My dial-up modem fantasy

[Green Xenon [Radium]]

Hi:

My internet-access fantasy involves dial-up modem telecommunications
technology devices which use PSK [Phase Shift Keying] as the modulation
scheme. This too-good-to-be-true PSK uses only 1-symbol-per-second but
with a Graham's-number amount of bits-per-symbol.

http://en.wikipedia.org/wiki/Graham's_number

Now that is a lot of bits-per-baud!

If it were possible for such PSK to exist, what would be the
disadvantages of it?


Thanks,

Radium

[DTC]

Post by Green Xenon [Radium]
If it were possible for such PSK to exist, what would be the
disadvantages of it?

Hmmm...let me think. Since its not possible to exist, its a moot point
in discussing any advantages or disadvantages

[Green Xenon [Radium]]

Post by DTC

Post by Green Xenon [Radium]
If it were possible for such PSK to exist, what would be the
disadvantages of it?

Hmmm...let me think. Since its not possible to exist, its a moot point
in discussing any advantages or disadvantages

Let's say it was possible to exist. What would be the drawbacks?

[John Levine]

Post by Green Xenon [Radium]

Post by DTC

Post by Green Xenon [Radium]
If it were possible for such PSK to exist, what would be the
disadvantages of it?

Hmmm...let me think. Since its not possible to exist, its a moot point
in discussing any advantages or disadvantages

Let's say it was possible to exist. What would be the drawbacks?

The laws of physics would have changed, so the universe as we know it
would cease to exist. Other than that, seems OK to me.

[Grant Edwards]

Post by John Levine

Post by Green Xenon [Radium]

Post by DTC

Post by Green Xenon [Radium]
If it were possible for such PSK to exist, what would be the
disadvantages of it?

Hmmm...let me think. Since its not possible to exist, its a moot point
in discussing any advantages or disadvantages

Let's say it was possible to exist. What would be the drawbacks?

The laws of physics would have changed, so the universe as we know it
would cease to exist.

I hate when that happens.

--
Grant

[henry cabot henhouse III]

300 bps ought ta be enuff for neone...

Post by John Levine

Post by Green Xenon [Radium]

Post by DTC

Post by Green Xenon [Radium]
If it were possible for such PSK to exist, what would be the
disadvantages of it?

Hmmm...let me think. Since its not possible to exist, its a moot point
in discussing any advantages or disadvantages

Let's say it was possible to exist. What would be the drawbacks?

The laws of physics would have changed, so the universe as we know it
would cease to exist. Other than that, seems OK to me.

[Nico Kadel-Garcia]

Post by Green Xenon [Radium]
My internet-access fantasy involves dial-up modem telecommunications
technology devices which use PSK [Phase Shift Keying] as the modulation
scheme. This too-good-to-be-true PSK uses only 1-symbol-per-second but
with a Graham's-number amount of bits-per-symbol.
http://en.wikipedia.org/wiki/Graham's_number
Now that is a lot of bits-per-baud!
If it were possible for such PSK to exist, what would be the
disadvantages of it?
Thanks,
Radium

I think there's no point. The limited data resolution available to
both older, analog phone lines and contemporary, digital phone lines
sets a hard, hard limit on the available bandwidth for *ANYTHING*
going over a phone line, and contemporary modems are already very
close to that theoreticallimit. So switching people over to a new and
entirely incompatible modem technology would provide no significant
benefit.

[Green Xenon [Radium]]

Post by Nico Kadel-Garcia

Post by Green Xenon [Radium]
My internet-access fantasy involves dial-up modem telecommunications
technology devices which use PSK [Phase Shift Keying] as the modulation
scheme. This too-good-to-be-true PSK uses only 1-symbol-per-second but
with a Graham's-number amount of bits-per-symbol.
http://en.wikipedia.org/wiki/Graham's_number
Now that is a lot of bits-per-baud!
If it were possible for such PSK to exist, what would be the
disadvantages of it?
Thanks,
Radium

I think there's no point. The limited data resolution available to
both older, analog phone lines and contemporary, digital phone lines
sets a hard, hard limit on the available bandwidth for *ANYTHING*
going over a phone line, and contemporary modems are already very
close to that theoreticallimit. So switching people over to a new and
entirely incompatible modem technology would provide no significant
benefit.

You're talking about bandwidth. A baud of 1-symbol-per-second uses only
a small amount of bandwidth, regardless of the amount of
bits-per-symbol. Right?

