# NextGen ADS-B Software-Defined Reception with Enhanced Techniques
## 5 Experimental Results  
Two major experiments were performed; the first one was done in the LASSENA laboratory of the ETS university with aim of key requirements validation and the second experiment was performed in the light aircraft (Cessna C-172) from Saint-Hubert (CYHU) Airport to Mirabel (CYMX) Airport to evaluate system performance in the operational environment. Figure 8 illustrates the simulation block of ADS-B In. It consists of the BaldeRF subsystem, converting complex inputs to magnitude, Enhanced preamble detection, Enhanced bit detection, CRC check and error correction, and UPD interface with UGC application. Cross-correlation and leading-edge are two major approaches that are examined in the Simulink environment based on the Figure 9 simulation test bench. Figure 9 shows that ADS-B message generator block is combined with primary interference FRUIT A/C; afterward, it is amplified and sent to the ADS-B message scheduler in order to send the message based on transmission rate (it could be periodically or random); then white Gaussian noise is added to the signal, and ultimately, the signal is transmitted by BladeRF with a sampling rate of 12 MHz and central frequency of 1090 MHz. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Register Address** & **Default Value** \\ \hline OUTER THRESHOLD HIGH & 0 \(\times\) 129 & 5 \\ OUTER THRESHOLD HIGH Decrease Step Size & 0 \(\times\) 12A(D[6:4]) & 2 \\ INNER THRESHOLD HIGH & 0 \(\times\) 101 & 10 \\ INNER THRESHOLD HIGH Decrease Step Size & 0 \(\times\) 123(D[6:4]) & 1 \\ INNER THRESHOLD LOW & 0 \(\times\) 120 & 12 \\ INNER THRESHOLD LOW Increase Step Size & 0 \(\times\) 123(D[2:0]) & 1 \\ OUTER THRESHOLD LOW & 0 \(\times\) 129 & 18 \\ OUTER THRESHOLD LOW Increase Step Size & 0 \(\times\) 12A (D[2:0]) & 2 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Slow attack AGC parameters and related registers and their default values. Figure 8: ADS-B In’s simulation. Figure 9: Simulation test bench for ADS-B In performance evaluations. Figure 10 demonstrates preamble detection accuracy for various tests including cross-correlation, Leading-edge in MGC mode and slow attack mode, and linear and logarithmic amplifier approaches. Linear and logarithmic amplifier approaches' values are exploited from the article [22]. Based on the results, slow attack AGC mode has a 100 percent preamble detection in 2 dB weaker signal power than the logarithmic amplifier approach. Similarly, the same test is performed for the measurement of packet and bit error rate of both central sampling and multiple sampling methods in various modes. Figure 11 illustrates explicitly that slow attack PER and BER in the multiple-sampling method is far better for poor signal than other methods. It is worthwhile to note that error correction is not applied during PER and BER tests. Figure 12 shows the test bench diagram which is designed to perform sensitivity tests in the lab. As the block diagram illustrates, the IFR6000 test equipment generates ADS-B signals, afterward, the signal is weakened by a variable attenuator. Then splitter provides two outputs of signal with the same signal strength; one of them is used as Rx input of ADS-B In for the SDR unit under the test and another one is used as spectrum analyzer  
Figure 11: Packet error rate and the bit error rate of central sampling method (**a**), and multiple-sampling method (**b**). Figure 10: Preamble detection accuracy for various approaches. input to do power measurements. Note that the power splitter is generating 3 dB losses for both parties. Therefore, the received signal power level at BladeRF RX and Spectrum analyzer input is the same. In addition, FAA proposed the following requirement need to be met at the end of the receiver's antenna:  
* The minimum trigger level (MTL) of an ADS-B receiver processing signals within the frequency span of 1089 to 1091 MHz shall respect the MTL constraints which are provided in Table 2[1].