Research In Motion expects to offer a BlackBerry mobile phone that also supports Wi-Fi, the company's CEO said.

Speaking at the JP Morgan Technology Conference, RIM's co-CEO Jim Balsillie said such a converged BlackBerry should come out "in the back half of this year."

RIM is behind its competitors in developing devices with both cellular and Wi-Fi.

Motorola and Nokia were both selling such phones, aimed at business users, last year. RIM recently hinted at forthcoming converged phones but until now hadn't said when they would ship.

"Wi-Fi was over-hyped," Balsillie said. "I was not a big believer in it for the first two or three years because it was hyped as something that would subsume everything, that you would get rid of your cell phone. We feel it's complementary of a cell phone."

The BlackBerry Enterprise Server (BES) that companies use to deliver corporate e-mail to BlackBerry users already supports roaming for customers that may travel between multiple operators so the BES would treat Wi-Fi networks just like additional cellular networks, he said. That capability enables the hand-off of data connections and voice calls between Wi-Fi and cellular networks as customers move.

In addition, the BES "presupposes the air-link is insecure," and so encrypts all voice and data transmissions using either technology, he said. The BES already supports Wi-Fi connections because the BlackBerry 7270 has Wi-Fi.

Many mobile operators, particularly those that aren't related to a landline service provider, have resisted fixed mobile convergence (FMC) because they can lose revenue by transferring calls from their cellular networks to a potential opponent's Wi-Fi network. But Balsillie said the operators are open to it. "Most of the carriers I've dealt with are supportive of FMC," he said.

Also, he's finding that an increasing number of operators have both cellular and fixed-line networks and those companies are looking for ways to leverage both assets. Services like FMC can allow those operators to offer another service rather than simply offering a single bill.