Wi-Fi married to a cellphone would surely be a union made in heaven—a wedding of cellular's ubiquity to the high data rates of local-area networking. It would minimize expensive cellular minutes, replacing them with free or cheap Wi-Fi time. Often, too, it would yield a higher-quality call, because cellular coverage is usually weakest where Wi-Fi excels—inside homes, stores, and offices. Walking inside while in the middle of a cellphone conversation, you wouldn't even notice as your handset switched seamlessly to Wi-Fi; and when you went back out, it would revert to the mobile network just as unobtrusively.

Sadly, while the engagement has been announced, the happy couple still hasn't set the date. To be sure, a growing number of PDAs include both technologies. A few, such as Hewlett-Packard's iPaq h6340, are even smart enough to use Wi-Fi when available or a GSM cellular network otherwise—but it can't switch between them automatically during a call. The two radios inside these devices barely communicate—like Romeo and Juliet, banished to their separate homes, they can only dream of final union.

Yet solutions are in sight. Several companies are working on two different ways to unite the worlds of mobile telephony and wireless networking within enterprises. Yet another system, from a small Chicago company, BridgePort Networks Inc., would let individual consumers roam freely between cellular and Wi-Fi networks, enjoying the best of both wireless worlds.

Furthest Along, perhaps, is LongBoard Inc., in Santa Clara, Calif. In January, its system was installed at a Hyatt Regency hotel in Osaka, Japan, completely replacing the internal wired phone network there. The hotel's 80 employees now use Wi-Fi phones—which work like cordless phones but use the Wi-Fi standard—within the building. So they can always be reached at the same phone number, even when far from their desks. Hotel guests, as well, are offered Wi-Fi phones for the duration of their stays, so they can answer calls to their rooms, even when down in the bar.

The LongBoard network can also hand calls off to a cellular network, although that feature hasn't been implemented yet.

Another system well on its way comes from a high-powered consortium consisting of Motorola Inc., Avaya Inc., and Proxim Corp. For companies with voice-over-IP internal telephone systems, which are growing in popularity, each employee will be able to use a single handset as a desk phone and a cellphone.

Last year, Motorola, in Schaumburg, Ill., made a proof-of-concept dual-system cellphone, the CN620,designed for workplaces. But for the phones to work in the real world, there has to be a special server, known as a gateway, to pass calls back and forth between a company's Wi-Fi network and a cellular system, so celebration may be premature [see illustration, ""Network Nuptials"].

This year, Motorola's partners completed the package: Avaya, in Basking Ridge, N.J., with a software enhancement to one of its corporate telephony offerings, Communication Manager; and Proxim, in Sunnyvale, Calif., with the gateway server. One of the most important aspects to the integration involved power management. Wi-Fi devices are notoriously power hungry, while cellphones are always held to a dancer's energy diet, to maintain their svelte profiles. So the Motorola phone's Wi-Fi radio remains asleep almost all the time; the system wakes it only when necessary.