While speed is certainly a compelling reason for enterprises to deploy 802.11a, capacity is an even better justification. Although 11b's paltry 83.5-MHz allocation in the 2.4-GHz band is enough to support three nonoverlapping radio channels, 11a offers much more: The FCC has allocated 300 MHz of the spectrum for unlicensed operation in the 5-GHZ band, 100 MHz each at 5.15 to 5.25 GHz, 5.25 to 5.35 GHz and 5.725 to 5.825 GHz. While regulations vary depending on the frequency channels, that's a lot of bandwidth--enough to support eight nonoverlapping channels, making it much easier to design 5-GHz cellular systems that don't have interference problems. Another big positive--at least for now--is that the 5-GHz band is not as polluted as the 2.4-GHz band, which supports 11b, Bluetooth, cordless phones, microwave ovens, wireless video-surveillance systems--you get the idea.
Whoa There, Cowboy
So why not skip 802.11b altogether and just implement 11a? First, there is the range issue, which means more access points must be deployed so the cost is higher. Second, and more important, there's no easy way to provide backward compatibility with the older 11b standard. Dual-mode access points and chipsets are due to appear later this year, a development that may simplify things, but the transmission range differences between 11a and 11b may still complicate deployment. The most common analogy is Ethernet, which improved from 10 to 100 to 1,000 Mbps, and with each advance, not only was multimode operation key to maintaining backward compatibility but UTP cabling upgrades were needed in many cases. However appealing the potential of 11a may be, you may not need the additional bandwidth for your applications, and there's no doubt that 11b offerings are less expensive and more mature.
Still, by year's end we expect all the major WLAN vendors to offer 11a products, with many offering dual-mode 11a/11b access points that are built using two radios. WECA (Wireless Ethernet Compatibility Alliance) will offer a WiFi5 certification program, which will help ensure interoperability between products based on different chipsets (there will likely be quite a few contending for your vendor's business). After that, we'll begin to see true dual-mode offerings--both access points and client NICs--built around new dual- and tri-mode chipsets that support 802.11a. 802.11b and 802.11g, which offers 54-Mbps OFDM at 2.4 GHz. The emergence of dual-mode clients will make deploying 11a systems much safer because all your client devices will maintain backward compatibility with home and hot-spot networks.
We also expect significant improvements in throughput and range of 11a systems, perhaps as much as 20 percent, in the second-generation chipsets. And we'll see support for enhanced security standards--provided they ever make it out of the 802.11i working group.
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