## 1 Introduction  
Recently, drones have become attractive for research and a variety of applications, because of their flexibility and the possibility of use in a wide range of applications, such as the security, control, monitoring, and exploration of terrestrial areas otherwise difficult to reach quickly. Furthermore, this is transformative technology, enhancing how first responders can reach and carry out rescue missions at the sites of natural disasters. In addition, it can provide support for delivering medical supplies, as well as for emergency management cases such as forest firefighting, critical infrastructure protection and inspection, coastal monitoring, and police augmentation, in addition to helping smart cities meet their public safety requirements. The relationship between public safety and the Internet of Things (IoT) was discussed in [1], while a taxonomy of the IoT-based smart city was provided in [2]. Applying IoT technologies to smart cities could lead to changes and improvements in the economy, safety, management of public utilization, and transportation in smart cities. The most attractive application of drones is the collection of data from IoT using wearable devices in smart cities or at events [3; 4]. A drone can communicate with heterogeneous devices on the ground that are unable to communicate over large areas and can send information to the intended destination in order to make a final decision and take action in a timely fashion. The development of such communication technologies will lead to changes in how we communicate with the vast number of things connected to the Internet. However, the IoT refers to the connections among the things themselves. The concept of IoT refers to things that are not intelligent, and does not include artificial intelligence (AI). Furthermore, the Internet of robotic things (IoRT) is an intelligent concept that gives the associated things the capacity for negotiation, reasoning, decision, and delegation [5]. In contrast, the Internet of public safety things (IoPST) refers to wearable things for first responders that are used for public safety and are connected via the Internet, such as cameras, sensors, and drones. IoPST covers different types of public service, such as emergency response, disaster relief, traffic control, crime control, investigating accidents, smart event management, etc., as shown in Figure 1.  
Wearable IoPST devices connect with each other in smart cities for the purposes of public safety, and allow first responders to share information with command posts and relevant parties. These connected devices can help relief teams and police to identify when or where disasters or crime have happened, as shown in Figure 2. On the basis of this, the police can successfully take decisions in order to track down perpetrators. However, due to the limited transmission power of wearable devices, they are unable to send data over long distances. Drone technology, however, is able to deliver services over a large geographical zone in real time. The use of drone technology represents the cheapest and most efficient way to  
Figure 1: An illustration of the IoPST concept. Figure 2: An illustration of devices connecting to a drone for the public safety network. monitor a criminal on the run, find a missing person, survey a disaster scene, etc., especially in time-critical situations. Therefore, the best features of the integration of drones and IoPST are those that are supposed to achieve and provide maximum benefits, such as their reprogrammability, good sensing capability, ability to interconnect and identify things, ubiquity, communication capability, etc. This article mainly focuses on the network performance of drones and IoPST. Furthermore, we introduce the novel concept of collaboration between drones and IoPST in smart cities, in order to enhance the network performance and maintain the QoS. Furthermore, we discuss drones in public safety applications.