Are these Line Quality stats OK?

[LukasD]

I switched to Vodafone Superfast 2 a couple of months ago.  The line has been ok, very few dropouts and decent download speed - upto 5.5MB per second.  I'm just wondering about the actual stats, SNR for example looks rather poor.

  Downstream Upstream

Current Rate	54999 kbps	5997 kbps
Maximum Rate	64442 kbps	9103 kbps
Signal-to-Noise Ratio	8.1 dB	8.5 dB
Attenuation	DS1 15.8 dB, DS2 41.4 dB, DS3 63.3 dB	US0 5.2 dB, US1 31.3 dB, US2 48.1 dB
Power	13.1 dBm	6.5 dBm
CRC Errors in last 24 minute(s)	0	95
K (number of bytes in DMT frame)	0	0
R (number of bytes in RS code word)	6	2
S (RS code word size in DMT frame)	0.0330	0.1693
D (interleaver depth)	16	1
Delay	0 ms	0 ms

[Jayach]

The SNR figures are a little high, which probably means DLM has found some problem and is trying to keep the line stable. By default it is usually about 6.3, but if the line is good DLM will drop it a bit to get more speed. (mine is currently 4.3 down which gives me a sync of just under 80)

Have you tried with it in the test socket?

What were you getting with your previous ISP?

[LukasD]

This is the same connection speed I was getting with BT (55GB), and is higher than the 35-40 they quoted.  I'm not noticing any problems, I was just curious about the stats.  I am pretty far from the cabinet and there has always been a hissing on the phone line.

I thought a higher SNR was meant to be better?

[Jayach]

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@LukasD wrote:

there has always been a hissing on the phone line.

That is not good, does it go away if you try the phone in the test socket without the router.

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@LukasD wrote:

I thought a higher SNR was meant to be better?

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It's better as the line will be more stable, but worse as the speed will be lower.

What do Openreach think your line capable of? BT Broadband (btwholesale.com)

[CrimsonLiar]

If you were much further than 600-900m from the cabinet the speeds would definitely be lower.

On the speeds, the SNRs listed are the margins.  If you have a noisy line then it needs a larger margin - a larger SNR leading to a lower speed.  On a good line you get a lower SNR margin, which means more of the capacity of the line can be used for your signal and hence a higher data rate.  So in this case a high SNR is bad and a good SNR is good.

*Anyone want to describe how distance affects the signal on a multi-tone VDSL2 signal?

[Jayach]

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@CrimsonLiar wrote:

*Anyone want to describe how distance affects the signal on a multi-tone VDSL2 signal?

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Definitely not me, I get really confused when the router gives multiple SNR's as well as multiple attenuations.

[CrimsonLiar]

So frankly, they are not brilliant, but whether VF will do anything about them probably depends on what you were promised speed wise!

Starting from the top:

The download SNR is high, which means that in normal circumstances you'd probably expect it to be lower, which would lead to a higher download speed.  However, the fact that you have an interleave depth of 16 suggests the line may be a little noisy.  On FTTC the closer you are to the cabinet the faster your connection should be, with the speeds you've reported I'd expect you to be about 600-900m (as the cable runs) from the cabinet.  If it's substantially less than that, then once again it might suggest problems!

Your upload SNR is also high, and the corresponding download rate is appalling in comparison to the download rate.  This is probably because the cabinet you are attached to doesn't appear to support interleaving - so when there are errors it leads to re-transmissions.  BUT 95 CRC errors on the upload in 24 minutes is not actually that high (probably because of the high SNR and low data/symbol rate).