## 6 Simulation Results and Discussion  
This section evaluates the number of LoRa/Sigfox devices that can coexist together in congested deployment and astutely estimates the number of nodes that can successfully transmit mitigating collision effects while reducing PER/re-transmissions and increasing the delivery ratio, which represents the effectiveness of transmission. In the Europe region, LoRa has three 125/250 KHz channels (i.e., 868.10, 868.30, and 868.50 MHz) as part of the EU 863-870 MHz band [15]. In terms of transmitted power, the maximum is 14 dBm (25 mW) with multiple options such as 11 dBm, 8 dBm, 5 dBm, and 2 dBm. Incorporating these limitations, LoRa still has potential as it takes advantage of orthogonality among different SF and sends multiple packets simultaneously. In order to conduct outdoor experimentation for generating data for a traffic generator, six LoRa SY1276 LoRa shields and six Arduino UNOs were programmed for transmission on same and different SFs along with two single-channel gateways. SY1276 works at 868 MHz, though less noise resistant in comparison to SY1278 working at 433 MHz. SX 1276 was chosen to draw a close comparison to Sigfox TD1207 (868 MHz). The Dragino single-channel gateway was placed on the rooftop of a seven-storey building (32 m), and LoRa devices were placed on buildings ranging from 7 m to 22 m in height. Devices used for the tests are shown in Figure 2, Figure 3a,b and spectrum of the same can be seen in Figure 4 while the test setup is shown in Figure 5. It is highlighted that tests for both LoRa and Sigfox were conducted in an outdoor environment with the line of sight (LoS) between devices and gateway. Data generated by the test setup in Figure 5 are shown  
Calculation of RSSI, SNR, and ToA was carried out to prepare data for the traffic generator. LoRa BW was fixed at 250 KHz and packet size at 25 byte. Devices were made to transmit in a 6 h cycle for two days to calculate average values. Further LoRa devices were programmed with different SF and same CR to check collision issues while transmitting \begin{table}
\begin{tabular}{c c} \hline \hline
**Variable Parameters** & **Value for Simulation** \\ \hline Number of Nodes & 50 to 10,000 \\ \hline Spreading Factor & 7–12 \\ \hline Code Rate & Fixed 4/8 \\ \hline Bandwidth & Fixed 250 KHz \\ \hline Message Length & Fixed 25 bytes \\ \hline Arrival rate \(\phi\) & 0.001 s\({}^{-1}\) bytes \\ \hline Duty cycle & 0.01 \\ \hline Transmission Power & 14 dBm \\ \hline Low data rate optimization (DE) & 1 \\ \hline Header (H) & 0 \\ \hline Path loss exponent (PLE) & 4 \\ \hline Preamble symbols & 8 \\ \hline Time on Air (ms) & SF7-41, 8-72, 9-144, 10-289, 11-578, 12-991 \\ \hline Gateway & 1, 2 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: LoRa and Sigfox Simulation Parameters. Figure 5: Test setup of LoRa devices as shown in Figures 2 and 3a,b. 100 up-link messages each to a single channel Dragino gateway, for Sigfox Lime SDR was programmed as gateway using GNU radio. Figures 6 and 7 show LoRa transmission simulation when 1000 and 5000 LoRa devices are transmitting simultaneously, green represents transmission success, while red denotes collision due to the same SF in the use of same-time transmission. Figures 6 and 7 show higher packet loss at higher SF, which is in contravention of LoRa giving higher SNR and higher noise resilience at higher SF. An analysis of the same presents that though the noise robustness is better at higher SF, higher SF also increases the number of chirps and thus increases ToA as calculated in Algorithm 2, which leads to more collisions with more number of re-transmissions. In the Sigfox traffic generator, we started with 50 devices simultaneous operation while keeping only one gateway and then further increasing it to three gateways for spatial diversity. Figures 8 and 9 show 5000 and 10,000 Sigfox devices transmitting simultaneously.