Seamless switching from gprs to wifi calling

Nicolas Bougues nbougues-listes at
Fri Jun 8 09:25:29 CEST 2007

On Thursday 07 June 2007 23:05:44 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?  

Be careful. UMA is not VoIP as is usually meant. UMA is more like "GSM over 
IP". Basically GSM signalling is carried by an IP network. So from the GSM 
network point of view, it's relatively easy to handle seamless handover.

What you'd rather want would be more IMS alike, with SIP used as a common 
signalling protocol across a wide range of support networks (TDMA, W-CDMA, 
wifi, wimax...). Unfortunatly, it won't be rolled out massively before a few 

So our best bet, as of now, and since we don't have GSM carriers on the 
bandwagon (yet!), is probably to have SIP and GSM co-existing on the same 
handset in the best possible way. The best products of that kind I'm aware of 
are currently the wifi-enabled Nokia N- and E-Series phones.

Nicolas Bougues
Axialys Interactive

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