Why do I want WiFi?

Andreas Kostyrka andreas at kostyrka.org
Thu Jan 18 14:23:41 CET 2007

* Paul Bohme <paul at bohme.org> [070118 13:58]:
> Gabriel Ambuehl wrote:
> >On Thursday 18 January 2007 09:54, Renaissance Man wrote:
> >  
> >>>Seamless swapping needs the carriers' help. And they won't do it
> >>>for free, rest assured.
> >>>      
> >>Already being done. See http://truphone.com
> >>    
> >
> >Doesn't really say how it works. "An all  SIP solution" doesnt really sound like it could ever be seamless with GSM. I'd really like to know just how this supposed to work, because if 
> >they pulled this off, it would be really huge.   
> Perhaps if were drop the assumption that it would try to go from IP-based SIP call to GSM voice call.  What if the phone were simply smart enough to go from wifi to GPRS - then it's 
> more a matter of having the endpoints able to withstand an IP address change mid-call.  Something like that could go BT->wifi->GPRS and back without missing a beat - assuming that each 
> step of the way involved a working IP address and the software were smart enough..

Problem here, no GRPS is fast enough to handle the 100kbit/s upload
needed. Even UMTS would be extremly stretched on this point.
(UMTS-HSDPA would satisfy the requirements of VoIP sipphones.)

And that all assumes that you can get an UMTS flatrate that allows for
sipphones. (E.g. the Eplus one in Germany explicitly forbids VoIP ;) )


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