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Noise margin drop

herojan
Grafter
Posts: 65
Thanks: 4
Registered: ‎15-08-2014

Noise margin drop

I have 40/2meg fibre. when i first signed up, many months ago I remember the maximum speed the router said I would connect at was 64meg,

 

a few weeks ago i noticed that had dropped to 54meg, and i think my noise margin had dropped to 10.x, with a line attenuation of 17.8

 

today the max rate the router says i would get is 48meg, and my noise margin has dropped to 8.9, but my line attenuation is still 17.8

 

my maximum upload speed seems to be unaffected. (just over 16meg)

 

of course I could be misremembering these numbers, but I do know that my max speed is defiantly going down as is my noise margin

 

I realise this is not currently impacting my speed, but at this rate it soon will.

 

my sync with the exchange (well the local cabinet I guess) is rock solid and stays up for months. I have a hub one

 

13 REPLIES
herojan
Grafter
Posts: 65
Thanks: 4
Registered: ‎15-08-2014

Re: Noise margin drop

more info:

 

i have an openreach mk2 faceplate. router is plugged into the appropriate socket. on the phone side i have the socket plugged into a call blocker and a phone. unpluggng the phone/blocker makes no difference.

 

sometimes I have occasional  intermittent noise on the line, but this seems to make no difference.

 

every time i try to run the phone line checker it comes back with "ooops something went wrong" (I tried it weeks ago and again today), and i really dont want to spend 45 minutes in a queue, when the online system should be working.

 

router info:

 

1. Product name: Plusnet Hub
2. Serial number:  
3. Firmware version: Software version 4.7.5.1.83.8.226 Last updated 30/09/16
4. Board version: Plusnet Hub One
5. DSL uptime: 32 days, 21:36:02
6. Data rate: 1999 / 39950
7. Maximum data rate: 16304 / 48534
8. Noise margin: 20.0 / 8.8
9. Line attenuation: 24.4 / 17.8
10. Signal attenuation: 27.9 / 17.8
11. Data sent/received:  
12. Broadband username:  
13. 2.4 GHz Wireless network/SSID:  
14. 2.4 GHz Wireless connections: Enabled (802.11 b/g/n (up to 300 Mb/s))
15. 2.4 GHz Wireless security: WPA2
16. 2.4 GHz Wireless channel: 11
   
18. 5 GHz Wireless connections: Enabled (802.11 a/n/ac (up to 1300 Mb/s))
19. 5 GHz Wireless security: WPA2
20. 5 GHz Wireless channel: Automatic (Smart Wireless)
21. Firewall: Default
22. MAC Address:  
23. Modulation: G.993.2 Annex B
24. Software variant: AA
25. Boot loader: 1.0.0

 

 

Community Gaffer
Community Gaffer
Posts: 17,667
Thanks: 659
Fixes: 163
Registered: ‎05-04-2007

Re: Noise margin drop

Hi there,

As you've pointed out, this isn't impacting your broadband speeds yet so we can't report a fault for that service,

 

However the intermittent noise on the line is something we can look at. I've just tested your phone line and it's not found a fault (that doesn't necessarily mean there isn't one), so the next step for the noise would be an engineers visit.

 

I'll create a support ticket on your account and get this emailed to you with the info we need to proceed, you'll be able to update this at https://portal.plus.net/wizard/?p=search

If this post resolved your issue please click the 'This fixed my problem' button
 Chris Parr
 Plusnet Staff
herojan
Grafter
Posts: 65
Thanks: 4
Registered: ‎15-08-2014

Re: Noise margin drop

hi

 

thanks for your help, I have responded to the ticket.

 

Here are my line stats for today:

6. Data rate: 1999 / 39950
7. Maximum data rate: 16360 / 46538
8. Noise margin: 20.0 / 8.2
9. Line attenuation: 24.4 / 17.8
10. Signal attenuation: 27.9 / 17.8

 

 

As you can see the noise margin for the download has dropped even more ( and hence the max rate), but the upload is unaffected, as it the line attenuation and signal attenuation.

 

 

At this rate it'll only be a week or so before my service is impacted.

 

 

Does anybody have any idea what this could be, it is quite specific in its behaviour?

 

 

herojan
Grafter
Posts: 65
Thanks: 4
Registered: ‎15-08-2014

Re: Noise margin drop

ok this is odd.

 

I've just rebooted the Hub One and things have gone back to normal

6. Data rate: 1999 / 39950
7. Maximum data rate: 16341 / 65428
8. Noise margin: 19.5 / 13.5
9. Line attenuation: 24.0 / 18.1
10. Signal attenuation: 25.2 / 18.1

 

Could this be the hub one misreporting, it only started in the last few weeks, following on from the latest firmware update?

I shall monitor this over the next few days.

