The basic concept and characteristics of satellite communication
Definition: Satellite communication refers to the communication between two or more earth stations using artificial earth satellites as relay stations to forward or reflect radio waves. Satellite communication is also one of the forms of cosmic radio communication, and cosmic communication refers to the radio communication to the object of the space flying body, it has three forms:
(1) Communication between space stations and earth stations; (Direct communication);
(2) Communication between space stations; (Direct communication);
(3) Communication between earth stations by means of retransmission or reflection by space stations. (Indirect communication)
The third type of communication is usually called satellite communication, or when the satellite is a geostationary satellite. Most communications satellites are geostationary (a satellite that is stationary relative to the earth when its orbit is at a certain altitude). A geostationary satellite is a satellite whose orbit is in the plane of the equator. The orbit is about 35,800 km above the ground (often called 36,000 km for simplicity).
Characteristics of geostationary satellite communication
(1) Advantages of geostationary satellite communication
A. The communication distance is long, and the cost is independent of the communication distance (as long as the transmission between the two stations is independent of the distance within the range of the satellite beam)
B. Large coverage area (three satellites can cover all places), can carry out multiple access communication (one round multiple reception)
C. communication bandwidth (500M) and large transmission capacity
D. Signal transmission quality is high, communication line is stable and reliable
E. It is flexible to establish communication circuit and has good maneuverability (as long as the satellite is covered, ground stations can be established for communication)
F. can be self-collected for monitoring
(2) Disadvantages of stationary satellite communication
A. The launch and control technology of geostationary satellite is quite complicated (so there are few satellite launches in China).
B.The polar regions of the Earth are communication blind areas (the orbit is parallel to the equator, and the poles cannot be reached by tangential direction), and the communication effect is not good in the high latitudes of the Earth.
C. There are eclipses (when the satellite is between the Earth and the sun) and eclipses (when the Earth is between the sun and the satellite). -- (The phenomenon can now be shortened by means of treatment)
D. has a large signal transmission delay (transmission and reception time) and echo interference.
-To be continued-