Officials at several U.S. agencies and wireless industry companies last week agreed on how to allocate spectrum in the hotly contested 5GHz band in a deal that gives wireless LANs more space but less priority over other signals.
The agreement among the Department of Defense, NASA, the Federal Communications Commission and others benefits the wireless industry because it allocates an extra 255MHz of spectrum for the WLAN standard 802.11a, which already has 325MHz of spectrum allocated.
However, the deal mandates that products running in the band become more sensitive to military signals in the area, which could ultimately slow those products.
For months, the Defense Department has resisted giving up any space in the 5GHz band, arguing that the military needs to keep channels clear for radar. But government and industry pressure has been mounting.
Sen. George Allen, R-Va., and Sen. Barbara Boxer, D-Calif., since last fall have been pushing a bill that would set aside 255MHz of new spectrum for WLAN hot spots. And several companies, including Microsoft Corp., have been lobbying the FCC for more spectrum.
Last July, the Redmond, Wash., company told the FCC that additional unlicensed spectrum in the 5GHz band would let the company deploy wireless broadband networks that would compete with digital subscriber line and cable modems.
Furthermore, the National Telecommunications and Information Administration and the FCC wanted to come to a consensus so that the country would look like a unified force with respect to the band.
“The [United States] is now able to formalize its position with respect to earth exploration satellite systems, mobile and radio location services at 5GHz and will now fully support these allocations,” said Nancy Victory, assistant secretary of commerce and an administrator at the NTIA, in Washington.
At the International Telecommunication Union-sponsored World Radio Conference in Geneva in June, a U.S. ambassador will argue for a worldwide allocation of space in the 5GHz band.
“The whole purpose of the WRC is to get all the countries of the world to have similar spectrum rules,” said Rich Redelfs, president and CEO of Atheros Communications Inc., the leading 802.11a component company, in Sunnyvale, Calif. “Radio [signals] dont stop at country boundaries.”
An international agreement at the WRC could free as much as 455MHz of “harmonized” spectrum in the 5GHz band worldwide.
FCC Chairman Michael Powell applauded the affected organizations for sharing the band.
“Consistent with the recommendations of the Spectrum Policy Task Force, the proposal would make additional unlicensed spectrum available to promote [WLAN] deployment while protecting radars vital to our national security,” said Powell in a statement last week. “The parties involved are to be commended for their efforts to reach this hard-fought compromise.”
Additional channels give 802.11a a certain leg up on competing standards. The reigning standard, 802.11b, and the upcoming 802.11g offer only three channels each in the lower 2.4GHz band. But prospective customers pointed to other issues.
“Tests have shown that 802.11gs lower frequency of 2.4GHz has potentially better range due to its ability to penetrate obstructions better than a transmitter operating at 5GHz,” said John Ashcraft, electronic formats coordinator at the Marston Science Library at the University of Florida, in Gainesville, which operates 185 802.11b access points and is evaluating 802.11a and 802.11g.
Until now, the United States has limited allocation of unlicensed spectrum in the 5GHz band to the area between 5150MHz and 5350MHz. The new agreement includes the 5470MHz-to-5725MHz spectrum. This puts the United States in line with most of Europe, which is allowed to use those additional bands.
But theres a rub in that the Defense Department insisted on new ground rules. Under the agreement, the military increased the required sensitivity of the access points. If an access point detects military signals at a certain decibel, it must get out of the way by hopping to a new channel.
The Defense Department required that the threshold be lowered from minus-67 decibels to minus-64 decibels for 1-watt-to-200-megawatt devices and to minus-62 decibels for devices that run less than 200 megawatts. This rule applies to the 5250MHz-to-5340MHz spectrum and the new 5470MHz-to-5725MHz spectrum.
“The debate has been about how sensitive you have to be,” Atheros Redelfs said. “The industry is worried about having to jump channels even when its just [radio] noise. Every time you jump channels, it slows things down a little bit. And now theres a slightly higher probability that we will view noise as radar. Theres not a lot of military radar in our neighborhoods.”
Existing 802.11a products wont be forced to adhere to the new rules, which arent likely to go into effect for several months and certainly not before the WRC meeting, according to NTIA officials.
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