>
>
> | By Shannon's law(?), a local caller (one A->D conversion) actually can
> | push at most 28K through the pipe (1/2 the sampling rate). Slightly higher
> | rates can be achieved if the analog device matches the sampling rate at
> | the Central Office.
>
> close....
>
> it's Nyquist's law that says that a signal bandlimited to B
> requires a sampling rate of 2B.
> our sampling rate is 8kHz. ergo, our signal is limited to (a
> theoretical maximum of) 4kHz.
>
> Shannon's law tells us that the Capacity of our channel
> (in bits/sec) is
> C = B*log2(1 + SNR)
>
> where our noise is (mostly) due to quantization (to 8 bits)
Yep, from reading the white paper it says since they are trying to
sneak a digital (not analog) signal onto the copper pair that the
above laws don't apply. They are assuming that most analog phone
lines are converted to digital immediately. They have one caveat
and its a BIG ONE, that there can be NO A/D D/A conversions between
the initial conversion to digital and the modem at the other end.
Ie, if there are any analog circuits in your C/O or your provider is
not using directly connected PRIs/digital modems, you are out of luck.
And ADSL is limited to 2 miles from the C/O.
Doesn't look like there is (yet) a 100% feasible way to get more
out of standard POTS lines for everybody.
*******************************************************************
Stephen Zedalis Exis Net Inc.
System Administrator Hampton Roads' Premier Internet Provider
tintype@Exis.Net Web Page: http://www.Exis.Net
Email: support@Exis.net
*******************************************************************