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All about Satellite communication
Satellite communication is one of the types of space radio communication, based on the use of artificial earth satellites as repeaters. Satellite communication is carried out between earth stations, which can be either stationary or mobile.
Satellite communication is the development of traditional radio relay communication by placing a repeater at a very high altitude. Since the zone of its visibility, in this case, is almost half the globe, the need for a chain of repeaters is eliminated - in most cases, one is enough.
Modulation and noise-immune coding:
A feature of satellite communication systems is the need to work in a relatively low signal-to-noise ratio caused by several factors:
Considerable distance of the receiver from the transmitter,
Limited capacity of the satellite (inability to transmit at high power).
In this regard, satellite communication is poorly suited for the transmission of analogue signals. Therefore, to transmit speech, it is pre- digitized using, for example, pulse-code modulation (PCM).
To transmit digital data over a satellite communication channel, they must first be converted into a radio signal occupying a certain frequency range. For this, modulation is used (digital modulation is also called manipulation ). The most common types of digital modulation for satellite communication applications are phase shift keying and quadrature amplitude modulation [18] . For example, in systems of the DVB-S2 standard, QPSK, 8-PSK, 16-APSK and 32-APSK are used.
Disadvantages of satellite communication
Weak interference immunity
In the case of satellite monitoring the huge distances between earth stations and the satellite cause the signal-to-noise ratio on the receiver to be very small (much less than for most microwave links). In order to provide an acceptable error probability under these conditions, it is necessary to use large antennas, low-noise elements and complex noise-immune codes. This problem is especially acute in mobile communication systems since they have a limitation on the size of the antenna and, as a rule, on the transmitter power.
The influence of the atmosphere
The quality of satellite communications is strongly influenced by effects in the troposphere and ionosphere.
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February 26, 2018 · Jamming devicesContact Us
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