###### Abstract  
Public safety agencies have been working on the modernization of their communication networks and the enhancement of their mission-critical capabilities with novel technologies and applications. As part of these efforts, migrating from traditional land mobile radio (LMR) systems toward cellular-enabled, next-generation, mission-critical networks is at the top of these agencies' agendas. In this paper, we provide an overview of cellular technologies ratified by the 3 rd Generation Partnership Project (3 GPP) to enable next-generation public safety networks. On top of using wireless communication technologies, emergency first responders need to be equipped with advanced devices to develop situational awareness. Therefore, we introduce the concept of the Internet of Life-Saving Things (IoLST) and focus on the role of wearable devices--more precisely, cellular-enabled wearables, in creating new solutions for enhanced public safety operations. Finally, we conduct a performance evaluation of wearable-based, mission-critical applications. So far, most of the mission-critical service evaluations target latency performance without taking into account reliability requirements. In our evaluation, we examine the impact of device- and application-related parameters on the latency and the reliability performance. We also identify major future considerations for better support of the studied requirements in next-generation public safety networks. public safety; cellular connectivity; wearable technology; IoLST; mission-critical services 202125902125902125902125902125902125902125902125902125902125902125902125902125902125902125902125902125902125902212590221259022125902212590221259022125902212590222125902  
alternative for LMR systems [4]. Deployment cost optimization and public safety service expansion are the main reasons considered by The Critical Communications Association (TCCA) to select the Long-Term Evolution (LTE) technology as the basis for future public safety implementations [5]. With the same perspective, we advocate the use of cellular connectivity for public safety communications and propose complementing these capabilities with wearable solutions for mission-critical applications. In our previous work published in [6], we provided a state-of-the-art overview of cellular connectivity for public safety communications and wearable technology in the Internet of Life-Saving Things (IoLST). We then conducted a performance evaluation of a mission-critical service (i.e., mission-critical PTT (MCPTT)) using cellular-enabled wearables, with a focus on latency as the performance indicator. In the present work, we build upon the state of the art and extend the performance evaluation of [6] as follows:  
* Identifying the solutions introduced by the 3 rd Generation Partnership Project (3 GPP) for the support of public safety communications. We review the identified solutions as enablers of cellular-based public safety networks, also referred to as next-generation public safety networks [4]. As part of this technology review, we track the enhancements of the identified technologies through the different 3 GPP releases. * Expanding and better illustrating the examples of IoLST use cases where cellular-enabled wearables can be employed. * Complementing the latency evaluation in wearable-based MCPTT private and group calls with reliability results. We discuss the obtained results and shed light on the need for latency and reliability trade-off mechanisms in MCPTT applications. * Providing standardization-related insights and future considerations for better support of the requirements of wearable-based MCPTT services in next-generation public safety networks. The rest of the paper is organized as follows. Relevant research works dealing with wireless communication technologies and solutions for public safety are discussed in Section 2. By reviewing these works, we identify the research gaps that we aim to address in this work.