RIM's long-awaited dual-mode BlackBerry holds out the promise of savings on cellular charges by letting workers use Wi-Fi for some voice calls, but the device may not yet be ready for enterprise customers that would seek to pair it up with an IP PBX infrastructure.

The BlackBerry 8820, announced earlier this month, is similar to the BlackBerry 8800 model launched in February. Both feature a more smartphone-like appearance than earlier models, and both also have built-in satellite navigation capability on top of the familiar BlackBerry push email and voice capabilities.

With the addition of 802.11 a/b/g Wi-Fi support, the new 8820 is the first BlackBerry capable of linking to both cellular and wireless networks. RIM also includes a voice-over-IP (VoIP) client to let users make voice calls over Wi-Fi.

However, RIM has opted to use the Unlicensed Mobile Access (UMA) IP telephony protocol, which is designed to link a handset back to the mobile carrier's network, rather than the Session Initiation Protocol (SIP) more commonly used to link with a corporate IP PBX or messaging server. For this reason, enterprise customers may be less likely to rush to adopt the new BlackBerry.

Mark Blowers, senior research analyst at Butler Group, said this decision looks odd given the positioning of BlackBerry as an enterprise device. "It really needs to hook into an IP PBX. Businesses will be looking to attach it to back-end systems and turn the phone into an extension of their enterprise infrastructure," he said.

RIM representatives declined to comment on the BlackBerry 8820 and its VoIP capabilities.

One carrier that will be supporting the new VoIP capability is Orange, which expects to have the BlackBerry 8820 available in the UK in August. It is initially targeting the device at employees that often work from home using a broadband connection.

"UMA is more appropriate for a home environment, and we'll be looking at technology that's more appropriate for enterprise customers in the future," said Simon Peralta, product manager for Orange Business Services.

Peralta said that Orange will offer the BlackBerry 8820 as part of its Unique service that lets Orange broadband customers have a single handset and phone number for making internet calls when at home, and GSM calls when elsewhere.

"You pair your device with an access point the same way as you would a laptop, and from then on all voice and data will be sent over Wi-Fi when you are within range. It will automatically hand over from Wi-Fi to GSM if you are in the middle of a voice session and wander out of range," said Peralta.

While Orange is not yet supporting SIP, Peralta said there was nothing stopping customers from acquiring a client from a third party and making good use of the built-in Wi-Fi in the BlackBerry 8820.

Blowers agreed that the ability to send and receive data over Wi-Fi would prove attractive if customers can get push email this way and have access to other corporate information.

"This is a good feature to have, as mobile GPRS networks have very limited bandwidth," Blowers added.