## 7 Results
### Energy Management  
Energy management is also a key factor in highly temperature-dependent and humidity-dependent conditions. The operational duration of the nodes depends on the capacity of the battery and the sampling period, so the analysis of the energy behavior of the node in an operational cycle is representative of the energy expenditure of the node in operational conditions. A digital power meter Yokowaga WT210 (Musashino, Tokio, Japan) was used for energy monitoring of the nodes.  
Wi-Fi SSID searching and data sending to the cloud server are the processes with the greatest consumption in the sensor node. In order to calculate the energy consumption in the worst scenario, the sensor node was programmed with five SSID, but only the last one was available. The different modes and routines are described in Figure 12.  
\begin{table}
\begin{tabular}{c c c c c} \hline
**Trial 1 (2018)** & **Total Data** & & & \\
**DOY 81–93** & **Measured** & **Received Packet** & **Lost Packet** & **\% Valid Data** \\ \hline Gateway & 1181 & 1180 & 1 & 99.9\% \\ Slave node 1 & 1181 & 1103 & 78 & 93.4\% \\ Slave node 2 & 1181 & 1171 & 10 & 99.1\% \\ \hline
**Trial 2 (2018)** & **Total Data** & & & \\
**DOY 100–120** & **Measured** & **Received Packet** & **Lost Packet** & **\% Valid Data** \\ \hline Gateway & 1691 & 1691 & 0 & 100\% \\ Slave node 1 & 1691 & 1682 & 9 & 99.5\% \\ Slave node 2 & 1691 & 1663 & 28 & 98.3\% \\ \hline
**Trial 3 (2019)** & **Total Data** & & & \\
**DOY 91–100** & **Measured** & **Received Packet** & **Lost Packet** & **\% Valid Data** \\ \hline Gateway & 920 & 920 & 0 & 100\% \\ Slave node 1 & 920 & 431 & 489 & 46.8\% \\ Slave node 2 & 920 & 897 & 23 & 97.5\% \\ \hline
**Trial 4 (2019)** & **Total Data** & & & \\
**DOY 102–112** & **Measured** & **Received Packet** & **Lost Packet** & **\% Valid Data** \\ \hline Gateway & 947 & 947 & 0 & 99.9\% \\ Slave node 1 & 947 & 716 & 231 & 75.6\% \\ Slave node 2 & 947 & 645 & 302 & 68.1\% \\ \hline
**Trial 5 (2019)** & **Total Packets** & **Received Packet** & **Lost Packet** & **\% Valid Data** \\
**DOY 245–256** & **Measured** & **Received Packet** & **Lost Packet** & **\% Valid Data** \\ \hline Slave node 1 & 959 & 910 & 49 & 94.9\% \\ Slave node 2 & 959 & 959 & 0 & 100\% \\ Slave node 3 & 959 & 878 & 81 & 91.5\% \\ \hline
**Trial 6 (2019)** & **Total Packets** & **Received Packet** & **Lost Packet** & **\% Valid Data** \\
**DOY 258–271** & **Measured** & **Received Packet** & **Lost Packet** & **\% Valid Data** \\ \hline Slave node 1 & 1281 & 1205 & 75 & 94.1\% \\ Slave node 2 & 1281 & 1214 & 66 & 94.8\% \\ Slave node 3 & 1281 & 1078 & 202 & 84.2\% \\ \hline \end{tabular}
\end{table}
Table 2: Data communication results for performance analysis.  
A large part of the consumption in each sampling cycle depends on the attempts to connect to the available communication network (Figure 12). For this reason, proper management of the networks allows for a reduction in energy consumption.  
During the tests carried out at land transport, different conditions of communication losses with the gateway were observed, as shown in Table 2. The environmental conditions and the location of each node within the transport cabin influence the communication quality and the power consumption. Figures 13 and 14 show the results of the evolution of the voltage during trials 5 and 6, where the different slopes and voltage variations can be seen in accordance with the communication packets lost due to not being able to connect to the first network and trying to connect to the five access points available in the list.  
Figure 12: Power required by the different processes used in a complete execution cycle of a sensor node.