 

 

 

 

herojan
Grafter
Posts: 65
Thanks: 4
Registered: ‎15-08-2014

Re: Noise margin drop & disconnect

The engineer came on wednesday to look at the voice fault, found a wiring fault and did some work on the wiring to fix it.

Haven't had any crackling on the line since.

However, there is still the variation on download noise margin, and there have been 4 disconnections since, which is unusual as the broadband normally stays connected for weeks.

Could somebody take a look please
Community Veteran
Posts: 5,177
Thanks: 482
Fixes: 20
Registered: ‎10-06-2010

Re: Noise margin drop & disconnect

The decreasing noise margin over many months, and the corresponding decrease in the max attainable rate, sounds quite normal. It's probably due to crosstalk. Crosstalk is the signals in neighbouring telephone lines interfering with each other (the signal in one line is noise to another). As more people on your cabinet sign up to FTTC, crosstalk increases, and so speeds decrease.

If someone else switches off their modem, the crosstalk will decrease temporarily, but when they switch it back on, the crosstalk will increase again.

Vectoring is technology that cancels the crosstalk, but it's not widely used, and there's no way of determining if it's in use on your cabinet from the stats provided by the Hub One.

There's not really anything to guarantee that your speed will never decrease, regardless of what it might have been in the past.

herojan
Grafter
Posts: 65
Thanks: 4
Registered: ‎15-08-2014

Re: Noise margin drop & disconnect

Thanks for your post, I had wondered about crosstalk.

This only seems to be in the last few weeks.
For example before one of my disconnects today the max rate was 61, once reconnected it was 58. Would this be consistent with crosstalk?

Community Veteran
Posts: 5,177
Thanks: 482
Fixes: 20
Registered: ‎10-06-2010

Re: Noise margin drop & disconnect

Yes, but what's not consistent with crosstalk is the sudden increase in the noise margin and max attainable rate. It's very unlikely that lots of other people all switched off their modems, cancelled their service, or their lines got disconnected due to some fault.

herojan
Grafter
Posts: 65
Thanks: 4
Registered: ‎15-08-2014

Re: Noise margin drop & disconnect

so something sounds a bit odd then.

 

can crosstalk really bring a line down from 64meg to 48 meg?

Community Veteran
Posts: 5,177
Thanks: 482
Fixes: 20
Registered: ‎10-06-2010

Re: Noise margin drop & disconnect

Yes, it's most noticeable for people who were among the first on their cabinet to sign up for FTTC, and then over months or years people lose typically 10 or 20 or 30 Mbps in total, perhaps depending on how many people sign up on that cabinet. Exactly how much one line affects another can be a bit random, depending on how close together the lines are within the large cables that contain maybe 50 lines. One line might not have much impact, but another line might knock off a few Mb.

I don't know what might have caused your max attainable rate to increase, I suppose it's possible some work might have been done at your cabinet, which, possibly by chance, improved things for you.

You need to buy a modem/router that works with a program like DSLstats if you really want to monitor what's happening to your connection.

herojan
Grafter
Posts: 65
Thanks: 4
Registered: ‎15-08-2014

Re: Noise margin drop & disconnect

thanks for your help.

 

i'll guess i'll have to chase plusnet to get openreach to have another go at sorting out the crackling, and fix the disconnections that are still happening since their last visit (which keeps dumping me onto the bng1 gateway which has speed all over the place)  :-( 

my stats today (from a max speed of 61meg a few days ago)

 

7. Maximum data rate: 16079 / 55690
8. Noise margin: 19.8 / 10.7
9. Line attenuation: 24.1 / 18.1
10. Signal attenuation:

25.5 / 18.1

 

when i got home about an hour ago the max speed was 50M, so it's gone up a bit.

 

i wish i'd left well alone, i'd still have the crackling and noise margin, but at least I wouldn't have the disconnections.

 

herojan
Grafter
Posts: 65
Thanks: 4
Registered: ‎15-08-2014

Re: Noise margin drop & disconnect

So, over the last few months things have got a lot worse, noise margin dropping to 7, and then I looked today:

6. Data rate: 1999 / 39950
7. Maximum data rate: 15731 / 38727
8. Noise margin: 20.3 / 5.3
9. Line attenuation: 24.6 / 18.1
10. Signal attenuation: 16.7 / 18.1

 

How can the noise margin drop, but not the line attenuation?

 

 

 

Browni
Aspiring Hero
Posts: 2,291
Thanks: 787
Fixes: 46
Registered: ‎02-03-2016

Re: Noise margin drop & disconnect

The line attenuation reflects the physical length of the line which shouldn't in theory change! The other figures are dependant on the noise levels on the line.
I must have been really bad in a previous life as this was my 3rd ISP in a row that used lithium.
Now you're stuck with me because my new ISP doesn't run a forum Cheesy