Piggbyacking on a FTTC cabinet?

Our community has just had FTTC delivered under the BDUK subsidy programme, but only to ex-EO (directly cabled) customers, for whom a new cabinet has been installed opposite the exchange.

Those who were already connected to the existing cabinet serving the western end of the village now discover that their (smallish - perhaps 50 lines) cabinet is not part of the current subsidy programme (which runs to 2018). And they are trying to examine their options.

The obvious solution would appear to be for those wanting Fast Broadband to have their circuits diverted at the exchange to run the extra 40m to the new FTTC cabinet. Looking at the works done for the new cabinet suggests that existing EO lines have been diverted in exactly that way.

The only difference would appear to be that such circuits would run through two cabinets: the total line distances (at 400-600m) are no longer than the longest-but-one ex-EO line which does get Fast Broadband. And they are a lot shorter than the 1.67km line to a farm which also qualifies for Fast Broadband (albeit at pretty low speeds).

Have I missed some technical subtlety that makes it impossible to route a circuit through two cabinets?

Or are the non-FTTC customers simply the victims of an Openreach policy which conveniently leaves angry people desperate for Fast Broadband, and so builds up political pressure for Openreach to be given a further round of public subsidy for conversion of remaining cabinets?

The conspiracy is simple, if covering 90% of the UK, there will be 10% missing out and with some dense areas already well above 90% the more rural areas will bear the lions share of missing out.

What you suggest is potentially possible but a decision somewhere will have been made to spend the money it would cost helping someone else to get a FTTC solution. Has the local project absolutely confirmed that your cabinet is going to miss out?

The technical subtlety is that you end up with a more custom solution for an area and may not fit in the phase 2 (extension project plans).

When you have ~26,500,000 households in the country, on ~5600 exchanges, and way more cabinets, in order to stand a chance of maintaining it you need a relatively standard architecture.

Meaning that a line goes to 1 cabinet, which goes to the exchange.

BDUK has a budget, iirc, of about £100 per house passed. 50 lines means that if it costs more than £5k to deploy a cabinet to you, it's too expensive. It would cost way more than £5k.

The layout you've just invented would work, but it would be unique in the whole country and won't be done.

In reply to a post by JohnGeddes:

The obvious solution would appear to be for those wanting Fast Broadband to have their circuits diverted at the exchange to run the extra 40m to the new FTTC cabinet. Looking at the works done for the new cabinet suggests that existing EO lines have been diverted in exactly that way.

Just to be clear - when you say "at the exchange" - the EO diversion will be just outside the exchange, rather than within it - the technical regulations (known as the ANFP) don't want the VDSL2 frequencies within the exchange building.

In reply to a post by JohnGeddes:

Have I missed some technical subtlety that makes it impossible to route a circuit through two cabinets?

You might have missed a technical subtlety. Not about routing through 2 cabinets as such (secondary cabinets already exist in the network), but about whether it is feasible to divert your cable at all. Not about copper, but about insulation and protection.

The subtlety stems from the fact that E-side cables are different from D-side cables.

E-side cables, feeding from exchange to cabinet, have lots of pairs, tend to be older, and can even be insulated internally with paper. They are often protected from water incursion using air pressure fed from the exchange. Keeping water out is vital, so there is a great desire to not break into these cables at all. The oldest E-side cables can be lead-covered - so any work requires the services of a skilled lead jointer who can re-seal afterwards. Rare.

Diverting an E-side cable means the portion between the diversion point and the existing cabinet will no longer be protected from water ingress. And may be made of a material that sucks water in.

D-side cables, feeding from cabinet to poles, have fewer pairs, and are more likely to have been replaced - so nowadays tend to be gel-filled for water protection. These are so much easier to break into, as the gel automatically keeps water out.

EO lines are a strange mix, but are much less likely to be large bundles of air-protected cable. That means there is a reduced risk from breaking into an EO bundle, and diverting it to a new cabinet.

So...

If your E-side cable is constructed this way, the last thing BT would want to do is to break into the cable - as this will remove any remaining protection as it runs from (just outside) the exchange to the PCP.

That means they would need to replace the entire length of the E-side cable to the cabinet, using a gel-filled alternative. Definitely not cheap.

Quite how much this applies to tiny village exchanges is another matter.

