# An Overview of Emergency Communication Networks
## 1 Introduction  
In the past few years, China and the world have witnessed an endless stream of disasters, such as earthquakes [1], hurricanes [2], and tsunamis [3]. Various natural and man-made disasters have caused huge losses of life and property, such as the 7.3-magnitude earthquake in Haiti, which caused at least 2248 deaths, with 329 people missing and 12,268 injured [4]. The United States has been hit hard by hurricanes which have triggered storm surges, floods, and other disasters. These disasters caused infrastructure damage and large-scale power outages, with economic losses of more than USD 95 billion [5]. From 1894 to 2021, the Uttarakhand Himalaya witnessed at least 16 major disasters. In 2021, glaciers in the Himalaya Mountains broke, causing a series of floods, mudslides, avalanches, and other disasters, which destroyed many bridges, dams, power stations, tunnels, and villages in Chamoli, North Akande, India, leaving 174 people unaccounted for and 32 dead [6]. If adequate communications support can be provided in the aftermath of a disaster, we believe that casualties and property damage can be reduced. The occurrence of major natural disasters and public safety accidents can even damage the existing communication networks, resulting in communication interruptions and preventing the disaster area fromcontacting the outside world [7]. Therefore, communication networks are very important during a disaster, because rescue and recovery largely depend on the communication channel provided. However, once a disaster occurs, the traditional communication network is fragile; at this time, a temporary communication system, namely an emergency communication network, should be built as soon as possible. Before a disaster, the emergency communication network can combine the data obtained from different systems to provide a technical platform for early warning, and disaster reduction and prediction, so as to improve the ability to monitor, manage, and control accidents and disasters. After a disaster, the emergency communication network can quickly and reliably restore communication in the disaster area, assist users, be used to rescue workers, support disaster relief headquarters, and realize on-site personnel scheduling, on-site data transmission, and other functions, to promote emergency rescue work. This can provide valuable time and first-hand information for the rescue, so as to save more lives. With the frequent occurrence of natural disasters and the tightening of the international security situation, countries all over the world are strengthening and improving the construction of emergency communication systems and related technology research, and striving to deploy a more reliable and stable emergency communication network. Emergency communication [8; 9; 10] refers to the communication means and methods needed for the extensive use of various communication resources to support rescues, including emergency rescues, and the necessary communication in the case of natural or manufactured emergencies. Because of the characteristics of disasters, making effective use of limited resources to provide the best communication services is a key problem. Unlike the traditional communication network, the emergency communication network is a complex network, and enables the implementation of emergency rescue activities and provides the primary conditions for the realization of emergency rescue functions. Its network structure has a significant impact on rescue efficiency. In different emergency situations, the demand for emergency communication is different, and the technical means used are different. Emergency communication mainly has the following characteristics: uncertainty of time and place; uncertainty of capacity demand; high degree of timeliness of the emergency communication; complexity of the environment; uncertainty of the degree of damage to the communication network itself; and diversification of information.