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Distinguished Guru
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Message 31 of 50

Re: Noisy line and terrible upload speed

Note that there are two different common things mentioned related to noise margin. The (actual) SNR margin and the target SNR margin. In very simple terms they are as follows.

(actual) SNR margin:
This is what your stats is showing for the current connection. In normally starts at around 6 when the connection is synced. It will then fluctuate as conditions change. If it goes down below 6 then that's not so good. If it goes up above 6 then that's no problem.
However unless the margin drops to a pretty low level then the connection should stay up. That's the whole point of the margin, to cater for fluctuations in SNR while still maintaining a stable fixed speed connection.

target SNR margin:
This is what is used at sync time to determine the initial SNR margin. So this is nornally set to 6.
However if the line experiences regular problems (excessive errors and/or connection drops) the DLM will up the target SNR margin in steps of 3 (so 9, 12, 15, ...) to see if that bigger initial margin is enough to keep the connection up.
If a line problem has been fixed eventually the target SNR margin should drop back to 6.
Some connections on capped speeds on very good lines will have a target SNR margin set higher than 6 because ... well because it can without affecting connection speed , so why not!

So a fluctuating SNR margin around an initial target value is normal. Too big a drop can kill the connection though.
A target SNR margin set above 6 can indicate a line problem, though depends on the circumstances.

Note that on ADSL a target SNR margin may be set to 3 if the line is very stable.
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Distinguished Guru
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Message 32 of 50

Re: Noisy line and terrible upload speed


@umpire wrote:

Some connections on capped speeds on very good lines will have a target SNR margin set higher than 6 because ... well because it can without affecting connection speed , so why not!

A target SNR margin set above 6 can indicate a line problem, though depends on the circumstances.
 

 

I'm actually going to now question my own statement about good lines on capped speeds. Smiley Happy

 

I'm not sure whether the target SNR margin is increased from 6, or whether the modem just ignores the target at sync time and uses a higher initial (actual) SNR margin because of the spare line SNR capability. Maybe an expert on this can answer that?

Unfortunately I don't know of any way to view the up/down target SNR margins for a line directly. In my opinion it would be useful if the BT Wholesale speed test displayed this info.

 

 

Anyway putting all that to one side my main point was about the two different aspects of SNR margin, sync time target and actual.

If a SNR margin is currently 8 is that good or bad? If the initial sync time margin was 6 then 8 is not a problem at all. If the initial sync time margin was 9 then that is still not an immediate problem, but can indicate an on-going issue with the line performance where the DLM has taken action and inceased the sync time target.

 

Another simple analogy is that the sync time initial SNR margin is like a bank account overdraft limit. Using some of it up is not a problem as that's what it's there for. Keep going over the limit and eventually the bank manager will suggest you increase it by a fair step (and also look into sorting out the underlying money flow issues). Smiley LOL

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BeardyDave
Contributor
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Message 33 of 50

Re: Noisy line and terrible upload speed

Well, here we go again. My line is now failing for the third time in about 18 months!

 

I noticed my HH5 reboot a couple of weeks ago but everything seemed ok at first but since them I've had multiple reboots, my upload and download speeds have severely dropped and I've got lots of noise on my phone line. So all the same issues are back again. Yay. Man Mad

 

I've had an engineer out who's confirmed that some of the aluminium cable between my house and the cabinet has degraded and that I'll need switching onto another spare pair of wires if any are left in the loom. So at best I can expect my connection to be working again in a couple of days, only to then fail again in a few months when that pair degrades. Then I'll have to start all over again, and again until the crappy alu cable is finally exhausted. Then and only then will BT Openreach finally do what should have been done decades ago and replace the cable with a modern copper one. But they'll probably only do a short section, leaving some more alu cable to break later. What a lovely future I have to look forward to as a BT customer. Man Mad

 

I'm seriously sick of this **bleep**. I need all of the alu cable replacing now or I'm going to go insane. I've made a complaint to BT but the complaints team are useless. They gave me a contact number that doesn't work, sent a text message to me to a mobile number I don't own and don't reply to emails. So I've now made a new complaint to complain about the broken complaints process. Sigh.

 

The thought of becoming an off-grid spoon whittler is starting to look quite appealing right now.

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BeardyDave
Contributor
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Message 34 of 50

Re: Noisy line and terrible upload speed

So apparently my fault has been fixed and my connection speed should have returned to normal within 3 days but as usual that's not happened. I usually get around 50Mbps down and 5Mbps up with a ping latency of around 15ms. I'm now getting 27Mbps down, 0.7Mbps up with a ping latency of 45ms. Based on my HH5 stats it's clear to me that my line has got stuck at a reduced speed the same way it has the last two times I've had line failures.

