Interference more likely as wireless devices become popular
Monday, June 3, 2002
Gary Oglesby thought it was odd that his wireless network at WorldCom Inc. got unusually congested early each morning and again just after quitting time.
Turns out a security gate at a parking lot just outside his group's offices shared the network's frequency. To reduce interference, Oglesby had to move an antenna away from the window.
As more people go wireless to access the Internet, it is only a matter of time before these kinds of conflicts abound.
"The frequency is getting a lot more crowded," said Oglesby, a managing engineer with WorldCom's Internet architecture and technology group near Washington, D.C.
In a high-tech community in Cary, N.C., Chuck Musciano wasn't getting the promised high Internet speeds with his wireless devices. He soon realized that half his neighbors had wireless networks as well -- all using Wi-Fi, or 802.11b, the most popular wireless protocol.
"Because of the houses being close enough together, all of the wireless networks were overlapping with each other," Musciano said.
His solution: Get his neighbors to space out frequencies they use. Because Wi-Fi transmissions use only a third of the allotted frequencies, adjacent antennas can be adjusted to minimize conflicts.
So far, such coordination is more the exception than the rule, as new wireless networks sprout up across the nation without any congestion.
'Just happy to surf'
When there is interference, a plant or a concrete wall may be the culprit. Often, users won't even realize they aren't getting the promised speeds.
"They are just happy to surf the Web," said Rick Doten, wireless product manager for the network security company Netsec.
Congestion is likely to become more noticeable, however, as devices proliferate. Cahners In-Stat Group projects that Wi-Fi sales will hit $5.2 billion by 2005, up from $2.4 billion this year and $660 million in 2000.
Companies and universities use wireless to avoid having to drill holes and lay wires in existing buildings. Airports and Starbucks coffee shops offer it for travelers. Apple Computer Inc. and other companies market devices for home wireless networks.
"Prices have come down to the point where people set them up for novelty purposes more than necessity," said Gary Schober, chairman of Berkeley Varitronics Systems Inc., whose devices help scan for conflicting wireless traffic.
Meanwhile, digital activists in several cities are trying to build public wireless networks that link homes, schools and businesses so someone with a laptop could log on from anywhere -- indoors or out.
While such networks can be beneficial, "it will be very interesting to see if they actually increase interference," said Bennett Kobb, consultant and author of "Wireless Spectrum Finder."
Headsets and other gadgets using the Bluetooth standard, newer cordless phones and microwave-powered, energy-saving light bulbs share the 2.4 to 2.483.5 gigahertz frequency range used by Wi-Fi. Household microwave ovens use radio waves in that range to heat leftovers.
Conflicts sometimes occur also at 902 to 928 megahertz, used by older cordless phones and some military radar. Ricochet Networks Inc. plans to launch a wireless service in major cities using that range as well.
These frequencies are appealing because the government does not require licenses to use them. But no licenses also mean no entity to coordinate.
Already, there are occasional problems at trade shows, office parks or neighborhoods like Musciano's.
For now, such problems can usually be resolved by coordinating and adjusting settings, said Matthew Gast, author of "802.11 Wireless Networks: The Definitive Guide." But coordination can be difficult, he notes, when competing networks aren't centrally run by the same company.
Anticipating the proliferation of these devices, Sirius Satellite Radio and XM Satellite Radio have asked the government to require that devices reduce their signal strength to prevent interference with the nearby frequencies used by satellite radio.
"We want them to take care of the problem now before it becomes a major problem," said Sirius spokesman Jim Collins.
Dennis Eaton, chairman of the Wireless Ethernet Compatibility Alliance that coordinates Wi-Fi devices, denies that existing products interfere with satellite radio and said any other interference is now minimal.