Is Wi-Fi Getting Too Crowded?

By Ed Sutherland

May 15, 2002

Some in the world of wireless networks think the 2.4GHz band is being overtaken by other users, both licensed and unlicensed.

Breaker breaker, good buddy. Remember the CB radio -- one of the preeminent fads of the 1970s and 1980s? The communication method of choice for gear-grinders and grandmas may be heading for an update. 802.11b "will end up being the Citizens Band of this era," according to Bay Area Wireless Users Group. Such ubiquity may not be all good, however.

Tim Pozar, spokesman for the San Francisco-based wireless group, says that an influx of myriad wireless makes the unlicensed 2.4GHz spectrum "certainly more unusable."

While the most notable resident of 2.4GHz is wireless networks, the bandwidth is also home to millions of devices ranging from magnetic resonance instruments (MRIs) to microwave ovens. Pozar says 802.11b is also used by cordless phones, home spy cameras -- even industrial paint driers.

"Already many licensed users, such as the microwave video transmission links, that share the band with 802.11b, are finding the band too crowded and are moving off," Pozar says.

A Federal Communications Commission (FCC) spectrum advisory group plans to recommend opening the 2.4 GHz to less interference-prone devices. The move was prompted by complaints from licensed amateur radio users reporting Wi-Fi gadgets interrupting the increasing number of amateur television broadcasts.

"The aggregate noise levels of what the FCC calls 'intentional and unintentional radiators' will increase on the 2.4 GHz [wavelength]," Pozar says.

Also a potential threat to any harmony within the 2.4GHz band is Bluetooth, the short-range personal area network technology. Industry market research firm In-Stat/MDR expects 644 million Bluetooth devices will be in use by 2006. Pozar believes Bluetooth's use of Frequency Hopping Spread Spectrum (FHSS) transmission technology may be a larger problem than 802.11b.

FHSS "hops" a signal over more than 75 frequencies. By permitting only devices transmitting at the same time over the same frequency, interference is reduced. Wi-Fi, on the other hand, employing Direct Sequence Spread Spectrum (DSSS), divides data transmitted while duplicating the bits of information, allowing a signal to survive interference.

"Many features that would reduce interference, like frequency coordination and automatic power limits were not built into [Wi-Fi or FCC regulations]," Pozar says. Even 802.11a, with its more expansive 5.8GHz home does not include the features, according to Pozar.

Allen Nogee, a wireless network analyst at In-Stat/MDR, says 802.11b has plenty of room. "Because 802.11b has three channels, I really don't know of many instances where that hasn't been adequate, maybe outside a few corporate installations with very large networks."

Up the West Coast from Pozar in Portland, Oregon, is the Personal Telco Project, another community-based public wireless network. Nigel Ballard, a spokesman for the group, spoke from steamy New Orleans, where the Cable2002 trade show was taking place.

"Thanks to one of the exhibitors leaving their 802.11b access points wide open, I'm able to log onto the net and check my e-mail. Gotta love this technology," Ballard said.

"What's the future?" asked Ballard. "We'll slowly migrate to 802.11g, but there is a ton of life left in 802.11b."

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