# Communication Technologies in Emergency Situations
## Conclusions  
Overall, the fourteen most relevant surveys related to Emergency Communication Systems found in the literature have been identified and described. The list included a bibliometric survey useful to identify future research trends in the topic, and more than ten more or less complete surveys addressing the most relevant communication technologies for emergency situations. It has been detected that most of them are complementary to each other, as they do not cover all the possibilities for emergency communications. For example, flying networks and IoT are briefly addressed in the most complete surveys and only found in specific surveys on those technologies but with the lack of focus in the emergency domain. Regarding satellite communications, either they are the backbone of the survey, disregarding any possibility without them, or they are usually found in a very superficial condition. In the present review, it has been intended to cover all the possible communication technologies for emergency systems, paying the same attention to all of them, with the objective of providing the most complete and balanced review of ECS conducted so far. In terms of networks for emergencies, several types of network classifications have been identified, which makes it difficult to compare the different surveys. For example, ref. [16] classifies the types of networks based on the data to be transmitted while ref. [20] classifies them based on the impact of the disaster, as congested, partial network, or isolated networks. The works mostly focused in the integration of these technologies, and thus, are more aligned with the point of view of the present paper, usually distinguishing between ground, air, and satellite networks, but this classification is considered too simplistic and not suitable for addressing the interoperability of such a ubiquitous and complex scenario. In this paper, the classification of types of ECS is performed based on the \"communication functionality\" (Coordination, Short Range, Warnings), as described in Section 2. In line with the heterogeneity of types of networks, a critical heterogeneity in terms of addressed ECS requirements has been detected. While the surveys mostly focussed on identifying the requirements (sometimes also referred to as challenges or objectives in the literature) agree on the list presented in Section 2, most of the surveys intentionally limit their scope to only some of them, making their surveys less accurate. Robustness and reliability are the most extended requirements among the identified surveys, but only two works, refs. [16; 19], identified multimedia services support as a requirement, as is considered in the present review. In contrast, Table 2 summarizes the ECS requirements addressed by the eleven most relevant surveys that have been reviewed in this section. Furthermore, in our systematic review of the ECS technologies (Section 4), not only the requirements targeted by each work are identified, but also the corresponding OSI level being addressed is extracted to have an even better picture of all the possible integrations in such a complex scenario and to identify all the still existing open issues in terms of interoperability.