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Network builders tackling cell vs. Wi-Fi choices

Stephen Lawson | May 31, 2013
Handoffs between networks are about to get smoother, but vendors are pushing their own tools to make them smarter

Ericsson demonstrated real-time traffic steering between Wi-Fi and cellular at CTIA Wireless.

Mobile users can probably look forward to being automatically transferred from cellular to Wi-Fi networks in the near future, but going back and forth for the best possible performance is another matter.

Software now in the works will use real-time knowledge about network conditions to make lightning-fast decisions about the best system for each user to be on at a given moment. The idea is that just because there's a Wi-Fi network nearby, doesn't necessarily mean your smartphone should start using it. If every subscriber near that hotspot got switched over to it, the Wi-Fi experience could suffer.

It's already common for Wi-Fi networks in public places to get overloaded at busy times. Automatic handoffs from cellular to Wi-Fi, while convenient, won't make that situation any better. To prevent those overloads, networks will need more management smarts, said Daryl Schoolar, an analyst at Ovum.

That's why both Ericsson and Nokia Siemens Networks announced technologies at CTIA Wireless last week for so-called real-time traffic steering. But the collection of standards that the industry is currently adopting for easy cell-to-Wi-Fi handoffs doesn't yet include this capability, so it may take a while for carriers to make it available.

Mobile operators increasingly are giving their subscribers access to Wi-Fi, both by deploying hotspots and by partnering with other providers. This can give the carriers extra capacity, without paying for another spectrum license, in areas where many people gather and use mobile devices. For subscribers, it can mean faster network connections, depending on the cellular coverage in the area.

Emerging technologies can authenticate users and put them on Wi-Fi automatically, eliminating the tasks of finding the network and logging in to it. However, that process is centered on the mobile device, which can lead to problems, said Sheila Burpee Duncan, head of Wi-Fi marketing at Ericsson. A phone or tablet may be set to automatically go onto Wi-Fi wherever it detects the signal, even though it doesn't know whether the Wi-Fi network is overloaded, she said.

The two types of networks still are largely independent, a problem AT&T is looking to solve, said Kris Rinne, AT&T's senior vice president of network technologies. Her company has one of the largest Wi-Fi deployments of any mobile operator.

"Today, they don't know anything about each other, and so you have to introduce that," Rinne said in an interview at CTIA. AT&T expects ANDSF (Access Network Discovery and Selection Function), a specification from the 3GPP, which oversees mobile standards from GSM through LTE, to help it solve the problem.

However, ANDSF isn't designed to make decisions about network choice in real time, Ericsson's Duncan said. Instead, it's directed by overall policies that are designed to be changed at particular times, such as when a train is scheduled to arrive at a station. Constantly changing those policies on the fly, such as whenever the station happened to get crowded, would put too big a burden on the network, Duncan said. Real-time traffic steering will complement ANDSF and other standards such as Hotspot 2.0, she said.

 

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