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Author Topic: Speculation: VDSL2 to be turned off to gained G.fast speed boost?  (Read 1010 times)

adslmax

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I just saw MrSaffron posted headline about this VDSL2 upcoming found here: https://www.thinkbroadband.com/news/8403-fifteen-more-exchanges-with-g-fast-ultrafast-broadband-are-now-live

"The interesting part will be if VDSL2 is turned off in different areas whether the spectrum used can be recovered and give G.fast a speed and range boost."

But question is .... What IF the customers want to remain staying on VDSL2 (FTTC) because of cheaper cost than expensive G.fast products?

[Moderator: Subject line adjusted.]
« Last Edit: May 11, 2019, 07:09:59 PM by burakkucat »
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re0

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Re: Speculation: VDSL2 to be turned off to gained G.fast speed boost?
« Reply #1 on: May 11, 2019, 02:29:17 PM »

First of all, I think VDSL2 is unlikely to be a target for a while, probably until full fibre. Openreach will be more focused on removing E-side copper, thus getting rid of POTS and ADSLx, before this.

But there are issues with their current implementation of G.fast that makes getting rid of VDSL2 and moving customers G.fast impossible in most areas:
  • Vectoring is intense, so current I believe current port capacity is 48 (96 underway) - compare this to max capacity of 288/344 of the higher capacity VDSL2 cabinets
  • They bolted it to the cabinet, so where can they put another pod? (Plus there's the question of vectoring across hardware)
  • Current power and fibre is supplied from the existing VDSL2 cabinet - there would need to be new sources

There are others issues I haven't touched on, regarding performance over distance, costs to ISPs to supply new hardware, etc.

However, in the scenario where this did actually happen, ignoring all issues relating to it, I imagine there would be an equivalent package of an equivalent cost to aid progress to move end users over.

My conclusion is that it won't happen and it can't happen under the current amendment (they would really need DP G.fast for it due to capacity). But if it did, then I think there would possibly be a package equivalent to the top tier VDSL2 one (80/20). Even if customers did not want to move, they would have no choice.
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Ronski

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Re: Speculation: VDSL2 to be turned off to gained G.fast speed boost?
« Reply #2 on: May 11, 2019, 03:40:47 PM »

If there was no VDSL then G.Fast could use the frequencies that VDSL uses and thus distance could be increased, I wonder if it would get similar speeds as VDSL at the longer distances if that was the case?
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burakkucat

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Re: Speculation: VDSL2 to be turned off to gained G.fast speed boost?
« Reply #3 on: May 11, 2019, 07:06:57 PM »

The logical progression to that train of thought would be FTTDP (Fibre To The Distribution Point) for those EUs where FTTP would prove to be too difficult or impossible to provide.
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re0

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Re: Speculation: VDSL2 to be turned off to gained G.fast speed boost?
« Reply #4 on: May 11, 2019, 07:31:02 PM »

I've wondered the same for a while. Without access to the specifications it is a bit difficult to judge (I wanted to look at the ITU documents but I cannot access the website). At least in the UK for G.fast, there's STIN 520 which documents the G.fast Pilot, but I don't know if this has been supersceded. Likewise for FTTC, there's SIN 498.

No question, G.fast utilising the whole 2-106 MHz spectrum could operate faster further away than with the current state of G.fast with co-existence with VDSL2. Though I would presume VDSL 17a would be able to operate faster than G.fast at the longer distances due to the transmit power being 14.5 dBm (versus 8 dBm with G.fast) alone, but we would probably be talking somewhere nearer to 800-1000m before VDSL2 would be faster. Vectoring can be ignored since the impact it has towards the extremes tends to be very little.

Bear in mind, I am just making a presumption. I have certainly not gone too deep into this. I don't understand what impact a different Divison Duplexing will have, I haven't really looked into the effects on upstream, I have not understood the impact of receiver sensitivity, etc.
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ejs

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Re: Speculation: VDSL2 to be turned off to gained G.fast speed boost?
« Reply #5 on: May 11, 2019, 09:16:04 PM »

There is the NICC ND1520 document all about options for G.fast using VDSL2 frequencies, and the latest ND1602 Access Network Frequency Plan document lists two scenarios in which G.fast is permitted to start below 18.3MHz. If I've understood the acronyms in ND1602 correctly, the first scenario depends on the distance between the G.fast pod/box and the cabinet, which would be practically zero for a G.fast pod on the side of a cabinet, and so not really applicable to G.fast from the cabinet. The second scenario is a rather unspecific "documented commercial agreement for a given SDF and associated G-SDFs, and as such is subject to consensus between DSLAM operator(s) and relevant CPs".

It's spectrum refarming (adjusting or overlapping the frequencies), rather than turning off VDSL2 completely.
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PhilipD

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Re: Speculation: VDSL2 to be turned off to gained G.fast speed boost?
« Reply #6 on: May 15, 2019, 02:27:17 PM »

Hi

At the end of the day the physical line and speeds supported is dependant on physics and attenuation of frequencies.

So assuming all technologies used the same frequencies they would at a certain distance end up all being a similar speed, and wouldn't go much further and would not be faster than a lesser technology.

