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uk.telecom.broadband (UK broadband) (uk.telecom.broadband) Discussion of broadband services, technology and equipment as provided in the UK. Discussions of specific services based on ADSL, cable modems or other broadband technology are also on-topic. Advertising is not allowed.

Line Attenuation etc - whats it supposed to be



 
 
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  #1  
Old December 28th 05, 12:58 PM posted to uk.telecom.broadband
paulfoel
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Posts: 21
Default Line Attenuation etc - whats it supposed to be

My router reports this but :-

What are the figures needed for the various speeds?

I'm getting 59.5 (near end?) and 31.5 (far end?)

  #2  
Old December 28th 05, 02:02 PM posted to uk.telecom.broadband
John
external usenet poster
 
Posts: 112
Default Line Attenuation etc - whats it supposed to be

In article .com,
paulfoel writes
My router reports this but :-

What are the figures needed for the various speeds?

I'm getting 59.5 (near end?) and 31.5 (far end?)


Your figures look almost the same as mine ...

Attenuation (dB) up/down = 31.5 / 60.0
Noise Margin (dB) up/down = 18.0 / 11.0

.... but you also need to look at the Noise Margin (Signal to Noise
Ration - SNR) down. As you can see mine is currently quoting 11.0 dB.

Assuming your SNR is around 18+dB, then you should be able to
synchronise at a 1Mbps line speed. Lower figures, down to 13dB, should
be OK as well. This doubling of line speed, assuming you are 512Kbps,
will mean you loose about 6dB, or so, from your Noise Margin.

As I understand, Noise Margins around 6+dB, or less, can give line drops
(synchronisation) problems. This is what I was getting, in great
quantities, last week.

I have now been connected for heading for 2 days, with no line drops.
However, I am still getting a considerable numbers of errors - see:-

Uptime = 1d 15:06
Errored Seconds (local/remote) = 53877 / 1095
Loss of link (remote) = 108

- I think this means that I am getting bursts of "near loss of
synchronisation" which my router copes with, and represents more than
1/3rd of the time I am connected (actually 38.4% of the time). Also,
there is correction for packet losses, meaning repeated requests for the
packet to be resent. This slows the file transfer speeds down. In my
case a single trial (need more than one) indicates the impact is to slow
my file transfer speeds down by about 18%.
--
John Clark
  #3  
Old December 28th 05, 02:33 PM posted to uk.telecom.broadband
Kraftee
external usenet poster
 
Posts: 422
Default Line Attenuation etc - whats it supposed to be

John wrote:
As I understand, Noise Margins around 6+dB, or less, can give line
drops (synchronisation) problems. This is what I was getting, in great
quantities, last week.

I have now been connected for heading for 2 days, with no line drops.
However, I am still getting a considerable numbers of errors - see:-

Uptime = 1d 15:06
Errored Seconds (local/remote) = 53877 / 1095
Loss of link (remote) = 108


Anything sub 10db can be problematic, in my experience in the field..


  #4  
Old December 28th 05, 03:55 PM posted to uk.telecom.broadband
John
external usenet poster
 
Posts: 112
Default Line Attenuation etc - whats it supposed to be

In article ,
Kraftee writes

Anything sub 10db can be problematic, in my experience in the field..


My current "good sync" period has recorded a Noise Margin of 7.5dB and
still run OK. The error second reports seems to be where the issue is
currently showing.
--
John Clark
  #5  
Old December 28th 05, 05:05 PM posted to uk.telecom.broadband
Mike News
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Posts: 3
Default Line Attenuation etc - whats it supposed to be

On Wed, 28 Dec 2005 at 14:55:01, John (John
) wrote:
In article ,
Kraftee writes

Anything sub 10db can be problematic, in my experience in the field..


My current "good sync" period has recorded a Noise Margin of 7.5dB and
still run OK. The error second reports seems to be where the issue is
currently showing.

So will this give me 8MB when our exchange is enabled. Presently on 2MB
running happily

Line Attenuation 30.5 db 15.0 db
Noise Margin 24.4 db 28.0 db
--
Mike
  #6  
Old December 28th 05, 08:05 PM posted to uk.telecom.broadband
Reg Edwards
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Posts: 168
Default Line Attenuation etc - whats it supposed to be


Line attenuation is expressed in terms of decibels per kilometre at a
particular frequency, e.g., at 1 MHz

No more and no less.

Anybody who refers to it in other terms doesn't understand whatever it
is he or she is waffling about and his/her reasoning powers are highly
suspect.

Do try to brush up on your technical education before contributing to
this newsgroup. Then we may get somwhere.

Attenuation, the loss in the transmission line between the
tele-exchange and computer, is decibels per kilometre at F MHz.

The first thing to understand is what is the decibel. Actually it is
one tenth of the Bell, a unit of electrical power measurement, named
after the Scotsman, Alexander Graham Bell, who invented the common or
garden telephone.

