Re: [tlug] FTTH ISP recommendation

[Edward Middleton <emiddleton@example.com>]

Curt Sampson wrote:
> On 2008-08-07 16:26 +0900 (Thu), Edward Middleton wrote:
>   
> > > As for the "SNR" stuff, well, err...I'm also not sure where even to
> > > start. You are aware that a piece of metal doesn't have a "bandwidth in Hertz", right? And that only communications channels, not wires, have a signal-to-noise ratio?
> > >       

> > Lets make it simple. A phone line is designed to support 3.1 kHz
> > bandwidth with an acceptable SNR.
> >     
>
> In a word, no.
>   

Perhaps a phone line was a poor choice of words.  We are obviously 
talking about the internal wiring from your phone outlet to the 
distribution box and frequencies from 400 Hz ~ 3.4 kHz.

From the ITU-T VDSL spec[1] it uses four bands from 138 kHz ~ 12 MHz.  
The ITU-T obviously believes it is possible to make a decent 100Mbit 
link over standard phone lines.  However the ITU-T specification is 
based on what they believe to be the conditions of most internal phone 
line wiring.  There are obviously conditions in which wiring could 
support standard phone lines but not support VDSL.

If you want to talk about upper limits with modulation this book is 
quite good[3].  I believe I have an earlier edition somewhere.

Edward

1. http://www.itu.int/rec/T-REC-G.993.1/en
2. http://bnoack.com/index.html?http&&&bnoack.com/data/cables/CAT5.html
3. 
http://books.google.com/books?id=Ga7PYE7E8kQC&pg=PA399&dq=nyquist-rate+define+bandwidth+symbols&as_brr=3&ei=O9dISLWfMpvQswO05eCICA&sig=C4mOrcE1NFKuWg3L-yOlCGJUEcU