# TSCH and RPL Joining Time Model for Industrial Wireless Sensor Networks
## 7 Real Testbed  
As the last phase of this study, a battery of tests with real nodes was carried out, in order to check if the analytical model allows the value of the synchronization and connection time of a new node to the network to be characterized in an approximate way.  
These tests have the same objective as the simulations, so the parameters to be modified in each of the protocols will be the same. However, given the duration of the real versus simulated tests, only a subset of these variations has been used. Table 6 shows the configuration parameters used during the real tests. As shown in the table, four different configurations were made with two period values of beacons and DIO messages and with two values for the number of nodes displayed.  
Figure 5: RPL simulation results.  
The equipment used to carry out the deployment of the protocol stack based on Contiki was a RE-Mote from the manufacturer Zolertia. This equipment is based on the SoC CC2538, which is compatible with the IEEE 802.15.4 standard and with the TSCH media access mechanism, unlike its previous versions which were not compatible.  
In the procedure of the real tests the same pattern as in the simulations was followed. A node was configured that will do the work of the root of the sensor network, and will start both the beacon sending process and the DIO message transmission. The rest of the nodes will be synchronized from the information generated by this coordinating root node, depending on whether it is a two or seven-node deployment. Once the first node phase is displayed, the node to be characterized is turned on, detecting through a screen log the time instants in which the node starts, the instant in which it manages to synchronize when receiving an EB message and the instant in which it obtains the information from the RPL tree from the reception of a DIO message. This process was repeated a total of 15 times for each of the variations presented in Table 6. Figure 6 shows an image of the deployment made for the real tests.  
Figure 7 shows the results obtained during actual testing with RE-Mote devices. In this case, the graphs represent the sum of the total deployment and configuration time, which includes the time it takes to synchronize the new node and to obtain the configuration of  
\begin{table}
\begin{tabular}{l l l} \hline \hline
**EB Period** & **DIO Period** & **Number of Nodes** \\ \hline
4s & 4s & 2 \\
16s & 16s & 2 \\
4s & 4s & 7 \\
16s & 16s & 7 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Real testbed configuration parameters.  
Figure 6: Testbed deployment using Zolertia RE-Mote platform.  
the RPL tree. As mentioned above, the contribution of the TSCH part has a greater weight than that of RPL, so the shape of the curve is more similar to that of the TSCH analytical model with a Y-axis offset.  
The results show how the values obtained for the total time of deployment of a new node fit the curve represented by the analytical model TSCH+RPL, so it gives a good estimate of the time required for a new node to synchronize and connect to a sensor network based on TSCH and whose routing mechanism is RPL. As happened in the simulations, the standard deviation dispersion is higher in those cases where the signaling traffic is considerably lower, and the case with more dispersion is that which uses a period of 16 s for the signaling traffic, both in TSCH and in RPL, and a number of nodes equal to 2.