[DTC]

Post by Green Xenon [Radium]
You're talking about bandwidth. A baud of 1-symbol-per-second uses only
a small amount of bandwidth, regardless of the amount of
bits-per-symbol. Right?

Wrong, but then trying to explain Shannon's Law to you would be a
waste of bandwidth.

Aww...what the heck. I'll feed the troll.

Use of the word baud is outdated as it can't adequately reflect the
additional data load achieved by advanced modulation techniques.

Technically speaking, 900 baud is the highest a standard "toll-quality"
phone line will support. So how did they get 2400 baud modems to work?
They didn't, they got 2400 bps modems to work. A 2400 bps modem is
actually a 600 baud device; but using phase modulation, they got four
different states per baud.

Do you really spend that much time on the john reading Popular Science?

[Green Xenon [Radium]]

Post by DTC
Use of the word baud is outdated as it can't adequately reflect the
additional data load achieved by advanced modulation techniques.
Technically speaking, 900 baud is the highest a standard "toll-quality"
phone line will support. So how did they get 2400 baud modems to work?
They didn't, they got 2400 bps modems to work. A 2400 bps modem is
actually a 600 baud device; but using phase modulation, they got four
different states per baud.

I know that.

Baud and bits-per-baud are two different things.

The only way the bit-rate is the same as the baud is if you have 1 bit
per symbol. The 2400 bps using a 600 baud is derived using 4 bits per
symbol. 6X4=24.

[Green Xenon [Radium]]

Post by Green Xenon [Radium]

Post by DTC
Use of the word baud is outdated as it can't adequately reflect the
additional data load achieved by advanced modulation techniques.
Technically speaking, 900 baud is the highest a standard "toll-quality"
phone line will support. So how did they get 2400 baud modems to work?
They didn't, they got 2400 bps modems to work. A 2400 bps modem is
actually a 600 baud device; but using phase modulation, they got four
different states per baud.

I know that.
Baud and bits-per-baud are two different things.
The only way the bit-rate is the same as the baud is if you have 1 bit
per symbol. The 2400 bps using a 600 baud is derived using 4 bits per
symbol. 6X4=24.

So back to my question.

Wouldn't a baud of 1-symbol-per-second use only 1 Hz of bandwidth
regardless of the amount of bits-per-symbol?

[DTC]

Post by Green Xenon [Radium]
So back to my question.
Wouldn't a baud of 1-symbol-per-second use only 1 Hz of bandwidth
regardless of the amount of bits-per-symbol?

Back to my original answer, NO. You really need to revisit
Communications Theory 101.

[Nico Kadel-Garcia]

Post by DTC

Post by Green Xenon [Radium]
So back to my question.
Wouldn't a baud of 1-symbol-per-second use only 1 Hz of bandwidth
regardless of the amount of bits-per-symbol?

Back to my original answer, NO. You really need to revisit
Communications Theory 101.

You're not answering his questions.

An encoding scheme that associated that 'bit/second' of data, and that
is the unit I'll use for reference, would have itself so much
information associated with the scheme that the rest of the data would
*already* have been transmitted. The overall bandwidth would be
limited to that of the medium, and the overall data the integral of
the available bandwidth. It's easy to get confused and caught up in
the details of 'phase encoding' and other technologies, but there are
fundamental limits to the available data/second transmitted set by the
signal levels and noise levels of the particular medium used.

The transmission of the sophisticated encryption scheme and the
associated meanings described by the original scheme here is that of a
one-time-pad: Any signal from that pad, even a one-bit signal, can
encompass an arbitrarily complex message. But the data of such a pad
is normally sent out of band, and isn't revealed by a casual glance at
the content of the transmitted signal. It's only when you count the
pad itself as part of the transmitted signal (as you should, for good
information theory analysis!) that the booby traps show up.

Does that make more sense?

[H. Peter Anvin]

Post by Green Xenon [Radium]
So back to my question.
Wouldn't a baud of 1-symbol-per-second use only 1 Hz of bandwidth
regardless of the amount of bits-per-symbol?

Depends on the modulation scheme, but basically yes. However, the
number of states you can support depends on your noise floor. In order
to get, say, 32768 bps over a 1 Hz channel, you would need a noise
margin of:

32768 = 1 log_2 (1 + S/N)

log_2(1+S/N) = 32768

1+S/N = 2^32768

S/N = 2^32768-1 ~ 2^32768

log_10 S/N ~ log(2)/log(10) * 32768 ~ 9864

log_10 S/N ~ 9864 B = 98640 dB

Even if you're only limited by quantum noise, this still requires a
trans-astronomical amount of power.

