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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.

 

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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.

 

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Message 70 of 283

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Expert

Re: Line Stats Analysis Results


JChin wrote:

 

Orignally did not get HD service at time of sign up. Added HD service alittle over a year ago.

Located in Mesquite Texas (Dallas area).


Great!  I am in Dallas also.  3 HD streams is available in our market.

 

You are currently still on the old profile of 1 HD stream.  In September 2008, AT&T began rolling out the 2 HD stream profile to all those who had HD service.  If your were a customer at the time but did not have HD service, you had to call to request an upgrade to the new profile.  So this explains why you kinda slipped through the cracks.  You should not have any problem being upgraded to 3 HD streams.

Message 136 of 283
Tutor

Re: Line Stats Analysis Results

That is great news, thanks texasguys37.

So I ask for the 3 HD and does it cost extra to move from 2 to 3? 

Message 137 of 283
Expert

Re: Line Stats Analysis Results


JChin wrote:

 

That is great news, thanks texasguys37.

So I ask for the 3 HD and does it cost extra to move from 2 to 3? 


Nope, no extra costs to be upgraded to either 2 HD or 3 HD.

Message 138 of 283
Tutor

Re: Line Stats Analysis Results

This is some fanstastic news, no more decision between wanting to watch HD game or record a HD movie. Do you have 3 HD stream already?

 

Message 139 of 283
Expert

Re: Line Stats Analysis Results


JChin wrote:

 

This is some fanstastic news, no more decision between wanting to watch HD game or record a HD movie. Do you have 3 HD stream already?

 


Yes, I do have 3 HD streams.  A few things to be aware of:

 

  1. You can watch 3 different HD channels at the same time
  2. You are limited to recording 2 HD channels at the same time
  3. If your are recording 2 HD channels, you cannot watch a 3rd HD channel on the TV connected to the DVR ; however, you can watch a 3rd HD channel on a TV connected to a non-DVR STB

 

I believe at some point an upgrade is planned that will allow 3 different HD channels to be recorded at the same time.  When that occurs, you should also be able to watch a 3rd HD channel on the DVR TV when 2 HD channels are being recorded.

Message 140 of 283
Tutor

Re: Line Stats Analysis Results

Thats some great information, thanks. You have been very helpful and I appreicate your time and in answering my questions.

Now to call them, do I ask for Uverse Tech support or is there a direct number to call?

Message 141 of 283
Expert

Re: Line Stats Analysis Results

Call 1-800-983-2811 and select the option for Technical Support.
Message 142 of 283
Tutor

Re: Line Stats Analysis Results

Great, thanks again for your help.
Message 143 of 283
Expert

Re: Line Stats Analysis Results

Good luck!  Keep us posted.
Message 144 of 283
Employee

Re: Line Stats Analysis Results

Texasguy can every customer in Dallas get 3HD or as many areas only new customers can get 3HD but not existing customers even if they are on the 32/5 profile. I hope since he was on 1HD they will put him on 3HD even if they don't allow other exsisting customers to get it yet.
Employee Contributor*
*I am an AT&T employee and the postings on this site are my own and don't necessarily represent AT&T's position, strategies or opinions.
Message 145 of 283
Expert

Re: Line Stats Analysis Results


Escapee wrote:


Texasguy can every customer in Dallas get 3HD or as many areas only new customers can get 3HD but not existing customers even if they are on the 32/5 profile. I hope since he was on 1HD they will put him on 3HD even if they don't allow other exsisting customers to get it yet.


I don't know to what extend it is being deployed, but I know that it is not limited to new customers in the Dallas market.  I have it, and I am not a new customer.

Message 146 of 283
Employee

Re: Line Stats Analysis Results

When you got it if I remember your post it sounded like you lucked up getting 3HD being an existing customer. If another CR had answered the phone you may still be on 2HD.  But Dallas and Austin get new stuff before other cities do. We know an upgrade is almost finished when Houston gets it. Spd got the 32/5 the other day so maybe that part of the upgrade will completed in a few weeks. I hope the CR tech gives it to him because he fell through the cracks on the 2HD upgrade.
Employee Contributor*
*I am an AT&T employee and the postings on this site are my own and don't necessarily represent AT&T's position, strategies or opinions.
Message 147 of 283
Expert

Re: Line Stats Analysis Results


Escapee wrote:


When you got it if I remember your post it sounded like you lucked up getting 3HD being an existing customer. If another CR had answered the phone you may still be on 2HD.  But Dallas and Austin get new stuff before other cities do. We know an upgrade is almost finished when Houston gets it. Spd got the 32/5 the other day so maybe that part of the upgrade will completed in a few weeks. I hope the CR tech gives it to him because he fell through the cracks on the 2HD upgrade.


I don't believe I have posted about this previously.  I don't think I lucked into it, and I don't believe the poster should have any problems being upgraded to the 3 HD profile.

Message 148 of 283
Tutor

Re: Line Stats Analysis Results

Please review and comment.

Thanks,

Dave

 

http://adslm.dohrenburg.net/tools/db-link.php?link=1657

 

Message 149 of 283
Teacher

Re: Line Stats Analysis Results

SomeJoe is a Tier 2 I think. Let me play the dumb guy in this forum too (I'am also good at it).

 

I have some questions:

 

1) What is Bridge Tap?

2) Can it be removed without great technical knowlegde? If so, can you please tech us?

 

I have an opinion:

 

1) Bridge Tap can be seen by tech support through their Quality Check thingy.

 

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