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Standard User asturini
(newbie) Fri 13-May-11 11:13:37
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How fast can FTTC go in the UK?


[link to this post]
 
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?
Standard User WWWombat
(member) Fri 13-May-11 22:34:36
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Re: How fast can FTTC go in the UK?


[re: asturini] [link to this post]
 
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.
Standard User Chrysalis
(eat-sleep-adslguide) Fri 13-May-11 23:13:03
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Re: How fast can FTTC go in the UK?


[re: WWWombat] [link to this post]
 
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).


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Standard User asturini
(newbie) Sat 14-May-11 06:54:28
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Re: How fast can FTTC go in the UK?


[re: WWWombat] [link to this post]
 
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.
Standard User Zarjaz
(knowledge is power) Sat 14-May-11 07:47:39
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Re: How fast can FTTC go in the UK?


[re: asturini] [link to this post]
 
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.

Standard User lockyatlrg
(fountain of knowledge) Sat 14-May-11 10:04:29
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Re: How fast can FTTC go in the UK?


[re: Chrysalis] [link to this post]
 
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

o2 LLU
ROUTER:-DGN2000
Sync 17848D 1412U Annex A
Att:-35.0dB Down 17.4dB Up
SNR:-1.5dB Down 3.1dB Up
Standard User Zarjaz
(knowledge is power) Sat 14-May-11 10:54:13
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Re: How fast can FTTC go in the UK?


[re: lockyatlrg] [link to this post]
 
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.

Standard User lockyatlrg
(fountain of knowledge) Sat 14-May-11 12:08:30
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Re: How fast can FTTC go in the UK?


[re: Zarjaz] [link to this post]
 
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.

o2 LLU
ROUTER:-DGN2000
Sync 17848D 1412U Annex A
Att:-35.0dB Down 17.4dB Up
SNR:-1.5dB Down 3.1dB Up

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

Anonymous
(Unregistered)Sat 14-May-11 12:18:32
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Re: How fast can FTTC go in the UK?


[re: lockyatlrg] [link to this post]
 
Chris it's playful what pings do you get in UT? I'm getting infinity installed on 1st June
Standard User lockyatlrg
(fountain of knowledge) Sat 14-May-11 12:36:57
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Re: How fast can FTTC go in the UK?


[re: Anonymous] [link to this post]
 
I don't play UT anymore mate, Battlefield BC2 and Cod is where I'm at laugh

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.

BT Ifinity
ROUTER:-HomeHub3
Sync 40000D 10000U Annex A

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

Standard User GMAN98
(committed) Sat 14-May-11 12:43:42
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Re: How fast can FTTC go in the UK?


[re: Zarjaz] [link to this post]
 
In reply to a post by Zarjaz:
I have seen 'unconfigured' FTTC DSLAM ports show 80meg sync downstream,


Yep.... also seen 80
Standard User WWWombat
(member) Sun 15-May-11 02:18:20
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Re: How fast can FTTC go in the UK?


[re: GMAN98] [link to this post]
 
That is promising smile Is that on the current 7.05MHz frequencies?

For those wanting to dream about the absolute maximums, I found another Ericsson graph about future speeds. Look at the bottom of this page and weep.

The text tells us that current VDSL2 technology at 17MHz is limited to 246Mbps (total bi-directional), and 30MHz is limited to 417Mbps.

Lookign at the graph at the bottom of the page suggests these values are available to 300M of the cabinet.

The *real* future stuff there suggests you could get to around 1Gbps almost to 150M from the cabinet. But that obviously starts to work with cabinets every other street.
Standard User asturini
(newbie) Sun 15-May-11 08:41:12
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Re: How fast can FTTC go in the UK?


[re: WWWombat] [link to this post]
 
I have done some digging around and found the attached news item on ISP Review http://www.ispreview.co.uk/story/2011/05/12/bt-uk-to... read the 10.55 addition. If true and Ofcom are OK then if BT use up to 17 Mhz rather than the current 7 MHz this does I think mean higher speeds for most lines.

What do others think? Is crosstalk a dead issue?
Standard User asturini
(newbie) Sun 15-May-11 14:39:14
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Re: How fast can FTTC go in the UK?


