# A Multi-Gateway Behaviour Study for Traffic-Oriented LoRaWAN Deployment
## 4 Simulations and Results Analysis
### Studied Scenarios
#### 4.2.1 Effect of the Payload Length  
Figure 3 shows the results obtained for two and five gateways while varying the payload length with a frequency of 1 packet/min and unconfirmed traffic. We can see from Figure 2(a) that the A-PDR was high for payload lengths from 60 to 100 bytes. The same figure shows that the A-PDR decreased significantly by using a payload length from 10 to 50 bytes. In addition, Figure 2(a) tells us that when the number of EDs increased, the achieved A-PDR decreased regardless of the payload length. We can explain this behaviour by the fact that using a low payload length (10 to 50 bytes) increases the number of sending packets over the network considerably, mainly when the number of EDs increases, as we can see in Figure 2(c). Thus, with such a high number of packets sent, the gateway suffers from a high interference level, leading to packet loss, as shown in Figure 2(e). However, we can see that we had the opposite behaviour concerning the A-PDR and LPI for a network with five gateways. As shown in Figure 2(b), the network achieved a better A-PDR in the case of a low payload length. In addition, the number of sending packets was nearly the same with a network of five gateways while varying the payload length, as we can see in Figure 2(d). Moreover, in Figure 2(f), we can see that with a high payload (ex. 100 bytes), the network suffered from a high interference level compared to the case of using a low payload. Such behaviour is related to the fact that using more gateways will make the ED use a low \(SF\) value, as shown in Figure 4. More precisely, Figure 3(a) shows that when we used one gateway, most of the EDs had an \(SF\) equal to 10, 11, or 12 since they were located far away from the gateway. However, with five gateways, as depicted in Figure 3(b), most of the EDs used an \(SF\) of 7. Such hidden behaviour had a significant impact on network performance. In fact, when an ED used a low \(SF\) (e.g., \(SF7\)), it could send more packets, as we can see in Tables 4 and 5. In addition, the airtime was low compared to using a high \(SF\). In addition, for the same used \(SF\), the payload length significantly impacted the airtime and the number of allowed messages to transmit. Figure 5 shows the results obtained for two gateways while varying the payload length with a different frequency of sending packets and unconfirmed traffic. Typically, with 1 packet every 3, 5, 7, and 9 min, the behaviour was still the same as we can see in Figure 4(a)-d. These figures confirm that using a low payload length (10 to 50 bytes) achieves a low A-PDR compared to a higher payload length (60 to 100). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Data Rate** & **DR5** & **DR4** & **DR3** & **DR2** & **DR1** & **DR0** \\
**(_SF, BW_)** & **(7, 125)** & **(8, 125)** & **(9, 125)** & **(10, 125)** & **(11, 125)** & **(12, 125)** \\ \hline airtime (ms) & 61.7 & 113.2 & 205.8 & 370.7 & 823.3 & 1482.8 \\
1\% DC (s) & 6.2 & 11.3 & 20.6 & 37.1 & 82.3 & 148.3 \\ msg/hour & 583 & 318 & 174 & 97 & 43 & 24 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Airtime and number of allowed messages according to different data rates for a payload of 10 bytes [27]. Figure 3: Performance results for two and five gateways while varying the payload length with a frequency of 1 packet/min—unconfirmed traffic. Figure 4: (a) \(SF\) allocation with 2 GWs ; (b) \(SF\) allocation with 5 GWs. \(SF\) allocation according to the number of gateways deployed in the case of 1000 EDs. Figure 5: Aggregated PDR results for two gateways while varying the payload length with a frequency of one packet every 3, 5, 7, and 9 min—unconfirmed traffic.