 

So I'll repeat my belief that the automatic line profile system that's supposed to ensure you always get the best speed your line can support is broken. At least on my line. So for the third time I'm now battling with BT to get the profile on my line reset and for the third time they're doing everything they can to avoid doing this by stating that my line is working perfectly when clearly it's not.

 

I've just spent about half an hour watching a help desk operative turn my HH5 wi-fi on and off and keep re-running the BT speed test because he seemed to think that might help. Smiley Mad He had no idea what the help desk line stats in the HH5 meant and refused to acknowledge that there was anything wrong. Apparently because my download speed is usually about 24Mbps there's nothing wrong with my line and they won't send an engineer to reset my line. That's despite me paying £50 a month for Infinity 2!

 

I'm supposed to be getting a call back from a supervisor tomorrow so I'll see what pearls of wisdom they can come up with. If they won't do anything about the problem I'll be cancelling my contract and contacting the telecoms ombudsman.

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Distinguished Sage
Distinguished Sage
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Message 35 of 50

Re: Noisy line and terrible upload speed

As an aside and it might help, if you normally get 50Mbps you would be better to "downgrade" to Infinity 1.

 

The Infinity 1 package is now "up to 52Mbps" which obviously would cover your previous speeds. Apart from the package being cheaper I believe that it re-sets DLM when you take out the new package. It would however at present mean you taking out a further 12 month contract.

Distinguished Sage
369 Views
Message 36 of 50

Re: Noisy line and terrible upload speed

I don't think it initiates a full DLM reset. Line bandings appear to remain in place.
If you want to say thanks for a helpful answer,please click on the Ratings star on the left-hand side If the the reply answers your question then please mark as ’Mark as Accepted Solution’
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BeardyDave
Contributor
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Message 37 of 50

Re: Noisy line and terrible upload speed

Thanks, I was actually thinking about doing that just before my line failed again. The only thing that was holding me back was the thought of being tied into a BT contract for another 12 months of torture. Now after going through the same cr*p again for the third time I'm sick to death of putting up with BT's non-existant customer server. They are truely the worse company I've ever dealt with. I'm now looking at moving to Zen Internet as I don't want to give BT any more money.

 

Screw BT.

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Moderator
Moderator
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Message 38 of 50

Re: Noisy line and terrible upload speed

@BeardyDave I'm sorry about the problems you've had with your line. If you need any help with this please use the 'contact the mods' link in my forum profile to send in your details. You can find the link by clicking on my username .

Thanks

Neil

BeardyDave
Contributor
332 Views
Message 39 of 50

Re: Noisy line and terrible upload speed

Thanks Neil, I've just sent you the info.
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Sage
Sage
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Message 40 of 50

Re: Noisy line and terrible upload speed


@umpire wrote:

@umpire wrote:

Some connections on capped speeds on very good lines will have a target SNR margin set higher than 6 because ... well because it can without affecting connection speed , so why not!

A target SNR margin set above 6 can indicate a line problem, though depends on the circumstances.
 

 

I'm actually going to now question my own statement about good lines on capped speeds. Smiley Happy

 

I'm not sure whether the target SNR margin is increased from 6, or whether the modem just ignores the target at sync time and uses a higher initial (actual) SNR margin because of the spare line SNR capability. Maybe an expert on this can answer that?

Unfortunately I don't know of any way to view the up/down target SNR margins for a line directly. In my opinion it would be useful if the BT Wholesale speed test displayed this info.

 

 

Anyway putting all that to one side my main point was about the two different aspects of SNR margin, sync time target and actual.

If a SNR margin is currently 8 is that good or bad? If the initial sync time margin was 6 then 8 is not a problem at all. If the initial sync time margin was 9 then that is still not an immediate problem, but can indicate an on-going issue with the line performance where the DLM has taken action and inceased the sync time target.

 

Another simple analogy is that the sync time initial SNR margin is like a bank account overdraft limit. Using some of it up is not a problem as that's what it's there for. Keep going over the limit and eventually the bank manager will suggest you increase it by a fair step (and also look into sorting out the underlying money flow issues). Smiley LOL


If a line is capped at say 55Mbps but capable of say 100Mbps (it does happen) then the noise margin could be up to about 35dB purely because the line is so good and has plenty of "wiggle room". Noise margin and max line speed are interlinked so the 6dB target only comes into play when max and actual are close.

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