## 3 Toward Next-Generation Public Safety Networks
### Additional Enabling Technologies  
Figure 2 depicts examples of cellular technologies that can be deployed in next-generation public safety networks. Service reliability can be achieved not only using D2D communications but also through the flexible use of radio resources provided by multiconnectivity and multiradio access technologies (multi-RAT). Mobile edge computing and software-defined networks (SDN) are among the technologies that can be deployed in cellular networks for improving latency and security in public safety services [22]. Furthermore, cellular networks offer novel capabilities for the management of various use cases with varying priorities, such as network function virtualization and network slicing [5]. For instance, in the case of big events or major accidents, the traffic prioritization mechanisms allow the necessary network capacity and performance for first responders in the first place, and for other users in the second place [22].  
Addressing new verticals and markets including the public safety industry, the 5G standard introduces several features that target different requirements and use cases. 5G networks can support a very large number of devices that can communicate with each other and exchange data. They are thus helping to address the IoT evolution. In 5G networks, IoT devices are expected to form significant sources of information for the public  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Technology** & **3 GPP Releases** & **Main Improvements** \\ \hline \multirow{2}{*}{ProSe} & Rel-13–Rel-16 & ProSe discovery and direct communication features in EPS, UE-to-network relaying for IoT and wearables \\ \cline{2-3}  & Rel-17 & Support of NR ProSe communications and UE-to-network relay over 5G networks \\ \hline \multirow{4}{*}{MCX} & Rel-14 & User authentication, service authorization, media and control signaling encryption \\ \cline{2-3}  & Rel-15 & Support of MBMS, interworking with LMR systems, and interconnection between cellular mission-critical systems \\ \cline{2-3}  & Rel-16–Rel-17 & Enhanced procedures and information flows in on-network and off-network architectures, identification of further requirements of MCX services \\ \hline \hline \end{tabular}
\end{table}
Table 2: Enhancements of public-safety-targeted cellular solutions.  
Figure 1: On-network and off-network functional modes for MCX services.  
safety community [34]. By processing this information and integrating it into public safety operations, first responders can be more proactive and their tasks can be moved from investigation to prevention of accidents and crimes [5].  
IoT device adoption among the public safety community will enable various use cases such as communication center alerting, accident video investigation, and connected and automated cars. Among these new examples, certain applications require very high data rates that can be achieved by the exploitation of techniques such as beamforming and small cells in 5G-enabled public safety networks [5]. Furthermore, 5G networks are expected to support network-based localization with an accuracy of less than 1 m [35]. This boost in localization accuracy, in comparison to LMR technologies, can help provide reliable and fast emergency responses through public safety networks [34]. Therefore, 5G-related 3 GPP specifications are outlined to include various features and functionalities that can improve the services offered by next-generation public safety networks.  
As discussed above, next-generation public safety networks can employ cellular solutions and technologies that are ratified by 3 GPP in its technical specifications for both 4G and 5G standards. Hence, one can raise the question as to which network deployment option to select. Actually, several public safety agencies are already implementing LTE-based, next-generation public safety networks since not all mission-critical capabilities are fully supported by NR networks. It is possible for them to eventually upgrade their networks and support both 4G and 5G capabilities [36].