Correlation between FTTC speeds and G.FAST?

A lot of the discussion about G.FAST estimates revolves around distance. Whilst it's possible to measure distance it's not really trivial and given how quickly speed drops off may not be accurate. So can anything be deduced from known VDSL speeds?

Using Google Earth and walking apps my line appears to be about 360 metres from the VDSL cabinet and perhaps 340 from the PCP. I currently sync at about 70Mb/s and in the past have seen attainable rates of 90Mb/s though that was several years ago when I had an unlocked modem.

Various articles suggest that 350 metres is the cut off point for G.FAST so that suggests VDSL syncing at 70Mb/s or TBB speed test results of about 68Mb/s are the point where G.FAST becomes untenable. Does that make sense?

Edited by Andrue (Sun 23-Dec-18 11:28:29)

There is a nice graph of VDSL speed versus distance here. It's possibly a bit conservative, i.e. with a clean line you may get higher speeds than indicated, and it predates the 3dB SNR changes.

But it suggests that if you get 70Mbps you are probably on a 400m loop, maybe as much as 500m.

As for G.fast, there's a table here and a graph in the last message on this page.

OpenReach don't offer G.fast unless they can guarantee 100Mbps, which means you're unlikely to be able to order it beyond about 400m.

I was getting 70Mbps FTTC sync on 3dB at 600m cable distance.

Edited by RobertoS (Sun 23-Dec-18 13:07:45)

I'd struggle to believe I was 400 metres from my cab. I can follow the inspection chamber covers along the pavement and the route seems fairly straightforward. It might cross the road and go round a small roundabout rather than straight across one exit but that isn't going to add more than 20 metres.

I don't currently have an unlocked modem but looking back at old IDNet posts I can see that several years ago I sync'd at 74399. I'm also pretty sure I used to see an attainable of just over 90Mb/s.

To be frank I don't need G.FAST but it just seems like VDSL speed would be a better gauge than distance.

Edited by Andrue (Sun 23-Dec-18 13:46:43)

In reply to a post by candlerb:

But it suggests that if you get 70Mbps you are probably on a 400m loop, maybe as much as 500m.

My parents are about 500m getting a 72Mbps sync on VDSL. I'm 470m from my cabinet and getting 49Mbps on 3.1db SNR today - guessing xmas lights effect, used to get 60 at start of month. No point fitting G.FAST here from that cabinet. About 60 flats here.

Probably within range, but from what I'm seeing not all gfast pods are equal, so might vary depending on whether nokia or alcatel

We are now seeing people with marginal just about 100 Mbps speed tests, but numbers are still low in terms of volume. Only 7,000 customers declared in last results

There is no direct correlation between FTTC speed and G.Fast speed.
Such high frequencies cause too many variables between lines.

A massive over simplification, but if someone doesn't get the full 80Mb (ignoring previous attainables, I mean now) then the chances are they are out of reach of G.Fast in its current form.
There will be a few who sync just under 80Mb who may just qualify for G.Fast but at the longer distances the upload would likely be smaller than FTTC.

The exact same question was asked on kitz forum last week.
https://forum.kitz.co.uk/index.php/topic,22858.0.html

edit: sync of 74399 is a capped/banded figure so the line was artificially held back so not good for comparison without the SNRM at the time.

Edited by j0hn83 (Sun 23-Dec-18 14:45:36)

Sounds like my line will be an interesting edge case. The DSL checker gives me a high of 80Mb/s on FTTC and historically noise was the biggest issue. I'm still not sure if I'd go for G.FAST but I'd be tempted, if only to satisfy my inner geek.

DSL Range A (Clean) 80 62.5 20 19 56.4 Available -- --
VDSL Range B (Impacted) 80 57.9 20 19 49 Available --

Curiously the last tested date has updated but now there's no speed on record.

Observed Speeds

G.Fast

VDSL

Other Offerings




Availability Date



VDSL Multicast -- -- -- Available -- --
ADSL Multicast -- -- -- Available -- --
Premise environment

Status

Bridge Tap U
VRI N
NTEFaceplate P
Last Test Date 11-12-2018

personally I think unless you vectored I wouldnt consider a 70m estimate at 400m conservative.

I am 365m, and the low (clean) estimate for me is just over 50mbit/sec, which means someone is getting speeds close to me in that ballpark.

I expect the upper distance to make g.fast viable is much closer to 300m than 400m as well. If you value your upload speed it will be less then that.

Edited by Chrysalis (Fri 28-Dec-18 16:12:11)

Hi Andrue,

Sorry that it is a late response, but cabinet 15 is already enabled for G.fast. "G.Fast" showing as a column in the observed speeds is a sign that G.fast is enabled on the cabinet.

