24mbits eircom product only available in 6.5%-15.4% of the state.

Sponge Bob

OK , who can get 24mbits.

1. Businesses in central business districts of large towns ( check)
2. Some residential .....but not very many

Lets do the Math.

a) Every enabled exchange in Ireland, and there are 900 of them out of 1200 exchanges total , can deliver 8mbits but ONLY if you live reasonably close and your line is OK.
b) Therefore eircom are looking at certain LINES that can ALREADY get 8mbits so that these can now get UP TO 24mbits .
c) Evidence is that eircom operate a policy where they only allow an upgrade if your line supports 11mbits MINIMUM meaning that this is an 11-24mbit product depending on distance and line quality.

So here is the question. How widely available is this product seeing as your exchange must support 11mbits.

1. Only 450-500 exchanges are ADSL2 enabled. Lets say 500. The older enabled exchanges stil do up to 8mbits like they always did.
2. 11mbits is possible on a perfect line at around 2km MAX. ( some disagreement on this number , see [edit] below and later posts)
3. 8mbits will work to around 3km , a bit further with certain RE profiles
4. Persons living 2-3km from their exchange cannot do any better than they are doing now unless eircom give them a 9 or 10mbit package in future by allwing synching at that speed.

From that it is possible to work out the coverage for the new product

Allowing the higher number of enabled exchanges and the 2km limit the coverage is as follows.

a) radius of circle = Pi x R Squared. Irish roads are never straight so we take the bendy roads and reduce the 2km radius to 1.7km as the crow flies.
b) the 24mbit package coverage of each exchange is 3.15x(1.7x1.7) which is only 9.1sq km
c) multiply that by 500 exchanges and you get max 4550 sq km.

Therefore eircom only really supply up to 24mbits in an area no more than the size of county Donegal. Aren't them laws of physics a bitch

The only possible speed bump after that is VDSL which only serves up to 1km ...meaning that if ALL the 500 ADSL2 capable exchanges in the coutry are upgraded then VDSL would be available to an area around the size of Offaly nationwide.

Even if eircom put ADSL2+ into all their exchanges no matter how small they would only reach max 11000 sq km with an 11mbit or higher service.

The state comprises 69000 sq km of land area so 4550 or indeed 11000 sq km is nothing.

4550km sq is 6.5% of the land area the state.

The NBS is supposed to cover around 20,000 sq km minimum.

The 24mbit business packages launched last year cover even less because they are Annex M products that sacrifice a bit of reach for the extra uplink speed.

[edit]

TBC ( further down in this thread) asserted that the 11mbit cutoff may be 3km not 2km so I revisited the figures above


If so the coverage from an exchange ( reduced for the crookedness of our roads) would be 2.6km radius x 2.6km radius x Pi for a single exchange or 21.3km sq coverage per exchange.

500 exchanges x21.3 sq km = 10647 sq km or 15.4% of the state.....that is 1.5 times the size of County Cork

15.4% = absolute maximum , I take it we are all agreed ??

If eircom upgrade all their 900 DSL exchanges to ADSL2+ then that goes to 19170 sq km or max 27.8% of the state

If eircom upgrade all their 900 DSL exchanges and 300 NON ENABLED exchanges to ADSL2+ then that goes to 19170 sq km or max 37% of the state.

Coverage reality is somewhere between those figures in the thread title.

Barring extensive reach extension initiatives nothing will change.

lucernarian

sponge bob wrote:

2. 11mbits is possible on a perfect line at around 2km MAX.

I do agree with pointing out how this is not going to be widespread. But where is your evidence of this particular claim?! Have a look at this graph: http://www.internode.on.net/residential/broadband/adsl/extreme/performance/ To be fair to this graph, this deals with attenuation at 300kHz. I thought eircom measured attenuation at a higher level. That would mean a 30dB recording by eircom here may actually translate into 25dB on the graph. But the distance measurements are also more conservative than eircom's. So I'd definitely expect more from a line than what that graph suggests. Even still, that graph suggests that lines up to 3km can enjoy 10 Mbps or more and further if you think the graph is too conservative in plotting realistic speeds.

