Any advantage to dropping POTS?

Deagol

As title says, is there any advantage for either / both VDSL - ADSL if you don't have a telephone service on the line?

I presume that if you drop the telephone service and have BB only then you don't need splitter? If so, is there more bandwidth available on the copper and less noise on the line?

murphaph

Deagol wrote: »

As title says, is there any advantage for either / both VDSL - ADSL if you don't have a telephone service on the line?

I presume that if you drop the telephone service and have BB only then you don't need splitter? If so, is there more bandwidth available on the copper and less noise on the line?

No advantage for BB except no need for a splitter, if that can even be considered an advantage.

It's the way things are going though. It'll all be VoIP in a few years IMO (my phone/internet provider here in Germany only offers VoIP so I have copper as far as the VDSL cabinet and that's it, from there it's fibre back to exchange. No POTS. Only the ex-state provider Deutsche Telekom even offer a line back to the exchange, no VDSL reseller offers it)

Deagol

Reason I asked was I noticed that with the splitter in place, the spectrum analyzer on the router shows a very big dip at around 2.2Mhz, which co-incidently is were ADSL2 stops.

It occured to me that perhaps the splitter is mucking up the VDSL2 signal. I don't think removing the splitter temporarily with a POTS signal is a valid test as the phone signal would cause noise then?

mpok

With VDSL the only splitter is already in the termination box the Eircom contractor installed when doing the eFibre installation. There would be no point in using an old xDLS splitter with a proper VDSL installation.

Dropping the POTS line, if actually implemented by removing the jumper in the cabinet rather than in the exchange, would get rid of a couple of km of line back to the exchange which would be picking up noise and degrading the VDSL signal.

ADSL is normally supplied from an exchange so dropping the POTS should make no difference.

Deagol

mpok wrote: »

With VDSL the only splitter is already in the termination box the Eircom contractor installed when doing the eFibre installation. There would be no point in using an old xDLS splitter with a proper VDSL installation.

Dropping the POTS line, if actually implemented by removing the jumper in the cabinet rather than in the exchange, would get rid of a couple of km of line back to the exchange which would be picking up noise and degrading the VDSL signal.

ADSL is normally supplied from an exchange so dropping the POTS should make no difference.

The engineer who installed my VDSL didn't have a clue. He freely admitted he was normally employed as a line puller and had been seconded to the job.

He didn't install anything really, he just picked a F1000 modem out of the van, plugged it in and asked me if it was working

If I'm reading this correctly, he should have installed a different termination box? (I have the one with the Eircom logo that was installed for ADSL about 5 years ago).

If I cancelled the Eircom POTS, would it be terminated at cabinet with the jumper or at the exchange do you think?

mpok

I don't know if there is a difference between the ADSL and VDSL termination boxes. I went from the phone only box installed by TE back around 95 to the VDSL box that was put in with eFibre. Bottom line is that a proper eFibre installation comes with a termination box that has separate phone and modem outlets and the appropriate filters for splitting them integrated. Standalone xDSL splitters would not necessarily pass the full VDSL2 bandwidth to the modem without loss.

The guys who did my installation appeared to be following a detailed script. They were happy to locate the router at the other end of some cat5e I had in place but insisted in reterminating with their own sockets rather than the ones I had in place. They ran speed tests from their iPad and then used the iPad to photograph their work.

ED E

The NTUs are the same. So if youve had an updated one fitted for DSL it'll work for VDSL.

The line voltage still comes from the exchange, so if you drop POTS service all that changes is you get a dummy phone number that cant ring or be rung, the same equipment is connected.

Deagol

Did some reading up on ADSL / VDSL splitters and gave eFibre tech support a quick ring to double check and that was same answer. No difference in splitters.

Love to know what causes the SNR dip at 2.2MHz though

Bit puzzled about what the line voltage would be required for if the POTS is discarded? Presume the DSLAM has its own PSU at the cabinet? It doesn't use line voltage surely?

ED E

Deagol wrote: »

Bit puzzled about what the line voltage would be required for if the POTS is discarded? Presume the DSLAM has its own PSU at the cabinet? It doesn't use line voltage surely?

The racks in a VDSL cab are all powered, but they dont supply line voltage. They just modulate the existing signal. Think of the DSLAM like DAC on a soundcard and the AXE/MDF in the exchange as the amplifier.

Deagol

Ah, that makes sense. Thanks for the explanation!

murphaph

ED E wrote: »

The racks in a VDSL cab are all powered, but they dont supply line voltage. They just modulate the existing signal. Think of the DSLAM like DAC on a soundcard and the AXE/MDF in the exchange as the amplifier.

But surely the option is there to sever the line back to the exchange and provide line voltage from the cabinet's PSU?

I understand that Eircom wholesale currently retain the line back but that will become redundant IMO as IP takes over all communications. As I mentioned upthread, German VDSL customers generally have no line back to the exchange and telephony is provided through VoIP only. It's only possible to even have/retain the line back if you are with Deutsche Telekom. No reseller offers it-VoIP only.

We want to move towards deeper fibre penetration over time, so I would be shocked if there's a dependency on the line back to the exchange for line voltage and that this dependency can't (easily) be removed and provided for by the cabinet's power source.

ED E

They could have done it that way, but didnt. The one upside to the way they have it now is that telephone exchanges very rarely lose power and when they do they have large battery banks that keep them online for a while. This means that the phones attached to them will rarely go dead. You can even use your phone line to power LED bulbs in a protracted outage(not advised, but possible). The cabs on the other hand are off local power, so if an area loses power so does its cab. If the phones were provided off that they're gone too. Not a huge thing IMO, but lots of Ireland is heavily reliant on their POTS line still(see all the OAPs living remotely). This *may* be why they did it.

They do have a VOIP system running already, so the backend is in place. A migration to VOIP only could be done later as long as the cabs have the space for PSTN cards to provide line voltage OR if the DSLAMS are capable of it themselves. Finding out that one would be next to impossible though unless you know somebody in Huawei.

fat-tony

In the longer term surely any home VoIP system would be linked to your trusty modem/router which would power whatever device you were using as a handset? I would have thought most modern handset devices used for VoIP would be powered over USB or other low voltage. Presumably the conventional handset requiring 50V+ for the ringer would go the way of the dodo? The disadvantage is obviously no 'phone service during a power outage. I would imagine the reason why the VDSL cabinets couldn't provide power back to the home during a power outage is one of footprint. The base of the cab is probably only big enough to provide sufficient battery backup for the cab for a period.
I would imagine that the reducing number of people to retain conventional POTS would be the ones least likely to change over to a VoIP solution, perhaps? I presume that the majority of telephony is digital in any case and that there are ADCs and DACs built into exchanges these days?

ED E

Nah, modern handsets dont need it, but VDSL requires a base voltage to run the signal on. That may work on way less than 50v though, I dont know.