Odd noise spikes causing speed issues and disconnections

[Azzaka]

BT coming out on Saturday to do a 6 hour test/checks...3rd time lucky!   

The engineer has been tasked for specifics, hence the 6hrs. If this doesnt work... then i'll have to start slapping harder.

[duckson]

The engineer has been tasked for specifics, hence the 6hrs. If this doesnt work... then i'll have to start slapping harder.

Well  or it'll be time to BT's rear.

[duckson]

BTO been again this morning, he said it was only a 2 hour slot though and not a 6 hour.....seemed a bit more proactive this time and after the usual speed check and check with the Hawk (said line was bob on quality wise) he changed my ADSLNation faceplate filter for a BT faceplate filter (i'd tried 3 other filters as well with no change so doubted this would do anything) and fitted an RF3 filter where my exterior cable meets the interior (just a junction box previously). Said he was going to remake the connection at the Green Cab and check the soldered connection at the exchange and then i was to see how it goes....if it didnt fix it i'd have to log it with my ISP again.
Anyway i synced up at 8128kbps / 7db for a couple of hours before the inevitable spiking occured and took out the sync, must of reconnected when the noise was still occuring.



I also mentioned REIN and he said he was a REIN engineer and he didnt think it was REIN when he'd viewed some of my logs.
Back to the ISP then but what now? Guess they are going to have to start swapping D+E side cables or lift+shift at the exchange..... 
Here's to 4th time lucky eh? 

[duckson]

Just to keep this up to date, a Lift and Shift is being done tomorrow (Saturday) morning, will keep this updated on how things turn out.
The noise spikes have varied from having rampant noise spikes and 12 losses of sync within 48hrs to having just one noise spike in 24hours!

[duckson]

Well lift + shift has been done (eventually, almost had to explain that is what the booking was for...) and its to early to tell if the resyncs/noise spikes are gone. One thing that is good though is my noise margin has got better. When synced up at 8128kbps its gone from ~7.5db to ~9db after the lift and shift (attenuation is the same).

[jeffbb]

 

[duckson]

Well it did drop shortly after in 2 occasions but since then i've now noticed i'm on Fastpath instead of interleaved, also my nosie margin is back at around 7-7.5db under daylight hours. Would Fastpath reduce my noise margin over interleaved? The noise margin when it had reconnected on Fastpath is somewhat more spikey/varying quite alot compared to before the resync.

[jeffbb]

Hi
quote Would Fastpath reduce my noise margin over interleaved?

No Your noise margin is totally dependant on the actual signal to noise ratio. The Margin can be thought of as the amount of elbow room between the the data and the Actual SNR .
see SNR explanation 
Interleave is part of the error correction system.
Regards Jeff

[duckson]

Thought i'd update this.
After the Lift+shift was done on the 6th Feb it didnt improve things and i was still seeing resyncs and noise spikes (sudden drops in noise margin for 1-2 minutes), it is now being monitored by BT but they wont pass it to the CFI team (as yet anyway).
I think this is because funnily enough over the last week its been the best its been since the fault reared its ugly head in early December. I seem to have been put on a 12db noise margin profile and I've had quite a number of days/nights where there have been no noise spikes at all plus my SNR Margin has varied day to night by 1db max, previous to this it was varying up to 2db day-night.....last night was the best yet, it moved maybe 0.5db compared to the daytime figure!
Now i've been connected at 12db and even 15db when i've had a 6db profile, i assume this would just operate the same even with a 12db profile? If i am connected at a 12db or 15db noise margin there would be no difference in performance/how the line is seen by the exchange etc with having a 6db or 12db noise margin profile (or target maybe a better word)?

Anyway link to my latest routerstats graphs:- http://www.duckworth.myzen.co.uk/router/Netgear/Feb/

So i dont know if something has been tweaked somewhere other than my target SNR Margin or whats going on! 

[roseway]

The target noise margin is only used at the time of negotiating the connection. It isn't taken into account continuously through the life of the connection. But all sorts of things can vary according to signal conditions, so a 12 dB noise margin at two different times could be made up in quite different ways, depending on the bitloading.

But none of this explains the current absence of noise pulses. That's not the result of differences in the mode of connection, it's because something has changed so that the interference isn't there at the moment. If the noise pulses are caused by an intermittent line fault, then that intermittent fault is currently in remission, so to speak; and if it's electrical interference, then the source of that interference isn't active at the moment. My guess (no more than that) would be an intermittent line fault, mainly because I see very similar effects on my own connection.

[jeffbb]

Hi

quote: Now i've been connected at 12db and even 15db when i've had a 6db profile, i assume this would just operate the same even with a 12db profile? If i am connected at a 12db or 15db noise margin there would be no difference in performance/how the line is seen by the exchange etc with having a 6db or 12db noise margin profile (or target maybe a better word)?

Not too sure what you mean?

Remember increased Target SNR reduces  synch rate .
Something else to be aware of is that the spikes of -3db seen at 15db  could well equate to a loss of synch if the same noise was produced when the margin was say 10db.

It would seem that your target may have been dropped from 15db to 12db on the 23feb this increased your synch rate to 7040 from 5888Kbps .

Seems like there are less spikes . last one seems to be on 25th where a resynch was forced  dropping the Synch rate a little to 6848 from 7040Kbps.

Regards Jeff

[duckson]

Hi Jeff,

When it was on 15db i had a 9db profile, it dropped and reconnected but must of been experiencing the noise at the time and hence synced at the lower kbps meaning a higher noise margin when the noise went away.

[jeffbb]

Hi
quote When it was on 15db i had a 9db profile

Not too sure what you are trying to say ? 

When you connect to the exchange that is when your target SNR margin is applied as part of the negotiation between your router and the DLM. So if you Connect at X speed with say 14.8 db SNRM then its likely that your target is 15db.

If at the time you connect you may get a low synch speed because the noise on the line is high. As the line quietens down then the snrm will go up .resynching at that point will result in a conection with a similar SNRmargin of around 15db  but with an improved synch speed .


If at the time you connect the noise on the line is low then you will still connect with the SNR margin reflecting your target SNR say of 15db
with a connection speed of Y Kbps. If the noise increases you will see the snr margin go down . Resynching at that point  will synch using the same target SNRM (say 15db) but because the increased noise on the line  the synch speed will drop.

Regards Jeff

[duckson]

Yes Jeff, what you explain is exactly what i said (or meant if you didnt get me!). I synced at 9db with a lower speed cus the noise was high at the time, when the noise went away (i'm taking 30-60 seconds later) then the margin went up to 15db.

[jeffbb]

Hi
The last resynch 25thfeb shows about 12db snr margin !.
I might have missed it but I have not seen any sign of a 9db SNR margin at synch time rising to 12 or more .

BTW  webpages where you have your graphs are , is shown as unsatisfactory by WOT  (Web Of Trust)

Regards Jeff