# Communication Technologies in Emergency Situations
)1 La Salle Campus Barcelona--Research Group in Internet Technologies and Storage, Universitat Ramon Llull, 08022 Barcelona, Spain; [EMAIL_ADDRESS] (A.C.-C.C. ); [EMAIL_ADDRESS] (A.Z. )1 La Salle Campus Barcelona--Research Group in Internet Technologies and Storage, Universitat Ramon Llull, 08022 Barcelona, Spain; [EMAIL_ADDRESS] (A.C.  
hindering the rescue operations. In spite of the fact that telecommunications companies own Emergency Communications Vehicles that can partially restore the communications in less than 30 min, this solution relies on expensive technologies (i.e., satellite) and may be too time consuming for disasters that occur in difficult-access areas. In addition, terrorist attacks might damage existing infrastructure and have disastrous effects on the population. To intimidate governments or society, to induce insecurity for political, religious, or ideological purposes, terrorism is currently a threat with a significant effect on the safety of the population. To effectively fight these emergency situations and mitigate their associated negative consequences, FRs together with all the interdisciplinary emergency services (administrations, radio amateurs, and general public) involved in the scene need as much in-field information as possible to forecast their strategy and operations. That is, they need a huge amount of time-critical data coming from multiple sources and services, even external ones such as social networks. This requires the rapid deployment of an Emergency Communication Systems (ECSs) aimed to link a set of personnel and apparatuses that must cooperate in extreme/hazardous situations with quick response times and under stress conditions. This reliable communications system must collect, transmit, process, and receive data required to continuously monitor and assess the disaster evolution. The context of this research work is, thus, the future Emergency Communications Systems, with a particular focus on the required integration of technologies in such a dynamic and demanding scenario. Indeed, this shares several similarities with a Ubiquitous Sensor Network (USN), where a dynamic set of heterogeneous sensors and actuators (e.g., FRs, citizens, devices) with different capabilities are deployed and, spanning a large-scale area, must cooperate. Several ECS solutions integrating innovative technologies such as Unmanned Aerial Vehicles (UAVs) [2] and Internet of Things (IoT) [3] have been deployed in the last years, but, usually, they are completely tailored to very concrete scenarios. Indeed, the more novel technologies are integrated within an ECS, and as more research works arise for specific application scenarios, the need of a standardized architecture to guarantee the interoperability and reusability of all these specific novel solutions and technologies is clearer. In this line, this paper first introduces the ECSs and their requirements in Section 2. Second, Section 3 includes desk research, collecting and analysing all the existing surveys/reviews on the topic and identifying the ECS requirements addressed in each of them, and third, an updated and extensive systematic review on ECS technologies is presented in Section 4, collecting the latest research works in the field and including an analysis of the proposed technologies. The paper concludes with a discussion chapter (Section 5) proposing an architecture for ECS based on the USN Architecture from the International Telecommunications Union (ITU) as a solution to the detected open issues, and details how it would be applied in an emergency scenario combining IoT, UAVs, Near Vertical Incidence Skywave (NVIS), and Edge Computing.