Radio waves used for communication between households or mobile users and fixed users, realizing mobile communication between two or more points. It includes space segment, ground segment and user segment.
The space segment can be a geostationary satellite or a medium-to-low-orbit satellite, serving as a communication relay station to provide connections between network users and signal control stations.
The ground segment usually includes signal control stations, network control centers and satellite control centers, which are used to connect mobile users to the core network and to control the normal operation of the entire communication network.
The user side is composed of various types of user terminals, including handheld, vehicle-mounted, ship-mounted, aircraft-mounted terminals, etc.
Satcom communication mainly has the following characteristics:
Wide communication coverage and long distance
A geostationary orbit (GEO) satellite can achieve long-distance communication of over 10,000 kilometers with only one satellite relay transmission, and three GEO satellites can cover the entire global surface except for areas with latitudes above 76°.
Satcom is not limited by geographical conditions and can be used to communicate anywhere, whether in big cities or remote mountainous areas, islands, etc.
Large communication bandwidth and capacity
The satcom communication channel is in the microwave frequency range, which is quite rich in frequency resources and can be continuously developed.
Good channel quality and stable transmission performance
The satcom communication link generally uses line-of-sight communication in free space, and the transmission loss is very stable and can be accurately predicted, while multipath effects can generally be ignored.
Strong disaster tolerance
Can provide stable communication during natural disasters such as earthquakes and typhoons.
The cost of communication equipment does not increase with the distance of communication, making it particularly suitable for long-distance communication and sparsely populated areas.
The cost of satellite launch and onboard communication payload is high. The onboard components of the satellite must use anti-radiation aerospace-grade components, and the lifespan of LEO and GEO satellites is generally only about 8 years and 15 years, respectively.
Large transmission attenuation of the satellite link. This requires ground and satcom communication equipment to have high-power transmitters, high-sensitivity receivers, and high-gain antennas.
Long satellite link transmission delay. The round-trip transmission time between GEO satellites and the ground is 239-278 ms; in a star-shaped network system based on a central station, small stations must communicate through double-hop links, and the transmission delay can reach 0.5 s, making the conversation process not smooth.