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The coding rules are as follows: 1, the number of consecutive 0 does not exceed 3, and the rule is the same as AMI; 2, if the number of consecutive 0 is more than 3, then every 4 0 is regarded as a bar, defined as B00V position 3, B and V meet the same polarity of V and adjacent non-zero symbols, polarity alternates between V and V without looking at V; 4. Generally, the first B takes 0, and the first non-zero symbol takes-1.

The operating environment of this tutorial: windows7 system, Dell G3 computer.

1. Coding rules:

1. If the number of consecutive zeros does not exceed 3, the rule is the same as AMI, that is, 0 remains unchanged, 1 becomes-1, + 1 alternates.

2. If the number of consecutive zeros exceeds 3, every four zeros can be regarded as a section, which can be defined as B00V, which can be-1, 0, + 1, V can be-1, + 1.

3. The specific values of B and V satisfy the following conditions: the polarity of V is the same as that of the adjacent non-zero symbol; when not looking at V, the polarity alternates; the polarity alternates between V and V.

4. Generally speaking, the first B takes 0, and the first non-0 symbol takes-1.

Extended data:

Principle: HDB3 code should not only include the alternating characteristic of AMI so that the output has no DC characteristic, but also avoid more than four connected zeros, so it can satisfy the latter first.

1. Replace "0000" with a replacement festival.

Rule: first separate the "0000", the first "0000" directly into "000V", and then count the number of "1" between the two adjacent "000V", the odd number becomes "0000 V" and the even number becomes "B00V".

two。 Update the symbol.

According to the textbook, B is always the opposite of the 1 or V symbol in front of it, V is always the same as the previous 1 or B symbol, and 1 is always the opposite of the previous V or B symbol, so you can make symbols.

For example:

Message code: 1 000 0 0 1 0 0 0 1 1 0 0 0 1 0 0 0 1 1 0 0 0 1

Intermediate code: 1 000 V 1 000 V 1 1 1 B 0 0 V 1 1 B 0 0 V 1 1 1 000 V 1

HDB3 code: + 1000 + V-1000-V + 1-1 + B 00 + V-1 + 1-B 00-V + B 00 + V-1 + 1-1000-V + 1

Second, the characteristics of HDB3 code:

1 the baseband signal determined by HDB3 code has no DC component and has only a very small low frequency component.

The number of serial 0 strings in 2 HDB3 is at most 3, so it is easy to extract timing signals.

(3) the coding rules are complex, but the decoding is simple.

III. Decoding rules

1 if we find the point that destroys the alternation of polarity from the received symbol sequence, we can conclude that the symbol and the three symbols in front of it must be a concatenated zero symbol, thus restoring the four concatenated codes.

2 after converting all the-1 to + 1, you can get the original message code.

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