It certainly looks like you are out of range, at least according to the DSL checker. It looks like you won't be able to get it, even if you wanted. I apologise if I am just repeating knoweldge.

If you were interested, you could contact a prospective ISP (not Plusnet since they do not offer it) to escalate the case with the wholesale and Openreach. But I really do not have hope for you to be able to receive it.

Interestingly enough back when the DSL checker was showing planned information for G.fast back in March 2018 it was telling me that my clean range was 330-330 Mbps for downstream!

Approx. 200m from the cabinet, probably a mix of copper and aluminium. Currently syncing max 80/20 6 dB downstream (actual usually ~6.8 dB) with G.INP. Sync speed has only ever been close to handback with an open profile, but with G.INP it has always been max.

I doubt that 330 Mbps will be possible when enabled, but we shall see!

DSL checker was showing planned information for G.fast back in March 2018 it was telling me that my clean range was 224-254 Mbps for downstream!

Approx. 248m from the cabinet with currently syncing 80/20 with 6dB downstream with G.INP enabled with low interleave with max rate of 83/28.

In reply to a post by j0el:

Sorry that it is a late response, but cabinet 15 is already enabled for G.fast. "G.Fast" showing as a column in the observed speeds is a sign that G.fast is enabled on the cabinet.

It certainly looks like you are out of range, at least according to the DSL checker. It looks like you won't be able to get it, even if you wanted. I apologise if I am just repeating knoweldge.

No, I wasn't aware. I didn't particularly want it (certainly don't need it having nearly 70Mb/s already). But it seems odd how it just goes live with no announcement and we weren't even on any roll-out list. I might enquire with IDNet anyway out of curiosity. Thanks for your help.

Those on the limits of G.Fast can't order and show as "Amber" instead of "Available".
If nothing shows at all then you are out of reach.

No idea what talking to an ISP is going to achieve, no idea why that was suggested to you, it won't help.

At 340m and syncing at 70/20 IF (That's an if, but in reality it's a no) you scraped on to a G.Farce package you would be getting nearer 100/10Mb.

Note that your upload halves at the very far end of the working G.Fast range.

Later amendments of G.Fast may reach those distances.

In reply to a post by j0hn83:

Those on the limits of G.Fast can't order and show as "Amber" instead of "Available".
If nothing shows at all then you are out of reach.

Thanks. That really does confirm the stupidity of G.FAST then. I had assumed that anyone getting 60Mb/s or higher would be within range but if even I can't the range must be lousy. I've posted before that it sounded like a good idea for small not spot deployment but when BT realised it wasn't feasible they should have knocked it on the head and rerouted the money into FTTP.

Oh well, it means I won't be wasting money on something I don't need anyway

Well after years and i mean years of badgering my isp (plusnet) and seeing 30+ bto engineers come and go bto have finally replaced the aluminum link in my run to the green box as it kept flooding and causing battery faults dramtic speed drops i.e 65mb to 28mbit drop.

Now i have a fully stable line showing a max sync of 82mbit and 28.5up at 6.5db with a distance of 398mtr. I am wondering if with my distance there will be any point ordering when it becomes alvailable to me.

It's in certain parts of my city but not my huawei cab yet.

Btw swapping from a 612 old bt huawei odem to a billion 8800axl same snr gave me 8mbit in speed difference.

Totally amazed me

odd how it just goes live with no announcement

Out of curiosity who should make the announcement. Openreach to all served by the cabinet or in this case G-Fast, BT Wholesale and the other wholesalers or the ISPs, not all of whom offer G-Fast.

The thing is, Openreach does do announcements on the news part of their website. They have announced and listed exchanges to get G.fast. Though, I am pretty sure that not every place is announced on there (or at least, so far, some places were not announced).

Granted, the announcements on the Openreach news site apparently does not give information regarding specific cabinets. But people can still at least enquire with their ISP regarding it if the exchange area is enabled.

Unlike with BDUK, which had local (usually by county or counties) projects and information to raise awareness of faster broadband (to increase take up), the commercial G.fast rollout does not have the same detail of information on the surface unless you are willing to go digging.

ISPs can list the packages on their website with the possibility for potential customers to be notified once the technology is available to them (like BT does).

In reply to a post by djay:

Now i have a fully stable line showing a max sync of 82mbit and 28.5up at 6.5db with a distance of 398mtr. I am wondering if with my distance there will be any point ordering when it becomes alvailable to me.

Nope.

Currently G.Fast uses higher frequencies than VDSL, so if you think about it any connection which can't reach 80/20 with some spare headroom is not going to be able to make use of G.Fast (the frequencies are just to high), unless of course their speed has been eroded by cross talk to under 80/20.

Huh, I'd never even thought of it like that but I see your point. Thanks.