Spectrum Management

Received signal power measurements were performed on the Common Air Route Surveillance Radar (CARSR) operating in the 1300 1370 MHz band in Cedar City, Utah, and on the Airport Surveillance Radar (ASR 9) operating in the 2700 2900 MHz band in Trout Creek, Utah. The measurements were taken at sites relatively far from each radar transmitter. The measurement locations represent different predicted propagation modes (such as line-of-sight, diffracted, tropospheric scatter, etc.) and varying predicted received signal powers (from strong to weak). Distances from the transmitter to the measurement locations varied from roughly 56 km to 141 km for the ASR-9 and 17 km to 194 km for the CARSR. Multiple peak received signal power measurements were made at each location to provide statistically significant results. In another effort, these measurements will be used to validate spectrum usage contours and the methodology used to generate them as developed by the Office of Spectrum Management (OSM) of the National Telecommunications and Information Administration (NTIA).

Keywords: radar measurements; airport surveillance radar (ASR); received signal power measurements; peak received power; Common Air Route Surveillance Radar (CARSR) ; spectrum usage contours

• TR-20-543 

This report is a case-history of the development, deployment, and operational experiences associated with 5 GHz unlicensed national information infrastructure (U NII) devices that incorporate a detect-and-avoid approach to spectrum sharing. Such dynamic frequency selection (DFS) technology was authorized by the Federal Communications Commission (FCC) to accommodate co-band operation of U NII transmitters among other incumbent radio systems, specifically radars. DFS-equipped U NII systems are designed to detect frequencies occupied by radar transmissions and then command their own transmitters to avoid operation on those occupied frequencies. Examining the historical and technical aspects of the development and deployment of 5 GHz DFS-equipped U NIIs, this report focuses on issues encountered with the deployment of this nascent DFS technology, particularly with respect to two government radar systems that have experienced harmful interference: Terminal Doppler Weather Radars (TDWRs) and Range Instrumentation Radars (RIRs). These interference interactions and the likely underlying causes are described, along with steps that have already been taken in an effort to mitigate existing and potential future interference interactions. This report’s narrative summarizes the DFS experience and shares the Lessons Learned from these experiences that may be applied to future similar spectrum-sharing approaches.

Keywords: radar; electromagnetic compatibility (EMC); band sharing; spectrum sharing; radio interference; out-of-band (OOB) emissions; spectrum measurement; unlicensed national information infrastructure (U-NII); terminal Doppler weather radar (TDWR); dynamic frequency selection (DFS); emission limits; spurious emissions; 5 GHz band; access point (AP); detect and avoid; range instrumentation radar (RIR)

• TR-20-544

As part of NTIA’s ongoing effort to identify candidate bands for repurposing to accommodate commercial wireless services, NTIA selected the 3450-3550 MHz band to study for potential sharing between federal systems and a variety of non-federal commercial wireless operations.  NTIA worked with the Department of Defense, which operates the federal systems in the band, to determine if commercial services could operate without causing impact to incumbent operations.  The report indicates that commercial operations would impact incumbent federal systems; however, spectrum sharing may be possible that provides both sufficient protection to incumbent operations and attractive opportunities for commercial business – subject to further analysis and deployment of innovative time-based sharing mechanisms.

Keywords: radar; interference; spectrum sharing; 3450-3550 MHz; airborne radar

• Technical Report 20-546 (73 MB)