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NTIA Offers Polar Weather Sat Frequencies for Broadband

On Monday the Department of Commerce's National Telecommunications and Information Administration (NTIA) released its report on spectrum currently used by federal agencies that could be reallocated for wireless broadband.

The report, An Assessment of the Near-Term Viability of Accommodating Wireless Broadband Systems in the 1675-1710 MHz, 1755-1780 MHz, 3500-3650 MHz, and 4200-4220 MHz, 4380-4400 MHz Bands has more than 260 pages devoted to a detailed analysis of the impact of reallocating this spectrum for wireless broadband. Out of all the spectrum studied, the NTIA offered 115 MHz: from 1695 to 1710 MHz and 3550 to 3650 MHz. The first band is currently used for weather satellite downlinks and for various other environmental sensors, such as weather balloons. The second band is currently used by the Department of Defense for a variety of tactical high-power radars.

The NTIA Fact Sheet on Spectrum Plan and Timetable, Fast Track Evaluation includes a table showing 120 MHz being reallocated from broadcast TV, but focuses only on Federal spectrum. Although only 115 MHz was offered in the Report, a significant amount of additional spectrum could be made available if sufficient time and funding is provided to relocate some existing Federal spectrum users.

As previously reported, agencies around the world, including the World Meteorological Organization (WMO) are opposed to reallocation of the 1695 to 1710 MHz spectrum for wireless broadband. The NTIA Report provides details on the use of this band. A short summary says that reallocation of these frequencies will not impact most users of the GOES (geostationary) weather satellites used to provide near real time images from their location 22,236 miles above the Earth or of the emergency weather information provided over these satellites by EMWIM. Most of the downlink frequencies used by the US GOES satellite and geostationary weather satellites from other countries are below 1695 MHz, although the 1694.3 to 1695.0 MHz band is used for numerous environmental and emergency data distribution networks.

Polar Earth orbiting satellite (POES) downlinks will be affected by reallocation of the 1695 to 1710 MHz band. All of the currently operating NOAA POES have high-resolution picture transmission (HRPT) downlinks in this band, as do the Feng Yun 1D, Metop-A, and Meteor M N1 polar Earth orbiting satellites. The POES satellites also use this band to provide data for the Land Remote Sensing Program.

The NTIA Report warns that "damage, due to loss of the data, would occur to the land remote-sensing program community and the mission of the DOI USGS to support disaster and hazard mitigation, emergency response, and major scientific activities. Any alternative distribution method must recognize current reliability and availability requirements."

The NTIA Report lists locations of critical downlinks that depend on spectrum impacted by reallocating the top 15 MHz of the band. These would need to be protected from interference by wireless broadband devices.

The report also makes this interesting statement concerning loss of direct RF reception from these satellites:

"Parties opposed to reallocating the 1675-1710 MHz band to mobile broadband also contend that they cannot confirm that, if the information currently available from the meteorological-satellite service were received at only a few receive sites and distributed via terrestrial services, this would be a functionally equivalent substitute for the direct reception of satellite and radiosonde services."

It noted that opponents had concluded that the "lack of reliability and of 'real-time' capabilities of terrestrial distribution" could have a significant impact on public safety.

In reading the Report, it's clear the NTIA is under a lot of pressure to reallocate spectrum for wireless broadband.

Another band under "fast track" consideration is the 4 GHz spectrum currently used worldwide for radio altimeters on aircraft. Reallocating this planned 115 MHz block of spectrum comes at a cost, as stated by the NTIA:

"Making the 1695-1710 MHz and 3550-3650 MHz band available for wireless broadband will require timely allocation of funding for affected Federal operations to engage in planning, and in some cases to make changes to their operations and redesign their equipment."

An example offered was in connection with the National Oceanic and Atmospheric Administration (NOAA). The Report observed that NOAA would have to do a redesign of the next generation of its geostationary meteorological satellites to place all communications below 1695 MHz. The other alternative would be to develop another communications methodology that recognized "current reliability and availability requirements."

It said that NOAA would also have to redesign the radio transmitters used on its weather balloons and similar systems in order "to use spectrum more efficiently to make room for satellite downlinks."

Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.