# LaRoAwan CubeSat with an Adaptive Data Rate: An Experimental Analysis of Path Loss Link Margin
## 5 Results  
### Experimental Results  
Since LoRa modulation is used, the signal below the noise level can be detected, allowing the total receive power to be expressed as Equation (18).  
\[P_{r}=RSSI+SNR \tag{18}\]  
where \(RSSI\) = Received Signal Strength Indicator,  
\(SNR\) = Signal-to-Noise Ratio.  
The result obtained at the gateway reception from the experiment is the \(RSSI\) and \(SNR\) values. Meanwhile, the total receive power \(P_{r}\) is calculated using Equation (18) and the various attenuation levels shown in Table 6.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Attenuation** & **0 dB** & **30 dB** & **60 dB** & **90 dB** & **120 dB** & **150 dB** \\ \hline \(RSSI\) (dBm) & \(-12.0\) & \(-26.0\) & \(-78.0\) & \(-108.0\) & \(-121\) & \(-128\) \\ \(SNR\) (dB) & \(9.5\) & \(4.4\) & \(-2.7\) & \(-9.1\) & \(-18\) & \(-21\) \\ \(P_{r}\) (dBm) & \(-2.5\) & \(-21.6\) & \(-80.7\) & \(-117.1\) & \(-139\) & \(-149\) \\ \hline \hline \end{tabular}
\end{table}
Table 6: Results received at the gateway side at different attenuation levels.  
Figure 8: Shielded box to create a Faraday cage-like environment to overcome signal leakage.  
Figure 9: Block diagram of attenuators used to simulate path loss in Figure 8.  
Each attenuation level was set for four hours to thoroughly monitor the received signal strength and signal-to-noise ratio. Figure 10 shows the signal RSSI behavior throughout the monitoring. Figure 11 shows the _SNR_ results obtained by attenuating the signal level from 0-150 dB with a step of 30 dB, showing significant performance of the end node during the four-hour window. The result proves the stability of the LoRa signal-to-noise ratio.  
Figure 11: Results of Signal\(-\)to\(-\)Noise Ratio (SNR) during the four-hour window.  
Figure 10: Observed Received Signal Strength Indicator (RSSI) at various attenuation levels during the four\(-\)hour window.  
Trend analysis of _RSSI_ and _SNR_ performance Figure 12 shows the correlation of _RSSI_ and _SNR_ concerning the attenuation level to simulate the path loss of spacecraft at an altitude of 550 km.  
As shown in the above experiment, it is observed that we received the signal at 150 dB, which is the maximum distance of our slant range. This confirms that the spacecraft at a minimum look angle will be able to transmit data.  
Notably, with a transmit power of only 14 dBm, signals can travel great distances without fading or being interrupted by external factors compromising signal integrity. LoRa's Signal-to-Noise Ratio (_SNR_) is an additional crucial aspect contributing to the signal's excessive range. Even at an _SNR_ of \(-\)21 dB, which indicates that the signal is buried by a factor of 20 or more below the noise floor, the receiver may still identify the signal. Moreover, signal performance shows sudden fluctuation whenever the device temperature increases. Fluctuation is noticed on both _RSSI_ and _SNR_ performance which in turns degraded the reception. ADR enables dynamic signal reception, which is a practical option for fast-moving satellites to mitigate the Doppler effect. In addition, during the signal attenuation experiment, it was discovered that the end device PCB circuit was leaking signal. In the light of this research, it is essential to note that when building a chipboard for an end product, shielding and proper circuit design should be considered, as well as all feasible angles to prevent signal leakage. Additionally, it is important to note that the inclusion of ADR in the system makes it more adaptable.  
Experimental results showed significant LoRa signal performance even at the lowest attenuated level. Under the line of results, it is proof that sensor devices, when transmitting a signal using a LoRa transmitter, can communicate to the LoRaWAN gateway even with a maximum distance of 2705.3 km (Table 3). As per observed results, it is clear that the LoRaWAN gateway can use as a payload for the CubeSats and is a comparatively cheaper solution while creating the system design of LoRaWAN sensor networks.