Wouldn't it be nice if people could leave their offices and take along one mobile device that works everywhere? Even better, what if that device were smart enough to forward calls to their mobile phones, but only during business hours?

That day is getting closer. Voice over wireless LAN, or VoWLAN, makes it possible to make and receive phone calls over a Wi-Fi network. And because coverage is based on your wireless network, it provides service in places a cell phone might not. Plus, a dual-mode, VoWLAN/cellular handset that uses a company's Wi-Fi network can lower cellular bills.

This concept has been around for more than five years, but the necessary pieces have been slow to come together. Until now, the handsets have been too pricey for the mass market, and the technology has lacked standards for roaming, quality of service, and power usage.

Sales of VoWLAN phones averaged about 100,000 to 150,000 units last year, according to research firms Infonetics and Synergy Research Group, and far fewer dual-mode phones were sold. Unit sales projections for 2009 are about 17 million for VoWLAN phones, with predictions for dual-mode handsets ranging from 30 million to 100 million. By comparison, more than 700 million cell phones were shipped last year, with unit volumes of 1 billion projected by 2009 or 2010.

Most businesses haven't embraced VoWLAN, but four industries have: health care, retail, warehousing and hospitality. Health-care workers, with their need for mobility and accessibility, have taken advantage of standards-based wireless, such as Vocera Communications Inc.'s badge-style wireless communicator. In retail, stores double the effectiveness of their existing wireless networks used for inventory by extending voice into every aisle and letting employees assist customers on the spot. For logistics and warehousing, cellular signals often don't penetrate the vast expanses of metal racks and shelving. But a VoWLAN system, such as the one offered by SpectraLink Corp., lets a salesperson in an office call a worker loading a truck to make a last-minute change. And the hospitality sector has substituted VoWLAN for private radio systems, letting managers use the same Wi-Fi infrastructure that guests use to surf the Web to connect to a bellhop or housekeeping.

Broader acceptance of VoWLAN will depend on maturation of the wireless infrastructure for quality of service and mobility, more pervasive Wi-Fi deployments, and a reduction in handset prices.

Coverage And Savings

Although the wireless-networking industry has matured, pervasive wireless deployments in the enterprise are far from common, and the complexities of transporting voice over these networks throw even the dominant wireless vendors into a spin. For companies whose employees stay in their cubicles, wireless is unnecessary. But in other organizations, mobile employees must be in contact with their peers, clients, and customers. With a VoWLAN system, a single extension is assigned to a mobile user, who can then be reached on it anywhere. VoWLAN also can provide complete coverage within a building, even in its subbasement if the wireless LAN installation exists.

The costs related to a VoWLAN deployment aren't for the faint of heart. Customers must bear up front the full cost of Wi-Fi handsets at $400 to $750 each. Plus, if you have a wireless infrastructure, you'll need to fill in gaps. Otherwise, you must purchase and build one from scratch.