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Standard User matthewcl375
(regular) Sun 03-Feb-13 01:25:22
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Re: Slow internet/low IP profile/high noise margin on Tesco


[re: RobertoS] [link to this post]
 
Ah, looks like a DLM job then, since the BT guy found the cause of the fault instantly when he got here smile

When I last synced, I got 15.6Kbps, it's now nearly 2AM and I'm up to 16.6, but from what I've read from the site I linked to above, it says this is a good thing, as it shows that my SNR has improved (gone up) since I have been connected, which shows I could get higher speeds if it wasn't for the SNR margin, does that sound right?

Also if the DLM notices an upward variation in the noise margin this would not affect how it calculates the target in a negative way I hope?

Sorry, another thing. On the robertos website it says that the stats on the router for SNR Margin are just showing how things have changed since a sync was last made. Does this mean that the SNR Margin stats on the router are not actually showing the current SNR Margin?

Edited by matthewcl375 (Sun 03-Feb-13 01:39:25)

Standard User XRaySpeX
(eat-sleep-adslguide) Sun 03-Feb-13 01:44:09
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Re: Slow internet/low IP profile/high noise margin on Tesco


[re: matthewcl375] [link to this post]
 
In reply to a post by matthewcl375:
When I last synced, I got 15.6Kbps
You talking about NM? It's measured in dB.

The router stats are the current instantaneous stats.

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 19 Meg WBC
Standard User matthewcl375
(regular) Sun 03-Feb-13 01:53:19
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Re: Slow internet/low IP profile/high noise margin on Tesco


[re: XRaySpeX] [link to this post]
 
Lol sorry it's late here :/ yes I did mean db, I'm struggling to see how an increased noise margin can have a positive effect on my sync rate if I rebooted.

I can understand how a higher SNR is better but surely a higher SNR Margin just means that the router is basing my sync speed on my connection SNR minus 16.6db, which can only be worse than if the SNR Margin was lower, say 15db crazy

BTW this is what I have gathered from the robertos website, so please correct me if I'm wrong tongue


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Standard User XRaySpeX
(eat-sleep-adslguide) Sun 03-Feb-13 02:13:36
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Re: Slow Internet/low IP profile/high noise margin on Tesco


[re: matthewcl375] [link to this post]
 
Remember, the Noise Margin is just a buffer against the noise rising.
In reply to a post by matthewcl375:
surely a higher SNR Margin just means that the router is basing my sync speed on my connection SNR minus 16.6db
No, your current sync speed was set "once-and-for-all" whenever you last re-synced with exchange in line with your Target NM of 15 dB (we assume); it is not set continuously.

So at the moment when you took those stats, you had a further 1.6 dB NM "to spare" whilst your sync speed is still the value chosen when the Target NM was 15 dB. So chances are that if you were to re-sync at that moment it would choose a higher sync speed when it reduces the NM, by 1.6 dB to the Target of 15db.

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 19 Meg WBC
Standard User matthewcl375
(regular) Sun 03-Feb-13 03:04:20
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Re: Slow Internet/low IP profile/high noise margin on Tesco


[re: XRaySpeX] [link to this post]
 
That makes sense, when I last resynced I got 15.6db is it normal for the router to give 0.6db more than the target?

Also how would rebooting at 16.6db give any higher sync speed? Surely it's still going to reboot with the target SNR 15db, the same as it did before?

Edited by matthewcl375 (Sun 03-Feb-13 03:07:33)

Standard User David_W
(experienced) Sun 03-Feb-13 03:30:45
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Re: Slow Internet/low IP profile/high noise margin on Tesco


[re: matthewcl375] [link to this post]
 
If the router syncs to a target noise margin of 15dB and the noise margin increases by 1dB, your noise margin is 16dB.

If the router syncs to a target noise margin of 15dB and the noise margin worsens by 1dB, your noise margin is 14dB.


Noise margin can be thought of as wasted sync speed - though you need some noise margin to keep the line from falling over or suffering from excessive errors. Because you had a line fault, your target noise margin has been jacked up to 15dB - a stable line will happily cope with a target noise margin of 6dB, which means you're wasting 9dB if your line is now stable.

The target is applied instantaneously at resynchronisation, so resynchronising when the noise margin is typically at its maximum will use a little more of the potential noise margin as sync speed. If you think of the typical noise margin as a graph against time, you're taking the figure at that point and defining it as the target, sliding the entire plot hopefully towards the x-axis (as you expect the fluctuations to be mainly downwards). Remember - on the same DSL line, the lower the noise margin, the higher the achievable sync speed.

Standard User XRaySpeX
(eat-sleep-adslguide) Sun 03-Feb-13 05:44:22
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Re: Slow Internet/low IP profile/high noise margin on Tesco


[re: matthewcl375] [link to this post]
 
In reply to a post by matthewcl375:
is it normal for the router to give 0.6db more than the target?
It's normal for the NM to fluctuate due to noise variation. With a steady signal, as the noise increases or decreases the NM correspondingly decreases or increases.

When you re-sync, the current NM is ancient history, but the decreased noise that gave rise to the increase in NM is probably still present for the short period it takes to reboot and with less noise it should be able to re-sync faster at the 15 dB Target NM.

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 19 Meg WBC
Standard User 4M2
(fountain of knowledge) Sun 03-Feb-13 14:37:43
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Re: Slow Internet/low IP profile/high noise margin on Tesco


[re: matthewcl375] [link to this post]
 
These small fluctuations in SNRM that you are seeing are pretty insignificant - essentially your connection is grossly under performing - even with a downstream ADSL MAX attenuation of 35dB and 12dB SNRM I was syncing at 8064Kbps with an IP of 7000Kbps.

Are you sure that your downstream attenuation is actually 6dB?
Standard User matthewcl375
(regular) Sun 03-Feb-13 17:13:40
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Re: Slow Internet/low IP profile/high noise margin on Tesco


[re: XRaySpeX] [link to this post]
 
@David_W that's really confusing, because people are saying reboot when the SNRM is highest as this shows less noise on the line, but you say "remember - on the same DSL line, the lower the noise margin, the higher the achievable sync speed. "
Surely if the SNRM is higher then it will give faster sync speed as there is less noise? And conversely, the lower it is, the more noise is being detected on the line, which would result in a lower sync speed?

@XRaySpeX so what role does the target SNRM play here? Let's say my SNRM fell to 14.4db and I rebooted the router. The router would still reboot at 15+db, in line with the target noise margin right?

and @4M2 yes my attenuation is 6db, we are a street away from the exchange, the problem is due to a fault that we had about a week ago with noise on the line
Standard User 4M2
(fountain of knowledge) Sun 03-Feb-13 17:35:43
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Re: Slow Internet/low IP profile/high noise margin on Tesco


[re: matthewcl375] [link to this post]
 
In reply to a post by matthewcl375:
and @4M2 yes my attenuation is 6db, we are a street away from the exchange, the problem is due to a fault that we had about a week ago with noise on the line


Would it be possible to try a different router and perhaps confirm the downstream attenuation if there is no change to your downstream SNRM and sync speed after several more days?
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