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    Attainable rates on Pro

    This is a discussion on Attainable rates on Pro within the Sky Broadband (Fibre) Help forums, part of the Sky Broadband help and support category; Originally Posted by Fryingpan77 <br /> Scubbie explained this problem in another thread. Its not the cross talk in the ...

    1. #11
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      Originally Posted by Fryingpan77<br />
      Scubbie explained this problem in another thread. Its not the cross talk in the vdsl cabinet that's the problem. Its the cross talk in the PCP cabinets and the copper part of the connection. The higher frequency used for vdsl causes more problems on the copper side. So more people connected on vdsl = more cross talk. <br />
      <br />
      Sent from my ST18i
      <br />
      <br />
      Would be interested in seeing the source of this info, any help? I've looked but can't locate it.<br />
      <br />
      You have fibre going into the VDSL cab, a copper connecting pair from the VDSL cab to the PCP cab, then your copper line to the premises. Copper in bother cabs, high frequencies in both cabs. I tend to think BTO would have thought about this before rolling out FTTC to the masses.<br />
      <br />
      <br />
      I live in a town centre location, where VDSL take up was very quick. My VDSL cab is full and has been for 5 weeks, so we can assume there are alot of VDSL customers passing through the PCP cab. I've noticed no negative impact on my line.
      There is no negitive affect if you are close enough to your cabinet. You will get the top speeds on offer. The speed drops at a higher rate the further you are from the cab. Crosstalk plays a part in this. BTO obviously took this in to account and that's why people get different estimates. Doesn't mean the whole thing doesn't work. Just means people will be on different speeds.

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    3. #12
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      Re: Attainable rates on Pro

      Quote Originally Posted by Fryingpan77 View Post
      There is no negitive affect if you are close enough to your cabinet. You will get the top speeds on offer. The speed drops at a higher rate the further you are from the cab. Crosstalk plays a part in this. BTO obviously took this in to account and that's why people get different estimates. Doesn't mean the whole thing doesn't work. Just means people will be on different speeds.

      Sent from my ST18i
      I see your point, but the reason estimates differ from actual sync speeds are due to the fact that VDSL estimators, BT, BTo etc, estimate the speed on theoretical values as there is no VDSL connection in place to test, not due to crosstalk. Infact, i would go so far to say that the trend seems to be under estimating, rather than promising a higher speed, only to receive less due to interference.

      Anyhow, can you point me in the right direction for Scubbie's post explaining this, I can't find it.

      Ta.


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    4. #13
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      No problem. Its the last post on page 45 of the sky fibre unlimited
      Pro rumor thread.

      Sent from my ST18i
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    5. #14
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      Re: Attainable rates on Pro

      Quote Originally Posted by fazedup View Post
      Anyhow, can you point me in the right direction for Scubbie's post explaining this, I can't find it.
      Try this: http://www.skyuser.co.uk/forum/sky-b...tml#post375908

      Quote Originally Posted by Scubbie View Post
      Before SFU was launched someone else posed this question and I didn't understand the issues. At the time I thought that they were suggesting Sky's traffic would share the same fibre optics to the exchange so said it shouldn't happen.

      However this isn't the problem. As Andrew has pointed out, the issue is with the copper cables.

      The higher frequency of FTTC on the copper wiring appears to be causing interference with other connections. I believe that this is why the connection estimates have so far proved to be significantly lower than what people have been getting. I also explains why, as more people become connected on the FTTC cabinets, that some people are finding that their maximum potential speeds are dropping.

      To the best of my knowledge, the Fibre connection from the FTTC cabinet to the Sky kit is not subject to this interference.

      PlusNet Fibre since Jan 2021
      Previously Sky Fibre & Sky BB since 2010.

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      Re: Attainable rates on Pro

      Cheers for that, I would have been wading through for donkey's years!

      Ok, that post didn't really help me out too much, as there just wasn't anything concrete to back it up.

      I completely agree that external interference can affect the copper line running into the premises, but I do not think it has anything to do with the copper connecting pair in the PCP cab, or that increased numbers of users in any given PCP/VDSL cabinet will result in decreased sync speeds. At worst, it'll neglegable.

      Obviously, I can't confirm this either, but when I look at this generally, I don't see many cases where sync speed, or Max Rates have dropped significantly as time has passed. VDSL has been in circulation for alot longer than Sky have been providing it, the VDSL Cabs have customers from a plethero of different ISP's. If this was a known to be a serious issue, other users from different ISP's would have made this apparent before now.

      I'm not saying there aren't isolated incidents, there are, but this could also be down to a number of different issues.

      Speeds tests tend to be conservative, rather than over estimated. Max Attainable rates may have dropped a little, but in the grand scheme of things, precious little.

      There just seems to be no evidence that the higher frequencies are affecting the copper in the PCP cabs and no evidence that increased numbers of users are affecting Max rates.


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    7. #16
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      Re: Attainable rates on Pro

      Vectoring will no doubt be introduced in time that will allow the crosstalk issue to be kicked into the long grass. Read: vectoring wouldn't exist if crosstalk didn't interfere with subscribers VDSL speeds...
      Maybe BTO compromised on 288 lines being the maximum for a cabinet to reduce the likelihood of a large reduction in speeds when it becomes full as well as the size considerations of course.
      Vectoring is a transmission method that employs the coordination of line signals for reduction of crosstalk levels and improvement of performance. From 2010 ITU-T G.993.5, Self-FEXT cancellation (vectoring) for use with VDSL2 transceivers, describes vectoring for VDSL2. The scope of Recommendation ITU-T G.993.5 is specifically limited to the self-FEXT (far-end crosstalk) cancellation in the downstream and upstream directions. FEXT generated by a group of near-end transceivers and interfering with the far-end transceivers of that same group is cancelled. This cancellation takes place between VDSL2 transceivers, not necessarily of the same profile.[4]
      Very high speed digital subscriber line 2 - Wikipedia, the free encyclopedia
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    8. #17
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      Re: Attainable rates on Pro

      Quote Originally Posted by Mystic Eddy View Post
      Vectoring will no doubt be introduced in time that will allow the crosstalk issue to be kicked into the long grass. Read: vectoring wouldn't exist if crosstalk didn't interfere with subscribers VDSL speeds...
      Maybe BTO compromised on 288 lines being the maximum for a cabinet to reduce the likelihood of a large reduction in speeds when it becomes full as well as the size considerations of course.

      Very high speed digital subscriber line 2 - Wikipedia, the free encyclopedia
      Now that's concrete!


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      Re: Attainable rates on Pro

      Actual sync rate has dropped to 65000 now
      Max attainable rate has RISEN to 75000.

    10. #19
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      Quote Originally Posted by gorebrush View Post
      Actual sync rate has dropped to 65000 now
      Max attainable rate has RISEN to 75000.
      Has your ping rate been affected at all ? Be interesting in a week or 2 to see where it balances out at.

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    11. #20
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      Re: Attainable rates on Pro

      I told myself that anything above 60 and I am happy.

      I think DLM has brought it down to 65000 and that is not to be sniffed at!

      Especially when my boss told me it was obscene. Though, I think that may be because he said he only gets 1Mb

     

     
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