GMDSS is the abbreviation for Global Maritime Distress and Safety System. It consists of satellite communication systems and ground radio communication systems and is mainly used for distress alerting, search and rescue coordination, positioning, and dissemination of maritime safety information. The GMDSS system includes various communication devices such as Inmarsat-C ship stations, MF/HF combination radios, VHF radios, emergency radio beacons, search and rescue transponders, NAVTEX devices, etc. The modernization of the GMDSS system is an important task of the International Maritime Organization (IMO), aiming to improve the efficiency and safety of maritime communication using modern communication technologies.