Helpful Links

Line Stats Analysis Results

Expert

Line Stats Analysis Results

This thread will contain the results of the analysis of everyone's line stats that have been posted in the Data/Stats Collection Thread.

 

My initial analysis is not focused so much on distance from the VRAD.  The reason for this is that not too many people have distances that have been told to them by a tech using their specialized meters.  Furthermore, different line conditions can cause inaccuracy in their measured distances.

 

As it turns out, distance from the VRAD isn't the most important thing regarding the type and quality of service that you get anyway.  Instead, the wiring gauge, presence/absence of bridge taps, and the noise margin (signal-to-noise ratio) of the line are much more important.

 

To this end, the data that has been posted in the Data/Stats Collection Thread led to a rock-solid and extremely useful correlation that can be used to immediately judge the quality of your line and the service you can receive.  That correlation is the Downstream Noise Margin and the Max Line Rate.

 

Using only these two parameters, you can tell if A) Your line is working properly (i.e.. no bridge taps), B) What gauge wire is running from the VRAD to your NID, and C) What line profile you should be able to get.

 

Please note that I arrived at the wire gauge conclusions here because there are two distinct groupings of data points.  I am assuming the difference between them is due to wire gauge, because A) It is known that different neighborhoods around the country use two different wire gauges, 22 gauge, and 24 gauge, B) Thinner wire (24 gauge) would have higher attenuation in the high frequencies, which would reduce the max line rate for a given signal-to-noise ratio, which is exactly what the graph shows.  It is possible that the two groupings of data are due to a different cause, but until I either gather more data or have references to other possible conclusions, I'm going to assume the difference is due to wire gauge even though I cannot currently prove that with certainty.

 

There is a 3rd grouping of data that shows some people with a drastically reduced max line rate.  I'm fairly certain these people have a bridge tap on their line that is reducing the max line rate.  If their line was conditioned by I&R to remove the bridge tap, their max line rate would jump up into one of the other two groupings.  I have witnessed this first-hand, as my initial installation was on a line that had a bridge tap.  When the bridge tap was removed, the max line rate shot up by over 15000 Kbps.  I unfortunately cannot compare the numbers that I had at that point to the numbers I have now because those older numbers were using the VDSL1 protocol and at least 2 revisions earlier of the RG firmware.  Those values cannot be reliably compared to today's values obtained with the VDSL2 protocol and the current RG firmware revision (5.29.135.47).

 

Here's the first fully analyzed chart:

 

 

 

 

 

You can plainly see how well the data groups are formed here.  There are two distinct lines of people with properly working service, and a 3rd line of people with service that is probably not running right.  In addition, you can see the very rare people who are so close to the VRAD that they are currently being capped to a maximum line rate of 64000 Kbps.

 

For those of you who have some background in statistics, the linear correlation coefficients (R^2) for each of the 3 trend lines on the chart was > 0.98.  (This means that the computed lines fit the actual data very nicely).

 

The allowable line profile areas were computed by assuming that a line capacity of 80% is required for properly working service.  Line capacity = downstream profile rate / max line rate.  For example, for a properly working 32/5 profile, the downstream profile rate is 32200 Kbps.  FOr a line capacity of 80%, that means that Max Line Rate = Downstream Profile Rate / 80% = 32200 / .8 =  40250 Kbps, which I rounded to 40000.  The other rates separating the profiles were computed similarly.  The exception is the border for No Service, where I upped the allowed line capacity to 85% to allow just a little less max line rate.

 

The people whom I believe have a bridge tap on their line are very interesting.  The bridge tap reduces the max line rate that the line could theoretically carry by nearly 30%.  In the particular case of the person with an 18.5 dBm noise margin and 29000 Kbps max rate, having the line conditioned could conceivably get him a max line rate of 41000 Kbps, which would boost his allowable profile from 19/2 to 32/5 !  He could conceivable go from 1HD/3SD to 3HD/1SD just by having the bridge tap removed.

 

The person with the 10.0 dBm noise margin and a 19200 Kbps max rate is certainly experiencing poor service.  The line capacity in his case is at 100%, with no margin for errors.

 

 

In short, this chart can tell you at a glance whether your service is operating in agreement with everyone else's service.  It can immediately identify what profile you should be on or be able to get.  It can tell you if your line needs conditioning to have a bridge tap removed.  Based on my assumptions, it can also tell you your wire gauge, although that parameter is questionable.

 

When people post their line stats, this chart can be very useful in quickly determining if they are experiencing line problems or if their service is in agreement with normally working service.

