So, T-Mobile is pretty bad at explaining all this, and majorly screwed up branding and markering.
T-Mobile has two related but different services, which have been called T-Mobile @Home, and T-Mobile HotSpot @Home (now called wifi calling). @home is a home-phone replacement service, which comes UMA-equipped with a POTS phone plug for you to plug a phone into. HotSpot @Home is actually the service the parent is referring to, which can be considered 'femtocell using wifi'.
The way it works is -- your phone needs to connect to T-Mobile's GSM core network one way or another. Normally it connects over the mobile network, but UMA-equipped phones can connect via a VPN (IPsec) connection to T-Mobile. Once connected it speaks the same GSM language as it would speak over the air, so everything works, voicemail, phone calls, text messages, etc.
UMA is actually pretty awesome -- it can hand-off midcall back and forth between wifi and the cell network, unlike AT&T's femtocell solution.
Another HUGE hidden feature: As long as you can connect over wifi, your phone can connect to T-Mobile's network and send/receive calls, text messages, everything, using home area rates. Anywhere in the world. Billing over UMA works just like connecting to the cell network when you're at home.. so if you have unlimited at home you get unlimited UMA, or if you have 500 minutes you get the same 500 minutes.
This works on ANY wifi network, not just T-Mobile's routers. T-Mobile's Hotspot network of Wifi routers is specially configured to let UMA-equipped phones connect to T-Mobile's GSM core without having to pay.
In summary, T-Mobile's UMA service is awesome, but T-Mobile doesn't seem to be able to tell the world how awesome it is.
Sidenote: I used to work for HTC, and I kept trying to convince everyone of how important UMA is. It's a technologically superior solution to femtocells, but for some reason femtocells seem to be 'winning'. They are slightly easier to explain (a miniature cell phone tower!), but they actually really suck in comparison to UMA. It's tragic to see it happen.
UMA-equipped phones support what is called Unscheduled Automatic Power Save Delivery, an extension to wifi which reduces wifi battery consumption both when idling and when on a call to about the same level as a cell connection.
UAPSD (branded as WMM Power Save) is part of the WMM WiFi extensions, which are a part of most consumer wifi routers.
T-Mobile has two related but different services, which have been called T-Mobile @Home, and T-Mobile HotSpot @Home (now called wifi calling). @home is a home-phone replacement service, which comes UMA-equipped with a POTS phone plug for you to plug a phone into. HotSpot @Home is actually the service the parent is referring to, which can be considered 'femtocell using wifi'.
The way it works is -- your phone needs to connect to T-Mobile's GSM core network one way or another. Normally it connects over the mobile network, but UMA-equipped phones can connect via a VPN (IPsec) connection to T-Mobile. Once connected it speaks the same GSM language as it would speak over the air, so everything works, voicemail, phone calls, text messages, etc.
UMA is actually pretty awesome -- it can hand-off midcall back and forth between wifi and the cell network, unlike AT&T's femtocell solution.
Another HUGE hidden feature: As long as you can connect over wifi, your phone can connect to T-Mobile's network and send/receive calls, text messages, everything, using home area rates. Anywhere in the world. Billing over UMA works just like connecting to the cell network when you're at home.. so if you have unlimited at home you get unlimited UMA, or if you have 500 minutes you get the same 500 minutes.
This works on ANY wifi network, not just T-Mobile's routers. T-Mobile's Hotspot network of Wifi routers is specially configured to let UMA-equipped phones connect to T-Mobile's GSM core without having to pay.
In summary, T-Mobile's UMA service is awesome, but T-Mobile doesn't seem to be able to tell the world how awesome it is.
Sidenote: I used to work for HTC, and I kept trying to convince everyone of how important UMA is. It's a technologically superior solution to femtocells, but for some reason femtocells seem to be 'winning'. They are slightly easier to explain (a miniature cell phone tower!), but they actually really suck in comparison to UMA. It's tragic to see it happen.