Topic: Long Line Noise Problem (Read 8785 times)

waltergmw · « **Reply #15 on:** April 16, 2009, 04:20:04 PM »

Thanks very much Kitz.

As you've gathered I'm just getting used to 2wire. The confusion came as I was using
http://192.168.1.254/xslt?PAGE=B01&THISPAGE=B03&NEXTPAGE=B01
which provides the normal line stats and modem parameter set up, but doesn't provide a link
to access the MDC from your in-home or office network by entering the following URL:
http://gateway.2wire.net/management

Kind regards,
Walter

kitz · « **Reply #16 on:** April 16, 2009, 06:54:47 PM »

yw

Glad you found it

waltergmw · « **Reply #17 on:** April 18, 2009, 09:24:12 AM »

Hi Kitz et al,

Here are the fruits of my investigations.
It's VERY frustrating that the modem usually syncs on the bottom rung of the 750 kbps bRAS and so can all too easily drop back to 500 kbps.

Kind regards,
Walter

http://www.scribd.com/doc/14356872/James-Line-Data

kitz · « **Reply #18 on:** April 18, 2009, 10:21:56 AM »

Is the PIR the conclusive culprit? - they are a known source of problems such as this.

Options are either to get the PIR checked out - or because the line does frequently dip into the 500 profile range trying a max capped profile 500 which will limit the line continually to 512kb, but at least save a lot of messing around with SNRMs & resyncs & new profiles etc.

waltergmw · « **Reply #19 on:** April 18, 2009, 10:39:48 AM »

Hi Kitz,

Many thanks for your thoughts.
I do occasionally cluck on about dI/dt but it leaves many people cold.

I have no absolute proof yet, but a very strong suspicion, as the cross talk was often worse in the very early morning in an area otherwise all asleep at that time.
The proof we have is that by shortening the next door's twin BT overhead line, which had been brought down by building operations and was left in a heap on the ground, the noise spikes decreased dramatically.

Within a few weeks new lines are to be installed in the adjacent house and I will do my utmost to get BT to re-route the dropwire away from the noise source cables.
If that fails perhaps we'll have to do as you say but only as a last resort. The user is an avid downloader and the difference between a bRAS of 500 and 750 is of great importance for him.

Kind regards,
Walter

kitz · « **Reply #20 on:** April 18, 2009, 11:12:41 AM »

I wouldnt have thought cross-talk would be causing the problems such as with that graph.. thats more EMI.

I have mentioned over the past few weeks or so that I have a problem with my own line whereby its gradually lost 1-2Mb of speed over the past year.
I cant find any source of REIN/EMI, but I am beginning to suspect crosstalk from other lines.

Look at the graph below and you'll notice that theres no single area where theres a problem - just a general decline over the frequencies probably in the range where users would normally get 6-10 Mb. Then look at how it increases again after tone 255 in the adsl 2+ higher speeds and Im getting practically fully bit loading. When you look at my SNR in this range its practically as good as it is at the lower frequencies.
Then you later get the 'normal bit loading decline' I'd expect to see just through general loop loss that cant be avoided.

NExT gets worse the more users that are on a dslam.. therefore I strongly suspect that as the MSAN has got busier and more users using tones 96 - 255, this is what has impacted on my own line.

As you can see atm Im only just hanging on in there at 22834 with an SNRM of 1.5dB - which has stayed pretty constant like that all through the school holiday easter break. I reckon if I resync'd now I'd only get about 21 to 21.2 Mb.

When the MSAN was new I could get just shy of 24Mb. The decline on this line is generally in those frequencies used across the adsl1 range and I include this graph to give you an idea of what I suspect is general loss of speed due to Near End Crosstalk looks like.

------
should mention that because Im on Annex_M then my tone allocation will be slightly different to 'normal adsl' ie the pilot tone and upstream tones are at different frequencies - but you should get the idea.

[attachment deleted by admin]

waltergmw · « **Reply #21 on:** April 18, 2009, 12:20:48 PM »

@ Kitz

Aren't you LUCKY to be getting those sorts of speeds compared to us wretcheds out in the sticks!

The reason I'd suggested cross talk in this case is that the two, currently dormant and left floating without master sockets, "bad lines" that we've cut back were in the same cable from the road pit as our two lines and that by doing a little pruning our performance has improved substantially. The four pairs in this cable are the only ones connected, but I've no idea how many more are live in the road joint.
When I had my Netgear DG834V4 modem on the line we achieved sync speeds of 352 kbps at 00:45 after a "foxy" noise spike, 704 kbps after the surgery the following day and 864 kbps when I swopped to the 2Wire.

I do realise we're actually doing very well on this line as the downstream attenuation @ 300 kHz is 82.7 dB and DMT gave an estimated line length between 6907 m and 8955 m.

Kind regards,
Walter

roseway · « **Reply #22 on:** April 18, 2009, 12:55:58 PM »

>> downstream attenuation @ 300 kHz is 82.7 dB

Ouch!

jeffbb · « **Reply #23 on:** April 18, 2009, 07:28:40 PM »

Kitz has lost more synch speed than my average download speed

kitz · « **Reply #24 on:** April 19, 2009, 11:57:08 PM »

>> ren't you LUCKY to be getting those sorts of speeds compared to us wretcheds out in the sticks!

Yep I know - thats why I feel so rotten moaning when Ive lost a few Mbps. I could just imagine calling out an engineer saying my sync speeds have dropped on average 2Mb since last year. Theyd probably laugh their socks off. But something has happened to my line which I cant put a finger on. If it was a longer line then someone would be moaning like hell because they'd lost that much speed.
I have a feeling though that because my bitloading was previously so good, then each dB of SNR lost is going to have previously been able to carry more bits, therefore the drop in speed is far more drastic than on a longer line which is isnt going to be able to carry as many bits per tone.

>> the downstream attenuation @ 300 kHz is 82.7 dB

OMG! Thats certainly over 5/6km - Its lucky to get sync - nvm 864

waltergmw · « **Reply #25 on:** April 26, 2009, 09:04:36 PM »

kitz · « **Reply #26 on:** April 27, 2009, 11:37:28 AM »

I must admit I haven't looked at all of them walter, but those I did look at seemed nice and stable. The blip on Friday seemed short-lived so they should be able to cope.
For such a long line its doing very well

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Author Topic: Long Line Noise Problem (Read 8785 times)

waltergmw

Re: Long Line Noise Problem

kitz

Re: Long Line Noise Problem

waltergmw

Re: Long Line Noise Problem

kitz

Re: Long Line Noise Problem

waltergmw

Re: Long Line Noise Problem

kitz

Re: Long Line Noise Problem

waltergmw

Re: Long Line Noise Problem

roseway

Re: Long Line Noise Problem

jeffbb

Re: Long Line Noise Problem

kitz

Re: Long Line Noise Problem

waltergmw

Re: Long Line Noise Problem

kitz

Re: Long Line Noise Problem