Billion UK Forum

I recently bought a 7800N to replace another router which died. I am on Plus.Net with ADSL2+.

The old router used to run at about 2.6 Mbps, and at one point the 7800N was running at 3, but has slowed down over the past few days, and is now only reaching 1.7. Are there any good ways of finding the best configuration, or any recommendations on what the settings should be?

My status:
DSP Firmware Version A2pB025f.d22k
DMT Status No Defect
Operational Mode ADSL2+
Upstream 378
Downstream 1682
SNR Margin(Upstream) 6.9
SNR Margin(Downstream) 9.5
Line Attenuation(Upstream) 43.0
Line Attenuation(Downstream) 72.0

Any help or pointers most welcome.

On a long line like yours ADSL2+ is probably not the best mode to use.

You can configure the 7800N to only connect in G.Dmt mode which if your ISP supports this could help your speeds.

Currently your downstream noise margin is higher than one would expect as most ISPs work at 6dB, maybe a call to them might help.

According to Kitz's speed checker, you shouldn't be getting anything with that Downstream Atten but as it usually gives about a meg less than what you would normally get, then your 1.6~ would be about right.

As tinytim has suggested, setting the router to just G.Dmt is the best for longer lines but as you have been getting higher speeds it's possible Plus.Net's DLM could have knocked you back because of a high error count on the line - although that would only normally happen where there had been a number of frequent disconnects.

Have you been rebooting the router much to try and get a better sync ?

An ISP 6dB profile is quite low for that Attenuation and I would have expected the Downstream SNRM to have been somewhere about 12dB for stability.

I would normally get a disconnect before my speed would come back lower, but that would normally be due to some interference lowering my SNRM or a fault on the line but as your SNRM is showing a healthy 9.5dB then as tinytim has also suggested - a call to Plus.Net may also help.

While there may not be much improvement at the moment with school holidays, I find that occasionally switching off the router overnight gives me a better sync speed, depending on the time I switch it back on but that is mainly when the SNRM is staying low and when doing that, it seems to recover to a better level.

Just some suggestions.

Thanks both, I will give that a bash and see what the outcome is.

Hi there,

As others have alluded to, you're doing well to be getting ~2Mbps with a downstream attenuation of 72db. The downstream target SNR will typically default to 6db and BT Wholesale's DLM systems will increase this if they see the line erroring or consider it to be unstable. The target SNR is increased in increments of 3db and for each increment you can expect your headline sync speed to drop by ~800kbps.

I can reset your downstream SNR to try and squeeze a little more out of your sync speed, however it will be at the sacrifice of stability and there's no guarantee the DLM systems won't force it up again.

Best regards,

Hi Bob,
thanks for that. I have set the router to run in G.Dmt only, with SRA and PhyR enabled, and set tge SNR to 50, and it has been up connected for over 2 days without a problem, but still slower than it was.

DSP Firmware Version A2pB025f.d22k
DMT Status No Defect
Operational Mode G.DMT
Upstream 448
Downstream 2240
SNR Margin(Upstream) 13.0
SNR Margin(Downstream) 8.4
Line Attenuation(Upstream) 31.5
Line Attenuation(Downstream) 63.5

If there is anything I can do to squeeze another few % uplift that would be great.

You could enter the tweaking value of 25 which will drop your Target SNR down to about 4.5dB but I wouldn't go any lower than that.

Applying the value of 50 should have dropped the SNR down to about 6dB but your's is still showing as 8.4 and may be because of changing the mode to G.Dmt.

Put -1 back in to default the Target SNR to see what it has settled at on G.Dmt as a reference, unless you had checked that before tweaking.

Enabling PhyR as you have, may help to prevent the DLM from knocking you back

You could leave the SNR tweaking alone, set everything in that respect back to default levels and I could reset the target value to 6db? You'd need to PM me your account username in order for me to do that though.

Best regards,

Cheers Bob. I have reset the SNR to the default, and will PM you my force9 userid.

TIA,
Fer

Hi Bob,
did you get my PM, or did I manage to fugger that up too? I did send it, but it shows in my outbox, not my sent items, so who knows...