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How are FTTC estimates calculated?

CX
Grafter
Posts: 745
Thanks: 2
Registered: ‎16-09-2010

How are FTTC estimates calculated?

I'm curious how BT determine estimates for FTTC. I had assumed that it was based purely on actual distance from cabinet, but is it?
For my telephone number, or my number plus post-code, I get an estimate of 49.9 / 10.9 Mbps - this is 385m from the cabinet. Overall street length is 270m.
For an address on the previous street, closer to the cabinet, the estimate comes out as 66.7 Mbps / 20 Mbps - this is 265m from the cabinet. Overall street length is 150m.
For an address on the next street away from the cabinet, the estimate comes out as 56.6 Mbps / 18 Mbps - this is 479m from the cabinet. Overall street length is 90m,
For an address on the street joined at the end of ours, the estimate comes out as 46.3 Mbps / 8 Mbps - this is 604m from the cabinet.
Each of the measurements has been the distance to the first property on that post-code, closest to the cabinet. I checked the address checker for both my house number and one at the other end of the street (250m away) and both come back with the same estimate.
Does this mean that the estimates are not really per-phone number or per-property, but instead an average for the centre of a given post-code/street? Or a worst-case for a given post-code?
6 REPLIES
Community Veteran
Posts: 19,101
Thanks: 443
Fixes: 21
Registered: ‎31-08-2007

Re: How are FTTC estimates calculated?

You need to know the actual cable length and route to the cabinet. It may not go the most direct route.
CX
Grafter
Posts: 745
Thanks: 2
Registered: ‎16-09-2010

Re: How are FTTC estimates calculated?

Thanks for replying.
It's impossible for the next street (with a higher estimate) to have a shorter line length. It's further away even as the crow flies.
My route I know for sure, as a BT OR engineer checked it when trying to find a fault. But if he was wrong, the only alternative route would make the length closer to 700m.
...unless there is aluminium in my line (unlikely for 1997 though right?), and they take that into account.
One thing I remember was on the leaked spreadsheets, the uplift for my post-code was a silly number, like 9999 (seems like a default or unknown). I think it was the uplift number, but I'd need to check.
Grff
Grafter
Posts: 352
Thanks: 2
Registered: ‎02-08-2007

Re: How are FTTC estimates calculated?

I've no idea on how they work the estimates, but I'd take them with a pinch of salt.
I was estimated at 55mb before I signed up to FTTC.  However on completion it was more like 35mb.
Community Veteran
Posts: 1,294
Thanks: 30
Fixes: 4
Registered: ‎22-06-2012

Re: How are FTTC estimates calculated?

I wish I knew the answer. However, my speed estimate was spot on & I'm over 600 metres fom my FTTC cabinet. Cheesy
Estragon
Rising Star
Posts: 811
Thanks: 10
Registered: ‎07-02-2012

Re: How are FTTC estimates calculated?

I'm 600 metres as paced out by me and confirmed by the engineer's JDSU. Estimate on the old 8c Profile was 29.4Mbps or so, actual was the full 40/10. Now on the 17a Profile of course, and the 80/20 product. Sync 54013/14933kbps, interleaved.
CX
Grafter
Posts: 745
Thanks: 2
Registered: ‎16-09-2010

Re: How are FTTC estimates calculated?

FTTC was connected up today. No problems with the installation.
Although I'm now using the supported Openreach modem, I had the Draytek 2950 connected whilst the Openreach engineer was connecting up the cabinet and it reported the following:
Basic Status		Upstream	Downstream	Unit
VDSL Profile 17a
Actual Data Rate 19999 79984 Kb/s
Attainable Rate 32754 101697 Kbps
SNR 153 83 0.1dB
Actual delay 0 0 ms
Actual INP 0 0 0.1 symbols
Actual INP 0 0 0.1 symbols

Way more than the estimate of 49.9Mbps/10.9Mbps, and still higher than the neighbour estimate of 60Mbps. I'm under no illusions and expect it to drop over time - I was told I am currently the only person with FTTC on the cabinet. I don't know how influential crosstalk will be, but it's bound to have some impact.
I'm just glad it's better than this!
		Downstream	Upstream
Rate 1946 660 kbps
SNR 5.6 5.4 dB
Attenuation 66.5 39.3 dB

Thanks for the years of service, little Netgear; you tried your best to polish a turd.  Smiley