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uk.telecom.broadband (UK broadband) (uk.telecom.broadband) Discussion of broadband services, technology and equipment as provided in the UK. Discussions of specific services based on ADSL, cable modems or other broadband technology are also on-topic. Advertising is not allowed.

Estimating ADSL & VDSL Speeds From Given Distances



 
 
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  #11  
Old November 18th 16, 04:30 PM posted to uk.telecom.broadband
Dick
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Posts: 104
Default Estimating ADSL & VDSL Speeds From Given Distances

On 18-Nov-16 1:06 PM, Java Jive wrote:

That is certainly a factor, but if what Dick says is true, that seems
to me to be a far greater problem.


From http://www.thinkbroadband.com/faq/se...radsl.html#301
I can vouch for it its authenticity, I am over 6Km from the exchange and
all the modems I had except one showed 63dB when in reality it was about
75dB. The table might be of interest.



My modem shows an attenuation of 63.5dB, but when I tried my friends if
showed 70dB, which is right?

Most ADSL and ADSL2+ modem/routers have limits on the size of the
downstream and upstream attenuation figures.

For downstream most routers only display a maximum attenuation of 63dB
(or 63.5dB). On the upstream side the limit is usually 31dB or 31.5dB.

This means if you see these figures, then your attenuation is likely to
be higher, and on a line that is perhaps 10km long it may be as high as
80dB.
Should my upstream attenuation be higher than my downstream attenuation?

As a general rule, downstream attenuation is roughly double that of the
upstream attenuation e.g. downstream attenuation 48dB, upstream
attenuation 26dB.

If a modem is showing the upstream attenuation higher than downstream,
it is usually down to the web page displaying numbers in the wrong column.
I am in my training period, can I switch off my modem?

One of the myths for the up to 8 Mbps and up to 24 Mbps services is that
you should not switch off your modem.

Switching off a modem overnight, or if going away for a few days will
not cause any problems with the training systems some providers use. The
only time it may cause problems is if you switch the modem off and on
multiple times in a short period, e.g. ten or more times in an hour.
How fast will a telephone line of a certain length be?

If you have an ADSL or ADSL2+ service already, then the best estimate is
by using the current data from the modem. If you only know the line
length, in terms of actual cable distance between your property and the
telephone exchange the table below may help.
Line Length (km) Attenuation Est. ADSL Speed Est. ADSL2+ speed % UK
lines shorter than this
0.5km 6dB 8128 Kbps 24576 Kbps 1.5%
1km 12dB 8128 Kbps 20700 Kbps 5%
1.5km 15dB 7900 Kbps 20000 Kbps 11%
2km 24dB 7350 Kbps 17500 Kbps 18%
2.5km 30dB 7000 Kbps 14500 Kbps 27.5%
3km 36dB 6300 Kbps 11500 Kbps 37.5%
3.5km 42dB 5300 Kbps 8200 Kbps 57.5%
4km 48dB 4200 Kbps 5600 Kbps 66%
4.5km 54dB 3200 Kbps 3400 Kbps 73%
5km 60dB 1900 Kbps 2250 Kbps 85%
5.5km 66dB 1100 Kbps 1600 Kbps 90.5%
6km 72dB 576 Kbps 800 Kbps 94%

The speeds above are estimates based on a mixture of sources, which
ranges from manufacturer estimates, to actual real-world feedback. The
line length distribution is taken from Ofcom UK telephone line data.

If you have obtained a distance estimate from the exchange to the
property by using a straight line on a map (radial distance) a rough
line length can be estimated by multiplying the radial distance by 1.4.
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  #12  
Old November 18th 16, 05:35 PM posted to uk.telecom.broadband
Michael Chare[_2_]
external usenet poster
 
Posts: 50
Default Estimating ADSL & VDSL Speeds From Given Distances

On 16/11/2016 14:33, Java Jive wrote:
I have been informed that our locality is not going to get FTTC during
the imminent local exchange rollout of it, so I am putting together a
case for bringing FTTC to us.

We have 59 premises, about 12% of the total for the local exchange, in
a reasonably small geographical area. Currently, we are all connected
by exchange only lines, which would have to be rerouted via one or
more cabinets. I have drawn up a map and a spreadsheet table of all
the addresses and calculated their roadside, cabled distances from the
exchange and proposed cabinet site(s).

