ADSL2+ Tones & Bitloading
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- Re: ADSL2+ Tones & Bitloading
ADSL2+ Tones & Bitloading
10-06-2012 10:46 AM
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I'm hoping that someone can help me understand the status of my connection. I don't have a problem as such, but I would like to understand what is going on.
There are several gaps in my tone and bitloading map for ADSL2 which have been there since day one. I don't beleive this is AM radio interference as the noise is too focused on one particular tone and seems to be very stable.
I've scoured the internet trying to find info that may explain the configuration that my particular connection has (See pics below). There are 7 gaps in total as follows:
Gap1 474kHz-479kHz (Tone110)
Gap2 548kHz-552kHz (Tone127)
Gap3 811kHz-815kHz (Tone188)
Gap4 824kHz-828kHz (Tone191)
Gap5 1048kHz-1052kHz (Tone243)
Gap6 1255kHz-1259kHz (Tone291)
Gap7 1501kHz-1505kHz (Tone348)
these tones are noted in nearly all the topics I have found on this subject, so I'm now wondering if this is some sort of MSAN/Chipset issue.
I'd appreciate any feedback especially concerning the same tones and the Vendor ID of the MSAN you are connected to.
cheers
Graham
Re: ADSL2+ Tones & Bitloading
10-06-2012 12:52 PM
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http://www.ebay.co.uk/itm/6x-FT114-43-Fair-rite-Ferrite-Ring-1-14-Diam-Ham-Radio-EFI-Balun-PAs-Ham-R...
Re: ADSL2+ Tones & Bitloading
10-06-2012 1:54 PM
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Personally I'd agree with the OP in it's not AM radio interference - for the same reasons - too focused on one frequency.
I'd be expecting to see a curve in and curve out centred around the relevant channel for the interference. I get this from Radio 5 live, Talk Sport and Virgin AM channels though I am on the top of a hill in central UK.
As well as interference from the above I also have the same gaps
at: 110, 127, 188,191,243, 291 and 348
Like you I've no idea why
If you don't get any more suggestions try asking on the Kitz Forum - there are some there who know a lot about a lot.
(sorry my router will not supply vendor ID info - the applicable command is removed from the cut down CLI version installed by Dlink)
Re: ADSL2+ Tones & Bitloading
10-06-2012 2:00 PM
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Re: ADSL2+ Tones & Bitloading
10-06-2012 7:12 PM
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Uk uses 6khz audio modulation so will cause rf energy +/- 6khz of carrier frequency.
I suffer from reduced bitloading of tone 46 caused by radio 4 lw, and also tone 58 caused by Rte ireland.
Rte ireland seems to have wider bandwidth and so causes reduced bitloading over several adjacent tones.
Also note that if radio transmissions are between tone frequencies, it will affect several tones as well.
Also if the lost or reduced bitloading is harmonically related, this is probably due to switch mode power supply, for instance if the supply switches at 100khz, you may see harmonics of this going up the bitloading graph.
Re: ADSL2+ Tones & Bitloading
11-06-2012 9:20 AM
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Gaps 2` to 6 and probably 7 are most certainly due to MW broadcast stations both in the UK and Germany & Holland, considering your location.
Gap 1, could be a number of things from Switch Mode PSU's to a possible aeronautical/maritime beacon or a modem - msan/dslam oddity.
A number of x47c's gaps could be Switch Mode PSU and harmonics.
Re: ADSL2+ Tones & Bitloading
11-06-2012 11:00 AM
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I have included a DMT screenshot for direct comparison with that of x47c's, and a snapshot of both Tone/SNR graphs for a clear side by side view.
One reason I'm sceptical of the AM interference stance, is that I've just switched from 20CN/ADSLMax to 21CN/ADSL2+ and have access to archived bitloading graphs from the same router over the same line for both the DSLAM and MSAN (one is included below for ref.).
The 20CN/ADSLMax graphs show absolutely NO radio interference and NO gaps in the spectrum. As 4 out of 7 of the tones mentioned above appear in both the 20CN/21CN frequency spectrum, I cannot believe that several new AM stations are broadcasting since I happen to have upgraded to 21CN/ADSL2+ or that my line has degraded to such a point it is now susceptable to radio interference.
