# Flying Real-Time Network to Coordinate Disaster Relief Activities in Urban Areas +
## 2 Related Work  
In order to properly analyze the suitability of communication technology that supports disaster relief efforts, it is important to remark that these mitigation processes involve several phases, and the technology that is suitable to support one of them is not necessarily suitable for the others. These phases are _preparedness_, _response_, _recovery_, and _learning_[14]. The problem addressed in this paper is limited to the communication support required during the response phase, particularly in the \"golden relief time\" (i.e., the first response), where there is almost no time to transport or setup large communication infrastructures, and where regular communication services (e.g., wired and cell phones) and power networks are usually unavailable. In this sense, the infrastructure of the communication media should be easy to deploy, allow the mobility of the users, and support intra- and inter-organization interactions. Considering these restrictions, it is evident why land mobile radio (LMR) systems are the most frequently used communication support in this period of the response process [15; 16]. The literature also reports several limitations of analog communication media to support this process (e.g., their inability to transmit digital information, control the access to shared information, and ensure the availability of a communication channel when required) [2; 3; 4]. For that reason, previous research works have proposed several kinds of mobile ad-hoc and opportunistic networks to try provide real-time and stable digital communication during disaster relief efforts. These proposals typically complement the use of LMR systems. For instance, a human-centric wireless sensor network was introduced in [1] to improve communication and the availability of critical information during SAR activities. While the added layer of human sensors can help input extra information into the network, the underlying deployed network allows such information to be shared, and therefore becomes an essential component for the success of the communication process. Then, in [17], the authors extend the previous work and propose a human-centric approach to model IoT-based solutions for man-made incidents such as train derailments or terrorist attacks. Both proposals consider the simultaneous use of stationary witness units (WUs) as well as land mules. These mules can be implemented using manned and autonomous vehicles, and their main role is to ease the exchange of information among working units (e.g., response teams, the IC, and WUs) when there is no direct communication path between them. Trying to deal with the dynamism of these networks and increase the usefulness of WUs, the NASA Glenn Research Center developed the Unmanned Aircraft System (UAS) to select and test a communication technology for the UAS Control and Non-Payload Communications (CNPC) link [18]. This organization evaluated the performance of several potential technologies for the CNPC link through the use of detailed software simulations, and LTE and 802.16 ranked as the top two. Similarly, the SMAVNET (Swarming Micro Air Vehicle Network) project at the Ecole Polytechnique Federale de Lausanne (EPFL) introduces a flying ad-hoc self-organizing network that uses swarming communication protocols to build an alternative wireless network for rescuers in emergency scenarios [19]. This initiative proposes the use of a kind of self-organizing mesh network, where the UAVs rely on multi-hop communications to better cover the operation area. Although interesting, the full deployment of FANETs at large scale may be too intricate in disaster scenarios, given that it would require dealing with non-trivial decisions such as dynamic routing [20]. In [21] the authors claim that there have been no practical solutions, outside of military applications, to quickly provide digital communication support in disaster relief scenarios.