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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.

what SNR/SNR Margin at 0.5Mbps for reliable operation at 1 Mbps



 
 
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  #1  
Old August 27th 04, 05:01 PM posted to uk.telecom.broadband
robert w hall
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Posts: 242
Default what SNR/SNR Margin at 0.5Mbps for reliable operation at 1 Mbps

OK, Now we've got the topic of what we mean by SNR and SNR margin well
staked out in its coffin...

Now to the question I really wanted to ask :-)

I have a 512kbps system working reliably at a downstream attenuation of
say 55 to 65 db.

What SNR/SNR Margin do I need to be seeing at 512kps to make it
worthwhile trying to upgrade to 1Mbps...? (see notes)

Bob

(Instruction to candidates
1) Credit will be given for clear, (or indeed any), reasoning
2) You should assume that the reliability required is that for normal
small business use (95/95 confidence limit??)
3) Do not write on both sides of the paper at once.)

--
robert w hall
  #2  
Old August 27th 04, 06:43 PM posted to uk.telecom.broadband
Kráftéé
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Posts: 126
Default what SNR/SNR Margin at 0.5Mbps for reliable operation at 1 Mbps

robert w hall wrote:
OK, Now we've got the topic of what we mean by SNR and SNR margin
well staked out in its coffin...

Now to the question I really wanted to ask :-)

I have a 512kbps system working reliably at a downstream
attenuation of say 55 to 65 db.

What SNR/SNR Margin do I need to be seeing at 512kps to make it
worthwhile trying to upgrade to 1Mbps...? (see notes)

Bob

(Instruction to candidates
1) Credit will be given for clear, (or indeed any), reasoning
2) You should assume that the reliability required is that for
normal small business use (95/95 confidence limit??)
3) Do not write on both sides of the paper at once.)


Well at 65db line loss you can't get it, simple as that...


  #3  
Old August 28th 04, 11:56 AM posted to uk.telecom.broadband
robert w hall
external usenet poster
 
Posts: 242
Default what SNR/SNR Margin at 0.5Mbps for reliable operation at 1 Mbps

In article ,
Kráftéé writes
robert w hall wrote:
OK, Now we've got the topic of what we mean by SNR and SNR margin
well staked out in its coffin...

Now to the question I really wanted to ask :-)

I have a 512kbps system working reliably at a downstream
attenuation of say 55 to 65 db.

What SNR/SNR Margin do I need to be seeing at 512kps to make it
worthwhile trying to upgrade to 1Mbps...? (see notes)

snip
Well at 65db line loss you can't get it, simple as that...


why? (or do you just mean 'won't')

I'd suspect the real limit is in SNR (*).
Bob

*I can think of a couple of hand-waving arguments, suggesting you could
need 6db of margin at 512, ie an SNR of about 12db; if so some of the
512kbps 60db setups I've seen quoted may be stretching it to get to
1Mbps.
But I am NOT SQEP in this area :-)



--
robert w hall
  #4  
Old August 28th 04, 10:27 PM posted to uk.telecom.broadband
P H
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Posts: 32
Default what SNR/SNR Margin at 0.5Mbps for reliable operation at 1 Mbps


"robert w hall" wrote in message
...
OK, Now we've got the topic of what we mean by SNR and SNR margin well
staked out in its coffin...

Now to the question I really wanted to ask :-)

I have a 512kbps system working reliably at a downstream attenuation of
say 55 to 65 db.

Only half meg is going "no limits" but for one meg the new limit will
be -60dB. -60.1dB or higher will not be provided. The new limit for two meg
is -43dB.
Your SNR figure needs to be as high as posible, anything under 12dB SNR
(approx) may have some problems. You should be able to improve SNR by
disconnecting old or poor extension wiring. Fitting of a SSFP or NTE2000 at
the BT master socket is the best way to raise the SNR figure. Look on the
Clarity.it website.

Phill.



