Scramblers

Question 1

What is scrambling?

Answer 1

Scrambling also known as randomisation is a process whereby a data stream
I’d added to the feedback loop(feed through) or the end of the shift register. (additive)

Question 2

What is an additive randomiser?

Answer 2

It generates an LRS of a given length and modulo-2 adds it to the data repeatedly.

Question 3

What are the advantages and disadvantages of additive scrambling?

Answer 3

Not prone to burst errors ( advantage)

Disadvantages

External sync area is required( adding overhead)

Frame width still evident in transmitted data.

Question 4

What is a feed through randomiser?

Answer 4

Each error in the data stream will be multiplied by the number of tap points in the register. As for each shift register bit a feed through input will also add a bit

Question 5

What are the advantages and disadvantages of feed through scramblers ?

Answer 5

Advantages

Self synchronising
Data appears random

Disadvantages
Prone to produce errors