.e., with transmission around 1 dBm RMS per antenna. It is worth noting that the tests were conducted over short distances, where free-space propagation attenuation is significantly reduced compared to over long distances, allowing the achievement of the operational limit conditions of STBs with a lower interfering signal power. However, the main metric to be observed in the tests was the PR value on the link. The short-distance tests, considering interference on channels \(n-2\) and \(n+2\), which allowed reaching the operational limit of DTV STBs, considered 5G-RANGE BS transmission powers close to 12 dBm and 22 dBm. Figure 4b shows the characterization of the RF signal delivered to one of the antennas for a transmission power of around 12 dBm RMS per antenna. The total power transmitted by the BS in this case is 15 dBm RMS or 0.03 W RMS. \(P_{\text{TX}_{\text{total}}}\) TVWS in this condition is 25 dBm, or 0.32 Wp. The ACPR for the lower and upper channels in this condition is \(-46.2\) dB and \(-46.7\) dB, respectively. Figure 4c presents the characterization of the RF signal delivered to one of the antennas for a power of around 22 dBm. The total power transmitted by the BS in this case is 25 dBm RMS or 0.32 W RMS. \(P_{\text{TX}_{\text{total}}}\) TVWS in this condition is 35 dBm, or 3.16 Wp. It is worth noting that this last power value considered for short-distance tests is higher than the 1 Wp limitation imposed by TVWS regulation in Brazil. The ACPR for the lower and upper channels in this condition is \(-49.2\) dB and \(-49.8\) dB, respectively. The transmission power values of 5G-RANGE that allowed reaching the operational thresholds of DTV STBs for each test condition are detailed in Section 3.1.2. Although some of the operational limit conditions of STBs were achieved with slightly different transmission powers of 5G-RANGE than those shown above, it is understood that the presented characterizations allowed for identifying the conditions of the interfering signal in each test. Regarding the reception station, Figure 5 illustrates the measurement setup that forms the mobile station (MS). The setup includes a BTS generator, model DTU-245 from Dektec based in Utrecht, The Netherlands, to provide a BTS stream in the DTV modulator input, which was generated with the same configuration used in the laboratory tests. Additionally, the MS consists of a Signal Combination Stage and a complementary arrangement for data collection and analysis.