Option to set (lower) Downstream and Upstream sync via router web interface, to reduce line errors

Being able to lower the sync rate would be useful, as many VDSL lines are quite error prone, particularly if G.INP / packet retransmission hasn’t been enabled on the line by Openreach (which it won’t be for many lines now).

Lowering the Downstream / Upstream sync rate should allow the user to have an almost error free connection. I’ve found that if the router connection is left synced for many weeks / months, thousands of errors accluminate.

Below, you can see my line synced at 49.13mbps Downstream, 14.99 Upstream, and the errors generated within a few minutes of resyncing the line (on the DWA0120 Router + Modem).

I noticed that after the line Resynced from ~50mbps Downstream, to 49.13mbps Downstream, that the error rates reduced, and the line was able to download large files at a more consistent rate, without drops in speed.

@cbdeakin I would not think that a small drop in Sync rate [from 50 to 49.13] would make any difference to your errors. Sync rate will vary like that in both directions depending on interference on the line at the particular time the ‘handshake’ occurs. Very often (especially on longer lines), the sync rate will be lower at night after the sun has gone down.

If a connection errors heavily, it will do that on either a higher or lower SNR margin. The SNR is basically how much scope has the DSL signal got to hang on. In the olden days target margins were between 6gb and 15db, whereas now 3 is usually the target, or banding is applied in extreme cases. Imagine the SNR like this, 15db is a thick brick wall, 6db is a thin wood wall. If you hit the wall with a sledgehammer, which one is likely to break easier? The thin wood wall, hence why the lower the margin the less room the connection has to hold on. Both walls would experience the same weather (errors on a DSL circuit).

Giving customers the ability to alter SNR margins would not be a good thing in my opinion: 1) because most don’t care and 2) if people start playing with it then it will mess up Dynamic Line Management. Having said that, in a very limited number of circumstances, if service providers like Cuckoo were able to do it, in situations where DLM does not work properly, they could apply different settings to counteract unfavourable DSL conditions. I know I mention my Fritzbox far too much, but essentially I can do what you are stating in your post. I’m having to up the Impulse noise protection because DLM won’t put my line on either vectoring or retransmission.

Having said that, on balance, I would highly caution against what you are suggesting.

@gouledw - Thanks very much for the info! I like the idea of changing the INP on lines (at least, to improve stability). The FRITz!Box 7590 does seem to be quite expensive though, so it would be a costly experiment!

This has got me wondering now if in my case, whether requesting that the line SNR profile be set to 9DB would be sufficient to eliminate all / nearly all line errors.

EDIT - I just noticed that the Fritz router also has the ability to influence the ‘SNR ratio’, this would be a nice feature to have, to enhance FTTC line stability.

There’s tons of DSL / VDSL line settings that can be tweaked on many Asus routers, according to this page:

Including ‘Stability adjustment’ which allows users to increase the SNR Margin.

There’s also another feature called ‘Enhanced Sudden Noise Protection’

Get a hacked OR modem off fleabay with LEDE installed. I got one for £30 You can manually adjust your snr then to gain more synce speed with more errors or indeed the inverse. This will be the cheapest way without shelling out for an expensive modem/router combo. Whole idea is kinda pointless though, if the errors were making any difference DLM would adjust it anyway, seeing lots of errors is just the joy of a VDSL line, glad I’m off that rubbish now.

I bought an Asus DSL-N16 VDSL router / modem for £10 on Ebay, It seems like its worth trying, since it was so cheap. After I test it, I will let you know what difference (if any) changing the SNR Margin + other options makes to line quality and errors.

I suppose if I get bored, I could try setting the SNR to 4DB as a test, interestingly, my current router has synced at 3db once or twice before, and the max speed was higher, but the download rate was much less consistent. I suppose the problem with this, is that it will increase line errors and it’s likely to eventually lead BT’s DLM system to reduce download/upload rates of the line.

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I installed the Asus DSL-N16 last night and it’s working well. Impressed with all the details given for the VDSL2 modem, particularly the real-time SNR Margin for the different frequencies of the VDSL2 signal (so you can see if the SNR Margin is not running at a consistent rate).

There’s also some useful options to monitor bandwidth usage in realtime.

Main thing is, I can stop the router from repeatedly switching between SNR Margins of 3DB / 6DB, but fixing it at a set amount, for now I’ve got it running at 9DB, to reduce line errors.