The average distance from the exchange is 8.81km, the furthest is
12.2km. All online ADSL checkers I've seen give either rather vague
estimates of 1Mbps speed for all the properties, or no result at all,
whereas in reality the best speed I've heard of is 2.5Mbps, while most
seem to get less than 1Mbps, and the furthest houses cannot get
landline broadband at all.

With one cabinet, the average distance from the cabinet would be
2.22km, the furthest would be 4.28km. With three cabinets - which
sounds unrealistic but would save BT relaying much of the local
cabling, and therefore might actually be cheaper - the average would
be 1.17km and the furthest 3.08km.

Does anyone know of formulae that I can use to give more useful
estimates of speeds for ADSL, and estimate the speeds available to
each property via VDSL - preferably in each case something I can put
in a spreadsheet formula?


1) You should be able to find speed / distance charts for ADSL and VDSL.

2) You need to know the cable distances, by following the cable routes.

3) I think the upper limit for VDSL is about 1.5km or maybe less.

A B4RN approach might work. A Gigaclear fibre project might be viable
if there are any nearby villages that you could also get interested.

Try the www.thinkbroadband.com web site forum for further help.



--
Michael Chare

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  #13  
Old November 18th 16, 06:32 PM posted to uk.telecom.broadband
Martin Brown
external usenet poster
 
Posts: 343
Default Estimating ADSL & VDSL Speeds From Given Distances

On 18/11/2016 15:30, Dick wrote:
On 18-Nov-16 1:06 PM, Java Jive wrote:

That is certainly a factor, but if what Dick says is true, that seems
to me to be a far greater problem.


From http://www.thinkbroadband.com/faq/se...radsl.html#301
I can vouch for it its authenticity, I am over 6Km from the exchange and
all the modems I had except one showed 63dB when in reality it was about
75dB. The table might be of interest.


I agree. I am a bit closer to the exchange about 4km and 47dB attn with
4200Mbps sync. That is already bad enough that to get a stable data
transfer requires interleaving on *and* the noise margin at 9dB. That
sync attn pair is very similar to what the table you quoted reckons
although it doesn't say at what noise margin.

Interleaving hurts ping times ~40ms and gaming so it doesn't bother me
since that is a worthwhile trade for better data integrity.

There was a time when I could run interleave off and 6dB but old rural
lines don't get on with the wet, wind and rain. Spiders and such like
entering the cabinets and flooding of cable runs doesn't help either it
is always slower and prone to fail in a wet winter.

My modem shows an attenuation of 63.5dB, but when I tried my friends if
showed 70dB, which is right?

Most ADSL and ADSL2+ modem/routers have limits on the size of the
downstream and upstream attenuation figures.

For downstream most routers only display a maximum attenuation of 63dB
(or 63.5dB). On the upstream side the limit is usually 31dB or 31.5dB.


This is only an issue for extremely remote installations when the
heuristic of 14dB/km attenuation is plenty good enough as a guide.

--
Regards,
Martin Brown
  #14  
Old November 18th 16, 07:36 PM posted to uk.telecom.broadband
Michael R N Dolbear
external usenet poster
 
Posts: 85
Default Estimating ADSL & VDSL Speeds From Given Distances


"Java Jive" wrote

From what I can tell round here fibre to remote node has been kicked
into touch since there is no way to power the remote node cost
effectively so without huge subsidies it doesn't get considered. There


How much power does it require to power each customer's part of a

remote node. Surely, with modern miniaturisation etc, it should be
possible to power it from the normal operating voltage of a POTS line?


Or a solar panel + battery like many items of highway and parking payment
equipment.


--
Mike D

  #15  
Old November 18th 16, 09:24 PM posted to uk.telecom.broadband
stephen
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Posts: 381
Default Estimating ADSL & VDSL Speeds From Given Distances

On Wed, 16 Nov 2016 19:42:10 +0000, Java Jive
wrote:

Thanks to both for your replies, but ...

On Wed, 16 Nov 2016 15:03:57 +0000, Graham J
wrote:

Google for vdsl speed vs distance ...

http://www.increasebroadbandspeed.co...ainst-distance
- has a nice graph.


Yes, I'd found that already ...