Or are the non-FTTC customers simply the victims of an Openreach policy which conveniently leaves angry people desperate for Fast Broadband, and so builds up political pressure for Openreach to be given a further round of public subsidy for conversion of remaining cabinets?

Whoever is left out will have a cadre of angry people - it doesn't need a policy from Openreach for this to happen. But there are probably more of them who think the political pressure should be to NOT give the money to Openreach.

Thanks for that detailed description.

Takes me back to the 1950s when lead-covered; and oil-impregnated insulation were the norm.

If I remember correctly, the "cloths" for moulding and dressing the large lead joints, like water plumbing, were moleskins.

The large "soup" ladles for transferring the molten lead to the joint/seal.

The piggybacking that I envisage would not requiring any cable diversion.

As showing in this schematic, non-FTTC customers would have an idenitcal topography as some (or perhaps all) of the ex-EO customers apart from having cables jointed in an extra, inert, street cabinet.

Notes on the schematic:

Ex-EO customers in areas A and B (at least) appear still to be cabled directly to the exchange - there was no reason that their routes would have crossed the road before the advent of the FTTC cabinet, and there are no civil works that suggest that they have been diverted as part of the upgrade. So presumably these lines are still connected to a frame in the exchange, with a new cable then connecting them 40m or so to the FTTC cabinet.

(Ex-EO customers in areas C and D might still have circuits via exchange, but their cables might have been intercepted at the footway box and routed directly to the FTTC cabinet.)

Given that it's OK for ex-EO areas A and B to have be routed home->exchange->FTTC cabinet, why is it so unthinkable for via-cabinet Area E to be routed home->non-FTTC cabinet->exchange->FTTC cabinet?

Are areas A & B actually routed to a FTTC cab via the exchange i.e. can order now or is it your assumption that this will happen.

Have seen exchange grounds gain a few cabinets for EO lines on travels

Nobody is going to be running any grease filled cables out of the exchange for E0 cab cut ins. Grease filled cables only go up to 100prs and pressurised cables go up to 4800prs. You can simply airblock either side of the cabinet and bridge with an air tube.

Nothing technically impossible with what you suggest. But the better solution is to cut a cab in for the E0 area and then fibre tube out to the existing cab and fit a second more effective FTTC cab.

As with all this game, it's about what is the best engineering solution and what is a quick solution that is second best. Second best is labour intensive jointing time that doesn't keep the punters happy for long.

Edited by deleted (Wed 09-Dec-15 21:39:50)

Yes - both areas have FTTC available to order now, and there is only one FTTC cabinet in the village.

In reply to a post by partial:

Nobody is going to be running any grease filled cables out of the exchange for E0 cab cut ins.

I agree with that entirely.

In this case, though, the OP mentioned the cab has 50 lines, so whatever the solution turns out to be, it isn't one of the large scale.

In reply to a post by partial:

You can simply airblock either side of the cabinet and bridge with an air tube.

That part I didn't know. Is it common to use this setup?

And coverage target can vary from county to county

In reply to a post by nemeth782:

... The layout you've just invented would work, but it would be unique in the whole country and won't be done.

To make an analogy: imagine a world in which there is a railway company with a nice fast main line from Leeds to London, but no main line from Bradford to London, just a local line from Bradford to Leeds. They have plans to build a spur that will remedy the situation - one day, when the cash is available. But for now, there is no way of running trains directly from Bradford to London.

How would the public react if my imagined rail company said that because they couldn't run the best option of through trains from Bradford to London, then they wouldn't do anything to help Bradford to London passengers? These people would like to make the best of the available infrastructure and travel on local trains to Leeds, and then on the main line from Leeds to London. But the railway company says that this is "not their normal way of operating" so they will not cooperate - they will not sell through tickets, and their timetables will be set so that Bradford-London passengers would have to wait ages at Leeds.

I think the public would think this amazingly stupid. There would be immense pressure to sell through tickets and to arrange decent connecting times so that - until the ideal solution is available - then Bradford customers could have the best service that could be squeezed out of the existing infrastructure.

And if it were a profit-seeking company, the shareholders would sack any management who deliberately avoided extra revenue. Unless, of course, they thought that they could use the dreadful Bradford service to extract a public subsidy for the extra trackwork needed for their preferred direct Bradford-London service.

To clarify the analogy - My via-a-non-FTTC-cabinet neighbours are Bradford residents. The new FTTC cabinet is Leeds City station with its fast service to London. But Openreach are declining to take simple actions that would offer them a great improvement on what they have today by running a connecting service.

