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What Is the Forward Error Correction in Satellite Communication?


When the fans are using the satellite terminal to receive satellite signal, they will see the word of FEC frequently. FEC is short for Forward Error Correction. It is the method used to improve the reliability of data communication. When an error is found in the unidirectional signal path, the receiver will not have the authority of asking for data transmission again. However, FEC uses the data itself to prevent this problem when great amount of data needs to be transmitted.
FEC is one of the significant parameters of the satellite receiver. In some early digital receivers, the FEC parameter has to be typed in by users. As the process rate of the CPU of digital receivers improves, today's digital satellite receiver can measure the FEC parameter automatically, thus users don't have to type in the parameter any more. This likes the improvement in the process of searching channels. Today's satellite receivers can search can search the channels automatically while the earlier machines have to type in the parameters. Then, what is FEC used for?
As we all know, the digital programs have much purer colors and much sharper vision effect than the analog programs. The picture of the digital program won't have the interference, too. These advantages are just owing to the perfect anti - interference characteristic of digital signal. In the digital signals, we put in layers of error correction codes in order to prevent the mutation of the signal caused by other signal's interference. This is because the digital signal is very sensitive in the decoding progress. It may not be able to decode just because of a little flaw in the signal. So the signal's affluent playing is also due to the setting of error correction code. In all kinds of error correction codes, the FEC is a very significant anti - interference algorithm. Using it will improve the reliability of satellite signal a lot.
In order to understand the FEC code, let's have a look at the following analogy. If the ES stream is the raw material of the factory, the PES is the raw products and the TS stream is the product with a package. In the transformation of PES to TS, CPU adds the FEC code. In the DVB - S standard, there are 1/2, 2/3, 3/4, 5/6 and 7/8 five types of rate of FEC code in the signal stream. For example, 7/8 means that in the TS stream, 7/8 of the data is the video and audio information while the another 1/8 data is used to protect the information. This proportion of data is the FEC code. The TV signal uses the 2/3 rate.



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