## 3 Use-Case-Based Categorisation of Technologies
### Transfering Clusters into an Application-Related Classification  
Basic ideas and concepts of a network and its structure can only be partly transferred to underground spaces. Due to the prior described environmental constraints, basic assumptions must be questioned, reviewed or even reconsidered. The clusters of wireless communication technologies in Figure 4, based on their data rate and range properties for aboveground applications, are only transferable to a limited degree to underground environments. In underground environments, the range of wireless technologies is highly dependent on the specific conditions and is significantly reduced for all technologies. The high signal attenuation underground causes wireless technologies to become more dependent on line-of-sight (LOS) conditions. The further a signal has to travel, and the more obstacles have to be passed, the more it is influenced by the conditions  
Figure 4: Data rate vs. (aboveground) range of radio communication technologies. Reprinted/adapted with open access permission from Ref. [27]. and dependant on propagation properties. This dependency is stronger at higher frequency bands [28], making technologies in the \"cellular\" and high-frequency technologies in the \"short-range\" cluster decrease in range even more underground. Low-Power Wide Area Network (LPWAN) technologies, which operate at lower frequency bands, have a weaker LOS dependency, but they still result in a decrease in range underground. In the case of such a transfer, the question of the timeliness of the technology itself for the underground application must be asked. It turns out that timeliness of a technology is linked to its use cases. If a technology fulfils the requirements of a use case, its timeliness is linked to the persistence of the use case itself. Nonetheless, the possibility for a network to be expanded, updated, or modified still stands with new use cases. The technology clusters introduced in Figure 4 experience a shift to lower range when deployed in the subsurface environment, which is also illustrated in Figure 5.  
Wireless communication technologies in mining are typically used for specific applications (e.g., Wi-Fi for machine supervision and control [29; 30]) and not as general-purpose networks, as in urban environments. In alignment with the technology mapping above, we therefore suggest a classification of the wireless technologies in an ordering context, which arranges the technologies in classes of a higher-level mining automation context connected to specific advanced mining operation application cases. These application cases must be viewed in the frame of individual timeliness of data. The mine operation communication should be realized in real time, but in this context, \"real time\" is to be understood as \"right time\", i.e., the information must be available \"in time\" for the process [1]. Thus, we suggest mapping the categories as follows:  
1. 'Automation and Teleoperation'  
The technologies in this cluster are characterized by high data rates, making them suitable for automation and teleoperation use cases; however, due to the high requirements regarding data rate, they are typically technologically limited to line-of-sight (LOS) and possibly near-line-of-sight usage. 2. 'Tracking and Tracing'  
The technologies in this cluster are characterized by a low data rate and short range, which makes them suitable for tracking and tracing applications, as well as local data transmission. 3. 'Long-Range Underground Monitoring'  
Figure 5: Data rate vs. (underground) range of radio: Shifted Technology Clusters due to harsh underground conditions. The further a signal must travel and propagate, the more it is influenced by the conditions and dependant on its signal propagation properties. The technologies in this cluster are characterized by low data rates and low power consumption.