voip over wifi via cell phone

Levi Pearson levipearson at gmail.com
Tue Feb 15 11:50:10 MST 2011

On Tue, Feb 15, 2011 at 10:27 AM, Jeff Moyes
<ml at mindstormdevelopment.com> wrote:
> Hey,
> I'm just wondering if anyone knows anything about the following (I'll
> ask lots of questions just to show the types of things I'm wondering,
> but any information about any of this would be helpful so please don't
> be turned off by the quantity of questions).
> I've heard that with smart phones, if you are in a wifi zone that you
> can connect to, you can reroute your calls over the wifi (using voip)
> and not use the cell radio (and therefore not use up cell minutes).

TMobile has a feature in their new Android phones called WiFi Calling,
which lets you route calls via WiFi instead of GSM.  It uses some
subset of the GAN specification for this.  The Android version
supports voice and SMS, but does not support handoff between GAN and
GSM, so you can't wander away from your WiFi access point in the
middle of a call.

Unfortunately, you do still use up your minutes while using this, but
as long as you make sure 'data roaming' is turned off, you can use it
abroad without incurring roaming fees.  I understand the call quality,
assuming a reasonable network connection, is very good.

I'm sure there are some other carriers that have some sort of GAN/UMA
access via WiFi, but I don't know the details about any of them.

> Does anybody know, is this just for some smart phones? or can
> essentially any smart phone do this? Of the phones that can do this, is
> it just built into the phone or do you have to go and grab your own voip
> client for the phone?

If there isn't a GAN/UMA implementation supplied with the phone, you
*may* be able to install Skype or some other voip app.  There are many
of them, including Fring.  Getting voip to work across multiple
handsets usually requires that the developers have access to those
handsets, so you might want to check with the apps you want to use to
make sure they work well with the handsets you're interested in.

> Is it possible to reroute cell calls through the voip (like by getting a
> SIP account and then getting a Google Talk account that is set up to
> also contact the SIP account whenever the cell number is called, and
> then just answering the SIP connection instead of the cell connection)?

I'm pretty sure you could set this up.  You can even transfer an
existing number to Google Voice now, though transferring a cell number
would shut down that cell account.  I think there's some way to work
SIP into the picture with Google Voice, possibly through Google Talk,
but I don't remember the details anymore.  If you can route things to
your Google Voice account, it's easy to have Google Voice take over as
the phone system for Android.


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