FTTC speed estimate - how can they possibly be correct?

From what I have seen of the spreadsheet that gives speed estimate uplifts, each cabinet will give the same uplift in speed to every connected line.

As far as I can see, the speed you get from ADSL is related to the length of the line between your premises and the exchange, via the cabinet.

The speed you get from fttc is related to the length of the line from your premises to the cabinet, regardless of how far the exchange is from the cabinet.

So how can it possibly be that all lines connected will get anything like the same improvement? You might be two miles from the exchange and 50 metres from the cabinet - that would give a vast increase. You might be two miles from the exchange and one mile from the cabinet, which ought to give a smaller improvement.

The speed estimates ought to be by postcode, calculated on the distance from the cabinet, not the same estimate for every line attached to a cabinet.

The problem is that the logic of the speed estimates seems nonsense, but it is used as the basis for more than just estimates. They make services available or not based on these flawed estimates.

Think the answer to that is not everyone lives exactly the same distance from the cab and the exchange.

How many properties are covered by the same postcode? 10, 20 30? Can be 200 to 300 yards radius. That alone would have an effect on FTTC from cab, especially if the cables dont all go the same route.
By also going with your suggested postcode test, it doesnt take in to account those like me on aluminium cable from the cab at 260 yards. Others will get better results 600 yards away using copper cable.

I got a big improvement from 0.75meg ADSL to 37.45 meg with FTTC. That is until changed to BT last week.
So for me its cut out 5.5km of alum or copper cable to cab but still have 260 yards of shocking alum 30 year old cable.

If i remember correctly all sites ask for postcode and a phone number!
What better way unique to that phone line.

It's very unlikely that there is massive difference is distances from a given cabinet, and from what people have said the estimates (and remember it's an estimate) have been on the conservative side.

They could well give the worst case for each cabinet based on the longest distance from the cabinet.

Edited by pete_thomson (Tue 29-May-12 14:16:13)

In reply to a post by hareng:

Think the answer to that is not everyone lives exactly the same distance from the cab and the exchange.

How many properties are covered by the same postcode? 10, 20 30? Can be 200 to 300 yards radius. That alone would have an effect on FTTC from cab, especially if the cables dont all go the same route.

Lines from the same cabinet definitely don't always follow the same route to the exchange. I have two lines and according to the BT database, one is 2238m to the exchange and the other 1877m to the exchange.

The difference, is that much smaller, when talking about the distance between, the cabinet, and the distance to your exchange.

FTTC delivers full speed up to several hundred meters from the cab , i believe.

When you get further than that, you drop speed yes, but nowhere near as badly if it were copper all the way from the exchange.

Not sure if anyone has posted a graph yet, of distance from cab to speed band. there used to be one for ADSL copper.

BT probably ran the numbers through a formula, they know the approx distance from each home to each exchange. those houses at the extreme from the exchange, are still going to be at the extreme, but just from the cab.

At any rate, its only the BT uplift multiplier, it doesn't really mean jack. All you really want to know is, 'how far am i from the cab'. and what speed will i get.

The key word is ESTIMATE ...

The uplift figure is based around the average that users of that cabinet are seeing on ADSL and what they might see (averaged) with VDSL.

The uplift figure in the leaked spreadsheets has nothing to do with your speed estimate.

It's a rough statistic used for area-by-area management purposes. You should not be looking at it. It has nothing to do with you.

They do not use these figures as a basis for anything that affects you or any other individual customer. They don't even apply to the current technology in use.

Edited by qasdfdsaq (Tue 29-May-12 17:29:10)