# Bell-X, An Opportunistic Time Synchronization Mechanism for Scheduled Wireless Sensor Networks
## 7 Conclusions and Future Works  
At the initial part of the article, the difficulties that are derived from using a MAC layer that requires synchronization, combined with a routing protocol that supports meshed networks, such as RPL, has been introduced. The proposal of using TSCH+RPL protocols to be used in industrial monitoring scenarios addresses the traditional problems wireless communications show in these types of environments, but still supposes a challenge to improve reliability during network joining time.  
This work proposes a dynamic, tuneable mechanism, Bell-X, which allows for an adaptive beaconing method to be implemented, which can be configured to reduce power consumption and improve connection time and connection success rate to solve this challenge. This mechanism has been implemented and simulated, testing its results against the other popular solutions, as proposed in RFCs or WSN OS implementations.  
The described mechanism can be configured to respond to different requirements, but focusing on the results that were obtained for simulations and comparisons; it shows better overall results, especially for the Bell-65 configuration, looking for a compromise between success and time to connect and power consumption. Figure 19 illustrates the difference in KPIs achieved by the different mechanisms tested and helps to identify the best option depending on the application and use case necessities.  
Bell-X mechanism is designed to be tuneable from the start, which means it is parameterized so that it could be used in combination with network and node state information, changing the shape of the bell. For instance, to enhance power savings, when batteries are low or the number of neighbours is high enough to transmit enough beacons, or even increase beaconing when the node is mains powered and adopts a role of time parents and relaying node to improve the connectivity. The configuration possibilities introduced by design in this solution open the way to future experiments and implementations, adapting to a wide range of use case and applications.  
Figure 19: Key Performance Index (KPI) Comparison for tested configurations.  
**Author Contributions:** Investigation, [PERSON]-P. and D.T.[PERSON]; Supervision, [PERSON] and [PERSON]; Validation, [PERSON] and [PERSON]; Writing - original draft, [PERSON] and [PERSON]; Writing - review & editing, [PERSON] and [PERSON].  
**Funding:** This work has been supported by the SCOTT project (Secure COnected Trustable Things) (www.scotproject.eu), which has received funding from the Electronic Component Systems for European Leadership Joint Undertaking under grant agreement No. 737422. This Joint Undertaking receives support from the European Union's Horizon 2020 research and innovation programme, and from Austria, Spain, Finland, Ireland, Sweden, Germany, Poland, Portugal, Netherlands, Belgium and Norway. It has also been funded by Generalitat Valenciana through the \"Instituto Valenciano de Competitividad Empresarial - IVACE\", and 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.  
**Conflicts of Interest:** The authors declare no conflict of interest.