Re: Does more bits-per-character but less characters-per-second make better use of bandwidth?

From: Phil Hobbs <pcdhSpamMeSenseless@xxxxxxxxxxxxxxxxxx>
Date: Tue, 18 Sep 2007 12:57:01 GMT

whit3rd wrote:

On Sep 15, 2:35 pm, Phil Hobbs
<pcdhSpamMeSensel...@xxxxxxxxxxxxxxxxxx> wrote:

How are you sending 'characters' if not as sequences of bits, then?

If the signal is binary (has only two recognizable states), one can
only send a
sequence of (at most) one bit symbols. If the signal can take on
values
-2, -1, 0,+1, +2, then there are five symbols, each having a little
over two bits
of information. Gigabit ethernet uses such a multi-level signal
scheme.

The 'SNR' part of Shannon's theorem represents the limit of how many
symbols
can be represented, and acts as the number of bits per symbol (it's
not the real
number of bits, just a MAXIMUM value, a limit). For gigabit
ethernet, there
are more symbols, but less noise tolerance, than for 100baseT. But
the two
standards use the same bandwidth and baud rate.

Sure. That's why I didn't understand the OP's confusion. Multilevel signalling depends on high SNR, but you win logarithmically with transmitted power, rather than linearly with bandwidth or number of parallel channels.

Cheers,

Phil Hobbs
.

References:
- Does more bits-per-character but less characters-per-second make better use of bandwidth?
  - From: Green Xenon [Radium]
- Re: Does more bits-per-character but less characters-per-second make better use of bandwidth?
  - From: Charles
- Re: Does more bits-per-character but less characters-per-second make better use of bandwidth?
  - From: Green Xenon [Radium]
- Re: Does more bits-per-character but less characters-per-second make better use of bandwidth?
  - From: Phil Hobbs
- Re: Does more bits-per-character but less characters-per-second make better use of bandwidth?
  - From: whit3rd

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