Seamless switching from gprs to wifi calling

[mathew davis]

Thanks for all the input.  Sounds very interesting.  I didn't realize that
UMA isn't VoIP.  I don't want to use t-mobiles system.  I was thinking of
how I could do it without using their system, but the same idea.  Sounds
like I have got a lot fo reading ahead of me and that this problem is bigger
than I thought it would be.  Just to make sure I got every thing right GPRS
is to slow.  Inorder to get something like this to work you need the
following:  Client software capable of handling 2 streams sip and gsm.  It
also has to know when to hand over from one to the other.  You also need a
server that can handle the 2 streams and know when to throw away the extra
data.  Does that sound right?  Just want to make sure I understand what you
guys wrote.  That IMS thing sounds interesting I will have to do some
research on that.  Thanks for the info.

On 6/8/07, Luit van Drongelen <openmoko at luitvd.net> wrote:
>
> To get back to what Mathew asked: I don't think a T-Mobile
> HotSpot at home is switching calls back and forth as you get in reach of
> a hotspot, and walk away from it. Secondly: this only works with
> T-Mobile! (for now) T-Mobile has probably set up a HotSpot at home call
> server near their GSM traffic backbone, on which your phone logs in,
> and through which your GSM traffic goes (with that UMA protocol) while
> you're logged in (in reach of a public (T-mobile) hotspot). Calls that
> already take place can't be re-routed I guess...
>
> Anyway, what I'm trying to say is that firstly: you need T-Mobile as
> your operator. Secondly: you need that T-Mobile HotSpot @home plan.
> Thirdly: you need a phone that's capable of routing your GSM traffic
> through UMA, to the T-Mobile UMA server/backbone/whatever they call
> it. As for the Neo1973 and OpenMoko: The phone can most likely do it,
> because the software just needs to know how to do it. BUT, I don't
> think T-Mobile will tell you how to log in. T-Mobile makes the phone
> software themselves for a reason. If they show you how to make a phone
> log in, you can make a program that logs your computer in too. So a
> FOSS solution for this probably won't come easily.
>
> --
> Luit
>
> PS: sorry for the double post Johnson, it bounced because I mailed
> from the wrong account
>
> On 6/8/07, Al Johnson <openmoko at mazikeen.demon.co.uk> wrote:
> > Check the archives for a full discussion of this. In short GPRS is
> unsuitable
> > for VoIP because of the high latencies, often in seconds. The GSM data
> mode
> > is more suitable even though it's only 9600. It should be possible to
> have
> > Asterisk route calls to the right VoIP endpoint, or to a GSM voice call
> if it
> > can place calls to the PSTN. The trick comes in knowing when to hand
> over,
> > and having a unified client that'll get Asterisk to do it.
> >
> > On Friday 08 June 2007 06:21, kenneth marken wrote:
> > > mathew davis wrote:
> > > > Dear community,
> > > >
> > > > I am not sure if this is a widely known thing or not, but I just
> found
> > > > out about it and had some questions about this working on the neo.
> > > > T-mobile has hotspots all around my area, but have been
> experimenting
> > > > with a new service called T-mobile HotSpot @Home.  It uses a UMA
> > > > (unlicensed mobile access) technology to allow phones to switch from
> > > > cellular connection to Wi-Fi connection.  And also makes it possible
> for
> > > > VoIP calls.  So this is something that is very interesting to me
> only I
> > > > would like it to be a little different, I don't want to use
> T-Mobile's
> > > > service I would like to use my Wi-Fi connection to my VoIP of
> choice.  I
> > > > know this has been talked about before with some options including
> an
> > > > Astrex box forwarding the call to your cellphone until your in range
> > > > then switching to Wi-Fi but that was not a very seamless transistion
> > > > from my understanding.  So I guess my question is could we impliment
> a
> > > > UMA type of technology for the neo that is customizable to use our
> VoIP
> > > > provider?  Or since that particular part is locked we wouldn't have
> > > > access to that part?  Just curious. When I get the phone I will be
> > > > playing with trying to find a solution to this problem.  I have very
> > > > limited knowlege about this kind of thing.  I am not an experianced
> > > > programmer yet.  I only have about 3 yers of indestry experiance,
> but
> > > > none of that is mobile development and almost none of it is linux
> > > > related, so I have a bit of a learnign curve so that is why I am
> asking
> > > > the question here.
> > >
> > > while not fully up to speed on how it all works, here is my quick take
> > > on it:
> > >
> > > as long as its a voip connection, and said voip service allows two
> ip's
> > > to share a account and call, there should be little to no problem
> having
> > > both a wifi and gprs connection open at the same time as one moves
> about
> > > (in my experience a gprs connection can be held open but not used).
> > > hell, one may even use bluetooth if it can handle the data transfer.
> > >
> > > the problem here is that ip thing. UMA has a normal mobile phone
> > > connections as one option so therefor dont have to think about
> multiple
> > > ip's. it just need to have a internet connected cell so to speak, and
> > > only hand the call over when the ip based connection is fully in
> place.
> > >
> > > however im guessing there are some issues with going between two wifi
> > > zones/networks or something similar...
> > >
> > >
> > > so mostly you need a voip service that allows you to log in from
> another
> > > ip without booting the old connection off or hanging up any calls.
> after
> > > that its mostly a case of the client software figuring out what of the
> > > two connections to send on. or maybe just send on both, expecting the
> > > service to throw away the data thats a duplicate. something that i
> think
> > > is a basic feature in mobile phone systems.
> > >
> > > one funny thing is that if your using voip, and have a flat rate data
> > > plan for your mobile phone, there is no need to go wifi anyways as the
> > > mobile data connection will probably be more reliable given that its
> > > already built to do what one is trying to make the wifi system do
> > > (handover, multiple connections and overlapping zones).
> > >
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