Nice analogy but telecoms world is different.

An often overlooked aspect is that the FTTC enabling actually brings part of the FTTP build needed for an eventual roll-out one day, and the components would have been scaled for the number of premises service by the EO cluster that has got FTTC now.

Has Openreach or BDUK Local Authority confirmed that there is no intention to provide FTTC to you? It is normal for cabs to be rolled out in stages, so it may simply be that a later phase will see you helped.

Your scenario requires wiring back from the VDSL2 cab into the exchange and then across to where your incoming lines in the exchange are located and intercepting in the building somewhere in a non standard fashion. The wiring in telephone exchanges is intended to be standard and the same across the UK so that engineers can turn up and be familiar with any exchange after a very short time.

This will also involve the RF signals from VDSL2 travelling through the exchange wiring looms, something that the regulations don't allow for, due to interference with existing ADSL/ADSL2+ services.

There are network rearrangement options where you can pay for custom work, but be prepared for the large bill.

In reply to a post by MrSaffron:

Has Openreach or BDUK Local Authority confirmed that there is no intention to provide FTTC to you? It is normal for cabs to be rolled out in stages, so it may simply be that a later phase will see you helped.

The local BDUK outfit (Digital Derbyshire) have indeed confirmed that the non-FTTC cabinet is outside their funded programme (which runs to 2018).

In reply to a post by MrSaffron:

There are network rearrangement options where you can pay for custom work, but be prepared for the large bill.

Any idea of rough cost of connecting a property across a highway to a pole perhaps 15m away, assuming that there is sufficient capacity back to the exchange?

The middle of the mostly-non-FTTC road that I am concerned with does in fact have a pole that does get FTTC (coming in across footpaths and gardens), but it currently only serves three properties on that road. A couple of closer non-FTTC properties could be served by new overhead wiring with above-streetlight clearance.

Would this be covered under "External Shifts of Exchange Line Wiring and Rearrangements of BT Network Equipment and Lineplant" in section 12.2 of the BT Pricelist, which appears to have a fixed cost of £193 inc VAT for residential customers?

In reply to a post by MrSaffron:

Your scenario requires wiring back from the VDSL2 cab into the exchange and then across to where your incoming lines in the exchange are located and intercepting in the building somewhere in a non standard fashion. The wiring in telephone exchanges is intended to be standard and the same across the UK so that engineers can turn up and be familiar with any exchange after a very short time.

This will also involve the RF signals from VDSL2 travelling through the exchange wiring looms, something that the regulations don't allow for, due to interference with existing ADSL/ADSL2+ services.

Hmm, I had a response that went along these lines, but it seems to have gone missing.

Still, it is an important point ... connecting back through the exchange frame is not allowed, because it is not allowed to have the VDSL2 frequencies.

Even worse, the FTTC cabinet will have power levels carefully chosen so that there is no interference to ADSL/2+ signals coming from exchange-based DSLAMs (or vice-versa). Wiring back to the exchange frame will negate this - leading to interference between the ADSL subscribers and VDSL subscribers.

Complete FUBAR.

It also very much means that areas A and B are not served in the way the OP presumes. Either they are already wired from the "right" side of the main road, or the diversion joints have been made in some other cable chamber outside the exchange itself.

Total aside: Some interesting pictures of the cables entering an exchange can be found here:
http://www.britishtelephones.com/gpo/cablechamber.htm
http://www.britishtelephones.com/gpo/jointbox2.htm

In reply to a post by JohnGeddes:

To clarify the analogy - My via-a-non-FTTC-cabinet neighbours are Bradford residents. The new FTTC cabinet is Leeds City station with its fast service to London. But Openreach are declining to take simple actions that would offer them a great improvement on what they have today by running a connecting service.

Using your own analogy, perhaps the better way to see what is wrong is to understand that the only way to accept services from Bradford is to serious interfere with services from Leeds (oh, and interfere with those seemingly unrelated services from York too). Intercity 225's would be left queuing behind Pacers all the way to London.

In reply to a post by JohnGeddes:

Any idea of rough cost of connecting a property across a highway to a pole perhaps 15m away, assuming that there is sufficient capacity back to the exchange?

Would this be covered under "External Shifts of Exchange Line Wiring and Rearrangements of BT Network Equipment and Lineplant" in section 12.2 of the BT Pricelist, which appears to have a fixed cost of £193 inc VAT for residential customers?