VDSL is only faster than ADSL because it uses more and higher frequencies, which is why it had to be moved nearer to homes, otherwise there is next to no speed increase.  We already know at a certain line length VDSL ends up performing very similar to ADSL at the same distance and has little advantage in long reaches.

G.Fast is faster again because it uses even higher frequencies, but due to various accounting decisions BT decided not to shorten the distance as they did with VDSL to save costs, therefore it only benefits those on lines that are very short.  If a line only gets say 60MB/sec on VDSL so already dropping high frequencies due to distance, it will not get that much more on G.Fast, there is nothing magical about G.Fast that suddenly means higher frequencies arrive at the other end that didn't before on VDSL.  At some distance assuming G.Fast can use all the same VDSL frequencies and powers, G.Fast will have no speed advantage.

Obviously this ignores technology improvements between the various flavours of xDSL that try to wring a bit more out of POTs, and G.Fast has vectoring which was never enabled on VDSL.  However at long line lengths these extra tweaks stop providing much advantage anyway.

G.Fast is trying to polish a turd that was already polished by VDSL, and G.Fast is a desperate attempt at trying to reuse POTs and avoid the inevitable of installing a new network fit for the 21st century.  Thankfully BT have realised this now and Fibre First is here.

Regards

Phil
« Last Edit: May 15, 2019, 02:30:37 PM by PhilipD »
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adslmax

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Re: Speculation: VDSL2 to be turned off to gained G.fast speed boost?
« Reply #7 on: May 15, 2019, 02:42:00 PM »

Thankfully BT have realised this now and Fibre First is here.

Regards

Phil

Sound like the customer who already got G.fast pod with live will not gettting fibre first (FTTP) or it will happen?
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PhilipD

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Re: Speculation: VDSL2 to be turned off to gained G.fast speed boost?
« Reply #8 on: May 15, 2019, 03:16:34 PM »

Sound like the customer who already got G.fast pod with live will not gettting fibre first (FTTP) or it will happen?

Not necessarily so, FTTP is in some cases is being built where G.Fast is already available, remember potential G.Fast customers on a cabinet may be a low percentage of the overall number of customers.

The plan is that everyone will have an FTTP connection with copper cable being retired completely, although we are a number of years away from that, but eventually we will all have fibre.

Regards

Phil
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adslmax

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Re: Speculation: VDSL2 to be turned off to gained G.fast speed boost?
« Reply #9 on: May 15, 2019, 03:38:06 PM »

The plan is that everyone will have an FTTP connection with copper cable being retired completely, although we are a number of years away from that, but eventually we will all have fibre.

Regards

Phil

 ;D ;D Good I shall wait for this FTTP, not bothered with g.fast. Staying with FTTC until FTTP come along.
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gt94sss2

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Re: Speculation: VDSL2 to be turned off to gained G.fast speed boost?
« Reply #10 on: May 15, 2019, 04:01:37 PM »

;D ;D Good I shall wait for this FTTP, not bothered with g.fast. Staying with FTTC until FTTP come along.

It could be a decade or longer though - so it depends how important/necessary higher speeds are for you
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ejs

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Re: Speculation: VDSL2 to be turned off to gained G.fast speed boost?
« Reply #11 on: May 15, 2019, 06:38:32 PM »

At some distance assuming G.Fast can use all the same VDSL frequencies and powers, G.Fast will have no speed advantage.

But G.fast uses Time-Division Duplexing, so it can use the whole frequency range for upstream and the whole frequency range for downstream.
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PhilipD

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Re: Speculation: VDSL2 to be turned off to gained G.fast speed boost?
« Reply #12 on: May 16, 2019, 08:06:12 AM »

Hi

Time division doesn't increase the total data rate, you just are able to split the ratio between upload/download speeds more easily than VDSL.  So if at a long distance you are only getting say 9 down and 1 up on G.Fast, the ISP could choose to swap the ratios to 5 down and 5 up, so yes you may benefit from G.Fast in that respect, but overall data-rate is the same, so no massive differences.

The over-riding limitation on telephone wires is the physical medium of the wire itself, and there is nothing that can overcome that. Despite G.Fast being a new technology, VDSL is also capable of similar speeds over the same shorter distances if allowed to use the same frequencies as G.Fast.

Regards

Phil


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Bowdon

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Re: Speculation: VDSL2 to be turned off to gained G.fast speed boost?
« Reply #13 on: May 16, 2019, 10:55:41 AM »

I thought the amount of G.fast ports per pod was very low compared to the VDSL2 cabinet?

There might not be enough ports to transfer everyone over to G.fast... and what happens to the people who was in range for VDSL2 but now out of range for G.fast? They got to go back to ADSL speeds?

I think the more likely change would be to the VDSL2 profile someone mentioned on the forum, 35b (?) as it extends VDSL2 range and would give us all better speeds.
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aesmith

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Re: Speculation: VDSL2 to be turned off to gained G.fast speed boost?
« Reply #14 on: May 16, 2019, 11:27:33 AM »

The plan is that everyone will have an FTTP connection with copper cable being retired completely, although we are a number of years away from that, but eventually we will all have fibre.

The cynic in me says that they'll find reasons not to provide fibre to properties currently on long copper paths.
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