3GPP R6 standards allow for IP in the network. 3GPP R99 mandates ATM only. R7 onwards I think is IP only. The likely reason they wanted to do ATM encapsulation is that:

a) they didn't want to get rid of their ATM network just yet.

b) their node B/RNC vendor doesn't allow mixed IP/ATM interfaces. (voice over ATM via PDH/SDH, data over IP via xDSL offload)

c) they don't have an IP RAN in place to support a full IP backhaul.

d) they may also be backhauling other stuff like 2G EDGE/GPRS traffic too.

Can anyone at T-mobile confirm?

So what is PPPoA?

Impossible. Can't be done. Definitely not what Homechoice used to use to deliver broadband video to the home in parts of the South East UK, long before the IPTV dreamers started slobbering over the "quad play" opportunities and calling Homechoice IPtv because they struggle to find a *real* IPtv success story so far. PPPoA? Completely different.

How would the T-Mobile 3G<>DSL model work in the UK? Upstream bandwidth wouldn't be much to write home about, and downstream would be a bit ropey if more than a couple of folks wanted to use a cell at the same time, especially if the transmitter was any distance from the exchange so the DSL sync speed was lowish. And when you're close to the exchange, the obvious place to put a base station is the exchange's very own roof, which already has power, all the fibre bandwidth you're willing to pay BT for, and planning permission. OK there are only a few thousand exchanges and 3G needs rather more base stations than that, so maybe there might be some mileage in this T-Mobile idea, especially in the areas fortunate enough to have LLU DSL coverage (which are probably also areas with 3G coverage).

But it may not bear thinking about for anyone who might be relying on using their 3G phone as back up to their DSL broadband ;)

Either use a mesh WiMAX setup between all the countryside base stations, or be really cheeky, add a few extra transmitters and use HSDPA and HSUPA on your own transmitters as the internet backhaul !

Sure a bit of cheeky fiddling could make it all work ! :-D