You are right that the work would come under the generic term of "network re-arrangement" but it wouldn't be under the that kind of fixed-price schedule. People before have been quoted thousands, but it can be hard to find anyone at an ISP who'll even listen to the kind of request you are making.

This kind of thing *has* been known to happen though, but rarely.

Note that there are also rules about wiring from poles in different circumstances, that can limit how many drop cables can be strung out in different directions. Just because a pole is there doesn't make it freely available either.

In reply to a post by WWWombat:

It also very much means that areas A and B are not served in the way the OP presumes. Either they are already wired from the "right" side of the main road, or the diversion joints have been made in some other cable chamber outside the exchange itself.

Thanks for this - but I am still a bit confused. I understand that VDSL frequencies make interference with ADSL a real issue - but surely there are VDSL and ADSL pairs in the same cables that run along the street, and with only a single trench across the main road from exchange to FTTC cabinet, every ADSL pair on the cabinet is running parallel to every VDSL pair.

If the crosstalk issues are manageable in such a topography, why is it unthinkable that VDSL should should be run via the MDF for those on non-FTTC cabinets?

The UK regulations stop BT running VDSL direct into the exchange - I believe Ofcom set those regulations.

It isn't VDSL2 until it reaches the FTTC cabinet from the headend exchange. Similarly it isn't VDSL2 from the FTTC cabinet back to the headend.

The only place the two are in close-together wiring is between the PCP and the premises. Where the problem is far more manageable than inside an exchange.

In reply to a post by RobertoS:

The only place the two are in close-together wiring is between the PCP and the premises. Where the problem is far more manageable than inside an exchange.

This is where I am struggling to understand. All the evidence points to about 100 D-side pairs running parallel from the new FTTC cabinet, along the pavement for about 20m, then under the road in a single set of ducts, before diverging at the point where the old EO cabling will - other posters assure me - have been intercepted.

Why is it easier to manage VDSL-ADSL interference between 40m of parallel-running pairs than it would be if carefully routed inside an exchange - especially one, like most, built for Strowger so presumably with plenty of empty space these days?

In reply to a post by JohnGeddes:

Why is it easier to manage VDSL-ADSL interference between 40m of parallel-running pairs than it would be if carefully routed inside an exchange - especially one, like most, built for Strowger so presumably with plenty of empty space these days?

The rules say no VDSL in the exchanges. BT don't make the rules, but they have to follow them.

The rules don't necessarily make sense, just like the fact that the motorway speed limit is still 70 mph when cars can stop much quicker than they used to doesn't make sense.

You have a tiny cab of 50 people - you won't be high up on the list I'm afraid.

Network rearrangement is likely to be thousands.

In reply to a post by JohnGeddes:

Thanks for this - but I am still a bit confused. I understand that VDSL frequencies make interference with ADSL a real issue - but surely there are VDSL and ADSL pairs in the same cables that run along the street, and with only a single trench across the main road from exchange to FTTC cabinet, every ADSL pair on the cabinet is running parallel to every VDSL pair.

The crosstalk problems arise when frequencies overlap *and* the signal level (aka power) differs *and* the pairs lie in close proximity. If one line runs at a higher power level, crosstalk can swamp the signal on a nearby line with lower power. Difference in power is key.

In proper wiring, the power level transmitted by the cabinet is carefully adjusted (for all overlapping frequencies) such that it matches the power level of the ADSL signals as they pass the cabinets. Because both signals run in the same direction (away from the exchange, towards the home) the signal levels continue to match in the parallel pairs. Both attenuate at the same rate, and crosstalk is managed.

If we assume that the FTTC cabinet is correctly configured for area D, then the VDSL2 power levels will be reduced slightly (in the ADSL spectrum) so that they don't accidentally swamp the signals of exchange-based ADSL subscribers in area D.

What about area A?
If area A has their wiring entirely rerouted via the same cabinet, with new cables across the road, then back again, this remains true, because both the cabinet-based VDSL2 signals and the exchange-based ADSL signals follow the new route. However, it requires that all signals within one cable bundle go in just one direction. The trench across the road could have separate cables for each direction , as the pairs in each cable would have reasonable separation - separate ducting would help.

