## 2 Proposal of the New Protection Definition
### The Methodology and the Setup Used for the Laboratory Tests  
The main laboratory test goal was to identify the PR limits of DTV receivers operating under the influence of interfering signals. The PR represents the minimum value of the signal-to-interference ratio at which a specific reception quality is achieved under specific conditions. The nomenclature used to display the test results regarding the occupied channel is that the signal under analysis, namely the DTV signal, occupies channel \(n\), while the interfering signal occupies neighboring channels to the desired channel and is identified as, for example, \(n-1\) and \(n+1\), when interference is applied in the adjacent lower and upper channels, respectively. The interference applied in the second lower or upper channel is further identified as \(n-2\) or \(n+2\). In the context of coexistence with the ISDB-T standard, it is possible to mention the ITU-R BT.1368 \(-\) 13 [16] recommendation as a baseline reference, which provides PR values for interference in the \(n-1\) and \(n+1\) channels as \(-26\) dB and \(-29\) dB, respectively. This relationship was defined for the ISDB-T system operating with a BW of 6 MHz, 64-QAM modulation, and a 7/8 encoding rate, and in the presence of interference from a signal also compliant with the ISDB-T standard. It is worth noting the PR values mentioned were defined for a bit error rate (BER) of \(2\times 10^{-4}\) measured before the Reed-Solomon decoder. The methodology adopted for conducting the laboratory tests involved evaluating the PR based on a subjective analysis of the decoded DTV video signal. This evaluation aimed to determine the threshold at which interference begins to degrade the quality of the received signal, using the quasi error free (QEF) and Threshold of Visibility (TOV) criteria. The QEF condition was established as the benchmark for distinguishing between an acceptable and a degraded signal. A signal is considered to meet QEF criteria when its decoded video is free from visually perceptible distortions, artifacts, or freezing over a 60 s observation period. The TOV is determined by progressively increasing the interfering signal level until visible artifacts, errors, or interruptions appear in the decoded video. This marks the point at which interference starts affecting reception, providing a reference for identifying the initial stage of signal degradation. Once the TOV threshold was identified, the interfering signal was gradually attenuated in 1 dB steps until the decoded video no longer exhibited any visible artifacts. At this point, the PR was calculated by [16; 46]  
\[PR\ (dB)=P_{\text{desired}}-P_{\text{interfering}}, \tag{1}\]  
where \(P_{\text{desired}}\) is the power of the desired signal in decibel-milliwatts (dBm) and \(P_{\text{interfering}}\) is the power of the interfering signal in dBm, at which the reception was restored to a QEF condition. Thus, the recorded measurements reflect the subjective analysis of the decoded video signal under QEF conditions, ensuring that the PR values accurately represent the interference tolerance limits of the DTV system. Figure 1 presents the setup diagram used to carry out the laboratory tests. The setup included a DTV generation station and another generation station of different technologies, in order to generate the called interfering signals. Additionally, the setup includes amplifiers, filters, attenuators, and radiofrequency (RF) combiners. The DTV signal was generated using a broadcast transport stream (BTS) player, model digital video recorder generator (DVRG), manufactured by Rohde & Schwarz based in Munich, Germany, along with a professional DTV modulator, model E-Compact, manufactured by Hitachi Kokusai Linear based in Santa Rita do Sapucai, Brazil. Channel filters, model 4352 from Hitachi Kokusai Linear, were configured on channels 46, 47, 48, 49, and 50 with 6 MHz of BW. The variable attenuators used were from HP based in Palo Alto, CA, USA, whose values and models varied depending on the desired configuration during the tests.