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Author Topic: BT's ADSLMax speed estimator, some observations  (Read 4101 times)

fence

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BT's ADSLMax speed estimator, some observations
« on: May 26, 2006, 10:12:45 PM »

I am new here, but it's a nice friendly place, for a little study like this.

Background:
I live in a lane of 29 houses, 28 terraced on one side of the road, and 1 detachad on the other side. The lane runs North-South. The exchange is 2.2 kilometers to the south. There is a BT  box at the south-end of the lane, and a cable then goes up to a telephone pole that directly services the 1 detacted house, and a series of poles (5 in number) that service the terraced houses.

I live at no3 of the terraced houses, which means I am on the 2nd pole and at the absolute shortest distance from that pole. (Like it's in my garden!)
(I maybe should explain that the houses in this terrace are numbered 1,2,3  to 28, not 1,3,5 etc.)

OK so far?

I moved in 4 years ago, at that time I used 192.com to download details of the entire lane - names, addresses, phone numbers.

Since we send each other Xmas cards, I have always kept some parts of the list up to date.

The point of the posting:
Earlier today on the Zen forum, there was some discussion of how the  BT Wholesale projected speeds are derived. And Zen's Phil indicated that it was simply distance related. I think that there is more to it than that.

I put my lane's phone numbers into the checker at /www.prodigynet.co.uk/menu.php?page=support/adsllinecheck.

Of 29 houses I could get ADSLMax download speed projections for 19.

3 had projected speeds of 4000

9 had projected speeds of 5000

7 had projected speeds of 5500


The nearest house to the exchange (in wire term), the one house on the first pole (and who has ADSL - fsnet, not maxed) is projected at 4000, and numbers 27 and 28 (the furthest from the exchange in wire distance) are projected at  5500  and 5000 respectively.

There are only 4 houses that currently have an ADSL connection - mine (projected at 5000) and the three that are  projected at 4000. I am the only one that has been maxed.

I've consistently synched at fast 8128 since conversion on 2 May, with SNR margins between 6.6 and 5.4.


Ray
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kitz

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BT's ADSLMax speed estimator, some observations
« Reply #1 on: May 29, 2006, 01:18:30 PM »

Hi ray and welcome

Some very interesting observations there.
I havent seen Phil Longs actual post but from what you say he indicated is how Ive always understood it is "supposed" to work.

However the BT database is often wrong and is supposed to be used only as an indication of what you may get.
From what you say it would certainly seem to be the "wrong way round" in your case and in a row of terraced houses the projected differences do seem to be way more than would you would expect in a real life situation of 19 houses that come out of the same green box. :/

Over the past couple of years Ive seen way to many instances of the BTw database actually being wrong - both underestimating and overestimating.  I suppose one of the good things about maxdsl is it does give the customers more of a chance to see what their line is actually capable of supporting rather than guessing what it may support.

The other thing to bear in mind is that internal wiring and even the modem/router you choose could very well affect what your maximum speed will be.

>> I've consistently synched at fast 8128 since conversion on 2 May, with SNR margins between 6.6 and 5.4.

Not bad for "5Mb" eh ;)  8)
I cant really comment on my own situation since Im very close to the exchange and always expected to get full sync.
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mr_chris

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BT's ADSLMax speed estimator, some observations
« Reply #2 on: May 29, 2006, 01:25:09 PM »

Hi there :)

Interesting that the BT checker is reporting different results for different houses. The projected max speed is supposed to be based on line capacitance and other such checks. I don't know exactly how the data is gathered and translated into a projected speed though.

What I do know is that the BT checker for Max speeds definitely seems to play it safe (unlike the one for fixed rate speeds, which can often give wrong results, both too high and too low).

My own line is reported on the BT checker as being able to get 3.5Mb, yet I've been syncing at 8128kbps since day one of being maxed over a month ago. My SNR fluctuates terribly though - which I really need to try and sort out. It's picking up some interference from somewhere which means it drops from a reasonably healthy 10dB to 0dB or less. Fortunately, even at 0dB SNR margin, my line stays up and is usable, albeit with a large number of errors!
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Chris

fence

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BT's ADSLMax speed estimator, some observations
« Reply #3 on: May 29, 2006, 10:04:23 PM »

But why, why should 3 houses: #1 , #6 and #20 be the only ones that are set at 4000 and be the only ones that have ADSL ('cept for me of course at #3!).
All I can think of is this:
Back in those days (April 2005) when we were all young and on 512, I paid Plusnet for a queue jump to the faster speeds.
Quote
[INTERNAL]
Customer is disappointed with recent regrade (see ticket 16440205) and feels he should have been able to receive 2mb - speed test results are as follows -
"good morning, on logging on this morning I found that I was connecting at 1152 - so clearly BT have been in and done what they had to do.
I am however surprised that I am only getting 1 meg. My noise margins (SNR) are currently 28 up, 26 down. Attenuation 31.5 up, 35.2 down. Any thoughts?"
Please either resubmit order (with no fee) to try again for 2mb or get BT to explain why this is not possible.
Regards,
M*** T****

Dear Mr Holden,
I apologise for this.
You only recived an upgrade to 1MB due to incorrect information from the BT speed checker.
I have resubmitted your 2MB order at no extra charge.
I apologise for any inconvenience caused.
Regards,
M*** P****
Real Quality CS! They were so good (April 2005)!

Now I wonder if all the other ADSL users in my lane were provisioned at 1 meg. and this has got factored into the calculations.

Quote
internal wiring and even the modem/router you choose could very well affect what your maximum speed will be.

Absolutely! Since I am hoping to get BE-LLUed in September, I put some effort in now into getting everything cleaned up.CurrentSNRMargin
(You don't happen to know anyone who could use 190 meters of  Dropwire No.10, do you? - I couldn't buy it by the metre, so I had to buy a reel.)

Ray
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kitz

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BT's ADSLMax speed estimator, some observations
« Reply #4 on: June 04, 2006, 12:39:53 PM »

>>> You don't happen to know anyone who could use 190 meters of Dropwire No.10, do you?

I live very near the exchange and was walking past their yard where they keep the BT vans the other night....
and there were 2 half empty reels of the stuff.
I could have quite easily jumped an appx 3 foot wall and "borrowed" some for you.
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