# 3 MSF: A Multi-Modal Adaptation of the 6 TiSCH Minimal Scheduling Function for the Industrial IoT
## 6 Conclusions  
The vast communication capabilities of modern wireless devices offer several opportunities that are currently not exploited by most common implementations of IIoT architectures such as 6 TiSCH. Allowing (virtual) links to be (re-)configured (at runtime) with different communication modes throughout the network would, e.g., eliminate the need for an often time-consuming/costly manual setup phase of new deployments, allow individual nodes to respond to sudden or highly localized phenomena, and potentially provide full coverage in environments where a single communication mode cannot.  
Based on these opportunities and the particular implementational flexibility of the 6 TiSCH link and routing layers, others have also proposed 6 TiSCH-based solutions for multi-modal IIoT networks supporting dynamic link reconfiguration. However, to the best of our knowledge, these are all either based on a single fixed timeslot duration to accommodate for the slowest communication mode or (if they do support variable-length superslots) they designate individual interface-modes as RPL neighbors, as is the case with the particularly interesting work of [PERSON] et al. (2016).  
To not incur the efficiency/latency penalty associated with fixed timeslot durations and to prevent the downsides of equating interface-modes to RPL neighbors (e.g., the clustering of parents belonging to a limited set of devices), we presented (in this paper) a multi-modal 6 TiSCH architecture that uses variable slot duration but sees devices as RPL neighbors instead. More specifically, we proposed a combination of a newly designed decentralized TSCH SF called 3 MSF and a slightly modified version of DRiPLOF ([PERSON] et al., 2016). As a basic proof of concept for many of the mechanisms described in this paper and to  
Figure 20: Number of times node #4 either switched preferred parent from #2 to #3 or only switched the frozen interface-mode towards #2 instead (represented as a fraction of the total number of simulations), by configuration. In the first configuration, all nodes possessed only the sub-GHz interface-modes. In the second configuration, all nodes possessed only one mode per interface, i.e., (2, 1) and (1, 1). In the third configuration, each node possessed all four interface-modes.  
showcase the flexibility/functionality of our solution overall, we designed and evaluated several scenarios through simulations. In summary, we envision our proposed multi-modal 6 TiSCH architecture as a fundamental building block for next-generation IIoT ecosystems, facilitating rapid deployment and continuous adaptation to ever-evolving industrial environments and requirements.  
Lastly, in the future, we want to explore the possibility of supporting nodes with dissimilar communication capabilities, conceivably by designing mechanisms intended to manage/disseminate, e.g., the superset of available interface-modes and supported supercell lengths.  
The full code base and curated data files are available online at [[https://www.mdpi.com/article/10.3390/s24082414/s1](https://www.mdpi.com/article/10.3390/s24082414/s1)]([https://www.mdpi.com/article/10.3390/s24082414/s1](https://www.mdpi.com/article/10.3390/s24082414/s1)).  
Conceptualization, R.E., E.D.P. and J.H.; methodology, R.E. and D.V.L.; software, R.E.; validation, R.E.; formal analysis, R.E.; investigation, R.E.; data curation, R.E.; writing--original draft preparation, R.E.; writing--review and editing, R.E., D.V.L. and E.D.P.; visualization, R.E. and D.V.L.; supervision, E.D.P.; project administration, R.E. and E.D.P.; funding acquisition, R.E. All authors have read and agreed to the published version of this manuscript.  
This research was funded by the Research Foundation--Flanders (FWO) through strategic basic research grant 95027: SDR-Based Industrial IoT: Towards Ubiquitous Wireless Connectivity.  
Not applicable.  
The data presented in this study are available as Supplementary Materials.  
The authors declare no conflicts of interest.