# Routing Topologies of Wireless Sensor Networks for Health Monitoring of a Cultural Heritage Site
## 6 Discussion
During the weekend, when the crowd intensity was the lowest, fewer messages were lost and the route was more stable since the motes almost did not change the parent identifier. Figure 10: Route distribution for each mote using the CTP protocol in Experiment 1. The analysis of the parent identifiers for each message during the last period of the WSN lifetime (displayed in Figures 12 and 13 for the XMESH and CTP protocols, respectively) provides more insight about the network behavior. The data shown starts when the first nodes disconnected from the WSN and ends when the last nodes disconnected. A detailed analysis was performed when multiple nodes simultaneously disconnected from the network, trying to understand if they depleted their energy or if they died because their parents died in advance. Figure 11: Lost messages (red color), number of hops made for a message to reach the base station (black color), and parent identifiers (blue color) with respect to time for each mode. Data corresponds to the XMESH protocol in Experiment 1. In the x-axis, “m” means morning, “a” is afternoon, and “n” is night. Figure 12: Parent identifiers of each message using the XMESH protocol during the last period of the WSN lifetime in Experiment 1. In the case of the XMESH protocol, Motes 13, 16, and 17 disconnected first from the network. Motes 13 and 16 depleted their energy since their parents were still connected to the WSN. Therefore, Mote 17 probably died because it did not have enough energy to connect with more distant nodes. Then, Motes 11 and 14 depleted their energy since they could have otherwise connected with Mote 12. After that, Mote 15 depleted its energy, because its parent was still alive. Finally, Mote 12 lasted a longer time and, therefore, it was the final parent of all motes. For the CTP protocol, Motes 22, 23, and 27 depleted their energy first, in this order. Then, Motes 21, 25, and 26 died due to the cascade effect created by their parent's death. Finally, Mote 24 lasted a longer time and was, therefore, the final parent of all motes. As previously mentioned, this experiment was repeated to check the robustness of the results obtained, the motes were exchanged but keeping the same general spatial configuration (Experiment 2). In this second experiment, similar results were obtained. Several conclusions can be drawn from the detailed analysis of Experiments 1 and 2. The CTP network performed better than the XMESH network in all the experiments, meaning that fewer messages were lost. The main reason for this behavior is that the XMESH network tends to reconfigure itself faster than the CTP network when there are communication problems, mainly caused by the movement of people in the real deployment. If the location of the network is static, this is a disadvantage because the time required to reconfigure the network can lead to message loss. The CTP algorithm is much more stable when reconfiguring the network structure, thus producing a smaller number of lost messages. In the almost absence of people interfering with the radio signal, during the evenings and weekends, as well as in Experiment 2, it was found that the behavior of both networks, in terms of its configuration, was very similar and the number of lost messages was relatively low. Another aspect related to the stability of the WSN is that, in the XMESH network, the percentage of lost messages increases with the number of hops given by a message from the source to the base station. It was also observed that the average hopping distance reached by each mote did not affect the message loss. Figure 13: Parent identifiers of each message using the CTP protocol during the last period of the WSN lifetime in Experiment 1. It is well known that batteries discharge more quickly in cold weather than in hot weather conditions. This might explain why the energy efficiency corresponding to Experiment 1, performed in late May, was high compared to Experiment 2, performed in January.