COFDM is a very widely used and commonly touched a lot of wireless technology, since the beginning of the last century, has been very mature.
Friends with high definition map transmission basically know that there is a map transmission called “COFDM map transmission”, so familiar friends often ask, COFDM technology is what technology?
COFDM (Coded Orthogonal Frequency Division Multiplexing) encodes orthogonal frequency division multiplexing
What does this Coded code do? That’s channel coding
Before OFDM modulation, the digital code stream is encoded. The specific method is:
1. For example, if 100 bits of data need to be transmitted after modulation, it will be converted into 200 bits first. When receiving the signal, even if 100 bits of the 200 bits have transmission problems, the correct data can be demodulated. This is called internal error correction (FEC) in COFDM systems and is an important parameter in COFDM systems.
2. In order to solve the multi-path problem (the transmitted signal reaches the receiving end through multiple transmission paths), the protection interval is inserted between the transmitted data bits, which is also an important parameter of the COFDM system.
Well, later someone asked the difference between COFDM and OFDM: it is to increase the error correction coding and protection interval before doing orthogonal modulation to make the signal more efficient transmission.
COFDM is currently the most widely used in DVB (digital video broadcasting), there are DVB-T, DVB-S, DVB-C, etc., in Europe, Southeast Asia, South America, Australia are widely used. OFDM is mainly used in LTE (4G), WIFI and other application systems.
We should have this experience, in the train, high-speed above the phone, mobile Internet will signal is not good, in fact, the pan mobile company does not back, their technology is not designed for high-speed mobile scenes.
And DVB-T is car TV, DVB-S is satellite TV, originally designed for mobile applications.
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