The main content of the principle of communication?
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Chapter 11: Error Control Coding (Channel Coding)
What is the purpose of channel coding?
By adding some supervisory symbols to perform error correction and error detection, the reliability of signal transmission is improved.
What are the error control techniques?
Error detection retransmission (ARQ), forward error correction, feedback check, error detection deletion. These can be used in combination.
What kinds of error correction codes are there? What are the characteristics of each?
Simple ones include parity supervisory code, constant ratio code, positive and negative code. Slightly more complex points are linear block codes and non-block codes.
Linear block codes include Hamming codes, cyclic codes, BCH codes and RS codes.
The Hamming code is a code capable of correcting one-bit errors and detecting multiple-bit errors. It relies on a set of formulas to add code elements. The core idea of this set of formulas is that the several supervisory code elements added later actually contain the situation of each error position code element and a correct situation. In this way, when a When the code is wrong, the error can be checked and corrected, while the multi-bit can only detect the error.
The cyclic code can only check one bit error code, but it has the strongest anti-interference ability. There is only one difference between the adjacent codes of the cyclic code, and the first and last cyclic codes have only one difference between the first and last codes.
The BCH code is a cyclic code capable of correcting multiple random error codes.
The RS code is a multi-ary BCH code with strong error correction capability.
Non-block codes have convolutional codes, which are more suitable for forward error correction and have better performance than block codes.