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.