[re: asturini] [link to this post]
 
Further investigation turns up a paper on the ICT Regulations Site discussing VDSL profiles http://www.ictregulationtoolkit.org/en/Publication.2... which has various graphs showing the distance and speeds the various standards will deliver. Profile 17a seems to be the standard BT may adopt if so figure 5b shows that at 1500 feet (approx 450m) you should get 80 Mb/sec down and 38 Mb/sec up which is in line with the BT statement.

The section on impulse noise management is also worth reading but look at figure 7 which shows that VDSL2 can deliver Next Generation services up to 3000 feet from the cabinet or around 900m which is a lot further than I have seen elsewhere. Suddenly you can start to see why BT likes FTTC and VDSL2 - it can easily support VOD services to most homes without installing lots of expensive fibre.
Standard User WWWombat
(member) Sun 15-May-11 20:08:11
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Re: How fast can FTTC go in the UK?


[re: asturini] [link to this post]
 
Thanks - hadn't spotted that one.

Assuming they stick to band plan 997 (almost certain), then the spectrum from 7MHz up to 12 MHz goes to improving the upstream - which may be why they talk about increasing the uplink speeds to 20Mbps. If pricing means that most ISPs kept uplink speeds at 2Mbps, it would be a chronic waste of spectrum.

The frequencies between 12MHz and 17MHz will then be allocated to downstream, and account entirely for the extra downlink bandwidth.

Searches online for "VDSL2 profile 17a" show some product specs which suggest the distance limit for the fastest speeds (85-100MHz) is around 1000ft, or 300M. I haven't figured the cutoff point, for where speeds would be back to today's 40/10. Certainly less than 1500M though.

I'm not sure crosstalk is ever a dead issue. It will always be there, in some form, and will always need to be dealt with.
Standard User WWWombat
(member) Sun 15-May-11 23:34:51
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Re: How fast can FTTC go in the UK?


[re: asturini] [link to this post]
 
Also interesting. I wonder how much crosstalk those graphs include, because they seem to predict longer distances than any equipment seems to want to live up to.
Standard User krazykizza
(fountain of knowledge) Mon 16-May-11 08:59:46
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Re: How fast can FTTC go in the UK?


[re: asturini] [link to this post]
 
If you look at the adverts... They say "Many of our customers are already recieving three times faster speeds" I make that out to be under 20mbps if you take an average broadband speed of 6-7mbps on ADSL. So where in that are they advertising the top speed, which by the way, a majority on this site are getting!

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
AOL > Virgin Media > Tiscali > Falconnet > UKFSN > Norfolk Internet
2mbps > Shapped 512k > 1mbps! > 6.5mbps > 4.5mbps > 6.5mbps
ADSL Joy. 31db att, 9db SNR, EntaFail.
Standard User asturini
(newbie) Mon 16-May-11 17:09:50
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Re: How fast can FTTC go in the UK?


[re: krazykizza] [link to this post]
 
The main Infinity website says "at least three times" and does clearly state the headline 40mbs. In July the new Ofcom code comes in which will require that isps give reasonable estimates to each new user. BT already do that. However the advertising gives a clear impression of a high speed greatly improved speed service which, luckily, most of us who have it get.

The days of promoting headline speeds few can reach are gone for the majors at least which is why I am sceptical of the opinion that holds that an increase to 80Mbs will only for the rare user whose live on top of a cabinet similar to the way 24Mbs is for ADSL2+ users. If that was true then BT would not have announced in the way they did in my opinion.

Time will tell as they seem to want to do this before the end of 2011.
Standard User asturini
(newbie) Mon 16-May-11 17:14:56
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Re: How fast can FTTC go in the UK?


[re: WWWombat] [link to this post]
 
Could you link to where you found those graphs as it would be interesting to contrast them with the source I found?

There is also a technology called vectoring which can improve performance but I can find little on this as yet. Have you any sources on that.

Time will tell whether this just headline stuff or a real improvement for most users. Not that it matters too much to me as I am still delighted in getting over 20 times my ADSL speed getting 40 times seems rather academic.
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