Seamless roaming between private and public GSM networks

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willnz

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#13708 25-May-2007 01:31

After reading this article in the Herald, I was wondering if it's possible to originate a call on the "private" network, and continue talking seamlessly as you roam on to say, the Vodafone NZ network.

To me this seems tricky, as how does the vodafone network know who the call is being made to/from and where to send the traffic? Obviously, you would have to either have a vodafone sim card (with the private network accepting connections from that sim card), or a roaming agreement with Vodafone to do this. But assuming that was the case, is it possible?

If not, surely that would completely screw Econet's plans - the second you drive out of auckland you'd have to call the person back... :P

freitasm

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#72212 25-May-2007 14:38

Of course it comes down to regulation in New Zealand - companies bought the spectrum and devices should not interfere with the spectrum allocation...

sbiddle

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#72214 25-May-2007 14:55

Roaming is not seemless between GSM networks that have roaming agreements. If you originate a call on one network and then move to another network you will be chopped off. To have a seamless handover your call would need to be simultaneously connected via both providers so it could switch, something that can easily be done in an IP environment such as handover between UMTS and WiFi on a PocketPC or Symbian device.

willnz

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#72216 25-May-2007 14:56

freitasm: Of course it comes down to regulation in New Zealand - companies bought the spectrum anddevices should not interfere with the spectrum allocation...

I'm sure Tex wouldn't mind lending me some of his, I mean, they're never going to use it

willnz

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#72217 25-May-2007 14:57

sbiddle: Roaming is not seemless between GSM networks that have roaming agreements. If you originate a call on one network and then move to another network you will be chopped off. To have a seamless handover your call would need to be simultaneously connected via both providers so it could switch, something that can easily be done in an IP environment such as handover between UMTS and WiFi on a PocketPC or Symbian device.

I guessed that would be the case - thanks for clarifying :)

sbiddle

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#72222 25-May-2007 15:48

willnz:
freitasm: Of course it comes down to regulation in New Zealand - companies bought the spectrum anddevices should not interfere with the spectrum allocation...

I'm sure Tex wouldn't mind lending me some of his, I mean, they're never going to use it

It's not Tex's to lend. You obviously don't keep up with the news - he got given the big boot several months ago.

willnz

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#72223 25-May-2007 15:50

I do - it's just not as fun saying "NZ Communications". The name is so dull and boring ;)

*goes back to corner*

inquisitor

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#72335 26-May-2007 21:17

sbiddle: Roaming is not seemless between GSM networks that have roaming agreements. If you originate a call on one network and then move to another network you will be chopped off. To have a seamless handover your call would need to be simultaneously connected via both providers so it could switch, something that can easily be done in an IP environment such as handover between UMTS and WiFi on a PocketPC or Symbian device.

That's not correct. Inter-network soft handovers (soft = without interruption) work flawlessly within GSM and even to and from UMTS networks. Of course the MSCs (= mobile switching centers) of both networks need to be connected and configured for such seamless handovers, but that isn't a big thing at all, since even within a certain opertor's network you regularly have dozens of MSCs, which all support soft handovers among each other. So that's a very basic function of GSM networks.
The main issue about handing over inter-network is the billing, which is a bit more complicated, as operators may use different billing systems, but even that can be solved.
Since O2 Germany has weak rural coverage they have a national roaming agreement with T-Mobile and so as an O2 Germany customer I'm regularly witnessing soft handovers from O2's (mostly) GSM1800 network to T-Mobile's (mostly) GSM900 network. And of course I see handovers from UMTS to GSM and vice-versa every day.
Further inter-network soft handovers even work with most foreign operators here in Germany. I've personally experienced a soft handover from O2 Germany to T-Mobile Austria a couple of years ago. However since customers couldn't realize those handovers and so couldn't be billed roaming tariffs after an inter-network soft handover, they limited those handed-over calls to 5 minutes or so. Afterwards you need to redial and then the higher roaming tariffs apply.

So roaming between two GSM-networks can work seamlessly, but may not be desired, as users won't realize the change of tariffs (if that applies).

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