# An Overview of Emergency Communication Networks
## 5 Sea Ad Hoc Network (SANET)
### Summary of Network Development Status
#### 3.2.2 Mobile Satellite Networks
\begin{table}
\begin{tabular}{c c} \hline
**Satellite Communication System** & **Characteristics** \\ \hline \multirow{4}{*}{International Maritime Satellite (Inmarsat)} & The fourth-generation Immarsat system consists of three geostationary orbiting satellites covering the globe between latitudes of 78 degrees north and south. As the satellite basis of GMDS6, the system provides Fleet Safety, RescueNET, and SafetyNET services, including maritime emergency communication services, such as distress alarm and maritime safety information sending and receiving. \\ \multirow{4}{*}{Iridium} & The system consists of 66 satellites in low polar orbit, achieving true global coverage. Voice and data communication functions are open to ships to complement the advantages of the GMDS8 communication system and improve the quality of maritime communication. \\ \multirow{4}{*}{Starlink} & Plans to launch 42,000 satellites into orbit to provide Internet access at speeds comparable to fiber optics, forming a low-cost, high-coverage space-based global communications system. \\ \cline{1-1}  & The ”sky star earth network” networking mode is adopted to realize the global service capability of the whole system through the globally distributed ground stations. \\ \hline \end{tabular}
\end{table} 
Table 4: Representative foreign satellite communication systems. \begin{table}
\begin{tabular}{c c} \hline
**Satellite Communication System** & **Characteristics** \\ \hline \multirow{4}{*}{BeiDou Navigation Satellite System (BDS)} & The unique short message communication function of the BDS system can provide two-way message communication between any two users within the coverage area. In addition, it will support the development of various new services. \\ \cline{1-1}  & The system is equipped with an automatic ship identification system, which can receive the information sent by the ship all over the world, fully grasp the navigation status, position, heading, and other information of the ship, and realize the monitoring and management of ships sailing in the open sea. \\ \multirow{4}{*}{Hongyun project} & The system has the characteristics of integration of communication, navigation, and remote sensing, global coverage, and independent control. It is proposed to establish a low orbit broadband Internet access system based on small satellites for the first time; this will provide a comprehensive information platform integrating “communication, guidance and remote sensing” for all kinds of users. \\ \cline{1-1}  & The Tiantong satellite mobile communication system will form a heaven-Earth integrated mobile communication network together with a ground mobile communication system to provide all-weather voice, data, short message, and other mobile satellite communication services for the territory, land and sea areas, and the surrounding areas of China. \\ \hline \end{tabular}
\end{table} 
Table 5: Representative domestic satellite communication system. covering the world after the Global Positioning System (GPS) of the United States and the Global Navigation Satellite System (GLONASS) of Russia. BeiDou satellites can not only provide rapid positioning and timing services for ground users worldwide, but also enable short digital message communication, which is one of the means of ensuring communication in an emergency. The Hongyan global satellite constellation communication system is planned to be composed of 300 low orbit small satellites and a global data service processing center, with all-time two-way communication capability under complex terrain conditions. It will provide users with global real-time data communication and comprehensive information services. The Hongyan constellation will integrate a number of satellite application functions. Its satellite data acquisition function can realize large-scale regional information collection and meet the needs of monitoring data information transmission in the fields of oceanography, meteorology, transportation, environmental protection, geology, and disaster prevention and reduction.