Where would we be without Bell? A person in the Victorian age who
endeavoured to make life acceptable for people afflicted from birth
with severe hearing and speech defects. We should be most grateful
to the Scots. I am just an English/Welsh-man.

But don't forget, line attenuation is measured in terms of decibels
per kilometre (or mile) at a particular frequency.
----
Reg Edwards.


  #7  
Old December 28th 05, 09:49 PM posted to uk.telecom.broadband
John
external usenet poster
 
Posts: 112
Default Line Attenuation etc - whats it supposed to be

In article , Reg
Edwards writes

Line attenuation is expressed in terms of decibels per kilometre at a
particular frequency, e.g., at 1 MHz
----
Reg Edwards.


Thank you Reg Edwards for returning us to the original meaning of
attenuation, or line attenuation. A point that needs to be expressed,
but ...

As you realise, whether punters know the real meaning of attenuation or
not, certain figures (expressed as Y dB) give the known limits at which
some broadband speeds (at the line frequency employed) will work or not.

It is that knowledge people are asking opinions about, and what line
speeds they might expect to be able to expect (given the figures they
inaccurately quote from their router/modem).

I realise this leads back in to the technical arguments and reasons of
why this happens. However, as knowledge and technical developments
advance the ability of POTS to run at faster broadband connection speeds
(subject to other factors related to synchronising) moves forwards.

An example was the 10+Km trials BT conducted over 2 years ago at Milton
Keynes, etc. This resulted in the 6th September 2004 announcement that
512Kbps ADSL could be extended beyond the, then, 5.5Km telephone line
length limit.

I agree this is for consistent and, as much as possible, fault tolerant
and maintenance free operation (for BT).
--
John Clark
  #8  
Old December 28th 05, 11:03 PM posted to uk.telecom.broadband
Phil Thompson
external usenet poster
 
Posts: 2,720
Default Line Attenuation etc - whats it supposed to be

On Wed, 28 Dec 2005 16:05:12 +0000, Mike News
wrote:

So will this give me 8MB when our exchange is enabled.


might just, anything you can do to improve the margin will help.

Phil
--
Tiscali - dialup speeds at Broadband prices, see
http://bbs.adslguide.org.uk/postlist...&Board=tiscali

AOL - the unlimited ISP of choice for heavy downloaders.
  #9  
Old December 28th 05, 11:36 PM posted to uk.telecom.broadband
paulfoel
external usenet poster
 
Posts: 21
Default Line Attenuation etc - whats it supposed to be


John wrote:

In article .com,
paulfoel writes
My router reports this but :-

What are the figures needed for the various speeds?

I'm getting 59.5 (near end?) and 31.5 (far end?)


Your figures look almost the same as mine ...

Attenuation (dB) up/down = 31.5 / 60.0
Noise Margin (dB) up/down = 18.0 / 11.0

... but you also need to look at the Noise Margin (Signal to Noise
Ration - SNR) down. As you can see mine is currently quoting 11.0 dB.

Assuming your SNR is around 18+dB, then you should be able to
synchronise at a 1Mbps line speed. Lower figures, down to 13dB, should
be OK as well. This doubling of line speed, assuming you are 512Kbps,
will mean you loose about 6dB, or so, from your Noise Margin.

As I understand, Noise Margins around 6+dB, or less, can give line drops
(synchronisation) problems. This is what I was getting, in great
quantities, last week.

I have now been connected for heading for 2 days, with no line drops.
However, I am still getting a considerable numbers of errors - see:-

Uptime = 1d 15:06
Errored Seconds (local/remote) = 53877 / 1095
Loss of link (remote) = 108

- I think this means that I am getting bursts of "near loss of
synchronisation" which my router copes with, and represents more than
1/3rd of the time I am connected (actually 38.4% of the time). Also,
there is correction for packet losses, meaning repeated requests for the
packet to be resent. This slows the file transfer speeds down. In my
case a single trial (need more than one) indicates the impact is to slow
my file transfer speeds down by about 18%.
--
John Clark


SNR is 15/20.

My current line speed is 512K but I'm still getting line sync drops
every 10 mins....

  #10  
Old December 29th 05, 12:07 AM posted to uk.telecom.broadband
Kraftee
external usenet poster
 
Posts: 422
Default Line Attenuation etc - whats it supposed to be

Phil Thompson wrote:
On Wed, 28 Dec 2005 16:05:12 +0000, Mike News
wrote:

So will this give me 8MB when our exchange is enabled.


might just, anything you can do to improve the margin will help.

Phil


I must disagree as a doubling of your speed will result in around 6dB
loss in your SNR & seeing as your SNR is apparently 15dB, 4Mb will take
it to 10dB (being optimistic) & a further doubling will take you to
4-5dB which will probably give you problems....


 




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