Or: vdsl speed calculator ...

http://www.speedguide.net/dsl_speed_calc.php


... and kitz has something pretty similar. The problem with all of
them is that they are designed for use by people with a connection who
can read their Attenuation directly from their router, whereas I need
to calculate from distance alone, and that is where the
errors/uncertainty are worst. For example, my attenuation as measured
by my router is 63dB, which leads such calculators, working at a rate
of 13.81dB/km, to assume I'm about 4.5km from the exchange, whereas
I'm just under twice that!

Which implies some forward thinking planner used better cable to
mitigate for the longer distance - bigger cores / better characterised
twists?

Trying a few values in this suggests the speed vs distance graph is not
a straight line



The killer problem for the planners is that ideally every customer
would like to have a straight line route = best performance.

The planners want the best service footprint at minimal cost for both
digs / build and cable - so the routes may double back to the end of a
high pair cable and so on.

so the other variable is how the cable length translates into physical
route and the assumptions made to translate between loss and distance.

No, I wouldn't expect to be, even as it tails off. Although I haven't
the background knowledge to do a detailed analysis, based on more
general scientific knowledge, my first guess would be that the
relationship is hyperbolic, where speed is proportional to 1/distance.

http://forum.kitz.co.uk/index.php?topic=10566.0 - this gives the basis
for calculation.


Yes, I'd found that already, and it works from attenuation as
described above. One of the pages linked thence gives more of the
background of the kitz calculator, and includes a spreadsheet which
does the same 'calculation'. However, examination of the spreadsheet
code shows that all it is doing is straight-line interpolating between
points on ...

http://www.internode.on.net/images/c...2-distance.jpg
.. which now gives a 404, but originally was almost certainly the
graph at ...
http://www.internode.on.net/resident...d/performance/

The problem with all such sources is that I can't 'interpolate' beyond
the end of the original data!

To whom will you be submitting your case?


Probably to funding bodies such as Highlands & Islands Enterprise,
MPs, MSPs, etc.

In a region I know of (near Holbeach St Matthew, nort-heast of Spalding)
BT are rolling out FTTP. There's no commercial need - probably there
are well under 60 houses, and it's not being extended to nearby farms
where it might be of some real use. So the only reasons I can think
it's being done is that:

1) it will demonstrate there's no commercial case, so BT will not push
it into other areas;

2) it allows BT to test all aspects of the roll-out in an area where
failure won't be noticed.

I can see that there's some point in the latter reason. So you might
adapt that to your case.


That does seem rather strange.

We know what you want is technically feasible. Evidently BT now have
"Remote nodes" which can be installed on eexisting poles. This avoids
rerouting exising cables through newly installed green cabinets. See:

http://www.ispreview.co.uk/index.php...d-network.html

http://www.ispreview.co.uk/index.php...t-q4-2014.html

Do let us know how you get on.


Thanks for the links, and I'll keep you up-to-date

On Wed, 16 Nov 2016 15:25:57 +0000, Andy Burns
wrote:

As for your spreadsheet, this page has general graphs and tables of
speeds by distance, obviously it's all variable and depends on cable
quality as well as distance.

http://increasebroadbandspeed.co.uk/2013/chart-bt-fttc-vdsl2-speed-against-distance


Yes, thanks, as discussed above, I'd already found that page, but I
was hoping for something I could just put in a formula, rather than
manually reading 59 values off a graph!

Stephen Hope
Replace xyz with ntl to reply
  #16  
Old November 18th 16, 10:34 PM posted to uk.telecom.broadband
Vir Campestris
external usenet poster
 
Posts: 235
Default Estimating ADSL & VDSL Speeds From Given Distances

On 18/11/2016 16:35, Michael Chare wrote:

A B4RN approach might work. A Gigaclear fibre project might be viable
if there are any nearby villages that you could also get interested.


BT did SFA for us. They told us it was December for 4 years in a row
(it's just slipped again) and only got around to doing _anything_ when
we started to get a community/commercial service. We wanted a fibre to a
house in the next village that has FTTC, a microwave link to the farm on
the hill, then a sector aerial to cover our village.

BT then announced that the other village didn't have the capacity (it's
been installed less than a year!) and the fibre would be 5K. And built
some FTTC cabinets.

That's perhaps an improvement on just slipping year on year as they did
_before_ we started on our project!

This week they announced that they won't be ready in December after all.

Nobody is surprised.

Andy
 




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