FCC Expands Rural Use of White Space Spectrum

At the October monthly meeting, the FCC modified its Part 15 rules to allow for better utilization of white space spectrum in rural America – a move that should provide a boon to fixed wireless technology. The term ‘white space’ refers to spectrum that has been assigned for over-the-air television broadcasting but that sits empty in and is not being used by a television station. In any given market there are channels of television spectrum that are not being used, and today’s ruling describes new ways that wireless ISPs, school systems, and others can better use the unused spectrum.

The FCC action follows a long-standing petition from Microsoft asking for better use of unused white space spectrum. The FCC asked Microsoft and the National Association of Broadcasters to negotiate a reasonable plan for using idle spectrum, and the actions taken by the agency reflect the cooperation of the parties. The FCC further plans to issue a Notice for Proposed Rulemaking to investigate other questions related to white space spectrum.

First, the FCC is allowing for increased height for white space transmitters. The transmitters were previously limited to being no more than 250 meters above the average terrain in an area, and that has been boosted to 500 meters. In case somebody is envisioning 1,500-foot towers, wireless companies achieve this height when placing towers on hilltops. The extra height is important for two reasons. Fixed wireless technology requires line-of-sight between the tower and a customer location, and the higher the tower the better chance of being able to ‘see’ some portion of a customer premise. Using higher towers also means that wireless signal can travel farther – white space spectrum is unique compared to many other spectrum bands in that it can deliver some broadband at significant distances from a tower.

The FCC order also is allowing increased power and has increased the maximum effective radiated power from 10 watts to 16 watts. Power levels are important because the strength of the signal matters at the customer location – higher power means a better chance of delivering full broadband speeds.

The order builds in some additional protection for existing television stations. The FCC order increases the separation between an ISP wireless signal and existing television station frequencies. Transmissions with white space spectrum tend to stray out of band and allowing broadband signals too close to television signals would mean degraded performance for both the television station and ISP. One of the questions to be asked by the NPRM is if there is a way to utilize the bands closer to existing television signals.

The FCC’s order also authorized the use of narrowband devices that use white space. This opens up the door to using white space spectrum to communicate with Internet of Things devices. In rural areas, this might be a great way to communicate with agricultural sensors since the white space spectrum can travel to the horizon.

Finally, the order allows for higher power applications in isolated geographic areas that can be ‘geo-fenced’, meaning that the transmissions can be done in such a way as to keep the signals isolated to a defined area. The envisioned uses for this kind of application would be to provide broadband along school bus routes or to provide coverage of defined farm fields.

These changes were a long time in coming, with Microsoft asking for some of these changes since 2008. The issues have been bouncing around the FCC for years and it finally took the compromise between the parties to make this work. Maybe some of the other parties arguing over spectrum allocation could learn from this example that cooperation beats years of regulatory opposition.

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