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Author Topic: Can you estimate Gfast speed from FTTC speed? Have you upgraded from FTTC to Gfast?  (Read 2195 times)

ktz392837

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I appreciate that there are quite a few variables but if you are trying to estimate if you can benefit from Gfast is there any correlation between the speed of a FTTC connection and the speed of a Gfast connection on the same line?

For example, if you connect at FTTC 67/19 with an attenuation of 17db (ECI cab) what would that equate to if upgraded to Gfast?

If anyone has FTTC stats before they upgraded to Gfast and know their Gfast sync speed could you post them?

Thanks
« Last Edit: December 14, 2018, 03:52:07 PM by ktz392837 »
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j0hn

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Every post I recall the person already received the full 80Mb.

Why not find an area with live G.Fast and work outwards from the cabinet and look for those with similar FTTC estimates to you.

My initials thoughts are you are probably out of reach of the current generation of G.Fast equipment.
The upstream in particular tends to drop below FTTC estimates at longer distances.
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kitz

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Too many variables.  Look how much vdsl2 can vary when you have 2 lines with the same attenuation.   The higher the frequencies in use, then the more variable any estimates are.

My daughter's line has an insertion loss of 8dB (true attenuation).  But line attenuation on g.fast is something like 40dB.   They previously got the full FTC 80Mbps and max sync with g.fast is about 240Mbps.   Its quite variable though and my daughter isn't too impressed at the line can often drop out.   Zen are supposed to be sending them a new router but  :shrug2: because they can't seem to decide if its full loss of sync or loss of PPP.    Lack of stats from the modem doesn't help, but there are some line stats in the relevant thread which I asked them to get from the Openreach Engineer for me.

 

 
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re0

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I would have to agree with both j0hn and kitz. The former having said you are likely out of reach is, in my opinion, almost certainly correct since your line length is probably exceeding 350-400 meters (at which point G.fast is simply unable to offer any benefits and upstream as j0hn said would be worse).

Its quite variable though and my daughter isn't too impressed at the line can often drop out.   Zen are supposed to be sending them a new router but  :shrug2: because they can't seem to decide if its full loss of sync or loss of PPP.    Lack of stats from the modem doesn't help, but there are some line stats in the relevant thread which I asked them to get from the Openreach Engineer for me.
I don't have G.fast but from the limited feedback/stats I have seen it could be said that drops seem to be a lot more common with G.fast than with VDSL (somewhat expected utilising a much larger frequency band with paper thin noise margins). Regardless of whether it resyncs in seconds, it is probably frustrating given that VDSL, for most people, can stay synced for days, weeks or, like the case here, even months.

Hopefully G.fast won't turn into G.farce, or perhaps it already was from the start. ;)
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ktz392837

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Thanks for replies.

As suspected I am out of reach of gfast especially as I pay for 80/20 for the faster upload which will probably be downgraded on gfast.

The only benefit might be crosstalkers moving to gfast and making my line return to 80/20 especially as ginp/3db is not happening.

That's assuming gfast is ever deployed for me.  Guess I am stuck with the eci cab.  Just hoping I don't end up at my bottom estimates again which are so bad I would need to downgrade to a lower package.
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re0

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Nobody will be selling it to you if all the estimates are under 100 Mbps anyway. It won't even show on the DSL checker. There's always the slim chance that you may be on the edge of the coverage but without much of a doubt it will be at a cost to your upstream. Some examples can be seen here and here, though it further proves that the upstream can be extremely enemic at further distances.

I did have a thought, and that is G.fast could actually be faster than VDSL for a very small number of people who are outside the range to receive 100 Mbps (approx. 350-450 meters, but still receiving ~70 Mbps on VDSL) meeting the following critera:
  • ECI cabinet - absence of XdB and G.INP (and vectoring in some BDUK areas)
  • Large number of subscribers (a lot of crosstalk)
Though the stability and consistency of performance can be questioned.

But fingers crossed that those eligible will upgrade so you can get a slight speed bump. ;D
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j0hn

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When lower end estimates get down below 100Mb then instead of available the line shows as "Amber".

Houses a considerable distance from the cabinet don't show G.Fast at all.


LS28 5JA is a good example of G.Fast with a wide range of high/low estimates.
It's part of P55 on Pudsey exchange (MYPUD).

I don't see a single instance of G.Fast available where the high estimate for VDSL2 isn't 80Mb.
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jelv

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I'm failing to see the point of G.Fast if it's only going to be for those who can get 80Mbps anyway.