  #5  
Old August 29th 04, 01:12 AM posted to uk.telecom.broadband
Nick
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Posts: 81
Default what SNR/SNR Margin at 0.5Mbps for reliable operation at 1 Mbps

P H wrote:
Only half meg is going "no limits" but for one meg the new limit will
be -60dB. -60.1dB or higher will not be provided. The new limit for
two meg is -43dB.

Phill.


Ahhh, another one with the 'Extended reach CD'

--
reply to news at nytoo dot co dot uk


  #6  
Old August 29th 04, 11:49 AM posted to uk.telecom.broadband
Nick
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Posts: 81
Default what SNR/SNR Margin at 0.5Mbps for reliable operation at 1 Mbps

Brian Morrison wrote:
On Sat, 28 Aug 2004 11:56:11 +0100, in article
robert w hall
wrote:

why? (or do you just mean 'won't')


Won't because even from 6th September BT's attenuation limits a

1Mbit 60dB


Correct

2Mbit 41dB


Wrong. It's going to be 43dB

--
reply to news at nytoo dot co dot uk


  #7  
Old August 29th 04, 02:46 PM posted to uk.telecom.broadband
robert w hall
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Posts: 242
Default what SNR/SNR Margin at 0.5Mbps for reliable operation at 1 Mbps

In article , P H
writes

Your SNR figure needs to be as high as posible, anything under 12dB SNR
(approx) may have some problems.


Ah - this is the sort of answer I'm after (and 12db confirms my
suspicions/prejudices) -- but

where does your estimate come from (MK trials, calculation, Ouija
board...)





--
robert w hall
  #8  
Old August 29th 04, 05:51 PM posted to uk.telecom.broadband
johnydeath
external usenet poster
 
Posts: 104
Default what SNR/SNR Margin at 0.5Mbps for reliable operation at 1 Mbps

robert w hall wrote:
In article , P H
writes

Your SNR figure needs to be as high as posible, anything under 12dB SNR
(approx) may have some problems.



Ah - this is the sort of answer I'm after (and 12db confirms my
suspicions/prejudices) -- but

where does your estimate come from (MK trials, calculation, Ouija
board...)







My sig/noise at 1/2Mb is quite happy at 5.5dB, line length of 6.5km,
with a downstream attn of 67dB. Its been 100% for best part of a year
using a good D-Link 504 router.

My old house was further with worse (expected) figures, but they still
gave me the service. Used to drop out in the winter nights though.

A few months ago both my figures were well outside what BT said was
technically possible. I'm pretty sure that 1Mb would be well pushing it
for me but its strange to see how the criteria changes over the months.



  #9  
Old August 29th 04, 10:04 PM posted to uk.telecom.broadband
Nick
external usenet poster
 
Posts: 81
Default what SNR/SNR Margin at 0.5Mbps for reliable operation at 1 Mbps

Brian Morrison wrote:
On Sun, 29 Aug 2004 11:49:00 +0100, in article
"Nick" wrote:

2Mbit 41dB


Wrong. It's going to be 43dB


I refer you to:

http://www.adslguide.org.uk/newsarchive.asp?item=1814


They're wrong.

that states that the attenuation limit for 2Mbps will remain at 41dB
for the time being.

But I believe that BT allow a margin of uncertainty on this in cases
where an actual measurement is deemed necessary.


The new figure is 43dB after all, it's on the training & software upgrade
CD for ADSL engineers, & as the software is used on our laptops for APtS
testing, it should be correct.



  #10  
Old August 30th 04, 12:27 AM posted to uk.telecom.broadband
Phil Thompson
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Posts: 2,720
Default what SNR/SNR Margin at 0.5Mbps for reliable operation at 1 Mbps

On Sun, 29 Aug 2004 22:04:32 +0100, "Nick"
wrote:

The new figure is 43dB


the press release didn't mention any change to 2 Mb, hence people
being under the impression it was going to remain at 41 dB.

Please to hear it isn't, I may just be eligible now.

Phil
--
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Come on down !
 




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