# TSCH and RPL Joining Time Model for Industrial Wireless Sensor Networks
## 8 Conclusions  
This article has focused on the characterization of synchronization times of wireless sensor networks based on the TSCH medium access mechanism and the RPL routing protocol. The phases of TSCH synchronization, together with the process of joining the RPL topology, allow the full time it takes for a node to be fully operational to start the exchange of messages with the WSN network to be determined, including the synchronization and the creation of the routing tables.  
For this purpose, an analytical model has been proposed to estimate the operation times of these two protocols, managing to estimate, in a simple way, an approximate value of the time it takes for a node to start its normal operation after deployment. Most articles focus on analyzing only the behaviour of TSCH synchronization, while in this article an analysis of the complete protocol stack oriented to industrial scenarios have been carried  
Figure 7: Testbed results—time of synchronization and RPL connection.  
out. In this way, by using the model it is possible to estimate these operation start-up delay for certain types of applications. For applications that require a fast connection and deployment of the whole network, a low transmission period for TSCH beacons and RPL Trickle Timer must be configured. However, this causes increased energy consumption in the long term, so using dynamic beacon mechanisms would improve this compromise between a fast deployment and low energy consumption during network operating time.  
The proposed analytical model has been validated through different simulations, and results were obtained that fit the behavior described by the model. In addition to the simulations, the model has also been validated through tests with real equipment, based on the CC2538 SoC wireless microcontroller, again with results that also fit the behavior described by the model.  
From the results obtained, it has been proven that in a WSN network based on TSCH and RPL, the synchronization phase has a greater contribution to the total time it takes to deploy a node. However, these protocols are closely related because the Trickle Timer algorithm, which characterizes the sending of signaling traffic in RPL, can reach very high transmission periods during the synchronization phase. Thus, by speeding up the synchronization process, the RPL timer value is not at its maximum value, which also speeds up the formation of the RPL topology. Through the model proposed in this article, it is possible to determine which configurations are optimal in each phase of network operation and for different types of applications. The model defines configurations that allow the times of formation of the network during the phases of deployment to be favored, against configurations that are centered solely on maintaining the life-span of the network as long as possible.  
Conceptualization, [PERSON] and [PERSON]; methodology, [PERSON] and [PERSON]; software, [PERSON]; validation, [PERSON] and [PERSON]; formal analysis, [PERSON] and [PERSON]; investigation, [PERSON] and [PERSON] and [PERSON]; writing--original draft preparation, [PERSON]; writing--review and editing, [PERSON] and [PERSON]. All authors have read and agreed to the published version of the manuscript.  
This work has been supported by the MCyU (Spanish Ministry of Science and Universities) under the project ATLAS (PGC2018-094151-B-I00), which is partially funded by AEI, FEDER and EU.  
Not applicable.  
The authors declare no conflict of interest.