@x47c, can you let me know your general geographical area, I'm in East Yorks, quite literally just East of York
Unless x47c is a neighbour of mine I couldn't accept local noise or aero/maritime frequencies as a possible source.
So, for me the question still remains.
Re: ADSL2+ Tones & Bitloading
11-06-2012 11:03 AM
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Edit:
I've also recently transferred to ADSL2+/21CN
I've now just dug out my DMT stored images from the days of 20CN - see graph attached
Like you I also see no gaps on 20CN (apart from the pilot tone).
Re: ADSL2+ Tones & Bitloading
11-06-2012 11:32 AM
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This is the noise on the line found by the router in its initialization process and before any ADSL signal is applied.
Obviously it is only collected/stored at the moment of switch on/re-sync.
Attached is mine - showing the spikes corresponding the the dips in SNR and bitloading displayed in the DMT program..
Re: ADSL2+ Tones & Bitloading
11-06-2012 12:24 PM
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not only that you've recently moved to ADSL2+, but the data supplied from your time on Standard DSL reinforces my thoughts on this being equipment related.
After a quick refresh on graphs in Excel I've attached my QLN graph, which also seems to support the hypothesis.
Your data clearly shows AM interference over several tones, denoted by the curved spikes, as you have previously stated. Mine shows no such behaviour.
Re: ADSL2+ Tones & Bitloading
11-06-2012 12:51 PM
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The reason you don't see the curved dips Graham is because you are much much closer to the exchange, a short line, probably underground, whereas x47c's is much longer, showing the same dips as 20CN and I'd guess he may have some overhead.
Why the MSANs are producing the results they are is curious to say the least. Thinking cap on.
A couple of questions to save me re-reading and digging through threads that may not have the answer, roughly what time of day did each of you sync at?
Are you both using the same or different modem/routers on 20CN as 21CN and what were/are they and do you know what chipsets they use?
Re: ADSL2+ Tones & Bitloading
11-06-2012 1:33 PM
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No need to apologise - I don't mind
Yes same Dlink router used on 20CN and 21CN - broadcom chipped
No idea when I re-sync'd. Under 20CN the unit stayed in sync for multiple weeks at a time.
I think the 21CN DMT image was taken shortly after I switched on/re-booted after a time away so probably mid morning.
My line is rural (2.4Km) but underground till joint box on D side. Then up pole, then around 50 yards total of drop wire to house, along eaves and down to NTE5 in hall. Being on the ridge of a hill I guess my dropwire is more suseptible to RFI.
Re: ADSL2+ Tones & Bitloading
11-06-2012 1:49 PM
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Currently the router has been sync'd just over 12 days, and last resync was around Noon on 30th May.
I'm on what can only be described as a small "market town" exchange (~3000 lines). My particular line is all underground, approx 1km from the exchange.
Exchange equipment is identified as IFTN - Infineon, which I beleive is a derivative of the Texas Instruments equipment, as Infineon bought the TI DSL CPE business back in '07.
Re: ADSL2+ Tones & Bitloading
11-06-2012 2:32 PM
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Quote from: Anotherone Now Graham has posted his alongside yours it stands out a mile.
Exactly, hence my initial enquiry. I find it strange that something like this does not have a "detailed explanation" or "contrived conspiracy" somewhere on the interweb.
Quote from: Anotherone The reason you don't see the curved dips Graham is because you are much much closer to the exchange, a short line, probably underground, whereas x47c's is much longer, showing the same dips as 20CN and I'd guess he may have some overhead.
Looking at it another way, it is that my line does not suffer from RF interference at all, and should not have any tones marked as unusable.
Quote from: Anotherone Why the MSANs are producing the results they are is curious to say the least. Thinking cap on.
Thinking cap on, Indeed
Re: ADSL2+ Tones & Bitloading
11-06-2012 4:47 PM
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http://forum.kitz.co.uk/index.php/topic,11216.0.html
They can provide a snapshot of your connection at any given time, or provide ongoing statistics graphs over a minute by minute, hour by hour, day by day or month by month period.
I have attached a couple of typical graph set examples.
Note that in the "snapshot" graphs QLN & Hlog data is only updated during the training period of a resync.
However, Bit-loading & SNR are constantly updated throughout the life of a connection.
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