[SI-LIST] Re: the right way to choose the scrambler
- From: steve weir <weirsi@xxxxxxxxxx>
- To: Giovanni.Guasti@xxxxxxxxxx, <si-list@xxxxxxxxxxxxx>
- Date: Thu, 24 Nov 2005 08:16:44 -0800
Gausti, there are only a few popular scramblers out there. Beyond the
2^7-1 PN scrambler for SONET that is weak for data, by far the dominant
scheme is 8b10b invented by IBM. It has a number of desirable
attributes: I believe the basic coding scheme patent has expired. I would
have to check, but there may be a couple of years left on a table
implementation patent filed a couple of years after the original patent.
1. The circuitry overhead is fairly low.
2. It can be made to go quite fast even in programmable logic.
3. It maintains DC balance.
4. It contains run-length to a narrow range.
6. The 20% bandwidth overhead is relatively modest.
There are other coding schemes to be sure, but the gains to be had are
small in any category and it requires reinventing the wheel.
In programmable logic, both Altera and Xilinx have 8b10b hardwired in with
their SERDES, and offer canned programmable solutions. Altera charges for
theirs, Xilinx' is free. In the shameless plug dept. I have a Xilinx
specific programmable implementation that is half the size and twice as
fast as the Xilinx's.
Steve.
At 09:45 AM 11/24/2005 +0100, Guasti Giovanni wrote:
>Hi gurus,
>does someone of you know a book or web sites where I could find an =
>analytical description about one way to choose the scrambler for my =
>custom high speed link?.
>
>The known parameters are
>the transmission channel
>the receiver/transmitter behaviours
>the frequency data spectrum
>
>I would like to find out the best scrambler BEFORE to make any measure =
>of BER/quality of signal or simulations.
>Best regards,
> Giovanni
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