In theory, could FTTC be "inverted"?

Not being familiar with the technology, is there a particular reason why e.g 40 Mbps down / 10 Mbps up could not be "inverted"?

I wouldn't be particularly interested in having a very fast down-link but a 40 Mbps up-link would be magic.

In my naive mind this would be a matter of swapping the frequency bandwidths reserved for each link. Is it more complicated than that? Probably.

/me awaits education

Edited by Northwind (Fri 03-Feb-12 16:02:14)

Yes, nearly, it can be run symmetrically.

Not going to happen for obvious reasons, consumer ISPs don't want people with miniature datacentres at home hosting services on their networks.

It could. Not swapping of frequencies but reassignment in the "Band Plan".

However, if it was done the customer would see a significant amount of noise, lost packets, corrupted data &c. The customer upstream data would be at a very low power by the time it reached the cabinet and with other customer lines in normal configuration there would be both up and down in the same frequency slots. As the downstream would be significantly higher, cross talk would affect the low power incoming signals and cause problems.

Similarly, the downstream on getting to the final pole could well pick up cross talk from a line running upstream in the same band and again, corrupted data.


So, it would require every line in the cabinet and bundle to be set up the same way.

For a property mere inches away from the cabinet, it is plausible that the upstream rate could be as high as 40Mbps, even using the current frequency bandplan. If that were the case, then it would "only" be a matter of getting the cap changed; downstream would be huge too, and there would be no need to cap it to get the upstream that high.

However, for real distances away from the cabinet, it would take a change to the frequency bandplan. And, because of crosstalk interference between lines, it would be important that every line in the cabinet share the identical bandplan.

That is why, as the 17a profile was rolled out at the end of last year, and it included a change in bandplan, it happened on a cabinet-by-cabinet basis.

That 17a profile actually moved some of the upstream frequency band to downstream, so there was a general change that improved everyone's downstream at the expense of the upstream. The opposite of what you want though...

Finally, the 17a profile and the ADE17 bandplan is now the only authorised setup for BT cabinets, according to the Ofcom ANFP. So no chance of getting it changed

Having said all that, the cabinets can be configured with different bandplans - including customised, non-standard ones.

So, in theory - Yes. In practice - No.

Thanks for all the replies, very informative as ever.

/me shelves plans for an "upside-down" ISP...

They won't do it because downloads are usually over quickly because only one person needs the download so doesn't saturate the network. If you are offerring a wanted file then more than one person is going to need the file and then the network is going to be running loaded with requests for that file.

In summary if you want to seed torrents then buy a seedbox. P.S. they invented this thing called itunes you can get almost anything you want on there without frustrating your network neighbours.

In reply to a post by Northwind:

/me shelves plans for an "upside-down" ISP...

Australia?