## 4 Wearable Technology in Next-Generation Public Safety Networks  
With the evolution of public safety technologies and services, there is an increasing number of devices that are being deployed in these networks. After having only PTT devices in LMR networks, safety, security, and healthcare professionals are using cellular-enabled mission-critical smartphones, laptops, tablets, as well as connected vehicles in PS-LTE networks. With the aim of further extending public safety use cases, new devices are being deployed in a novel ecosystem of public safety communications, known as IoLST [37]. Similar to the general definition of IoT, the IoLST is a network of devices that collect data and use various communication technologies to share it in real-time. However, its purpose is specific and focuses on improving public safety responses to emergencies [37]. IoLST represents an extension of LMR and PS-LTE capabilities. In detail, IoLST solutions extend the public safety use cases with new types of applications including, but not limited to, real-time video sharing using body-worn cameras, traffic system control with sensor-equipped vehicles, healthcare and vital sign monitoring of first responders, and drone  
Figure 2: Examples of cellular technologies for next-generation public safety networks. surveillance systems [38]. These IoLST use cases involve a variety of devices among which wearables are gaining the attention of the public safety community. One characteristic of the public safety workforce is mobility. Public safety personnel across law enforcement, firefighting, and EMS primarily operate in the field and deal with dangerous situations outside of their response vehicles. Hence, relying on laptop computers is no longer an alternative for first responders to stay connected. Hands-free operation is another peculiarity of public safety services, where the personnel is generally equipped with protective gloves that make it difficult for them to hold smartphones or tablets. Regarding these challenges, the IoLST ecosystem involves wearable devices to make use of their form factor and their capability to encompass advanced sensors. Wearable-empowered IoLST aims to offer unique capabilities for the highly mobile workforce and mark an important shift in the daily operation of the public safety personnel [37]. Admittedly, wearables can complement other cellular-enabled devices and ensure that users stay closely connected to the data they need. Therefore, wearable technology can deliver reliable in-field communications, enhanced situational awareness, and improved first-responder safety. In Figure 3, we illustrate examples of IoLST use cases, where emergency first responders employ a multitude of wearable devices for various public safety applications. For instance, EMS workers in outdoor locations can use smart glasses for remote assistance from indoor experts and professional doctors. Furthermore, outfitting first responders with smart-bands enables the measurement of exposure to toxic substances and the monitoring of their vital signs (i.e., glucose, blood pressure, and heart rate) while operating in dangerous environments [39]. Other examples of wearable solutions for public safety can include smart gloves and exoskeletons for supporting manual tasks. As depicted in Figure 3, several wearable devices can be utilized for the transmission of potentially life-saving communications in a large-scale emergency response. However, watch-type wearables are expected to be a game changer for public safety operations [40]. The ability to send real-time location, monitor alerts, make calls, and acknowledge the reception of messages while working allows first responders to perform their critical tasks in a safer and more responsive manner [40]. In terms of communication capabilities, several cellular-enabled smartwatches are currently available in the wearable market. Specifically, these devices utilize cellular low-power wide-area (LPWA) technologies, namely, LTE machine-type communications (LTE-M) and narrowband IoT (NB-IoT).