Advantages of R8ZS encoding | Disadvantages of R8ZS encoding
This page covers advantages and disadvantages of R8ZS scrambling. It mentions benefits or advantages of R8ZS encoding and drawbacks or disadvantages of R8ZS encoding.
What is R8ZS scrambling ?
It is scrambling technique in which 8 consecutive zeros are replaced by sequence "000VB0VB". The 'V' in the sequence denotes "violation", which is nonzero voltage that breaks an AMI encoding. It is opposite polarity from previous ones. The 'B' in sequence denotes "Bipolar" which means nonzero level voltage as per AMI rule.
Example #1 : Previous level is positive (i.e. '1' or +ve voltage)
Input : [ 0 0 0 0 0 0 0 0 ]
Output : [0 0 0 +ve -ve 0 -ve +ve] which is as per "000VB0VB" rule of encoding.
Example #2 : Previous level is negative (i.e. '1' or -ve voltage)
Input : [ 0 0 0 0 0 0 0 0 ]
Output : [0 0 0 -ve +ve 0 +ve -ve] which is as per "000VB0VB" rule of encoding.
Benefits or advantages of R8ZS encoding
Following are the benefits or advantages of R8ZS encoding:
➨Unlike block coding, R8ZS encoding does not increase bits i.e. bit rate.
➨It removes long string of zeros from digital data and produces enough transitions which helps in synchronization at the receiver.
➨The technique maintains DC balance as it balances positive voltage levels and negative voltage levels during encoding process.
➨Bipolar AMI has narrow bandwidth and it doesn't create DC component. Moreover R8ZS removes long sequence of 0s from
the original pattern. Hence Bipolar AMI can be used for long distances along with R8ZS.
➨It offers built-in error detection capability.
Drawbacks or disadvantages of R8ZS encoding
Following are the drawbacks or disadvantages of R8ZS encoding:
➨A single bit error at R8ZS decoder input will result in an error on descrambled data.
➨If not reset properly, it results into massive error propagation.
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