A sizeable proportion of the cabinets with G.Fast will, in a few years, have many of the users outside of the 80Mbps zone moving to FTTP. As people realise what the full benefits of a genuine fibre connection (as opposed to hybrid fibre) are, people who can't get FTTP because they have G.fast available are not going to be impressed. So why divert energy in to what can only be seen as a temporary stop-gap? Crack on with FTTP I say.
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re0

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I can understand why you have that opinion. It is not necessarily an unpopular opinion to have on the forum. VDSL 35b would have certainly been a better upgrade path compared to the idea of mounting G.fast pods to cabinets as opposed to distribution points. The current amendment and possibly even later amendments are not going to be as effective as the standard could allow because of the issue of co-existence and effective network arrangement to allow for pods closer to the customer (and at such a point, why not just FTTP?).

Bearing in mind that it's probable that some of the shortcomings may have influenced their decision to reduce planned future G.fast footprint to some degree in favour of more FTTP. In some denser areas, it may be possible to cover in excess of 70-80% of premises with 100+ Mbps with G.fast eligibility but the reality is that areas that had plans scrapped probably were not very good candidates as they may have been sparse or had cabinet coverage where there copper network rearrangements would have been necessary to give reasonable coverage; we all know too well that sometimes addresses or even whole streets are connected to cabinets several hundreds of meters away when they might even be right next to one that serves the surrounding area.

I don't know for sure so it's all just a bit of speculation. Pinch of salt advised.
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ktz392837

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I did have a thought, and that is G.fast could actually be faster than VDSL for a very small number of people who are outside the range to receive 100 Mbps (approx. 350-450 meters, but still receiving ~70 Mbps on VDSL) meeting the following critera:
  • ECI cabinet - absence of XdB and G.INP (and vectoring in some BDUK areas)
  • Large number of subscribers (a lot of crosstalk)
My PCP is also 30m closer than my FTTC cab (perhaps longer depending on cable routing).  I also have a massive range on my estimates (25Mb) so I would actually meet the gfast only for current 80Mb fttc criteria.  Going off what everyone is saying though it is probably not going to be worth the risk even if it does become available.
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j0hn

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Quote
ECI cabinet - absence of XdB and G.INP (and vectoring in some BDUK areas)

Missed this part.
BDUK exclusively used Huawei cabinets.
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tiffy

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Likely off original topic but within the current topic trend:

Surely more extensive roll out of vectoring would have produced improved VDSL2, FTTC performance to a much larger percentage of users than G.Fast in it's present format is ever likely to do, obviously accepting the 80 Mbps upper speed limit.

I can fully appreciate that vectoring is not perceived to be a very good business prospect to BT, considerable financial investment in hardware and man power, FTTC cabinet compatability issues etc. with no quick way to recoup some of the outlay with increased tariff as per G.Fast, realistically, never likely to happen now.
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kitz

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When Openreach first announced g.fast, I think a lot of us foresaw benefits of it, because in 2017 they said they were trialling g.fast using FTTdp.    IMHO this would have been progression to bringing full fibre one step closer.   

The fact they only seem to be deploying from the cab means that only a small portion of users will be able to benefit from g.fast (ie those already getting 80Mbps) :(
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re0

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Missed this part.
BDUK exclusively used Huawei cabinets.
In my haste ... ;) Thanks for adding it.

Surely more extensive roll out of vectoring would have produced improved VDSL2, FTTC performance to a much larger percentage of users than G.Fast in it's present format is ever likely to do, obviously accepting the 80 Mbps upper speed limit.
Vectored 17a would have almost doubled data rates over standard 17a, providing ultrafast (100+ Mbps) to around 500m. I won't go into detail, but I would love to rant about how 35b would have been so much better than G.fast to cover with ultrafast speeds (and able to co-exist with 17a) and give even 300+ Mbps to approx. the same distance. Deutsche Telekom use 35b.

When Openreach first announced g.fast, I think a lot of us foresaw benefits of it, because in 2017 they said they were trialling g.fast using FTTdp.    IMHO this would have been progression to bringing full fibre one step closer.   

The fact they only seem to be deploying from the cab means that only a small portion of users will be able to benefit from g.fast (ie those already getting 80Mbps) :(
Quick 'n' dirty deployment. Bolt 'em up and watch 'em go. I can't remember if we discussed it on the forum before regarding reverse power, but perhaps it may have been part of the reason.

Anyway, I feel bad for brining this away from the intended topic. :-[
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j0hn

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Are you sure?

Profile 17a is limited to 100Mb, despite attainables offering way more.

Vectored 17a would have given "up to" 100Mb.
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