# NextGen ADS-B Software-Defined Reception with Enhanced Techniques
## 5 Experimental Results
* Each ADS-B receiver must correctly detect and decode at least 99 percent of all ADS-B messages without the presence of interference and excessive load providing that the input signal level is limited to MTL +3 dB and 0 dBm. The result of the test for various scenarios including Manual gain control, Slow attack AGC mode, and slow attack AGC with error correction is shown in Figure 13. It reveals that sensitivity improved significantly by activation of slow attack AGC and tuning its related parameter. Additional accuracy is achieved by applying the error correction algorithm which is explained in Section 3.3. Furthermore, it was completely necessary to use a Distance Measuring Equipment (DME) antenna for the flight test to capture and record ADS-B messages as the DME antenna frequency range covers 1090 MHz of ADS-B. Figure 14 shows all the required equipment for the flight experiment. It is crucial to shield BladeRF with the aluminum box to avoid interference impact on the GPS device. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Minimum Trigger Level & \(-\)84 dBm \\ Frequency range & 1090 \(\pm\) 1 MHz \\ Modulation & Pulse-Position Modulation (PPM) \\ Rate & 1 Mbps \\ \hline \hline \end{tabular}
\end{table} 
Table 2: ADS-B Class “A3” Device Receiver Specifications. Figure 12: Sensitivity test bench block diagram. Considering above mentioned result, slow attack AGC help to leverage ADS-B In sensitivity. Comparing the result of fixed gain and AGC activation demonstrates that in the case of AGC activation, sensitivity criteria are fulfilled and ADS-B In performance is improved significantly since both poor and strong signals power are mapped into the specific range of power signal levels to be detected and decoded. This leads to an extension in reception coverage range as flight tests' results reveal, ADS-B In coverage range is increased significantly from 20 km to over 500 km according to Figure 15. The result was extracted from the flight test which was conducted in August 2022. Kindly note that there were no ADS-B signals in the distance range of 230 km to 630 km. Figure 14: (1) Aircraft DME antenna; (2) Installed System inside Aircraft; (3) BladeRF V2 SDR; (4) Aircraft; (5) PC (Cincoze system; (6) Connector to DME antenna; (7) ulbox(GPS); (8) ulbox antenna. Figure 13: Measured accuracy for various modes. Apart from real-time displaying ADS-B In results, the flight test post-processing and logs analysis was done to validate system performance. In summary, two flight tests were conducted on 13 July and 1 August 2022, the flight duration was about 80 minutes and 70 minutes respectively. Overall, over 137,000 messages without error were decoded, and 185 unique flight IDs were identified. In Addition, the top ten detected flight IDs were identified and validated with FlightAware [30] log history data. Figure 16 shows the top 10 detected messages related to the call sign during the flight on the 1 st of August 2022. It is important to mention that the call sign is extracted from BDS08 burst data which broadcasts every 5 seconds, and it is used to match position and velocity data to aircraft identification based on ICAO. The sample result of the comparison is demonstrated in Figures 17 and 18. Figure 17 shows position elements including latitude, longitude, and altitude comparison of sample aircraft with FlightAware logs. In addition, Figure 18 provides velocity factors consisting of speed and heading comparison for the same aircraft data with FlightAware logs. In both cases, the results are quite matching for a considerable time range (8 min). It signifies  
Figure 16: Count of top 10 detected callsigns during flight test. Figure 15: (**a**) Flight test route; (**b**) Percentage of decoded messages distribution in PDF and CDF vs distance in Km. that the system is capable to track aircraft continuously without missing any data and it validates the system integrity performance. Figure 19 shows the number of correctly decoded messages per second.