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RE: Is DSL really "broadband?" [7:79175] posted 11/14/2003
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This should help a little;

Analog is defined as a signal that has a continuously and smoothly varying
amplitude or frequency. Human speech, and everything else we hear, is in
analog form, and early telephone systems were analog as well. Analog signals
are often depicted as smooth sine waves, but voice and other signals are
more complex than that, since they contain many frequencies. The figure
below shows the typical distribution of energy in voice signals.

The figure below (No figure included) shows that the voice frequencies that
contribute to speech can extend from below 100 hertz to above 6000. However,
most of the energy necessary for intelligible speech is contained in a band
of frequencies between 200 and 4000.

In order to eliminate unwanted signals (noise) that could disturb
conversations or cause errors in control signals, the circuits that carry
the telephone signals are designed to pass only certain frequencies. The
ranges of frequencies that are passed are said to be in the pass band. Zero
to 4000 hertz is the pass band of a telephone system voice channel-a VF
channel. (Sometimes this band is called a message channel.) Bandwidth is the
difference between the upper limit and lower limit of the pass band; thus,
the bandwidth of the VF channel is 4000 hertz. However, the transmission of
speech does not require the entire VF channel. The voice pass band is
restricted to 300 to 3300 hertz. Hence, any signal carried on the telephone
circuit that is within the range of 300 to 3300 hertz is called an in-band
signal, and any signal that is not within the 300 to 3300 hertz bands, but
is within the VF channel, is called an out-of-band signal. All speech
signals are in-band signals. Some signaling transmissions are in-band and
some are out-of-band


An ADSL circuit connects an ADSL modem on each end of a twisted-pair
telephone line, creating three information channels -- a high speed
downstream channel, a medium speed duplex channel, depending on the
implementation of the ADSL architecture, and a POTS (Plain Old Telephone
Service) or an ISDN channel. The POTS/ISDN channel is split off from the
digital modem by filters, thus guaranteeing uninterrupted POTS/ISDN, even if
ADSL fails. The high speed channel ranges from 1.5 to 6.1 Mbps, while duplex
rates range from 16 to 832 kbps. Each channel can be submultiplexed to form
multiple, lower rate channels, depending on the system.

To create multiple channels, ADSL modems divide the available bandwidth of a
telephone line in one of two ways -- Frequency Division Multiplexing (FDM)
or Echo Cancellation. FDM assigns one band for upstream data and another
band for downstream data. The downstream path is then divided by time
division multiplexing into one or more high speed channels and one or more
low speed channels. The upstream path is also multiplexed into corresponding
low speed channels. Echo Cancellation assigns the upstream band to over-lap
the downstream, and separates the two by means of local echo cancellation, a
technique well know in V.32 and V.34 modems. With either technique, ADSL
splits off a 4 kHz region for POTS at the DC end of the band. 

And to learn more about DSL go to they have a good section
on learning about DSL

Scott Van Waterschoot
Verizon Communications
8000 Forbes Place
Springfield, VA 22151
703-816-5866 (O)
703-425-3040 (F)

-----Original Message-----
From: nobody@xxxxxxxxxxxxxx [mailto:nobody@xxxxxxxxxxxxxx] 
Sent: Thursday, November 13, 2003 10:33 PM
To: cisco@xxxxxxxxxxxxxx
Subject: RE: Is DSL really "broadband?" [7:79175]

Well, it's an old one (looks like 1999? -- it says things like 1.5Mbps costs
$900/month :), so honestly you would be better off with some recent white
paper (unless you want to laugh).

Let me know if you are still interested, and I'll see what I can do (got to
ask if it's public).



Steiven Poh wrote:
> Can I have a copy the Presentation Slide?
> Quoting Zsombor Papp :
> > I found a DSL presentation. Slide headline: "What is
> broadband?"
> > 
> > Answer on the slide: "Broadband = Megabit data rates"
> > 
> > I think that sums it up. :)
> > 
> > Jonathan V Hays wrote:
> > > technology that allows "splitter-less" DSL, which means
> they somehow
> > > manage to do all the necessary bandwidth splitting at the
> CO.
> > 
> > Yes, it's G.Lite, but it's not new and I don't think it has
> lots of
> > merrit.
> > First, installing that filter for the normal DSL line is not
> an issue,
> > second the G.Lite solutions didn't work all that great
> without the
> > filter
> > after all (if I remember correctly).
> > 
> > Thanks,
> > 
> > Zsombor
> > **Please support GroupStudy by purchasing from the GroupStudy
> Store:
> >
> > FAQ, list archives, and subscription info:
> >
> > 
> > 
> ----------------------------------------------------------------
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