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[GrahamC]

Hi all

I'm new to the Kitz forum and am here to pick up on your experiences and thoughts on the current crop of broadband equipment in relation to the topic subject.

I started a thread over at the PN forums some time ago trying to resolve what seems to be a quirk with my connection on ADSL2+ using a new router and a newly installed MSAN at the exchange.

The thread can be seen here: http://community.plus.net/forum/index.php/topic,105398.0.html which I know some of you are aware of.

From a few other posters and my own tests it seems, to me at least, that there are a few tones which do not seem to be used between certain routers and an IFTN MSAN. I've tested this with both a BDCM and TI AR7 based router.

I'd appreciate any feedback and thoughts.

cheers
Graham

[GrahamC]

To flesh this out a little and explain more of what I'm looking at I've attached a comparison of the SNR per Tone (the one displayed by the DMT utility) of two ADSL2+ lines. Besides that both are ADSL2+ lines, they are far apart geographically and in performance.

The gaps in both graphs are:

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)

[Bald_Eagle1]

Hi Graham & Welcome to the Kitz forum.

Thanks again for helping out with the Zoom X7N Graphing Scripts.

Do you happen to have the raw data for those graphs?

There has been a suggestion that DMT Tool may on occasions have a slight glitch in the way that some data is presented.

You may recognise the attached graphs that don't exhibit the same gaps in SNR, but they do exhibit them in the bit-loading graph 

[GrahamC]

Hi BE and thanks for the welcome  and happy to be of help with the X7n Graphing.

I don't think I have the actual data from those DMT graphs only the screenshots, but it was interesting to see the exact same layout from another user. There was a couple of graphs taken from Routerstats that show both the Tone SNR and Tone SNRM on post#46 of the the original thread. I'll post them here if I can locate them.

As for the graphs posted above, I certainly do recall them. I have no explanation as to the difference exhibited but even the QLN graph shows no significant SNR spikes, all being < -100dbm.

Hence the quest for more info and examples.

cheers
Graham

[GigabitEthernet]

Welcome, it's Gigabit from the Plusnet forum .

I will be switching to ADSL2+ soon (probably by November) so when I do I will be happy to give you some data if its applicable to this (e.g. same MSAN, etc.).

[Bald_Eagle1]

As for the graphs posted above, I certainly do recall them. I have no explanation as to the difference exhibited but even the QLN graph shows no significant SNR spikes, all being < -100dbm.

No, but if you look closely, slight dips in the QLN plot (i.e. quieter) can be seen that directly correspond with the gaps in the bit-loading graph.

[GrahamC]

Welcome, it's Gigabit from the Plusnet forum .

I will be switching to ADSL2+ soon (probably by November) so when I do I will be happy to give you some data if its applicable to this (e.g. same MSAN, etc.).

Much appreciated and I'll look forward to some more sample data.

From what you have said I presume you are still on 20CN with a DSLAM?

I was in this situation for a short time (5 days) from getting the router to being switched to 21CN. During that time I had no gaps in the Tones (except for the Pilot Tone) while connected to the 20CN DSLAM. Connected at the full 8 Meg with plenty of headroom. I tested this scenario once I had moved to 21CN/MSAN (i.e. forcing an ADSL1 G.992.1 connection) which prodeuced the following gaps:

Gap1 276kHz-280kHz (Tone64) Pilot
Gap2 574kHz-578kHz (Tone133)
Gap3 634kHz-638kHz (Tone147)
Gap4 656kHz-660kHz (Tone152)

Now these are different tones to those missing in the ADSL2+ list, but they are consistent and repeatable when switching between the two modes.

cheers
Graham

[GrahamC]

No, but if you look closely, slight dips in the QLN plot (i.e. quieter) can be seen that directly correspond with the gaps in the bit-loading graph.

I agree with slight, but would you consider that to be sufficient to wipeout the bitloading for the whole tone?

[GigabitEthernet]

From what you have said I presume you are still on 20CN with a DSLAM?

Yes, I am on 20CN with an Alcatel DSLAM. One of the older DSLAMs I believe.

[Bald_Eagle1]

I agree with slight, but would you consider that to be sufficient to wipeout the bitloading for the whole tone?

Ah, but is it the slight change in QLN that wipes out the bit-loading, or is it the lack of bit-loading that causes the slight change in QLN?

If these are common issues on different connections (with varying QLN, SNR & Hlog levels), it really does point to either a modem or DSLAM/MSAN matter.

If the same modem on a different DSLAM/MSAN doesn't exhibit the issue, it would appear to narrow it down to the DSLAM/MSAN.

here's another ADSL2+ connection, but this time the spikes in QLN (noisier) appear to be affecting the bit-loading AND SNR.

These graphs are from a connection using a Huawei HG612 modem operating in ADSL2+ mode.

[Bald_Eagle1]

Here's another ADSL2+ connection (Netgear 834 router), this time from a Sky connection.

[GrahamC]

Ah, but is it the slight change in QLN that wipes out the bit-loading, or is it the lack of bit-loading that causes the slight change in QLN?

Hmmm...the $64000 question?

Looking at the data from the other two lines, 1st one does spike up to 30-40dbm, the second 20-30dbm, with more noise on the line during the QLN test, the data from my setup shows very small variation.

Here's the 2 graphs I spoke about earlier from Routerstats, the 1st is SNR by Tone, the 2nd SNRM by tone. I've never seen anything like this before and none of the other graphs from any program or script give any indication as to why, considering the sharp spikes of 30-40db shown on the SNRM graph.

[ColinS]

To flesh this out a little and explain more of what I'm looking at I've attached a comparison of the SNR per Tone (the one displayed by the DMT utility) of two ADSL2+ lines. Besides that both are ADSL2+ lines, they are far apart geographically and in performance.

The gaps in both graphs are:

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)

Graham,
These dips, or even nulls, are very familiar - allowing for regional variation.  Here's my QLN noise graph:

And here's what a little analysis (confirmed by my wife's trusty portable radio):
Tone,   Frequency Khz,   AM Station
48,   207,      Radio 4 LW,
128,   552,      ?
188,   811,      Radio Scotland
211,   909,      Radio 5 Live
252,   1089,      TalkSport
267,   1152,      Clyde 2
282,   1215,      Absolute Radio
355,   1530,      Celtic Music Radio
I suspect yours are something similar.

BTW I have the OR NTE5A faceplate that includes the same REIN filter as both the OR RF03 REIN and the IS-plate, no bell wire, and even a ferrite core on the DSL lead.
Hope this is of some help.