## 5 Results
### In-Orbit Results
#### 5.2.2 Measurements over Populated Areas  
The measurements performed close to populated areas are shown in Figure 8a, and they are referred to as interference measurements hereafter. The 90% (red line) and 10% percentile (blue line) and the median (black continuous line) of all average power spectra measured over populated areas are compared to the median of the noise measurements over non-populated areas (black dashed line) plotted in Figure 8b. The 10% percentile signal spectrum has about the same power level as the noise median spectrum. A band-limited signal of around 300 kHz of low power can be observed in the 10% percentile signal spectrum, but it is more visible in the signal median and the 90% percentile spectrum as it has higher power. Since the band-limited signals appear clearly in the signal median, they are present at least in half of the measurements. Furthermore, the 90% percentile spectrum has around 7 dB higher power than the median in the centre frequency and there seems to be a wide-band signal in addition to the band-limited signal. The dispersion of the spectra can be analysed using the CV in Figure 8c. The 10% percentile is close to the median of the CV for noise measurements. The CV for the signal median and the signal 90% percentile have a different tendency to that of the noise measurements. The CV in these cases is higher, which means the dispersion is higher and the probability for communication to be hit by interference significantly larger than the average power is higher than for AWGN. In the CV for the median, we observe that the increase of the dispersion is band-limited, as seen in the average power spectrum (Figure 8b), while, for the 90% percentile, the band-limited signal is combined with other wide-band signals with even higher dispersion. Figure 7: Time behaviour of measurements over non-populated areas. (**a**) Normalised LME second moment for different time windows in 3D. (**b**) Normalised LME second moment for different time windows in 2D. The Empirical Cumulative Density Function (ECDF) of the measured interference power of all frequency bins shows the probability of getting hit by an interference no larger than a certain power. The ECDF for the interference is estimated for three regions \(R1\)-\(R3\) covering West and East Europe and northern Africa, together with the Middle East (Figure 9). In the map shown in Figure 9a, the northern parts of the plot are between \(35^{\circ}\) and \(70^{\circ}\) (marked with crosses in the map and with dashed lines in the plot), and the southern part is between \(0^{\circ}\) and \(35^{\circ}\) (circles in the map and a blue continuous line in the plot). Each of the northern regions represents \(35^{\circ}\) of longitude, while the southern region represents \(70^{\circ}\) of longitude. The points in the map represent the sub-satellite points where the satellite measured received power. The power of all frequency bins within the 3 dB bandwidth is included to estimate the ECDFs (Figure 9b). As a reference, the red curve is the distribution of all regions. There is a clear difference between the interference experienced in the regions in the north (\(R1\) and \(R2\)) and south (\(R3\)). The region \(R3\) is affected in less than \(20\%\) of the points by signals with a power higher than \(-38\) dB. The power increases about \(7\) dB for regions \(R1\) and and \(6\) dB in \(R2\) for \(20\%\) of the points in relation to region \(R3\). In general, the sub-satellite points with lower latitude experience less interference because they were acquired over less populated areas. Nevertheless, their distribution is different from the noise distribution (dotted black line). Figure 8: Time-frequency behaviour of measurements over populated areas. (**a**) Sub-satellite points for measurements over populated areas. (**b**) Spectrum of average power (\(m_{2k}\)). (**c**) CV. A high CV indicates high spread in the measured envelope.