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.

 

Message 1 of 283 (8,803 Views)
Expert

Re: Line Stats Analysis Results

SoxFan,

 

I think there's some subtle evidence that you may have a bridge tap on your line.  For your distance, the max rate seems to low and the upstream power level seems too high.  For 1900 feet, I would expect a 42 - 45 Mbps max rate.  Yours is only 37 Mbps.

 

Call tech support, have them send a premises tech, and have him check your line.  He may need to call the linesmen's group (I&R) to come and find the bridge tap.  If you do have a tap, your bitloading graph implies that it's very far away from your house, up near the start of the line.  If you have one and it gets removed, the max rate should come up by 5-6 Mbps, and then your 32/5 profile will run properly.

 

If they can't find a bridge tap and can't condition the line any further to improve the max rate, then you will have to have the line moved to the 25/2 profile to prevent the errors that are occurring.

 

Message 271 of 283 (1,445 Views)
Mentor

Re: Line Stats Analysis Results

Thanks Joe I will give them a call today.  What should I tell tech when I call them? Just request a tech to come out and test the line? Will ATT go for that?

Message 272 of 283 (1,445 Views)
Guru

Re: Line Stats Analysis Results

You'd want to tell them that you think that there may be a bridge tap on the line.

 

Or, you can skip the whole "script reading phone people" and email AT&T's uVerse Tier-2 Technician Team at uversecare@att.com.  Just give them your uVerse Account Number, a good phone number to be called at, and a good time to be called at as well.  Or you can just send them an email with your uVerse Account Number and tell them in the email what we told you.

Message 273 of 283 (1,445 Views)
Mentor

Re: Line Stats Analysis Results

I called up uverse. They said that the bridge tap as been removed from my line. However there is alot of "noise" on the line.

 

They are sending a line tech out tomorrow to determine the problem.

Message 274 of 283 (1,448 Views)
Highlighted
Scholar

Re: Line Stats Analysis Results

Please tell me how mine looks.....

 

2884iD58EE4A7B462E91D

 

2886i0AD64FC8527BB702

 

Thanks!

Message 275 of 283 (1,448 Views)
Guru

Re: Line Stats Analysis Results

We will have to wait for your images to be approved but when they are we'll be sure to look at them.
Message 276 of 283 (1,448 Views)
ACE - Expert

Re: Line Stats Analysis Results

flhthemi, I'm seeing the classic bridge-tap sinusoidal wave, But unless you're experiencing issues, I don't know that I'd worry about it.  You're getting 32/5 and have some room to spare.

 

*The views and opinions expressed on this forum are purely my own. Any product claim, statistic, quote, or other representation about a product or service should be verified with the manufacturer, provider, or party.
Message 277 of 283 (1,448 Views)
Guru

Re: Line Stats Analysis Results

I'd still say to get that bridge tap removed, any bridge tap (don't care if it's not causing issues now) should be removed for it can cause problems later on down the road.

Message 278 of 283 (1,448 Views)
Expert

Re: Line Stats Analysis Results

There looks to be a small bridge tap there.  However, you're close enough and on a good enough line that you have the highest available profile and it looks to be working correctly.

 

Unless you're getting pixelation or freezing you probably don't need to worry about it.

 

Message 279 of 283 (1,448 Views)
Scholar

Re: Line Stats Analysis Results


SomeJoe7777 wrote:

There looks to be a small bridge tap there.  However, you're close enough and on a good enough line that you have the highest available profile and it looks to be working correctly.

 

Unless you're getting pixelation or freezing you probably don't need to worry about it.

 


Thanks for the reading! I do get a little freezing and some pixelation on occasiion. I'm guessing a bridge tap looks like a splitter? If so there are two on the side of my house that were put there at inital installation.

Message 280 of 283 (1,448 Views)
Expert

Re: Line Stats Analysis Results

No, a bridge tap is a length of wire that is connected to your pair somewhere in the middle of your line, and then goes to nowhere.  Usually this happens when a previous resident in another house had been assigned your pair sometime in the past.

 

Bridge taps will interfere with the U-Verse VDSL signal.

 

Message 281 of 283 (1,176 Views)
Scholar

Re: Line Stats Analysis Results

Well it's not something I can take care of. Think I should request service?

Message 282 of 283 (1,176 Views)
Guru

Re: Line Stats Analysis Results

Yeah, I would if I were you.  Tier-2 Contact info is below...

 

Please see the following thread...
Or, simply email David and Matt at uversecare@att.com. Simply send an email explaining the situation as best as possible with your uVerse account number, a good phone number to be called at, and a good time to be called at as well. If you have any past trouble tickets that you are aware of, include them as well; any extra information is going to make David and Matt's job easier.
Message 283 of 283 (1,176 Views)
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