-hpa

[Green Xenon [Radium]]

Post by H. Peter Anvin

Post by Green Xenon [Radium]
So back to my question.
Wouldn't a baud of 1-symbol-per-second use only 1 Hz of bandwidth
regardless of the amount of bits-per-symbol?

Depends on the modulation scheme, but basically yes. However, the
number of states you can support depends on your noise floor. In order
to get, say, 32768 bps over a 1 Hz channel, you would need a noise
32768 = 1 log_2 (1 + S/N)
log_2(1+S/N) = 32768
1+S/N = 2^32768
S/N = 2^32768-1 ~ 2^32768
log_10 S/N ~ log(2)/log(10) * 32768 ~ 9864
log_10 S/N ~ 9864 B = 98640 dB
Even if you're only limited by quantum noise, this still requires a
trans-astronomical amount of power.

In the real world, what is the maximum amount of bits-per-symbol that
can be achieved using PSK without exceeding the dynamic range of a phone
line?

[DTC]

Post by Green Xenon [Radium]
In the real world, what is the maximum amount of bits-per-symbol that
can be achieved using PSK without exceeding the dynamic range of a phone
line?

Lets dispense with confusing references to bits, symbols, phase shift
keying, etc. and get down to the nitty gritty....

Answer: About 48 Kbps data rate.

[Green Xenon [Radium]]

Post by DTC

Post by Green Xenon [Radium]
In the real world, what is the maximum amount of bits-per-symbol that
can be achieved using PSK without exceeding the dynamic range of a
phone line?

Lets dispense with confusing references to bits, symbols, phase shift
keying, etc. and get down to the nitty gritty....
Answer: About 48 Kbps data rate.

I am specifically interested in the bits-per-symbol only. I wasn't
asking about the date rate -- i.e. the 48 Kbps you described. I am
asking only about the bits-per-baud.

Assuming a baud of only 1-symbol-per-second, what is the maximum amount
of bits-per-symbol that can be achieved using PSK without exceeding the
dynamic range of a phone line?

[R.L. Horn]

On Sat, 14 Jun 2008 12:32:44 -0700, Green Xenon [Radium]

Post by Green Xenon [Radium]
Assuming a baud of only 1-symbol-per-second, what is the maximum amount
of bits-per-symbol that can be achieved using PSK without exceeding the
dynamic range of a phone line?

I believe the maximum using any encoding should be in the neighborhood of 8
bits. That's assuming an SNR of around 24dB, which is...optimistic. In
practice, a fairly conservative figure of 20dB is often seen, which yields
6.66 (oooh, spooky) bits in 1 Hz of bandwidth (or 26.6kbps in 4kHz).

V.90 manages better than that, but it requires one end be connected directly
to a digital trunk.

[H. Peter Anvin]

Post by Green Xenon [Radium]
In the real world, what is the maximum amount of bits-per-symbol that
can be achieved using PSK without exceeding the dynamic range of a phone
line?

Well, given the fact that most telephone circuits are digitized to
64 kbps at the central office, that is an absolute maximum.

The copper lines themselves are obviously capable of much higher
capacity with a suitable change of equipment at the central office.
This is the technical basis for ISDN and DSL.

-hpa

[henry cabot henhouse III]

sorry, those of us who clone advanced life forms in our supersonic colonic
colliders don't like to talk about such things...ooops gotta run, the
Interociter is whizzing...

Post by Green Xenon [Radium]
My internet-access fantasy involves dial-up modem telecommunications
technology devices which use PSK [Phase Shift Keying] as the modulation
scheme. This too-good-to-be-true PSK uses only 1-symbol-per-second but
with a Graham's-number amount of bits-per-symbol.
http://en.wikipedia.org/wiki/Graham's_number
Now that is a lot of bits-per-baud!
If it were possible for such PSK to exist, what would be the disadvantages
of it?
Thanks,
Radium

[R.L. Horn]

On Wed, 28 May 2008 01:49:05 GMT, henry cabot henhouse III

ooops gotta run, the Interociter is whizzing...

Is that a quantum interociter or an n-field multiversal interociter? I've
noticed that the latter really kick up a racket when the neutron-flow
polarity gets out of whack.