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From: Daku on 5 Aug 2010 11:04
I understand that they are different domains (Hz - analog and bits/sec
- digital), how would one
convert e.g., 1Gbit/s to corresponding Hertz
frequency ?
From: Tim Wescott on 5 Aug 2010 12:53
On 08/05/2010 08:04 AM, Daku wrote:
> I understand that they are different domains (Hz - analog and bits/sec
> - digital), how would one
> convert e.g., 1Gbit/s to corresponding Hertz
> frequency ?

Without knowing more, one can't. In general, for a given modulation
scheme, increasing the data rate involves scaling everything down
equally in time, which scales everything up equally in frequency.

But there are so many different ways to encode data onto a signal that
the bandwidth vs. data rate spread is pretty wide. There are practical
systems that have 16-point constellations (four bits/symbol) that can
pack in four bits/Hz; there may be practical (or at least fitfully
practical) systems that can do six bits/Hz. On the other hand, there
are systems that are vastly spectrally inefficient; with those the sky's
the limit as far as wasted bandwidth.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html
From: Tom Biasi on 5 Aug 2010 16:19

"Daku" <dakupoto(a)gmail.com> wrote in message
news:1f08b0d9-9d6a-4cf3-93cc-19803e81b278(a)y32g2000prc.googlegroups.com...
>I understand that they are different domains (Hz - analog and bits/sec
> - digital), how would one
> convert e.g., 1Gbit/s to corresponding Hertz
> frequency ?

Hi,
Tim is quite knowledgeable on these subjects and gave some usefull info but
maybe your question is not quite so deep.
Hertz is used to describe cycles/second (cycles per second). If you allow it
to mean events per second then a bit can be an event.
So 1Gb/sec is 10^9bits / sec or 1 Ghz.
This is for mental clarity and the actual units may vary.

Tom


From: Grant on 5 Aug 2010 16:49
On Thu, 5 Aug 2010 16:19:00 -0400, "Tom Biasi" <tombiasi(a)optonline.net> wrote:

>
>"Daku" <dakupoto(a)gmail.com> wrote in message
>news:1f08b0d9-9d6a-4cf3-93cc-19803e81b278(a)y32g2000prc.googlegroups.com...
>>I understand that they are different domains (Hz - analog and bits/sec
>> - digital), how would one
>> convert e.g., 1Gbit/s to corresponding Hertz
>> frequency ?
>
>Hi,
>Tim is quite knowledgeable on these subjects and gave some usefull info but
>maybe your question is not quite so deep.
>Hertz is used to describe cycles/second (cycles per second). If you allow it
>to mean events per second then a bit can be an event.
>So 1Gb/sec is 10^9bits / sec or 1 Ghz.
>This is for mental clarity and the actual units may vary.

Yes, Tim touches on the old baud rate (symbol rate) vs frequency that
you're suggesting as the simple answer.

Both are not incorrect (double negative only to show grey area).

For example 100Mbps network link bangs four symbols on each of 1/25MHz
to get the speed, and Gbps copper network links don't run at 1GHz, they
run slower speed, using a couple pairs in each direction.

So, in this case, context matters.

Where I said symbols, Tim said constellation, Tim is more accurate :)

Grant.
From: krw on 5 Aug 2010 18:25
On Fri, 06 Aug 2010 06:49:33 +1000, Grant <omg(a)grrr.id.au> wrote:

>On Thu, 5 Aug 2010 16:19:00 -0400, "Tom Biasi" <tombiasi(a)optonline.net> wrote:
>
>>
>>"Daku" <dakupoto(a)gmail.com> wrote in message
>>news:1f08b0d9-9d6a-4cf3-93cc-19803e81b278(a)y32g2000prc.googlegroups.com...
>>>I understand that they are different domains (Hz - analog and bits/sec
>>> - digital), how would one
>>> convert e.g., 1Gbit/s to corresponding Hertz
>>> frequency ?
>>
>>Hi,
>>Tim is quite knowledgeable on these subjects and gave some usefull info but
>>maybe your question is not quite so deep.
>>Hertz is used to describe cycles/second (cycles per second). If you allow it
>>to mean events per second then a bit can be an event.
>>So 1Gb/sec is 10^9bits / sec or 1 Ghz.
>>This is for mental clarity and the actual units may vary.
>
>Yes, Tim touches on the old baud rate (symbol rate) vs frequency that
>you're suggesting as the simple answer.
>
>Both are not incorrect (double negative only to show grey area).
>
>For example 100Mbps network link bangs four symbols on each of 1/25MHz
>to get the speed, and Gbps copper network links don't run at 1GHz, they
>run slower speed, using a couple pairs in each direction.
>
>So, in this case, context matters.
>
>Where I said symbols, Tim said constellation, Tim is more accurate :)

Not really. Symbols are the stars in a constellation of stars. The symbol is
the basic unit of information transferred. A constellation is a
representation of the possible physical values (voltage, frequency, phase,
whatever).

A little more specifically, a symbol may be a specific value in the
constellation or a transition from the current point to another.
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