# Experimental Study of LoRa Transmission over Seawater
## 4 Experimental Results and Analysis
### LOS Scenario
#### 4.1.2 ISM 434 MHz  
The experiments carried out at 434 MHz were performed using a pair of ODT transceivers, exploring the same LoRa parameters as in the case for 868 MHz band. In addition, the experimental setup was identical and deployed to operate simultaneously with the 868 MHz setup. Figure 15 shows results for the following parameters: \(BW=125\) kHz, \(SF=7\), and \(CR=4/6\). It can be seen that the RSS is remarkably high during the whole measurement, the minimum value is \(-88\) dBm. Its moving average values fluctuate 3 dB peak-to-peak indicating a small-scale multipath propagation. This also can be concluded if we compare it to the corresponding results at the 868 MHz. Namely, the difference yields approximately 12 dB. However, due to negligible terrain shielding in this case (see Table 2) and consequent free-space propagation, the difference should be 6 dB, provided there are no multipath effects on propagation path. We can also observe a very small packet loss during the whole experiment which yields \(PL=0.15\%\). The SNR fluctuations do not follow RSS fluctuation trend during the whole experiment. Referring to Figure 8, this can be easily explained. Namely, the SNR measurement chain is deeply in the saturation region, reflecting the oscillations that can be observed for RSS values lower than \(-100\) dBm. Figure 16 shows the distribution of the moving average values of RSS and SNR calculated in the 1-min window, as well as distributions of the difference between their current and moving average values. The results shown are obtained using the following LoRa parameters: \(BW=125\) kHz, \(SF=7\), and \(CR=4/6\). We observe that difference between current and moving average values of RSS is nearly bimodal which is expected since small-to-medium-scale multipath effects can be observed. On the other hand, it can be noticed that for the same difference of SNR values there is a bimodal distribution, which may be explained by the deep saturation of the SNR measurement chain; however, this claim needs further investigation in order to be confirmed. In Figure 17 results for the following LoRa parameters are given: \(BW=125\) kHz, \(SF=10\), and \(CR=4/6\). As in the previous experimental case, RSS fluctuation of moving average values are approximately 3 dB peak-to-peak. The difference between the corresponding RSS values for the same LoRa parameters at 868 MHz is slightly lower yielding 10 dB. The same conclusion as in the case for \(SF=7\) can be applied; this is also valid for SNR. Figure 15: RSS, SNR, and PRR for ODT at 434 MHz in LOS channel conditions for \(BW=125\) kHz, \(SF=7\), and \(CR=4/6\). Figure 16: RSS and SNR histograms for ODT: \(f=434\,\mathrm{MHz}\), \(BW=125\,\mathrm{kHz}\), \(SF=7\), \(CR=4/6\), LOS. Figure 17: RSS, SNR, and PRR for ODT at 434 MHz in LOS channel conditions for \(BW=125\,\mathrm{kHz}\), \(SF=10\), and \(CR=4/6\). Figure 18 shows RSS and SNR distribution of 1-min moving average and the difference between current values and moving average for the same LoRa parameters. Again, the small-scale multipath effects can be distinguished by inspecting the difference between current values and moving average values in Figure 18b. On the other hand, the moving average fluctuations in Figure 18d this time show Gaussian distribution, but the SNR measurement chain is on the onset of the saturation region, where the characteristic of the measurement chain is different than in the deep saturation region. Finally, Figure 19 shows experimental results for the most sensitive mode of the ODT transceiver: \(BW=125\,\mathrm{kHz}\), \(SF=12\), and \(CR=4/6\). The RSS fluctuations in this mode are the highest, and multipath propagation is clearly observed. However, PRR is constantly \(PRR=1\), which is expected due to highest sensitivity mode of operation. However, it should be noted that, counter-intuitively, these LoRa settings can also yield the highest packet loss due to very long packet air time (above 1 s) and increased susceptibility to interference.