What is a Scrambler (Except Wikipedia please)

[gkn_ozcan]

As far as I understand from wiki, it is a encoder-decoder block for cryptology things. however, my administrator said that it is used to keep a signal away from channel errors rather than hackers outside..i mean the main purpose of scrambling is making a signal more reasonable, such as filtering, eg. removing peak powers and recovering some loss part according to previous signal values..but i could not see such a description on the net.

can anybody please tell what a scrambler really is and what is it exactly used for?

thanks all!

 

[keith1200rs]

Sorry it is a wikepedia link, but I think what you are talking about is spread spectrum unless I have misinterpreted your question. If so, I apologise in advance.

https://en.wikipedia.org/wiki/Spread_spectrum

Keith.

 

[eltonjohn]

The term SCRAMBLER originated in the electronics world as box capable of encoding radio tty transmition codes like AMTOR .Also encoding tv signals in such a way that only if you have the descrambler you could warch it it was a very crude type of encryption system .It was analog .You added some componnent to the signal or get the lines out of order .And reorganize or filter the signal in the descrambler. This days the term scrambler is also not well defined .But i means to encrypt some signal .Usually a tv or radio signal.

Regards

 

[gkn_ozcan]

Scrambler has two purposes depending on the application
1) Usual encryption/decryption
2) Importantly : to facilitate timing recovery in the receiver for accurate symbol/bit synchronization

For efficient symbol synchronization, it is desirable to have as many 0/1 transitions as possible. So a PN sequence is used to randomize the data that is being sent.

If the synchronization is not proper , then the timing recovery loop may break leading to undesirable channel errors. This may cause the received data to be sampled at wrong time instant and can cause irreversible data errors. So a Scrambler's main aim is to provide protection against channel errors rather than encryption/decryption.

Regards
Mathuranathan
https://gaussianwaves.blogspot.com

hmm. how does scrambler faciliate timing recovery?

Added after 9 minutes:

I think I got the point now. It is funny that I am gonna give a wiki reference now

https://en.wikipedia.org/wiki/Satellite_modem
read under "Scrambling" sub-title:

Scrambling is a technique used to randomize a data stream to eliminate long '0'-only and '1'-only sequences and to assure energy dispersal. Long '0'-only and '1'-only sequences create difficulties for timing recovery circuit. Scramblers and descramblers are usually based on linear feedback shift registers.

A scrambler randomizes the data stream to be transmitted. A descrambler restores the original stream from the scrambled one.

Scrambling shouldn't be confused with encryption, since it doesn't protect information from intruders.