models for simulating a dsl link
Bookmark this page:
 Yahoo!
 Google
 Windows Live
 del.icio.us
 digg
 Netscape
|
|
|||||||||||||||||||||||||||||||||||||||||||||||||
|
Posted by Eeyore on May 24, 2007, 8:24 pm
Please log in for more thread options A couple of recent threads about the effects of DSL (micro)filters gave me the idea of analysing their effect under various conditions in a simulation package. I've got several examples of filters of varying designs here and I'd really like to know how much difference and indeed what kind of differenc(es) they can make. As some know from previous threads I'm a bit sceptical about how much they affect the DSL signal itself. Before I can do this I need some suitable 'models' for the various bits of telecom gear involved. Can anyone point me in the right direction ? Graham | |||||||||||||||||||||||||||||||||||||||||||||||||
|
Posted by Paul Hovnanian P.E. on May 24, 2007, 9:55 pm
Please log in for more thread options Eeyore wrote: >
like
> I've got several examples of filters of varying designs here and I'd really > to know how much difference and indeed what kind of differenc(es) they can
make.
>
> As some know from previous threads I'm a bit sceptical about how much they > affect the DSL signal itself. > > Before I can do this I need some suitable 'models' for the various bits of > telecom gear involved. Can anyone point me in the right direction ? Unlike cable (DOCSIS) modems, DSL comes in many flavors with widely varying performance specifications. Take a look at the Wikipedia article for a start (http://en.wikipedia.org/wiki/DSL). I don't think there is an industry standard like there is for cable broadband. Each manufacturer has their own specs. As far as the DSL filters go, since they are intended to be placed on all of the other (non DSL) equipment on the shared line, their performance might also depend on the nature of the telephone equipment connected downstream of them. -- Paul Hovnanian mailto:Paul@Hovnanian.com ------------------------------------------------------------------ All men are mortal. Socrates was mortal. Therefore, all men are Socrates. -- Woody Allen | |||||||||||||||||||||||||||||||||||||||||||||||||
|
Posted by Eeyore on May 24, 2007, 10:06 pm
Please log in for more thread options
"Paul Hovnanian P.E." wrote: > Unlike cable (DOCSIS) modems, DSL comes in many flavors with widely
> varying performance specifications. Take a look at the Wikipedia article > for a start (http://en.wikipedia.org/wiki/DSL). I don't think there is > an industry standard like there is for cable broadband. Each > manufacturer has their own specs. That won't affect the basic physics though, which is all I want to model. > As far as the DSL filters go, since they are intended to be placed on
> all of the other (non DSL) equipment on the shared line, their > performance might also depend on the nature of the telephone equipment > connected downstream of them. That's exactly one of the things I'd like to experiment with. Graham | |||||||||||||||||||||||||||||||||||||||||||||||||
|
Posted by Rich Grise on May 25, 2007, 5:11 pm
Please log in for more thread options
On Fri, 25 May 2007 02:06:21 +0000, Eeyore wrote: > "Paul Hovnanian P.E." wrote:
> >> Unlike cable (DOCSIS) modems, DSL comes in many flavors with widely
>> varying performance specifications. Take a look at the Wikipedia article >> for a start (http://en.wikipedia.org/wiki/DSL). I don't think there is >> an industry standard like there is for cable broadband. Each >> manufacturer has their own specs. >
> That won't affect the basic physics though, which is all I want to model. > >> As far as the DSL filters go, since they are intended to be placed on
>> all of the other (non DSL) equipment on the shared line, their >> performance might also depend on the nature of the telephone equipment >> connected downstream of them. >
> That's exactly one of the things I'd like to experiment with. Find someone nearby with DSL, and ask them if they have a spare filter. My DSL provider gave me a handful of filters - just see if you can get somebody to give you one, and hack it and find out what's actually inside the thing. By Occam's razor, it's probably just an ordinary LC low-pass filter, probably balanced and impedance-matched to the line(s). Good Luck! Rich | |||||||||||||||||||||||||||||||||||||||||||||||||
|
Posted by on May 25, 2007, 7:11 pm
Please log in for more thread options
> > By Occam's razor, it's probably just an ordinary LC low-pass filter,
>
> See above. The third is stuffed full of bits. 3 x 2-section inductors, 5 caps, > and 2 Rs. > > > > probably balanced and impedance-matched to the line(s).
>
> Not so sure about impedance matched. What impedance is a phone anyway, never > mind 4 in parallel ( the max load for a line and a single filter is *supposed* > to cope ) ? Although it may be a pass through, what is shunted across the line is important. Like a recent post here, where sync only occured when the phone was lifted. What happens on the phone side will be reflected onto the ADSL side. > > probably balanced and impedance-matched to the line(s).
Tlelephone twisted pair has a characteristic impedence, for high spec cables the mfr usually quotes it, along with figures for NEXT and other line characteristics. You can do it the hard way and start from the dielectric constant of the insulation, the wire spacing (thickness of the insulation), and the wire diameter. Old timers will remember the Royal Core of Signals bible The Handbook of Line Transmission, and the various BT books. There are also test sets for measuring line parameters. You can measure anything, it's really a matter of determining what you need to measure, and how it relates to the real world. | |||||||||||||||||||||||||||||||||||||||||||||||||
| Similar Threads | Posted |
| models for simulating a dsl link | May 24, 2007, 8:24 pm |
| Efficient 5861 hardware models vs. firmware ? | January 4, 2006, 10:29 am |
| D-Link DSL-302G | July 18, 2004, 10:21 am |
| Link initialisation | December 6, 2005, 4:54 pm |
| d link dsl -300T | April 12, 2006, 2:33 pm |
| ADSL link OK but no IP address | August 9, 2005, 2:20 pm |
| Westel Link Light??? | October 4, 2005, 5:28 pm |
| Still can't access remote admin on D-Link DI-804 | July 12, 2004, 1:33 am |
| D-Link 704-UP Logs only Rejected Packets | August 23, 2004, 1:01 pm |
| SBC Yahoo DSL and D-link router problems | December 31, 2004, 11:55 am |
| D-Link Router - resets connection | January 1, 2005, 2:28 pm |
| D-Link DSL-300G+ Line quality | April 23, 2005, 10:40 am |
| Reporting a broken link to Verizon DSL, or trying to | December 28, 2005, 9:07 pm |
| D-Link 300T configuer problems | May 28, 2006, 3:19 pm |
| D-Link configuring problem not working with DSL modem | July 24, 2004, 9:30 am |
> A couple of recent threads about the effects of DSL (micro)filters gave me the
> idea of analysing their effect under various conditions in a simulation