Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[guest]

Can I add fuel to the fire by suggesting that if I had FTTC available now I almost certainly would not be taking it.
As it is, until BDUK puts it in, I won't have the option anyway.
But so far as I use the web an achieved download speed of 12Mbps on ADSL2+ is quite adequate here.
Quite what I would do with a FTTC supply of 80Mbps as I'm 100 yards from the cabinet I really don't know.

I'm sure this will change in the future - but that time is some way off.

I think the change will come when you don't even think about the speed your connection is running at (as a techie), and I'm sure that isn't going to happen with VDSL.

To some extent I have that on downstream anyway, upstream is a lot more of a pain in the backside due to Sky's asinine profiles which (because they are profiles) don't degrade gracefully - you come close to the profile speed and pings go through the roof etc instead of the (slightly) more graceful way TCP would work on a line not artificially limited. For those of you who remember how ADSL worked years ago (before DLM/profiles) then you could run upstream at close to max (-10kbps or so) and latency would be normal. Try that these days

Upstream would be the main driver for me but both of the kids are likely to be off to uni (poor sods) inside 3 years so not much point in that. If FTTP is £1k or less for this house next year then I think we'll just do it as all the houses here are much of a muchness so FTTP might swing the sale.

[JGO]

From my viewpoint the article is useful because it points up the damaging effects of extension spurs.
I suspect a lot of connections are not running at full capability because their owners can't understand that just because it works OK at 300-3000 Hz, the extension it isn't good for ADSL, and they will be disapointed  on going to FFTC/VDSL where the effect is worse.   

[burakkucat]

Correct me if I'm wrong but I believe that the article in question was written when the original VDSL specification was current.

Now, with VDSL2, the situation will be actually worse due to the even higher frequencies used. 

[JGO]

"Correct me if I'm wrong but I believe that the article in question was written when the original VDSL specification was current.

Now, with VDSL2, the situation will be actually worse due to the even higher frequencies used. "
--------------
As the article is dated 2000 you are probably correct, don't know for sure.  I find it is quite difficult to find system parameters.
Yes obviously the situation will be even worse on a wider bandwidth system !!
 

[guest]

Correct me if I'm wrong but I believe that the article in question was written when the original VDSL specification was current.

Now, with VDSL2, the situation will be actually worse due to the even higher frequencies used. 

As you increase frequency then the current will flow in a decreasingly small cross-section of a conductor - known as skin-effect. As that happens the signal is more likely to radiate even in really good TP bundles.

The other problem is that as the frequency increases then the wavelength shortens. This means that (for example) a 15m pair run with one leg disconnected will become a pretty efficient noise emitter as it'll look much like a half-wave dipole to some of the frequencies.

Vectoring will help but only up to a point and faults are going to cause much more havoc than now.

[renluop]

And those faults, will they just affect the FTTC community, or also muck it up for the plebeians like me on ADSL+ and normal phone users?

[burakkucat]

And those faults, will they just affect the FTTC community, or also muck it up for the plebeians like me on ADSL+ and normal phone users?

Everyone, to a greater or lesser extent. 

[guest]

And those faults, will they just affect the FTTC community, or also muck it up for the plebeians like me on ADSL+ and normal phone users?

FTTC really as most of this stuff will be happening above 3MHz - it starts getting serious around 10MHz which is 30m wavelength (15 for half-wave dipole) as you can reasonably expect those sort of lengths on DP runs - which is where most faults are.

The significance of that is when you get to full, half (or even quarter in some instances) wavelength on the conductor it will start to become very efficient at "broadcasting" the VDSL signal so it won't just be affecting the local cable bundle. It will to all intents and purposes become an aerial if one of the TP legs is disconnected.

ADSL2+ for example would have a minimum wavelength of around 130m so if something similar happened then it'd be conductors in very close proximity which would be affected as it wouldn't make a good aerial.

Make any sense?

[JGO]

There is another factor which no one has mentioned. The Short wave bands are NOT empty bandwidth just waiting for VDSL !!  They are heavily used  so  interference is possible from both radio and electrical - I seem to remeber reading that car ignition could clobber TV in Band 1 at 40- 70 MHz if not supressed. 

  Also, in response to renlulop, not quite clear what you mean by "faults"  but I think the variation of noise level on my ADSL, till I interupted the bell wire, was due to received electrical noise?
As to it happening to 'phones, it was commonplace in Rugby till GBR on 16kHz shut down a year or so ago !