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More than 50 airports in the world have or are slated to have in the next quarter some basic wireless connectivity for travelers. Airports' adoption of some form of the Institute of Electrical and Electronics Engineers' wireless LAN (WLAN) standard has led the way for other installations in hotels, corporations, and anywhere else people gather with their laptops.

A number of airports and wireless vendors have recently announced plans to expand airport Internet access. United Airlines with Aerzone (formerly Laptop Lane) announced plans in October to roll out high-speed WLAN access in all domestic and select international airports at its Red Carpet Clubs, gate areas, and terminals. American Airlines with MobileStar Network Corp.-touted as the first to offer service, in 1998 in San Jose-has extended service to 11 additional airports. Delta Airlines, also with Aerzone, finalized a deal earlier in the year for its Crown Room lounges with service to begin in 2001. Wayport Inc.'s high-speed access is found in a number of airports, including the Dallas/Fort Worth International Airport and the Austin-Bergstrom International Airport.

Advantages to wireless networks

* Improved productivity with real-time access to information, regardless of location

* Cost-effective network setup for hard-to-wire locations, such as older buildings and solid-wall structures

* Reduced cost of ownership-particularly in dynamic environments requiring frequent modifications-thanks to minimal wiring and installation costs

Airports are using wireless systems for more than just meeting laptop travelers' needs. For example, Avis Group Holdings will install wireless services in its multilevel operations at the San Francisco airport rental car facility-one of 700 planned installs at Avis locations. Also, Sabre Holdings Corp. recently introduced Sabre Aerodynamic Traveler, a new suite of passenger processing applications designed to expedite the airline check-in process. American Airlines already uses other Sabre wireless devices: Gate Reader system in more than 150 airports and Sabre's CurbSide in 65 domestic airports. The airline also plans to deploy RovingAgent in nearly 25 airports.

The basics of WLANs

WLANs have been around for more than 15 years, but WLANs are somewhat uncharted territory for net administrators. A WLAN is a data transmission designed to provide location-independent network access between computing devices by using radio waves rather than a cable infrastructure. The demand for WLAN access was limited initially by the low throughput first specified, but with the "high-rate amendment," known as IEEE 802.11b, performance is now comparable to a wired Ethernet. The high-rate amendment standardizes the physical layer support of two new speeds, 5.5 megabits per second (Mbps) and 11 Mbps.

Any LAN application, network operating system, or protocol, including TCP/IP and Novell Netware, will run on an 802.11-compliant WLAN as easily as it runs over Ethernet. The high-rate amendment affects only the physical layer, adding higher data rates and more robust connectivity.

Airports have become early adopters of this standard because the computer-carrying public is an all-important consumer group to serve. Roughly 70 percent of business travelers carry laptop computers, and about 80 percent carry cell phones. About 75 percent of frequent business travelers surveyed by Aerzone are interested in having fast and easy access to the Internet in airports. There are nearly 8 million constant fliers (those who make one or more trips a month) counted in the United States today.

How these technologies work

Simply speaking, a WLAN uses radio frequencies to securely transmit data over short hops to a small antenna, which sends the signal to an Ethernet backbone. Antennae are placed throughout a location and allow a user to access the Internet without having to search for a telephone line or data port.

For example, Aerzone's WLAN approach installs small devices in ceilings or on walls of an airport. Over these access points, the network carries fast two-way communication at speeds up to 11 Mbps for every user. This speed is about seven times the speed of a T1 line, the most common office connection.

Within two years, wireless technology is expected to support connectivity at speeds up to 54 Mbps. Aerzone spokespeople brag that its approach does not rely on any specific frequency, vendor equipment, or commitments to either licensed or unlicensed parts of the spectrum. Aerzone's preferred wireless technology vendors are Cisco and Nokia.

It's true that the 802.11b wireless transmitters operate on the 2.4-gigahertz radio band, which does not require a license to use. Some bandwidth experts worry that this band may be congested and bring a wireless data gridlock. Alleviating that worry may be the goal of post-802.11b WLANs, which will operate in the unlicensed 5-GHz band.

The overall 802.11 standard specifies two modes: infrastructure mode and ad hoc mode. In the infrastructure mode, the wireless network consists of a minimum of one access point connected to the wired network infrastructure and a set of wireless end stations. This configuration is called a Basic Service Set (BSS). An Extended Service Set (ESS) is a set of two or more BSSs forming a single subnetwork. Most corporate LANs work this way because of access issues with printers and file servers.

However, ad hoc mode-also known as peer-to-peer mode or an Independent Basic Service Set (IBSS)-is most often used at airports. In this mode, a set of 802.11 wireless stations communicates directly with one another without using an access point or any connection to a wired network. This setup is often created for areas where wireless infrastructures do not exist (like airports) or where access to the wired network is not given, such as for consultants at a client site.

Wireless operations are easy to install

WLAN setup and management is relatively easy. To install a WLAN, you configure access points (APs) and PC cards. The most important concern is the placement of the APs to ensure coverage and performance. Proper installation requires several time-tested steps, such as a site survey, access to electrical power over Ethernet cable, and appropriate configuration tools. Airlines themselves generally do a site survey first to determine where to place the APs and to record signal strength.

Some vendors ship access points that can be powered over an Ethernet that connects the access point to a wired network. This piece of equipment takes the data connection from the wired switch and outputs DC power over unused wire pairs in the networking cable that runs between the module and the access point. This makes installs quicker, because it eliminates the need to run an AC power cable out to the access point on a ceiling.

WLAN products differ from standard 802.3 and 802.5 wired LANs only in their layers, so the same level of manageability with the same tools used for wired LANs will work.