tmobile wifi voice calls

Al Johnson openmoko at
Thu Jul 17 23:32:06 CEST 2008

On Thursday 17 July 2008, Carl Karsten wrote:
> "Make and receive unlimited nationwide calls over Wi-Fi with your home
> phone."
>plan=T-Mobile- at Home
> Anyone know if the FR will work with whatever VoIP protocol t-mobile uses? 
> does anyone even know what protocol it uses?   I found this:
> "The technology T-Mobile is using is called Unlicensed Mobile Access, or
> UMA. UMA takes the protocol used by GSM handsets and encapsulates it into
> an IPSec VPN for transmission over the public Internet. The VPN is
> authenticated using the subscriber's SIM card via a protocol called

Nice prompt for a little background reading. From what I see it seems 
unlikely. strongSWAN appears to support IKEv2 and EAP-SIM but somehow I doubt 
T-Mobile will hand out the certificate needed in addition to the SIM. The bit 
that looks tricky is the signalling part to tell the mobile phone network 
that it can pass the call data over to the wifi connection. This is the sort 
of thing that's normally buried in the cellular modem, and I don't know of an 
open version of that. I could be pleasantly surprised though - it would be a 
good addition to have.


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