FCC Reveals Plans for 'Interference Temperature' Implementation

The FCC revealed its plans for using the "Interference Temperature" methodology to allow unlicensed devices to share spectrum with licensed facilities. As reported in the Nov. 17 RF Report and the FCC news release FCC Begins Inquiry and Proposed Rulemaking Regarding 'Interference Temperature' Approach for Interference Management, the 6.5 GHz satellite uplink and fixed service band and the 13 GHz band used by broadcasters, cable companies and fixed services were chosen for the first rollout of interference temperature methodology.

The Notice of Inquiry and Notice of Proposed Rulemaking (FCC 03-289) released Nov. 24 provides an overview of the interference temperature methodology and discusses how it should be implemented. The NOI asks for comments on four general questions concerning implementation:

* Is there is a general metric that can be used to gauge the success of the introduction of the interference temperature devices into a new frequency band?
* Is there a simple metric that can be used to gauge the effect of these unlicensed devices upon the incumbent services?
* Should the introduction of interference temperature devices be done in stages to ensure that the incumbent services do not suffer undue interference?
* If the introduction were to be done in stages how should we limit the initial introduction of interference temperature devices to protect the incumbent systems?

For the first test of this methodology, the FCC is proposing to allow unlicensed operation in the 6525-6700 MHz band, currently used for satellite uplinks and terrestrial fixed microwave links and in the 12.75 to 13.25 GHz band, currently used by broadcast auxiliary stations, cable relay stations and other fixed microwave services. Devices operating in these bands would have to be able to monitor the frequency to avoid causing interference to existing services using technology similar to that specified for unlicensed devices operating in the new 5 GHz U-NII spectrum. The FCC said it believes it is possible for unlicensed stations to use EIRP levels as high as 36 dBm without causing interference to existing users in the 6.5 GHz and 13 GHz bands.

The Notice of Inquiry and Notice of Proposed Rulemaking (FCC 03-289), in addition to providing an excellent tutorial on how the interference temperature methodology should work, asks many technical questions about how it should be implemented and how interference temperature should be measured.

While the introduction of this interference control concept in the 6.5 GHz and 13 GHz bands is relatively simple, extending it to other bands is much more complicated. For example, one way to manage interference is to continuously monitor the spectrum to determine the interference temperature. This information would then be communicated to devices subject to the interference temperature limit. The devices would then adjust power or change frequency to stay within the limit. It was suggested that this information could be transmitted using ancillary data over radio or TV broadcast transmitters.

If you are interested in the impact of this methodology on your existing use of the spectrum or if you are interested in exploring the opportunities this methodology presents for new use of the spectrum, take time to read the FCC's Notice of Inquiry and Notice of Proposed Rulemaking (FCC 03-289).