Still, for some operators, sticking with Wi-Fi instead of femtocells makes sense. T-Mobile late last year said many of its Android phones would ship with software that allows people to use Wi-Fi to make phone calls and send SMS and MMS messages. That offloads traffic from T-Mobile's cellular network and shifts the expense of backhaul to the Wi-Fi network.
T-Mobile invested in a backend system from Kineto four years ago that lets it manage the Wi-Fi use, including counting minutes of use on Wi-Fi against a subscriber's plan. That may have made the choice to stick with Wi-Fi easier but a company executive said it was a clear choice.
"Femtocells have a math problem and a customer service problem," said Joshua Lonn, director of product development for T-Mobile. From an investment standpoint, buying femtocells would cost T-Mobile tens of millions of dollars, he said. Many T-Mobile customers already have inexpensive Wi-Fi routers that can instead serve as a coverage extender. Also, most smartphones today come with Wi-Fi.
In addition, femtocells can be challenging to install, he said. "They're a pain to set up and a pain to optimize on the network," he said. "Wi-Fi is robust. Why do something as complicated as femto?"
The downside to using Wi-Fi currently is that users still have to actively turn on Wi-Fi on their phones before using it. But both Kineto and Ruckus talked about work going on internally and in standards bodies to make roaming between the cellular and Wi-Fi networks automatic.
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