For example, the line I currently am using is over 2 km long according to my attenuation. This is 28dB. I am currently connected at 19487 kbps and 1021 kbps upload on this line.

To say that 2 km is max for 11 mbps on ADSL2+, is inaccurate. I feel 3km is a more realistic expectation and this would make a significant difference (in population coverage at least) to your figures.

watty

if more users are on a cable (more likely in area where higher speed works) then cross talk is higher and in fact 3km may only do 7Mbps.
4th Nov 2009
http://www.techtir.ie/forums/showthread.php?t=2307
Registration may be required to view images (stops bandwidth theiving).

Almost all graphs assume good lines, very little crosstalk etc.

Crosstalk rises the more users in one cable bundle subscribe.

I'd always thought myself that < 10% would EVER get 20Mbps+ xDSL speeds. I'll not argue with 6.5%.

The fact is we needed a major rollout of DSL to be complete 6 years ago. With decent priced LLU. We have missed the boat. It's now obsolescent technology.

To say that 2 km is max for 11 mbps on ADSL2+, is inaccurate. I feel 3km is a more realistic expectation and this would make a significant difference (in population coverage at least) to your figures.

Originally I thought 10Mbps for 3km. But that is one perfect pair of of Cat3 cable, not in a bundle with other cables (multicore/multipair). In the real world 7Mbps is top speed in majority of cases at 3km. Of course some people will get faster (10Mbps to 11Mbps) and also some will get less.

Sponge Bob

To_be_confirmed wrote: »

To say that 2 km is max for 11 mbps on ADSL2+, is inaccurate. I feel 3km is a more realistic expectation and this would make a significant difference (in population coverage at least) to your figures.

It is unrealistic if takeup is low. If It becomes too common then the throughput will drop from Crosstalk with other users in yoru area like Watty says.

ADSL2+ BUSINESS products from eircom such as the one you seem to have TBC , they use Annex M

ADSL2+ RESIDENTIAL products form eircom seem to use Annex A profiles

This is the graph from that article you posted earlier TBC . I am relying on a graph from the Broadband Forum Page 18 ( formerly the DSL Forum who are a dsl standards body) which showed 2km

I accept that the reality is probably nearer 3km than 2km like TBC excepting the effects of bundle Crosstalk. Lines are in bundles of 400 and 100 in thick cables near exchanges and in 100s and 50s on roads and boreens.

Accordingly I amended the thread and added a further calculation showing the BEST POSSIBLE case of 3km




The DSL Forum Graph.

lucernarian

Fair enough, crosstalk effects are an important consideration. I wouldn't consider myself qualified to comment fully on the extent of its effects. If my understanding of things like cable transmission is right, wouldn't the higher frequencies of ADSL2+ be even more subject to crosstalk in a Cat3 spec cable?

As for my ADSL2+ connection, it's a BT "LLU2" connection. ADSL2+ Annex A I think. Merrion exchange.

I wish ComReg would approve/companies would use Annex L, which I think is the reach extended profile. It would make a small difference to people on long lines out in the sticks, but every little helps!

watty

This is why 100baseT and 1G-etherent is on Cat5e, not Cat3. Even then the 1G works by using all four pairs to transmit both ways at once and advanced Hybrid/Echo cancellation.

Cross talk on Cat3 is huge at DSL frequencies. The POTS was designed only for 3KHz on subscriber loop, not 30MHz!

patch panels, MDFs etc may have long untwisted parts (doesn't matter for speech), whereas for RF twisted pair the untwisted part must be wires of equal length and very very short. Again compare visual of a typical roadside cabinet and a CAT5e Structured Wireing patch panel spec.

So each Exchange MDF and roadside (or pole mounted, or subterrain juction box) cabinet may substantially degrade the performance.