802.11a and 802.11g Evolve the WLAN Space

 
 
By Jason Brooks  |  Posted 2002-05-06
 
 
 

Ten or so megabits per second is more network speed than most business users need, but this hasnt stopped the march of wired networking gear from there to 100M bps to Gigabit Ethernet to 10 Gigabit Ethernet.

That same need for speed—particularly for applications such as streaming video—has driven the development of the 802.11a and 802.11g extensions to the popular 802.11b specification on which most WLAN (wireless LAN) products are based.

802.11a is an extension of the 802.11 standard family that operates in the 5GHz band. By replacing the direct sequence spread-spectrum transmission technology of 802.11b with an OFDM (orthogonal frequency division multiplexing) encoding scheme, 802.11a can deliver speeds up to 54M bps.

Wireless networking access points and adapters based on 802.11a began shipping a few months ago. (eWeek Labs review of 802.11a gear from SMC Networks Inc. and Proxim Inc. can be found at www.eweek.com/links.)

Because it exists in a separate part of the electromagnetic spectrum, 802.11a equipment cant interoperate with existing 802.11b gear—a problem for companies that have already invested in 802.11b infrastructure. However, operating in the 5GHz range is also a significant advantage for 802.11a because the 2.4GHz portion of the spectrum is crowded with potentially interfering Bluetooth devices, microwave ovens, baby monitors and cordless phones. In addition, 802.11a gear uses eight nonoverlapping channels, compared with three for 802.11b, which enables companies to deploy their 802.11a access points more densely than is possible with 802.11b.

802.11g uses the same OFDM scheme as 802.11a and will potentially deliver speeds on par with 802.11a. However, 802.11g gear operates in the 2.4GHz swath of spectrum that 802.11b equipment occupies and for this reason should be compatible with existing WLAN infrastructures. Like 802.11b, 802.11g is limited to three nonoverlapping channels.

The 802.11g specification currently exists in draft form only. Both IEEE ratification and Federal Communications Commission approval will be required before products based on 802.11g can begin shipping, which we dont expect will happen until next year.

With 802.11a products already shipping and 802.11g still incomplete, 802.11g may have a tough time taking off. As for the backward-compatibility benefits of 802.11g, vendors including Cisco Systems Inc. have begun shipping dual-radio 802.11a/b products that should help companies smooth the transition between or coexistence of 802.11b and 802.11a wireless networks.

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