# On Ad Hoc Communication in Industrial Environments
## 6 Conclusions  
This work examined the time-variant network topology of ad hoc communication under industrial conditions. Existing methods for the extraction of these topologies from network traces were examined. It is concluded that the direct observation of encounters with a novel custom protocol can more accurately represent the behavior of an ad hoc network compared to the work in [28]. The custom protocol was implemented, tested, and used in an industrial environment. The protocol is made available for researchers and engineers to analyze the behavior of other network applications. The time-variant topologies that were recorded are also made available. The examined production facility followed the principles of Industry 4.0. To the best of our knowledge, we are the first to provide comprehensive measurements that characterize ad hoc network behavior in this context. With these recordings, researchers and engineers (can for the first time) analyze, simulate, and test industry-specific communication solutions for the factory of the future. Additionally, the acquired topologies were analyzed in terms of general network behavior with the goal to give general recommendations for communication system design. The ad hoc channels in an industrial environment present some challenging characteristics. The observations of network connectedness (sparse vs. fully meshed) suggest that interference impacts the channel availability in the industry. Mobility of the clients, however, has by far higher effects on the availability of channels between nodes. The analysis of the bidirectionality of the available channels suggests that many existing MANET protocols are not applicable to the shop floor. The high percentage of unidirectional connection (30% to 35%) highly impacts the search for routes and increases the resulting routing overhead. The network performance is further impacted by the low route lifetime. For the ad hoc channels between mobile clients in the industrial environment, an average route life time of 1.21 s was observed. In regards to route lifetime, interference in the industrial environment has the higher impact factor, compared to the mobility. Lastly, the effects of multi-hop networks on the network connectedness and route lifetime were observed. Both benefit especially from the inclusion of the first and second relay/hop. This is an interesting observation when considering the availability of technologies like Side-Link for 5G. Even more hops have an even bigger effect, but the benefit decreases. The presented observations are currently limited to the wireless peer-to-peer channel of IEEE802.11 interfaces. However, the proposed methods are applicable to any other broadcast-enabled communication technology. Figure 5: Network connectedness over time and CCDF of route lifetime in a mobile industrial scenario utilizing multi-hop relaying. The presented results illustrate the benefits of industrial MANETs, as well as the challenges. In the future it is planned to acquire more NEPs from a rich set of industrial and other environments and a variety of wireless communication technologies. This data-set will benefit us in the design and testing of industrial MANETs and a unified communication framework for mobile robots in the industry. Additionally, the acquired NEPs shall be used to test different routing protocols, where the results will be validated by experimental MANET implementations in production facilities. Conceptualization, C.S. and M.S. ; methodology, C.S. ; software, C.S. ; validation, C.S., M.S. and E.L.; formal analysis, C.S. and E.L.; investigation, E.L. and C.S. ; resources, C.S. ; data curation, C.S. ; writing--original draft preparation, C.S. and E.L.; writing--review and editing, C.S., E.L. and M.S. ; visualization, C.S. ; supervision, M.S. ; project administration, C.S. All authors have read and agreed to the published version of the manuscript. This research received no external funding. The authors declare no conflicts of interest.