# Robust Downlink Mechanism for Industrial Internet of Things Using LoRaWAN Networks
## 4 Results  
### Effect of Interference Sources in Network PDR  
The first consideration for validating the interference sources lies in checking their effect on the received interference signal's power for each node, as they are located all around the scenario. The power received during 24 h from all interference at each node's receiver, activating or deactivating the interference sources implemented (in saturation and real scenario tests), can be seen in Figure 9 below, which shows the maximum power received from interference for each node. The position of the nodes in the scenario can be derived from Figure 8. The mean values in dBm during the simulation are not shown, as they show little difference between configurations of realistic interferers (short pulses with same power as the network's signals) and an interference-less scenario because the contribution of the four external interference sources is diluted by the contribution from the other 199 nodes around the map (that is, intra-network interference). Obviously, introducing interference sources that saturate the channel, with a higher power level and long duration, causes the average to rise above the realistic and noise-less cases. On the other hand, focusing on the maximum values of interference power received, the configurations with the external interference activated inject more power than the noiseless network, especially for the furthest nodes, where the contributions of noise signal are additive along the way. In the case of the saturated scenario, peaks are distributed around nodes closer to the interference sources, and become higher in nodes in the middle rooms, as they are near more interference sources than nodes on the outermost sides of the floor plant and thus have the chance to overhear long interference signals more often. There are two additional considerations of significance for interpreting these results. First, in terms of power received, the DR parameter configured does not have an impact on the results, because the DR only regards the time on-air and the SNR margin to recover data, so the effect of this parameter is seen in the number of lost packets, but not on the raw value of power received. Secondly and relatedly, the value of raw noise power must be considered not directly related to packet loss, as it also depends on the power of the information packet received and the SNR margin that enables the node to recover this information. \begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{2}{c}{**General Configuration**} \\ \hline Parameter & Value \\ \hline Number of nodes & 200 \\ Number of interferers & 4 \\ Area & 2000 m \(\times\) 500 m \\ Downlink packet size & 100B \\ \(\mathrm{PLR_{max}}\) & 10\% \\ Beacon period & 128 s \\ Ping periodicity & 128 s (1 slot per beacon period) \\ TX power nodes \& GW & 14 dBm \\ \hline \multicolumn{2}{c}{Real Scenario} \\ \hline TX power interferers & 18 dBm \\ High frequency period duration & 1 h (3 times per day) \\ High frequency interference duration (t\({}_{\mathrm{on}}\)) & 150 ms \\ High frequency interference periodicity (t\({}_{\mathrm{off}}\)) & 150 ms \(<\) T \(<\) 30 s \\ Low frequency interference duration (t\({}_{\mathrm{on}}\)) & 150 ms \\ Low frequency interference periodicity (t\({}_{\mathrm{off}}\)) & 5 min \(<\) T \(<\) 10 min \\ \hline \multicolumn{2}{c}{Saturated Scenario} \\ \hline TX power interferers & 28 dBm \\ Interference duration (t\({}_{\mathrm{on}}\)) & 120 s \\ Interference periodicity (t\({}_{\mathrm{off}}\)) & 220 s \(<\) T \(<\) 10 min \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Configuration parameters for simulation. Therefore, the real effect of these external interference sources can be seen by analysing the number of lost packets due to interference during the simulation. In Figure 10 below, the simulations for 24 h of the network can be seen. In this case, configurations without external interference sources show little or no packet loss during downlink, which is consistent with theoretical results for class B operation in LoRaWAN.