Seamless switching from gprs to wifi calling

[Luit van Drongelen]

Hi,

As I said, to do the T-Mobile thing, you'd need a GSM/UMA backbone
that's capable of routing calls through both. Though I don't think
it's easy to reroute (hand over) a call from one of the protocols to
the other. It requires timing, which requires computing power, which
requires a mighty strong backbone for all the people using the
service. So my guess is that T-Mobile's Hotspot services only lets you
use one of the two protocols. As long as you're near a hotspot, you're
logged in to the UMA backbone, and your phone number is assigned to
that hotspot service. If you're not logged in, incoming and outgoing
calls are routed through GSM normally.

And there's the problem for doing it yourself. You can't really decide
for yourself where the calls for your number are routed to. The
service provider decides, and without a "T-Mobile Hotspot @ home"-like
service backbone, you can't do this. You can either call through WiFi
using SIP, but it'll use your SIP number, not your GSM number. And
vice-versa.

It's all up to the service provider to enable goodness like this... :(


--
Luit

On 6/8/07, mathew davis <someoneinjapan at gmail.com> wrote:
> 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).
> > > >
> > > > _______________________________________________
> > > > OpenMoko community mailing list
> > > > community at lists.openmoko.org
> > > > http://lists.openmoko.org/mailman/listinfo/community
> > >
> > > _______________________________________________
> > > OpenMoko community mailing list
> > > community at lists.openmoko.org
> > > http://lists.openmoko.org/mailman/listinfo/community
> > >
> >
> > _______________________________________________
> > OpenMoko community mailing list
> > community at lists.openmoko.org
> > http://lists.openmoko.org/mailman/listinfo/community
> >
>
>