## 6 Test Results
### Synthetic vs. Real-World Signature Impact Analysis  
The results presented in the previous sections were obtained by generating the interference through the replay of raw I/Q sample data captured in the field by the STRIKE3 monitoring sites. In addition, a set of tests was also conducted using a second approach for the threat generation; creating synthetic I/Q data with properties that are representative of the real signals and replaying them with the VSG. The advantage is that the generated signal is free of multipath and GNSS PRN codes, hence it is cleaner than the one recorded in the field. However, this approach has limitations when the original signal is complex and difficult to re-create synthetically, such as in the case of chirp tick signal, as the resultant interference signal may not accurately reflect the real one and, therefore, the impact on the receiver performance may be different. Sensitivity testing with synthetic interference signals was performed only for the MM RUT. In particular, the following four, out of the five threat signatures described in Table 3, were possible to be re-created via VSG: Wide swept frequency with fast repeat rate, multiple narrow band signals, triangular, and triangular wave swept frequency. The results are summarized in Table 7, which also includes the results obtained with live interference data recorded in the field. For each performance metric, the column with label \"S\" contains the results for synthetic signature, whereas the column with label \"R\" contains the results for recorded signature. As it can be observed from Table 7, the synthetic signatures have a stronger impact on the RUT. This is shown by the reduced availability of the position fix due to the longer time needed by the receiver to recover from the interfering event. J/SPVT_reobtained takes values in the range of 30-45 dB when recorded interference is used, while it is in the range of 0-25 dB in the case of synthetic threat signatures. In one test case (i.e., triangular wave swept frequency signal, MM04), the RUT is capable of reobtaining the PVT solution only after the interference has been turned off. As an example, the difference in the impact to the receiver between the recorded and synthetic signature can be seen in Figure 10, which shows the East-North-Up deviations of the receiver's solution from the true position in the test case MM04, using recorded interference and synthetic interference. It is observed that the number of epochs in which the RUT is not capable of providing a position fix is significantly higher when synthetic interference is used. This could be due to the fact that the synthetic signatures are free of multipath and GNSS PRN codes and hence are much cleaner than the recorded ones. This is indeed an empirical conclusion from the perceived tests, which would require further investigation in this direction. It would always remain a challenge to reproduce a real-world detected interference event, since the reproduction of the signal will always be based on the digitized raw In-phase Quad-phase (IQ) samples in the presence of a real GNSS signal. On the other hand, the reproduction of a synthetically generated signal does not have any GNSS signature in it, as the samples are taken from the real jamming device and then reproduced via VSG.