# Communication Technologies in Emergency Situations
## 3 Desk Research
The paper concludes by identifying the main research topics in the area: radio resource management, transparent handover, and the combination of emergent technologies such as Long-Term Evolution (LTE), software-defined networking (SDN), device-to-device (D2D), software-defined radio (SDR) and cognitive radio (CR). Although the paper includes interesting information about satellite and aerial communications not found in previous surveys, some more details are missed on the integration with terrestrial communications, as only mobile communications are considered. Ref. [22] is similar to the previous one, but much more complete. Ref. [22] also presents a survey in satellite-air-ground integrated networks, using the term SAGIN to refer to the same concept as HSAT in [21]. The proposed architecture is also similar in both works, but while ref. [21] includes more details on high aerial platforms (HAPs) and low-medium aerial platforms (LMAPs), ref. [22] puts more emphasis on several types of satellite communications (GEO, MEO, LEO). Indeed, the comparative analysis of the different networks is also complementary in both works; while ref. [21] includes a more extensive list of characteristics including cost, mobility, cell radius, or system deployment (among many other), ref. [22] includes a more detailed classification of the relationship between network performance (in delay, throughput, etc.) and network factors of the physical, the data, and the network layers. Moreover, in [22], the physical layer characteristics and spectrum allocation of SAGIN are detailed, as well as the mobility management and routing. An extensive list of research works on both topics is included and classified based on their objective (as for example channel estimation or data rate maximization in physical layer characteristics and resource allocation, and traffic offloading or routing algorithms in mobility management and routing), and network scenario (satellite, air-ground, ground-satellite, etc.). Another important contribution of [22] is the specific survey of works on system integration and performance analysis, also considering diverse types of network scenarios. Finally, they introduce several contemporary network architectures applied in terrestrial systems with respect to their extensibility and feasibility to support integrated space-air-ground networks. Overall, it is a very complete survey, but it is not focused on emergency scenarios, and thus, in our point of view, the importance of IoT and Flying Networks (although mentioned as emerging networks and future challenges at some point in the document) are too poorly addressed. In contrast, in our review, both topics will be thoroughly analysed. Finally, refs. [21; 22; 23] present a survey on space-aerial-terrestrial (the same concept as before now referred as SATIN) integrated 5G networks. Again, the analysis on the non-terrestrial communications is very complete, but then, it only focuses on the integration of those to 5G networks. It is also important to value that the paper addresses standardization issues which are indeed important in this domain, but usually disregarded by the researchers. Overall, ref. [23] covers an interesting topic but differs from our work because it is not specific for emergency scenarios, and it is limited in terms of terrestrial communication technologies. Refs. [24; 25] are two up-to-date surveys with a clear focus in aerial communications. Ref. [24] presents an overview of aerial wireless relay networks (AWRNs) focused on emergency communications during large-scale disasters, with an interesting comparison between balloons' and multicopters' features and a review of the key issues of flying schemes in the AWRNs with multicopters. In contrast, ref. [25] is a much more complete survey on the Internet of Flying Things (IoFT), but not focused on emergency scenarios. Even if both works are far from the objectives of our review, they are an interesting source of information of the emergent topic of aerial networks.