Sharing this article which explains how wi-fi offloading has been used to support the GSM network in Australia.
Optus customers can make and receive calls and texts via Wi-Fi, using their mobile phone number, when the Optus mobile network leaves them in the lurch.
Optus’ WiFi Talk app is available for Apple and Android mobile devices, acting as a gateway to the mobile network. Pre and post-paid Optus customers can make calls or send texts using the app, paying the same rates as if they were using the mobile phone network. They’re also chewing through Wi-Fi data, around 300KB per minute for voice calls or 80KB per hour when running in the background.
An advantage of WiFi Talk over other mobile VoIP apps is that you can also receive incoming calls and texts sent to your Optus mobile number. This lets Optus customers use Wi-Fi as a fallback when they’re in mobile blackspots, offering an alternative to femtocells which divert calls via broadband or repeaters which boost the mobile signal. Vodafone is working on something similar to WiFi Talk.
Optus has retired its Home Zone femtocell, which was hampered by the fact that it only worked at your home and you needed at least a sniff of the Optus mobile network for it to function. The Home Zone cost a few dollars per month, but in return you could make unlimited local, national and mobile calls using the primary mobile associated with your Home Zone.
Asking you to pay full price for WiFi Talk calls seems a bit rich when you’re helping Optus avoid the expense of improving its mobile network. Before you get too excited about the global roaming potential, the app supposedly only works in Australia.
One quirk of Optus’ WiFi Talk app is that when it’s running in the background it becomes the default contact method – even when you’re within reach of the Optus mobile network. So if you’re connected to your home Wi-Fi network and have a strong mobile signal, calls will still be switched across to Wi-Fi. You might expect it to be the other way around, treating Wi-Fi as the fallback.
Treating the mobile network as a fallback feels like a scheme to offload voice traffic from Optus’ mobile network, just as the Telstra Air Wi-Fi network feels like an attempt to offload data traffic from Next G. Thankfully you can specify which Wi-Fi networks are used with Optus’ WiFi Talk app, to ensure you only use it in places where you need it.
WiFi Talk doesn’t run over new Wi-Fi networks by default, you need to opt-in for each Wi-Fi network. This is useful because the app might not work on some Wi-Fi networks, especially corporate networks, depending on the firewall settings.
Once you opt-in to WiFi Talk for a Wi-Fi network, Optus automatically diverts incoming calls over the internet so they go through to the WiFi Talk app. This way the handset’s built-in phone app doesn’t attempt to answer the call. If the internet-based call can’t reach the WiFi Talk app then it’s diverted back to the mobile phone network where it will go through to voicemail if you don’t answer.
You can’t roam from Wi-Fi to the mobile network and back mid-call, although this will be possible with Voice over LTE which Optus intends to support in the future. Taking advantage of this will require a compatible handset, making WiFi Talk a handy workaround for older handsets which don’t support VoLTE.
For now if the Optus network often leaves you in the lurch then you might see WiFi Talk as a great solution to your problems.
Source: Sydney Morning Herald