 

10,265 Views
Message 1 of 283

Accepted Solutions
Expert

Re: Line Stats Analysis Results

OK, here is a revised Noise Margin vs. Max Line Rate graph, now that it is known that the data shows a correlation between profiles rather than wire gauge.

 

 

 

 

 

This graph shows a bit more information than the previous one.

 

For properly working service that won't have a lot of errors, you need two things:

 

1) Sufficient max line rate so that the line capacity doesn't exceed approximately 80% when compared to your profile rate.  Line capacities exceeding approximately 80% causes the line to begin to take some errors.

 

Line Capacity = (Downstream Profile Rate / Max Line Rate) * 100

 

2) Sufficient noise margin such that the line does not take errors.  From people's stats, I am estimating the minimum required noise margin to be around 12.0 dB.

 

These two parameters gives rise to the two red areas on the graph, where the noise margin is too low for reliable service, or the max line rate is too low even for the 19/2 profile.  The minimum required max line rate for the 19/2 profile is given as 21800 kbps.  This is where the 19/2 profile line (derived from customer data) hits the 12 dB noise margin, for a line capacity of 88%.  This line capacity is a little high, but since the alternative is no service, it may turn out to be sufficient.

 

Similarly, the 25/2 profile line intersects the 12 dB noise margin limit at 30400 kbps, establishing that as the minimum required max line rate for the 25/2 profile, at a line capacity of 83%. 

 

Finally, the 32/5 profile line intersects the 12 dB noise margin limit at 39700 kbps, establishing that as the minimum required max line rate for the 32/5 profile, at a line capacity of 81%.

 

 

What is very interesting here is how we now know that the noise margin changes significantly with the selected profile rate.  We also know that the max line rate stays relatively constant when the profile rate is changed (see djrobx's data a few posts above).  Because of this nearly constant max line rate and the consistency of the customer data which has given us the profile lines, we can now predict where you will end up on the graph when your profile rate is changed.

 

For example, let's look at the customer who is currently on the 25/2 profile line (red) at an 18 dB noise margin and 41000 kbps max rate.  When this customer is upgraded to 32/5, the max line rate will stay nearly constant at 41000 kbps (it may go down slightly, no more than a few hundred kbps), but his service point will jump horizontally to the left (constant max line rate) to land on the blue 32/5 profile line at a much lower noise margin.  We can predict from the graph that his noise margin will be around 13.0 dB.

 

Since we know what the new noise margin will be due to the profile lines, we can now also identify by noise margin alone those people who should be able to move to a higher profile.  For example, people on the 19/2 profile who exceed a noise margin of 19.0 dB should be able to move to the 25/2 profile, since their new noise margin will be above 12.0 dB.  Similarly, people on the 25/2 profile whose noise margin exceeds 16.5 dB should be able to move to the 32/5 profile, again because their new noise margin will be above 12.0 dB.

 

And just for fun, we can also estimate that those people on the 32/5 profile with a noise margin exceeding some value would theoretically be able to move to an even higher profile.  Assuming the noise margin drops 6 dB for an increase in the profile rate of 8-10 Mbps, we could theoretically predict the existence of a new 40/5 profile that would be eligible for rollout to people on 32/5 who exceed 18 dB of noise margin and 50000 kbps of max line rate.

 

 

Now, since noise margin and max line rate are locked together on these profile lines, predicting whether a person has a noisy line or a bridge tap becomes more problematic.  The Dohrenburg DMT plot can be instrumental here.  Removing a bridge tap or removing a noise source can raise the max line rate (and noise margin with it), possible allowing someone to upgrade their profile.  However, this has to be done on a case-by-case basis, as there is no guarantee how much additional max line rate/noise margin you can achieve.

 

Tags (1)
Message 70 of 283

All Replies
Explorer

Re: Line Stats Analysis Results

Just a question, I don't want to sound like an idiot, but how can I tell if I am on VDSL or VDSL2.  I'm sure I missed some simple clue somewhere...

Message 256 of 283
Expert

Re: Line Stats Analysis Results

 


WB9OUF wrote:

Just a question, I don't want to sound like an idiot, but how can I tell if I am on VDSL or VDSL2.  I'm sure I missed some simple clue somewhere...


 

You can look at http://192.168.1.254/xslt?PAGE=C_1_0 on your RG, look under the DSL Details section, and look at the Protocol.  G.993.2 is VDSL2, G.993.1 is VDSL.

 

All U-Verse installations were upgraded to VDSL2 during late 2009 - early 2010.

