Internet Offload and UMA

“Internet Offload” is the ability for a dual-mode phone to connect directly to the internet through the Wi-Fi radio. The phone which comes to most people’s mind is the iPhone, but Wi-Fi enabled HTC and Nokia E/N series support this feature too.

When the iPhone enters a Wi-Fi environment, the GSM radio stays on (for circuit voice and mobile packet data services), and the Wi-Fi radio can be used for accessing internet services like Google Maps directly.

For some reason, the market seems to think that a dual-mode phone can support either UMA or Internet Offload, but not both simultaneously.

This is not true!

Internet Offload and UMA are fully compatible functions of a dual-mode phone.

In fact the strongest example is the family of UMA-enabled Blackberries (8820, Curve/8320, Pearl/8120) which all support UMA and Internet Offload concurrently.

Here’s how it works:

When a UMA-enabled Blackberry enters Wi-Fi, the UMA tunnel is established. The UMA tunnel is used to transport services which reside in the mobile core network to the phone. The easiest example is voice services. But any data application which is delivered from the mobile core is accessed through the UMA tunnel, applications like MMS or any stream media services offered from the network (MobiTV,…)

A key advantage of using the UMA tunnel for service delivery is mobility. Any application or service which takes advantage of the UMA tunnel maintains session continuity between the Wi-Fi network and the outdoor macro network.

But it’s the way UMA-enabled Blackberries also support Internet Offload which is most interesting. When the phone tries to access web based services like Google Maps, the traffic is routed directly to the Wi-Fi access layer and out to the internet. No going through the UMA tunnel, no burdening the mobile core with non-revenue generating internet traffic. Note this is also how the Blackberry accesses mail services when in Wi-Fi, directly over the internet.

The trick is that the Blackberry maintains a basic router function in the handset. For application which are ‘hosted’ (circuit voice, SMS, MMS,…), the traffic is routed through the UMA tunnel and to the mobile core. For browser based applications, the traffic is routed directly to the internet.

Note there is no 'seamless mobility' for services routed via Internet Offload directly over Wi-Fi. When the phone moves outside of Wi-Fi coverage, the session ends. The session can be restarted over the macro RAN, but there will be a drop in service.

Why is Internet Offload + UMA important?

First, it’s important to clear up the misunderstanding in the industry. Early UMA phones didn’t support the Internet Offload feature because operators specified they wanted UMA-enabled dual-mode phones to work ‘exactly the same’ in Wi-Fi as in GSM. Therefore, all the packet traffic was to be routed via the UMA tunnel to the mobile core when on Wi-Fi, because all packet traffic is routed to the mobile core when on GSM. [It’s in this way that UMA is really a RAN technology, making Wi-Fi an access radio for mobile services.]

With dual-mode phones supporting Internet Offload on the market, operators are again saying they want UMA-enabled phones to operate ‘exactly the same’. But now this means adding support for Internet Offload concurrently with UMA by routing some traffic over the UMA tunnel and other traffic directly to the internet.

Second, support of Internet Offload is a critical component of making the mobile phone an integral member of the ‘connected home.’ There is a movement underway to bring household electronics together into a cohesive fabric. But a mobile phone without Internet Offload capabilities* will be excluded from supporting local connections in the home. Thus the phone will continue to be outside the ‘connected home’ vision.

By highlighting UMA and Internet Offload support concurrently in the same device, UMA devices can now easily fit into the vision of the ‘connected home’.

Now Nokia N series handsets can support UMA along with the existing Internet Offload capabilities. In fact, the Nokia N95 was one of the first handsets to demonstrate support for DLNA, a ‘connected home’ protocol standard.

[* - There are two ways to make the handset a member of the 'connected home'. First is to have a dual-mode Wi-Fi enabled handset with Internet Offload capabilities. The second, pioneered by the Femto Forum, is to proxy a standard 3G handset into the connected home network via a femtocell.]