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Wireless Connectivity for Mobile PCs
by Vinit Nijhawan

Start ý Local-Area Wireless ý Mobile Computer Technology ý Applications ý Sources and PDF

LOCAL-AREA WIRELESS

The use of wireless LANs began in the 900-MHz UHF frequency band and then evolved to the 2.4-GHz band. Future WLANs will operate in the 5-GHz range with added throughput. Spread-spectrum radio technology used for WLANs is derived from military technology, like the original two-way radios. The military devised spread-spectrum to allow radio transmissions that were low power and could not be intercepted or jammed by the enemy.

In civilian use, spread-spectrum allows multiple radio systems to operate in the same geographical area without interfering with each other. As a result, spread-spectrum frequency bands are unlicensed (i.e., the FCC grants any radio device spread-spectrum compliance to operate without the need for a license). The 2.4-GHz band is available for unlicensed users in a majority of the world.

Wireless LAN technology initially was used in retail, manufacturing, and warehousing operations for inventory management. Recent growth areas for wireless LANs are in multi-PC homes for Internet connectivity, campus networking (high-speed wireless Ethernet), and most recently, in last-mile high-speed Internet connectivity.

Also, 2.4-GHz wireless connectivity has been used for RF-ID applications, such as in-premise asset tracking, personal ID (e.g., the Mobil Speedpass system, which allows users to pump gas without any data entry), and cable replacement. According to Frost & Sullivan, a market research firm, the total worldwide wireless LAN market will grow from $305 million in 1998 to $1.63 billion in 2005, a compound annual growth rate of 27%, with close to 12 million units shipped in 2005.

Several standards have been written to allow multiple-vendor, wireless LAN interoperability (see Table 2). None of them has truly lived up to their claims of universal interoperability. Most recently, the Bluetooth standard will allow low-cost replacement of cables at a 1-MBps data rate between devices in a 30ý radius. The concept allows cell phones, Personal Digital Assistants (PDAs), and laptop computers to communicate with other devices without the need for a cable. In a way, Bluetooth is replacing IrDA infrared communications, which is available on more than 60 million devices, yet rarely used because it is line-of-sight, limited to three feet, and often not interoperable. Bluetooth is still more than a year away, waiting for single-chip radio technology to make it affordable for portable devices.

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