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Standard User Elmlea
(regular) Sat 28-May-11 19:55:12
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Speed vs Attenuation/SNR


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Hello all,

I'm on Sky Unlimited; my first LLU; and was expecting at least a tiny increase in speed. We're about a mile from our exchange and were getting around a 2-3Mbit/s throughput with Vivaciti prior to changing over, and Sky's pie-in-the-sky guess was that we might see as much as 8Mbit/s when we changed to them.

Using Sky's provided Sagem router, I end up with a sync speed of 4660kbps. Downstream attenuation is 45.5dB, noise margin 6.2dB. Upstream is fine at 796kbps, 27.3dB attenuation and 14.2dB SNR.

With 45.5dB attenuation I'd expect a bit better than 4660kbps. I'm on a new filter, plugged into the master socket. There's an extension immediately after it to run the line to the Sky HD box, but removing that makes very little difference. Trying another router dropped me right back to 4000kbps, and with the occasional reset the best I've managed is just shy of 5000kbps.

The line appears normal when I make a phone call. Anyone got any idea if there's something awry here, or if there's something I should do? Would trying DLM again from scratch be likely to give me an improvement? I can live with 4660kbps as it's 50% faster than I had on non-LLU ADSL, but if I can squeeze more out I'd like to.

Thanks in advance!
Standard User Rockh
(eat-sleep-adslguide) Sat 28-May-11 20:05:20
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Re: Speed vs Attenuation/SNR


[re: Elmlea] [link to this post]
 
Have you tried the router in the test socket ??

Dave
Standard User Elmlea
(regular) Sat 28-May-11 20:06:24
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Re: Speed vs Attenuation/SNR


[re: Rockh] [link to this post]
 
Sure have; the faceplate's dangling off right now, the extension upstair's disconnected (although I've left the filter in it just in case) and the Sky box is unplugged too. It's just a filter in the test socket with the router and phone connected.


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Standard User mixt
(experienced) Sat 28-May-11 20:26:40
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Re: Speed vs Attenuation/SNR


[re: Elmlea] [link to this post]
 
Looks like that's all your gonna get from that line then (unfortunate).

You could request Sky to lower your target SNR to 3dB, and have interleaving switched on. You'll probably grab a bit more speed from the line. But if latency and instability isn't your friend, best to not do this.

And the above is assuming they could even honour this request, maybe they can't (or wont).

Now on <aaisp.net>
Previous ISPs: Virgin Media (50Mb/Cable), Be* Un Limited, ZeN
Is Linux routing your internet connection?
Need to make BIND geo-aware?

Edited by mixt (Sat 28-May-11 20:30:40)

Standard User tommy45
(fountain of knowledge) Sat 28-May-11 20:34:50
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Re: Speed vs Attenuation/SNR


[re: mixt] [link to this post]
 
In reply to a post by mixt:
Looks like that's all your gonna get from that line then (unfortunate).

You could request Sky to lower your target SNR to 3dB, and have interleaving switched on. You'll probably grab a bit more speed from the line. But if latency isn't your friend, best to not do this.

And the above is assuming they could even honour this request, maybe they can't (or wont).
Sorry to butt in, but i have to say that sky enables interleave by default, maybe if they disabled DLM then maybe a higher sync would be possible, as no doubt it will of effectively capped the max sync rate, as a result a lower snr will do little if anything to increase the sync
as for them changing the default profile of a (7-db margin interleaved ) is very doubtful they do what they call a gaming mode( reduce interleave delay level ) as they will not enable fastpath , which would be another way that you could of got a bit more out of your line

Edited by tommy45 (Sat 28-May-11 20:36:13)

Standard User BatBoy
(legend) Sat 28-May-11 20:38:24
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Re: Speed vs Attenuation/SNR


[re: Elmlea] [link to this post]
 
In reply to a post by Elmlea:
Hello all,

I'm on Sky Unlimited; my first LLU; and was expecting at least a tiny increase in speed. We're about a mile from our exchange and were getting around a 2-3Mbit/s throughput with Vivaciti prior to changing over, and Sky's pie-in-the-sky guess was that we might see as much as 8Mbit/s when we changed to them.

Using Sky's provided Sagem router, I end up with a sync speed of 4660kbps.
You start off on 4Mb with Sky. How long have you been with sky?



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Standard User Elmlea
(regular) Sat 28-May-11 21:07:03
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Re: Speed vs Attenuation/SNR


[re: BatBoy] [link to this post]
 
About 4-5 weeks, I think. Didn't realise it might be artificially capped?
Standard User BatBoy
(legend) Sat 28-May-11 21:10:03
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Re: Speed vs Attenuation/SNR


[re: Elmlea] [link to this post]
 
You start off on 4Mb and this should gradually raise over say, 10 days until a stable level is reached. You online account should say whether your line is still in training or not.

However, after 10 days you can ask Sky to put you on the Gaming profile which will uncap your line and lower your latency.



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Standard User Elmlea
(regular) Sat 28-May-11 21:11:36
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Re: Speed vs Attenuation/SNR


[re: BatBoy] [link to this post]
 
Ah, no, I'm past the 10 day training period. It started at just below 4, but only managed to crack 4976 or something, and since then has meaned between that and 4500 whenever a reset's been required or happened by accident.

Who do I speak to to get set on a gaming profile? What's that going to do for me?
Standard User Elmlea
(regular) Sat 28-May-11 21:18:32
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Re: Speed vs Attenuation/SNR


[re: Elmlea] [link to this post]
 
Just found a site that checks some stats for me; this is the output.

You are synced at 4,660 kbps. This sync will have a max throughput of about 0.47 MiB/s or 3,868 kbps.

Your expected max sync depends on many things, mostly the quality of the line and the target Signal to Noise margin at the time of sync.
Expected max syncs are:
3db Fastpath: 11,182
6db Fastpath or 3db Interleaved: 10,105
6db Interleaved: 8,257


You appear to be on the standard Signal to Noise margin and with set.
Your sync is 56% of the estimated maximum for a line with and standard SNR at your line length (3,295 meters).
As your sync is not above 81% of the estimated maximum you might wish to investigate a potential problem.

Signal to Noise

You appear to have a noise issue on the line as the upstream and downstream SN margins vary by too much:
1) that has caused the DSLAM to sync you at a higher SNR on the upstream.
2) there was noise on the downstream frequencies when you synced that has now lessened. This noise is likely to return.
3) there is noise on the upstream frequencies now that was not there when you synced.
4) there could be faulty equipment on the line.


Can someone help me interpret that? I'm not sure what it's getting at when it says the SNRs vary by too much, or what I can do to try and sort that.
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