03.01.2006 12:00 AM
Senate Bills Would Open TV Channels for Unlicensed Devices
Two U.S. Senate bills introduced on Feb. 17 to open TV "white space" for use by unlicensed devices appear to be gaining support. Sen. George Allen (R-Va.) and Sen. John Kerry (D-Mass.) introduced the Wireless Innovation Act of 2006 (WINN Act). The act requires the FCC to permit unlicensed use of unassigned broadcast spectrum between 54 MHz and 698 MHz within 180 days of enactment. The WINN Act was cosponsored by Sen. John Sununu (R-N.H.) and Sen. Barbara Boxer (D-Calif.).

Senate Commerce Committee Chairman Ted Stevens (R-Alaska) introduced the American Broadband for Communities Act of 2006 (ABC Act). This act would allow unused TV spectrum between 72 and 698 MHz, excluding channel 37 (reserved for low power medical devices and radio astronomy), to be used for unlicensed devices. The ABC Act directs the FCC to craft technical requirements for unlicensed devices in the TV bands that would protect TV stations and requires that "manufacturers of unlicensed devices designed to be operated in this spectrum to submit a plan to the Commission to remedy actual harmful interference to the extent that harmful interference is found by the Commission which may include disabling or modifying the unlicensed device remotely."

The news release from Kerry's office announcing the WINN Act does not mention specific regulations to protect TV stations from interference, although it includes a quote from Sununu stating, "Thankfully, advances in technology have eliminated any real claims of harmful interference by existing licensees in this spectrum band." Unlike the ABC Act, the WINN Act does not have detailed language on how the FCC must protect TV reception.

A press release from Stevens said the ABC Act will open spectrum for unlicensed devices in both large and small markets. "Broadcasters are allocated hundreds of megahertz of spectrum to provide television service across the country. But in any one market some of the spectrum goes unused. Some studies have indicated that there is more than 150 MHz of spectrum in Anchorage, Alaska, and Honolulu, Hawaii, that could be used by unlicensed devices for wireless services. Even in large cities like Boston and Chicago it is estimated that nearly 50 MHz of spectrum goes unused." Regarding interference to TV stations, the statement indicated the devices would be "designed to sense their environment and identify what spectrum is in use and would only use portions of the broadcast spectrum not being used by broadcasters."

Both bills state that opening up TV spectrum for unlicensed devices will bring affordable wireless broadband Internet access to more people in urban and rural areas.

Consumers Union sent a letter to Allen supporting the WINN Act. In the letter, the group said airwaves suitable for wireless broadband are in short supply and that unused TV channel spectrum was too valuable to allow it to "lay dormant." The letter states, "Opening the white spaces for new and innovative technologies is an essential step toward bridging the digital divide, bringing 21st century telecommunications to rural areas and providing affordable access to all Americans."

In its Freeing Our Unused Spectrum: Toward a 21st Century Telecom Policy report, the Technology CEO Council lists use of TV "white space" in Recommendation 6: "Given the importance to our economy of unlicensed services, the FCC should make more unlicensed spectrum available. For example, the FCC should promptly complete its TV white spaces proceeding (docket 04-186) and permit other uses of the spectrum, on a non-interfering basis, in areas where it is not used by television stations."

The 6 MHz TV channel bandwidth limits this spectrum to lower data rates than consumers are used to with 802.11g and the new MIMO based 2.4 GHz Wi-FI systems. This may not be adequate for in-home networks where consumers are likely to want to use higher speed connections to share files or watch video from other computers in the household. There could be an advantage, however, in using VHF for UHF for lower speed neighborhood or regional broadband access. In Australia, lower VHF TV channels not being used for TV broadcasting are being used to interconnect distant rural communities over great distances. Data rates are not exceeding fast, but the low VHF spectrum works well for these long point-to-point connections.

It appears that this may be the best use of the "white space" spectrum -- point-to-point links over distances that are not practical for Wi-Fi, UWB, or the new 3.6 GHz band. At the distant end of a VHF or UHF spectrum link, it would be easy to use readily available Wi-Fi devices to connect consumers to the VHF or UHF transceiver. Such use would allow links to be licensed, through a simple process similar to that established for 3.6 GHz users, and would make it easier to track down sources of interference. Ideally the licensing system would also reject application for licenses that would impact authorized TV broadcast facilities. This is important, as otherwise systems could be built that work in today's environment, but when stations shift channels in Feb. 2009 after analog TV shuts down there could be significant interference problems, as stations with out-of-core channels move into the "white space" that exists now.

Charlie Rhodes outlined a potential problem with unlicensed devices on TV channels in his column this month in TV Technology: Unlicensed Devices Could Compromise EAS.

For more information, see the full text of the WINN Act in Senate Bill S.2327 - To require the FCC to issue a final order regarding white spaces. The ABC Act is in Senate Bill S.2332 - To amend the Communications Act of 1934 to promote and expedite wireless broadband deployment in rural and other areas, and for other purposes.


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