A Match Made in Packets

Coming soon: cellular handsets that can use a Wi-Fi network

4 min read

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.

The consortium's system, and the LongBoard one as well, works only with GSM cellular networks right now. GSM, one of the two main cellular technologies nowadays, is the European standard and is also widely used in Asia. Though late coming to the United States, it's now used by two of the top five wireless carriers there.

Once all the parts are in place, you'll be able to start walking out of your office during a call, get in your car, and drive off, still talking. It remains to be seen, though, whether use of such systems will be largely confined to employees of large organizations or whether everybody eventually could be using them.

LongBoard, like Avaya, Proxim, and Motorola, is looking to the corporate market. According to David Schwartz, LongBoard's marketing director, more than 30 percent of all calls in a typical office are received on cellular phones, even though the cellphones are usually within 2 meters of land-line phones.

There are other differences between the approaches taken by Avaya and by LongBoard. Most significantly, in the Avaya system, phone calls flow through the gateway server located within the organization, avoiding some cellular charges. For LongBoard users, the cellular carrier would handle the calls.

Yet another company that is in the Wi-Fi-cellular game, BridgePort Networks Inc., bridges the two protocols by means of what might be thought of as a very clever hack. It relies on the way that a cellular phone tied to one home network, say, T-Mobile's, can roam onto another network, say, Cingular's.

"When you get off a plane in San Francisco, for example, and you turn on your T-Mobile phone, it registers with the local switch, which may happen to be Cingular's," says Sanjay Jhawar, BridgePort's senior vice president of marketing. The San Francisco switch realizes it doesn't "own" you, so it looks up your phone in what's called a home-location register, which tells it what your home switch is. "Suppose that [register] is in New York," says Jhawar. "It sends a signal to the New York switch, saying 'I've got your caller now, if you have any calls for him, send them to me.'"

BridgePort's trick is to make the Wi-Fi network look like just another cellular network for the purpose of handing off calls from a Wi-Fi service to a cellular one. Correspondingly, the cellular network is made to look like an Internet-based one when calls go the other way. "Think of the way calls are handed off from one cellular network to another as you drive around in your car," says Jhawar. "The entire Internet looks like a cell from the point of view of the home network."

Jhawar says that Bell Canada is just one of several carriers around the world testing BridgePort's system right now. Similarly, the Avaya/Motorola/Proxim consortium is concluding trials "with several large companies," says Greg Fern, a director of product marketing at Motorola.

The LongBoard and Avaya systems may let workers unify their desk phones and their cellphones by the end of this year. BridgePort's technology holds out a similar hope of roaming between Wi-Fi and cellular networks for the rest of us. But until that promise is realized in the indefinite future, sadly, the relationship between these two key wireless technologies will continue to be "Look, but don't touch."

Steven Cherry

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