If, however, you send those VDSL2 signals (which are already reduced to match power with area D) back to the exchange frame, you cause a problem. The VDSL2 signals will have attenuated on their way back again, so will now be reduced in power even more. They will then share the frame with ADSL signals that have higher power (still at full, exchange-based, power). Because it is the ADSL signals that are higher power, they could swamp any reduced-power VDSL2 signals they run alongside.

If the crosstalk issues are manageable in such a topography, why is it unthinkable that VDSL should should be run via the MDF for those on non-FTTC cabinets?

Crossing the road, with careful cabling design, is one thing. Bringing different power signals to the MDF is a recipe for disaster. There is much less scope for careful design there, and much more risk of running pairs in a way that causes problems.

Plus the fact that signals above 2.2MHz aren't allowed there.

In reply to a post by WWWombat:

Bringing different power signals to the MDF is a recipe for disaster. There is much less scope for careful design there, and much more risk of running pairs in a way that causes problems.

There are some examples of MDF wiring here:
http://www.kitz.co.uk/adsl/telephone_exchange.htm
and here
http://www.telephonesuk.co.uk/exchange_inside.htm

All those loose green+yellow jumper wires show the problem - there is little way to manage those in a way that would guarantee proximity (or lack of) between services.

John

You are correct about the pairs running from the Old cable to the FTTC Cab, there will be two 100 pair cables one from EO cable to FTTC cab and one back to the cable from the cab to continue to the premises served by the Cab. There should be NO ADSL on these pairs as they have been provided to only take those customers having FTTC service.

The VDSL signals are only going away from the Cab/Exchange so can be configured to reduce conflict with the ADSL signals from the exchange once they travel on the cable out to customers from that point.

The rule were not designed for Equipment inside the exchange or right outside the exchange BUT only prohibit installation in the exchange.

BT therefore can place a cab outside the exchange and OFCOM have turned a 'blind eye' to this in order to help those customers on EO pairs.

BT takes the risk of the crosstalk affecting ADSL customers further away and has to overcome this with by reducing the power of the FTTC signal from cabs close to the exchange.

Consequentailly FTTC from an Cab outside the exchange ( serving EO lines) tends to be not as good on long lines from its location as a Cab a long way from the exchange would be on a similar lengh line from it's location.

This is why lines 1 mile from the Exchange sited cab may not get FTTC whilst lines 1 mile from a remote cab may get a resonable speed.

In reply to a post by kitcat:

John

You are correct about the pairs running from the Old cable to the FTTC Cab, there will be two 100 pair cables one from EO cable to FTTC cab and one back to the cable from the cab to continue to the premises served by the Cab. There should be NO ADSL on these pairs as they have been provided to only take those customers having FTTC service.

I may have completely misunderstood but why would there be no ADSL on those pairs? If those customers were ADSL subscribers then there would be. The lines aren't routed through to the new (copper) EO cab only when someone orders FTTC.

Icarus

You are correct in the short term, but the number islikely to drop towards Zero very fast so it is easier to say zero for simple understanding.

They do not route all pairs via the new cab. OR will pick the DPs that are most likely to benefit to move to the new Cab.

So discount all those on DPs a long way away that won't benefit as OR won't move those.

For a WBC or LLU exchange. Discount those close to the exchange that already have good speeds ( 12Mb+) as OR won't move these.

There will be some ADSl customers left but these are those that are likely to move to FTTC fairly quickly as they will benefit the most, ( medium distance 3-6Mb speeds in my opinion). So in the short term you are correct but in the longer term you can discount them also.

Those ADSL that are on the pairs are likely to see a degradation in their existing service ( first from the extra 100m of cable then from crosstalk with VDSL), there is some evidence of this on these forums, but not a lot, and will therefore move even faster to FTTC .

Those getting below 2Mb are likely to be too far away to benefit from FTTC, those above 12-15Mb are unlikely to move to a higher priced product.
( Most of of on here are speed junkies compared to the normal and we should not get our rush to speed confused with that of most customers who are price sensitive.)

There will always be exceptions to all the above cases of distance, speed and requirements BUT OR will only plan on the averages to maximise the cost / benefit equation even when subsidised by BDUK.

Frim what I've seen they do route all remaining EO lines through a cabinet eventually. I've not seen it where they leave some DPs still EO.

But I'll take your word for that. I work in an urban area so it could be different in rural exchanges, where like you say they'll only route lines through the new cab that are going to DPs that would benefit.