The once-straightforward world of wireless local area networks has gotten more complicated. An emerging standard,...
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802.11g, is garnering praise as products based on it begin to hit the market, while the future of the other high-speed wireless standard, 802.11a, may not be as bright as it once appeared.
Today, most wireless local area networks (LANs) use the Institute of Electrical and Electronics Engineers (IEEE) standard 802.11b, which gives users 11M bit/sec of throughput in the 2.4 GHz frequency. But now there are two choices for moving data at speeds of up to 54M bit/sec. The newest of these two, 802.11g, is backward-compatible with 802.11b. The other, 802.11a, is not.
The 802.11a standard transmits data in the 5 GHz frequency. The higher frequency gives 802.11a some advantages, but there is one significant disadvantage: it is incompatible with the dominant 802.11b standard. Right now, companies have not shown a lot of interest in 802.11a, said Gemma Paulo, a senior analyst with the Scottsdale, Ariz., research firm In-Stat/MDR.
The 802.11a standard uses a higher frequency than 802.11b and 802.11g, so it does not transmit as far, and the signal drops off more quickly. It also does not travel through walls as well, said Mark Van Pelt, a wireless LAN consultant with Manchester Wireless in East Brunswick, N.J. But that shortcoming may not necessarily be a bad thing, he said.
Far from clear
In New York's high rises, wireless LANs are so prevalent and so close together that it can often be tough to get a clear signal. In addition, microwaves and cordless phones also operate at the 2.4 GHz frequency on the wireless spectrum. Wireless LANs only have three channels in the 2.4 GHz range, which means that, as more people use the network, it simply may not be possible to find a clear signal.
That kind of congestion was a problem for Jonn Martell, the wireless project manager at the University of British Columbia in Vancouver. The high bandwidth and clear frequency of 802.11a appealed to him. But because of the prevalence of 802.11b cards in student notebooks and handhelds, the university decided to install an 802.11b network.
As he began to map the network, he found that in many areas there was simply too much interference from microwaves and cordless phones. So, in those areas, the university installed dual-mode access points that use both 802.11a and b.
Since 802.11a runs at a different frequency than b, the signals behave differently. It loses bandwidth more quickly at a distance from the access points, Van Pelt said. So setting up a dual-band network can be tricky. Martell said that he mapped the network for 802.11b and hopes that the dual-mode nodes will work in that configuration, but many of the nodes are easily moved if need be.
Cisco Systems Inc. one of the leading vendors of access points for the enterprise market, is betting that companies will want dual-mode access points. Many of its 802.11b access points can easily be turned into a/b access points, said Shripati Acharya, a senior product marketing manager with Cisco's wireless networking business unit. More laptops are beginning to hit the market with embedded 802.11a/b cards in them, he said. As those dual-mode cards become commonplace, users will not know or care which standard they are using.
Parts of the spectrum are off-limits
While the U.S. market may see a growth in dual-band networks, the international market may never see 802.11a wireless LANs. In many countries in Europe, as well as in Japan, the 5 GHz frequency on the spectrum has already been allocated, often to the military, so it is off-limits. Without these markets, 802.11a may have a hard time creating a large market, said John Chang, a senior analyst with the Oyster Bay, N.Y., research firm Allied Business Intelligence.
Despite these issues, 802.11a can make sense for some companies, Van Pelt said. For starters, it is a ratified standard -- unlike 802.11g, which will not be ratified until later this year. And unlike 802.11g products, many 802.11a products have received certification from the Wi-Fi Alliance, which guarantees interoperability. For those looking for a Wi-Fi-approved higher-bandwidth wireless LAN today, 802.11a is the only choice.
Van Pelt said that, for companies located in cities where multiple 802.11b networks may be in conflict, 802.11a can be a good solution. With wireless security such an overriding concern, the fact that 802.11a has a hard time penetrating walls may turn out to be a good thing after all, Van Pelt said.
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