 

Message 257 of 283
Explorer

Re: Line Stats Analysis Results

I figured it was right in front of me:smileyhappy:

Message 258 of 283
Contributor

Re: Line Stats Analysis Results

2724i61FAD5509657858E2722iDF195FA855643B662720i86D8C602BF2755B8Hello

 

I'm posting my specs to get some feed back.  I have a pair bonding install.  Asked to get moved to the 2 HD stream but was told no.  I think I have a line issue on the first copper line.

2718iE793335418B5C02A

Tags (1)
Message 259 of 283
Expert

Re: Line Stats Analysis Results

Your images are awaiting Mod approval; give it a little time so people here can see them.

Message 260 of 283
Tutor

Re: Line Stats Analysis Results

Hey all, just had my uverse installed.  Tech said I was only about 500 ft from the nearest VRAD and the signal at the NID was very strong so would have no problem installing.  Tech was also on the phone trouble shooting with someone and said the loop length was long so thought he had to switch me down to the 25/2 profile but as of right now, still on the 35/5 profile and the TVs are running fine in HD.

 

Internet on the other hand is an issue.  Getting only about 14mbps downstream and 0.3mbps upstream which really disappointing me because that was what I was getting with cable internet before and one of the reasons why I decided to try uverse was the higher upstream.

 

Called the prem tech and he said he detected a bridge tap on the line and has opened a ticket for someone to come out and fix that within a day or two.  I definitely see a sinusoidal wave in the bitloading graph mentioned before for a bridge tap.

 

 

Tags (1)
Message 261 of 283
Expert

Re: Line Stats Analysis Results

dontcallmejeff,

 

I think you could be moved to 25/2.  Contact tech support one more time and request it, if they won't do it, post back here and we'll put you in touch with David & Matt's team.

 

There is the low noise margin reading on line 1, but I've seen some other iNIDs do that and it doesn't appear to cause problems.  The bit allocation analysis seems to indicate that the lines could handle 25/2.

 

Tags (1)
Message 262 of 283
Expert

Re: Line Stats Analysis Results

alpha,

 

You have a large bridge tap on the line.  Call tech support, have them send a premises tech, he will call I&R (the linesmen group) to have them remove it.

 

Once it's removed, 32/5 should perform very well for you.

 

Tags (1)
Message 263 of 283
Highlighted
Contributor

Re: Line Stats Analysis Results

Thanks for getting back to me.  I've tried twice to get tech support to move me to 25/2 but they refuse.  I would like to try it to see if there any problems.  My only current problem is that the battery backup for the router has gone bad.  Looks like it's hard wired to the router so quess I will need to schedule some one to come out and replace it.

Tags (1)
Message 264 of 283
Mentor

Re: Line Stats Analysis Results

I am looking for some help on explaining my Line Stats. I'm pretty close to a VRAD it says 1900 ft, but I'm certain its closer. I have yet to google the actually length from my door to the VRAD. 

 

Thanks in advance for your help. 

 

 

Stats.png

Tags (1)
Message 265 of 283
Guru

Re: Line Stats Analysis Results

Alright dontcallmejeff, please send an email to uversecare@att.com with your uVerse Account Number and ask for them to bump you up to the 25M profile.  The uversecare guys are Tier-2 Technicians, they aren't phone script readers.

 

Just send an email to them, they will get it working for you.

Tags (1)
Message 266 of 283
Guru

Re: Line Stats Analysis Results

SoxFan894, we'll have to wait for a moderator to approve your images but once they do, we'll take a look at them and see what suggestions we can give you.

Tags (1)
Message 267 of 283
Mentor

Re: Line Stats Analysis Results

 


trparky wrote:

SoxFan894, we will have to wait for a moderator to approve your images but once they do, we'll take a look at them and see what suggestions we can give you.


 

trparky,

 

Thanks for the quick response. Do you need me to post the Bitloading graphs?

Tags (1)
Message 268 of 283
Expert

Re: Line Stats Analysis Results

SoxFan, please post the bitloading also.  Your line is currently on too high a profile.  Depending on the bitloading, you might be able to raise the max rate instead of lowering the profile.

 

Tags (1)
Message 269 of 283
Mentor

Re: Line Stats Analysis Results

Bitloading.png

Here is the bitloader. Thank you joe

Tags (1)
Message 270 of 283
Share this topic
Announcements

Having service trouble? There is an app for that! Use our troubleshooting tool or text myATT to 8758 to download the app on your device.
It allows you to troubleshoot in the palm of your hand - quickly and easily!
You will also find some helpful articles below.

Additional Support