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Standard User bowdon
(member) Fri 30-Jan-15 13:03:25
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Why do VC FUP their upload speeds?


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Virgin Cable seems like a good idea. Like a kind of FTTH thing. But why do they cripple the upload speeds so much? Is there something in the technology that means they have to slow peoples uploads to get better download speeds? I'm not sure I understand.

Demon => Freeserve => Pipex => Be => Sky => BT Infinity 2
Standard User Ignitionnet
(knowledge is power) Fri 30-Jan-15 22:36:02
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Re: Why do VC FUP their upload speeds?


[re: bowdon] [link to this post]
 
Capacity on the upstream is quite limited as the networks were originally built for delivering cable TV and still have some of that heritage left over.

This will change as Virgin continue to evolve their network more towards broadband delivery.
Standard User farnz
(member) Sat 31-Jan-15 20:35:51
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Re: Why do VC FUP their upload speeds?


[re: bowdon] [link to this post]
 
Cable is a shared copper medium between several homes, as it was originally designed to operate like a shared antenna system - exactly the same way as one TV aerial used for multiple houses in a neighbourhood. In some areas, the split is very good (around 25 houses sharing one copper medium), in the worst cases, it's awful (over 1,000 houses sharing one copper medium).

That shared copper medium has (in current standards) around 80 MHz of spectrum reserved for data from the houses to the cable company, and around 900 MHz of spectrum reserved for data from the cable company to the houses. Granted, TV comes out of the 900 MHz of spectrum that's reserved for downstream, but that's still more than a 10:1 disparity between spectrum for upload and spectrum for download.

Plus, because all the download is originated at the same physical point on the cable, it's easier technically to use high bit rate modulations. Download peaks at a bit over 6 bits/s/Hz, whereas upstream is limited to around 4 bits/s/Hz. So, if VM got rid of TV completely, they could run around 5.5 Gbit/s split among all houses on a single medium downstream, but only 320 Mbit/s upstream.

Now, TV does take a bite out of downstream, so there's no way for VM to run that fast downstream today, but this means that in the best areas, they've got around 200M down, 12M up per house. In the worst areas, it's more like 5M down, 300k up per house; because this is shared dynamically, you can "borrow" from your neighbours to the limits of the available spectrum, and can thus get the full 152M even in the worst areas, just not when your neighbours are also trying to make heavy use of their connection.

VM thus have to manage things on the basis of expected congestion in a neighbourhood; while 1,000M down, 100M up is a great headline speed, in the best areas, VM would only need 4 customers saturating upload before they saw a slowdown, while 5 customers could saturate down before they saw a slowdown. 150M down, 15M up is lower contention, and thus you're less likely to see congestion effects (the nature of contention is such that 10000:100 contention is less visible than 100:1 contention, despite the ratios being the same).


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Standard User Chrysalis
(legend) Sun 01-Feb-15 18:01:16
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Re: Why do VC FUP their upload speeds?


[re: farnz] [link to this post]
 
interesting post, so it seems it comes down to a bit more than if in a student area or not then but rather luck of the draw on the network build in the particular area.

My question is why dont VM make all areas equal in terms of # of properties per shared cable, but I guess the answer to that is ££££.

Standard User farnz
(member) Sun 01-Feb-15 19:10:20
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Re: Why do VC FUP their upload speeds?


[re: Chrysalis] [link to this post]
 
In reply to a post by Chrysalis:
interesting post, so it seems it comes down to a bit more than if in a student area or not then but rather luck of the draw on the network build in the particular area.

My question is why dont VM make all areas equal in terms of # of properties per shared cable, but I guess the answer to that is ££££.

I believe VM have improved the split ratio as part of the DOCSIS 3.0 rollout, by exploiting the increased density of modern kit to fit multiple head ends into one active cab.

In the end, though, decreasing the share ratio is expensive - new fibre, more power, more cooling, possibly more active cabs out there (VM also have passive cabs, so that they can run a thick coax to a passive cab, and split it into per-household coax at a cabinet). Same sort of thing as GPON - yes, you could do home run fibre for everyone, but it's cheaper to run one fibre to a shared point and split it, and decreasing the split ratio costs money.
Standard User farnz
(member) Mon 02-Feb-15 10:21:28
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Re: Why do VC FUP their upload speeds?


[re: Chrysalis] [link to this post]
 
In reply to a post by Chrysalis:
My question is why dont VM make all areas equal in terms of # of properties per shared cable, but I guess the answer to that is ££££.

It's also worth remembering the basic economics of the telecoms business; a telco converts very large sums of capex into ongoing revenue streams. There's no point spending money in an area if it won't increase your revenue streams by enough to pay for the capex.

Thus, in areas where the split is awful, VM will only fix it if they think they'll make more money with a smaller split ratio than with the current large split; in turn, that depends on competition etc.
Standard User bowdon
(member) Mon 02-Feb-15 13:28:56
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Re: Why do VC FUP their upload speeds?


[re: farnz] [link to this post]
 
Thanks for the post farnz. Very insightful.

The only thing that really lets VM cable down is the FUP on upload speeds. If they didnt have those slowdown policy's then they would be a genuine alternative to BT based technologies.

If there is a gamer who streams content to twitch.tv he's not able to do that because of the restrictions placed on him (maybe they could introduce a gamers package?).

If there wasnt the uploaded FUP's in effect then as I say VM would be competing for DSL traffic on an even field.

I think in the next few years VM need to make some bold moves in either expanding their network reach and/or capacity, and removing the FUP effecting uploads in particular, or they are going to be slowly drifting behind.

I think its good for all companies, and especially consumers, to have competition so I'd hate to see VM drift in to the slow lane and not be able to maintain itself.

Demon => Freeserve => Pipex => Be => Sky => BT Infinity 2
Standard User Chrysalis
(legend) Mon 02-Feb-15 16:22:37
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Re: Why do VC FUP their upload speeds?


[re: farnz] [link to this post]
 
of course, they will do what they can get away with.

Cheaper for them to give complainers a discount than to do the split.

Standard User farnz
(member) Mon 02-Feb-15 16:43:23
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Re: Why do VC FUP their upload speeds?


[re: Chrysalis] [link to this post]
 
In reply to a post by Chrysalis:
of course, they will do what they can get away with.

Cheaper for them to give complainers a discount than to do the split.


Just like any telco. When splitting a node is going to cost you £30,000, get you £100/month in new business, and let you avoid £40/month in discounts to the affected parties, it's simply not worth doing; you're only looking at £150/month to pay it back with, or around 16 years.

FTTC partly escapes this calculation by reducing the cost of future G.fast (and eventually FTTP) deployment; you do 80% of the work of a full FTTP solution, pay 20% of the cost, get something you can sell now, and you can spend the other 80% of the cost later to go FTTP.
Standard User Chrysalis
(legend) Mon 02-Feb-15 16:54:17
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Re: Why do VC FUP their upload speeds?


[re: farnz] [link to this post]
 
is amazing how things have changed.

It used to be VM could always outdo BT at speeds, and they only need flick a switch to roll out new configs to bump them up, but flip side heavily congested.

Now is new copper technologies vdsl2 is rolled out with g.fast planned, BT are now looking for the first time in ages to possibly be in a few years ahead at mass market speeds whilst having nowhere near the same amount of long term congestion issues.

Edited by Chrysalis (Mon 02-Feb-15 16:54:25)

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