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Making the wireless connection with Wi-Fi

Wi-Fi's strong but short; cellular networks are weak but broad. Now an IBM technology will let users jump between both. Anybody got a wireless card?

IBM will unveil an updated version of its wireless gateway Monday that will let devices roam between Wi-Fi networks and cellular carriers' wireless networks.

Big Blue's latest version of its "Everyplace Wireless Gateway" will first be used by the Toronto Police Department. By using the technology, officers will be able to file reports directly from their patrol cars while parked close to a precinct house. When out of Wi-Fi range, network equipment automatically switches over to a cellular network.

The gateway from IBM is part of a push by wireless equipment makers to couple Wi-Fi and cellular networks. Cellular telephone networks use a weaker signal, but can cover greater distances. Wi-Fi networks, or those networks that use the 802.11b wireless standard, extend a much more powerful signal but can only be tapped about 300 feet from the source.

Companies such as GTran Wireless have already begun selling "hybrid modems," or a single card that slips into a laptop or personal digital assistant and can access both Wi-Fi and cellular networks.

U.S. wireless carriers have indicated they want to start selling access to the growing number of Wi-Fi hot spots in hotels and airports. So far, though, only VoiceStream Wireless has begun offering any kind of Wi-Fi services, offering networks in hundreds of Starbucks retail stores.

The earliest adopters of these so-called "multi-mode" networks are police departments, which are using them to add more zip to networks they use to shuttle incident reports or suspect information. The idea is the faster officers can file an incident report, the quicker they can catch criminals.

Agencies in Orange County, Calif., Oakland, Calif., and Baltimore are using software from a company called Padcom, which allows users to roam between cellular and Wi-Fi networks.

Navin Sabharwal of ABI Research believes that wireless carriers eventually will migrate to similar technologies for their larger networks.

"It's easier for a police department to implement this," he said. "For a carrier it's a much bigger strategic decision; there's a lot more due diligence. They have to worry about coverage, how many access points to put up, what type of billing they will have."

Why Wi-Fi? WLANs (wireless local area networks) let anyone with a laptop and a modem get wireless Internet access from up to 300 feet away. Although WLANs operate through the 802.11 standard, there is an alphabet soup of versions of the standard that have varying levels of security or speed.

For example, Wi-Fi networks operate on 802.11b, but 802.11a and 802.11g have been developed to be more secure.

The 802.11b version runs on three channels in the unregulated 2.4GHz spectrum, which is also used by cordless phones, microwave ovens and many Bluetooth products. Bluetooth is a wireless technology that uses radio waves to send data between devices. Because the information is transmitted through the air, a person can "capture" the information as it travels.

The 802.11a strain is an approved standard that broadcasts a more powerful signal, running on 12 channels in the 5GHz spectrum, and transfers data up to five times faster than 802.11b. There are a very limited number of 802.11a networks, even though the 802.11a chipsets have been sold for nearly a year. Though it is faster, it has not been backward compatible to 802.11b.

Another Wi-Fi standard, known as 802.11g, which is more secure than 802.11b and has the speed of 802.11a, is also in the works, but has yet to be approved by the appropriate standards bodies.