How fast can FTTC go in the UK?

Yesterday in their results BT suggested that FTTC could be made to go at 80 Mb/sec from next year and potentially could hit 100 Mb/sec.

In other posts the comment has been made that those speeds would only work for those on very short loops. In another thread WWWombat linked to a BT presentation that stated that the average D side link was 420m and also included an Ericcson document http://www.ericsson.com/us/ericsson/corpinfo/publica... that showed on p43 the expected distance that VDSL can travel. That graph shows that at 400m you should get around 20 Mb/sec. Well my line has D side link of 400m approx and I get 35 Mb/sec against a predicted 22 Mb/sec and whilst I understand the discussion about crosstalk my speeds have been stable on a cabinet that has been available for 12 months and if the number of times an OR van is parked beside it they appear to be selling lots of connections.

So is VDSL more robust in the wild than these documents suggest or are BT blowing wind in their results? Both documents are from 2008 and I wonder if it is working better than they expected. BT have been cautious marketing Infinity so they can claim high average speeds making people with predicted speeds below 15 Mb/sec have another product so it would be unlikely they change that to allow a headline speed for a few like ADSL2 or is it?

In reply to a post by asturini:

In other posts the comment has been made that those speeds would only work for those on very short loops. In another thread WWWombat linked to a BT presentation that stated that the average D side link was 420m and also included an Ericcson document http://www.ericsson.com/us/ericsson/corpinfo/publica... that showed on p43 the expected distance that VDSL can travel. That graph shows that at 400m you should get around 20 Mb/sec. Well my line has D side link of 400m approx and I get 35 Mb/sec against a predicted 22 Mb/sec and whilst I understand the discussion about crosstalk my speeds have been stable on a cabinet that has been available for 12 months and if the number of times an OR van is parked beside it they appear to be selling lots of connections.

The green line is that one that plots the downstream for profile 8d, and I reckon the estimate is for 37Mbps. That seems pretty consistent with your current result. Are you sure your line is 430M long though? Mine is 500M (following the path, not direct) and gets an estimate of 30.
The black line, for profile 17a downstream, suggests that a bandwidth increase to 17MHz isn't going to improve the speeds for many people - A 5-10Mbps increase if you live less than 400M from the cabinet.

With graphs like that, I don't see how BT hope to get into the 70-80Mbps region for any sensible number of subscribers. A distance of 100M is very short... unless they are planning to put cabinets on every street.

I seen the news on it also, looking at those graphs I wonder if BT are reverting to old adsl2+ behaviour and going to market speeds that only the top few % can get (which to me isnt right and shouldnt happen).

In reply to a post by WWWombat:

The green line is that one that plots the downstream for profile 8d, and I reckon the estimate is for 37Mbps. That seems pretty consistent with your current result. Are you sure your line is 430M long though? Mine is 500M (following the path, not direct) and gets an estimate of 30.
With graphs like that, I don't see how BT hope to get into the 70-80Mbps region for any sensible number of subscribers. A distance of 100M is very short... unless they are planning to put cabinets on every street.

The estimate was given by the engineer and it seems about right when you walk it. What puzzles me is why BT are apparently going to advertise headline speeds only a few can get when Ofcom are talking about changing the rules. Perhaps its a case of the suits saying something the engineers don't think will work. Very strange.

I think you hit the nail on the head....

That graph shows that at 400m you should get around 20 Mb/sec. Well my line has D side link of 400m approx and I get 35 Mb/sec against a predicted 22 Mb/sec and whilst I understand the discussion about crosstalk my speeds have been stable on a cabinet that has been available for 12 months and if the number of times an OR van is parked beside it they appear to be selling lots of connections.

My D-side is 566m long, and I have held perfect 40000 meg sync down, and 10 meg up sync it's installation in November.

Attenuation d/s 18.2db snr 7db sync rate 40000Kbps
attenuation u/s 12.2db snr 17.3 sync rate 10000Kbps

I have seen full sync on 890m of 0.5 copper, (new-ish build buried estate) but then have seen only 16meg on 700m, this being almost entirely aluminium from cab to pole. Before anyone shouts, we swapped the entire length of this slow line, and it still did not improve, so this wasn't due to a 'fault'.

Hasn't everyone one here who has been given an estimate found it to be lower than the eventual speed ?

I have seen 'unconfigured' FTTC DSLAM ports show 80meg sync downstream, though how far this would travel, I don't know, (possibly 8a rather than 8c.) There are currently around 40 users off my DSLAM.

So, yes, I believe it can go faster/further than estimates.

When the eng installed my line, I asked how long the Dside was, it said on the JDSU that it was greater than 300 meters, anyone know what this means apart from the obvious?

I get perfect 40/10 sync and the line by path is 350 meters

Lots of the 'additional info' on the JDSU screens is very vague/inaccurate. IE If you are testing VDSL sync, the data about this is accurate, sync rate, attenuation, SNR, etc, but also on the same screen is a 'guesstimate' of line length, which is usually flakey, at best. For an accurate measurement of D-side length, the JDSU would be set to TDR and measured from the PCP. I guess the engineer had already been and done the cab work before you asked them for a reading.

Yeah, The cab work had been done and all he did was install the Vdsl modem, He plugged the JDSU in, I remember the SNR etc over 17 for both U/D and Attenuation being 7 and 12. he then changed to a different screen and that was it.

The line is only 4 years old when the estate was built, the normal cab is the same age and all the lines are new and underground, so it's prob 0.5 copper line.

I know the route of the line as it's the only way into the estate and there is BT access points to the ducting about every 30 meters. one is on my door step.

Edited by lockyatlrg (Sat 14-May-11 12:17:09)

Chris it's playful what pings do you get in UT? I'm getting infinity installed on 1st June

I don't play UT anymore mate, Battlefield BC2 and Cod is where I'm at

But pings to multiplay and BBC etc in dos is 13ms, my default gateway is located in Leicester or Nottingham, depending on which one it connects to when I reboot the HomeHub.

Speeds are between 35 and 38 depending on time/congestion and upload is always 8.2

I assume you live down south somewhere so your pings will be better I would predict about 8-10ms

Edit, If you want me I'm on IRC now mate.

Edited by lockyatlrg (Sat 14-May-11 12:41:58)