## 4 Experimental Design
### Experiment Implementation
#### 4.2.3 Communication Behavior
Figure 6: Number of nodes with confidence over the threshold (per number of beacons in scenario) in the ranges of (**a**) 30 m, (**b**) 50 m, and (**c**) 80 m.

For the 25% beacon scenario, the \(T_{>60}\) nodes show an increase of 4.95 and 4.50 nodes on average when the communication range is augmented from 30 to 50 m (Figure 6a,b), and then from 50 to 80 ms (Figure 6b,c), respectively. Meanwhile, \(T_{>0}\) nodes show an increase of 2.25 and 10.81 nodes, going from a communication range of 30 to 50 m, and from 50 to 80 m. Finally, when 50% nodes are present in the scenario, the number of \(T_{>60}\) nodes increases by 14.41 and 8.56, while the \(T_{>0}\) node amount grows by 21.62 and 3.60 nodes for the corresponding increments in the communication range. ### Findings

There is a direct relation between the number of beacon nodes present in the scenario and both the number of nodes that know their position and the fitness scores of such a scenario. Having more beacons increases the likelihood of non-beacons finding neighbors that know their positions (_i.e._, nodes with fitness scores over \(T_{>0}\)). This allows more non-beacons to estimate their positions, and allows for higher average fitness scores in the scenario. There is also a direct relation between the number of beacon nodes present the scenario and the energy consumption. Beacon nodes carry an additional cost associated with using a positioning strategy, namely establishing and maintaining communication with the provider (e.g., GPS satellites, a centralized server), and activating the required peripherals. Thus, if more beacons are present in a scenario, the overall energy consumption tends to increase. However, the individual energy consumption of non-beacons tends to decrease, because fewer positioning requests are required to obtain meaningful positioning information from their neighbors. Augmenting the communication range improves the confidence levels of the scenario, but increases the energy consumption. Greater communication ranges allow non-beacons to reach more neighbors when requesting positioning information, facilitating collaboration and thus increasing both the average fitness score of the scenario and the number of nodes that know their positions. However, having a greater range entails greater energy consumption. Given that more nodes are reached by each positioning request, more energy is consumed through communication. Conversely, lowering the communication decreases the number of nodes that know their position and the confidence of the scenario, and increases the energy consumption. This is because fewer neighbors are reached by non-beacons requesting positioning information. Since non-beacons are less likely to estimate their positions, the number of nodes over \(T_{>0}\) and the overall fitness scores tend to decrease. Moreover, since isolated individual nodes are unable to reach viable neighbors, they must expend more energy sending additional positioning requests. Finally, limiting the communication of devices to a single channel is less energy-demanding than allowing multiple channels. When using a single communication channel (_i.e._, Wi-Fi), only one positioning request has to be sent; when using multiple channels, a request has to be sent from each of the corresponding peripherals (one per available channel). On the other hand, sending requests through multiple channels implies that some requests will be received more than once by some neighbors, and others will be lost if no neighbors are capable to receive them. This translates into greater energy consumption, due to the additional communications. ### Tuning the Model Based on the Findings

The model was improved based on our findings, and additional experiments were performed. Figure 7a shows the average number of non-beacons that know their position at a given time (equivalent to Figure 6b), which was obtained during the performance simulations. The communication range has been set to 50 m at maximum, and the number of beacons at 25%.