No, I don't think its easy at all. I spent 20 years wondering why someone (ITU maybe) had allocated the same 12 MHz band HF frequency the Post Office for radiotelephone ship communications as they had allocated to Norddeich Radio in Germany. 12 MHz being a good frequency for comms of the west coast of Central America....

I got my cable wrong in my previous post.

I am about 500 metres (as the cable goes) from the FTTC which serves me. Same cable, same wooden pole, the person across the road has ADSL.

I would have thought (dangerous, I know) that the cross talk in that 500 metres would be as bad as a FTTC on the "wrong" side of the exchange wall.

Cheers!

The crosstalk isn't "leaked" in the pairs as there is a small gap between the upper ADSL frequencies and the lower VDSL frequencies.

The issue is with the higher power output from the VDSL kit can interfere with the ADSL kit in the exchange, breaching the ANFP.

Here's some light reading http://www.niccstandards.org.uk/files/current/nd1602...

Edited by deleted (Sun 21-May-17 21:55:29)

In reply to a post by Ancient_Mariner:

So what about two customers on the same cabinet and same cable back to the exchange, where one is on ADSL and the other on VDSL?

They aren't. At least, not in the way I read your post.

The PCP <> exchange copper down which the ADSLx travels doesn't change when someone goes on to FTTC. Have a read of this well out of date page. The connections and traffic movements are correct though.

Frequently these days the optical fibre doesn't even go to the phone exchange, it goes to a bigger one in the area which has the Openreach kit to hand over the FTTC to ISPs. VDSL2 only exists between the FTTC cabinet and the end user.

The FTTC cabinet contains a DSLAM, as in olden days the exchanges had. (I expect some still do, but MSANs are the latest stuff with more capability). The DSLAM merges digital traffic from the fibre exchange with the analogue phone signal giving an analogue output with phone and VDSL2 frequencies present. Splits them on the way back from the user.

I went back and looked at the early part of the thread. It is pretty laughable.

The reason we don't get VDSL DSLAMs in the exchange is indeed crosstalk. And there are all manner of RF electrical engineering reasons why crosstalk is a threat to DSL.

However, the reason that this crosstalk is a threat in Britain but not NZ is, well, typically British...

In reply to a post by lee111s:

Here's some light reading http://www.niccstandards.org.uk/files/current/nd1602...

The ANFP tells you what is and isn't allowed. But it doesn't really go into details *why*.

There's a newer report out of NICC as a result of a study whether VDSL2 could ever be allowed from the exchange:
ND1517: Report on the Technical Feasibility of Deployment Options for VDSL from the Exchange

That document makes it clear that, if EO lines were really pure EO lines, then VDSL2 would be feasible.

The problem is that EO lines aren't really pure - they can share the E-side and/or D-side with cabinet-based lines - and that such shared wiring isn't well documented. Even worse, EO lines have been patched into cabinet-based D-sides in small segments, as part of fault-fixing.

It also seems that the biggest risk appears to be to upstream signals, especially as UPBO is in use.

Thank you for that detail. With Mrs S having being involved, the accuracy cannot be disputed.

In reply to a post by witchunt:

I think they brought the facilities management back in house

BT Property Services, BT Property Management or some such-like named entity, I will presume.

When did our esteemed staff member/Editor decide on a gender re-assignation?

Heh!

BTFS - BT facility services

In reply to a post by RobertoS:

The FTTC cabinet contains a DSLAM, . . .

To be absolutely correct, the Huawei SmartAX MA5616, the SmartAX MA5603T and the ECI Hi-FOCuS MiniShelf M41 are all MSANs . . . which are just used as DSLAMs.

In reply to a post by RobertoS:

When did our esteemed staff member/Editor decide on a gender re-assignation?

I wondered if anyone would question that! But knowing the significance of your prefix S, I don't think I need to type any more.