New TV white-space rules provide more flexibility in rural areas

Wireless Internet service providers hoping to ply their trade in TV white space are cheering three significant FCC rule changes that will make it easier to use the spectrum to deliver broadband service in remote and rural locations, particularly those punctuated by hilly topographies.

The commission decided on April 4 to increase the maximum height above average terrain (HAAT) for sites where fixed white-space devices may operate, modify the adjacent channel emission limits to specify fixed rather than relative levels, and slightly increase the maximum permissible power spectral density (PSD) for each category of white-space TV bands device (WTBD), which limits out-of-band emissions into adjacent channels. "These changes will result in decreased operating costs for fixed TVBDs and allow them to provide greater coverage, thus increasing the availability of wireless broadband services in rural and underserved areas without increasing the risk of interference to incumbent services," said the agency.

The FCC's new rules were made in response to five petitions for reconsideration pertaining to its previous white-space Memorandum Opinion and Order. The most significant rule change is that base station sites can now extend to 250 meters (820 feet) HAAT rather than being held to the previous 76-meter HAAT limit. Parties that petitioned for the rule change argued that the 76-meter ground HAAT limit was too low to allow the installation of fixed stations in rural, mountainous and hilly areas where broadband service to the public is already lacking.

"This rule change will lower infrastructure costs and afford WISPs greater flexibility in network design," said the Wireless Internet Service Providers Association (WISPA), one of the petitioners.

However, the commission did not raise the maximum antenna height, which remains limited to 30 meters above ground level (AGL) in order to minimize the potential for interference. "Under the modification we adopt herein, a site with an elevation of up to 220 meters above average terrain could be used with a 30-meter antenna, or a site with a higher elevation above average terrain could be used with a shorter antenna, provided the sum of the site elevation above average terrain and antenna height above ground does not exceed 250 meters," said the FCC.

The commission also modified the rules for adjacent channel emission limits to specify fixed values, rather than vary the limit relative to the in-band power. Specifically, it adopted a fixed adjacent channel emission limit for each category of WTBDs that is equivalent to the current emission limit for devices operating at maximum power. "Devices operating at less than the maximum permitted power will not be required to suppress emissions below the fixed limits we are establishing. This eliminates the need for a device operating at less than the maximum permitted power to unnecessarily suppress adjacent channel emissions below the levels needed to prevent interference to other services in the TV bands, thus simplifying equipment design and reducing its cost. A fixed emission limit also simplifies compliance measurements, because the emission level can be measured directly rather than by comparing the in-band and adjacent channel power measured in two different bandwidths," said the FCC.

The FCC raised the maximum PSD by 0.4 dB for each category of WTBDs so they can operate at the maximum permissible power in a bandwidth of 5.5 MHz instead of 6 MHz, thus allowing a 250 kHz roll-off from the in-band channel to the adjacent channel.

In addition, the commission moved to require that geographic coordinates or other information concerning cable headends in the TV bands database be made publicly available. The cable TV industry sought to restrict access to information on cable headends, arguing that they are considered critical infrastructure and could be subject to sabotage and other security threats. However, the FCC noted that information on the locations of cable headends is already publicly available from other sources, and the TV bands databases will only list those facilities that are outside the protected contours of the over-the-air TV stations being received and that the headend operator chooses to register.

The TV bands consist of six-megahertz channels designated 2 to 51 in four bands of frequencies in the VHF and UHF regions of the radio spectrum (54-72 MHz, 76-88 MHz, 174-216 MHz, and 470-698 MHz). Two categories of unlicensed devices, fixed and personal/portable, are allowed to operate in the vacant white space between channels.

For more:
- see the FCC Memorandum Opinion and Order here
- see this Telecompetitor article
- see this WISPA post

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