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Radar/Communications Spectrum Sharing: ISART 2011

ISART-2011

On July 27-29 NTIA will host the 12th Annual International Symposium on Advanced Radio Technologies (ISART) at its Boulder, CO Institute for Telecommunications Sciences. The theme this year is “Developing Forward-Thinking Rules and Processes to Fully Exploit Spectrum Resources” with a special focus on radar bands.

For the third time since his retirement from FCC, NTIA was kind enough to invite your blogger to speak at this important meeting, but due to a conflicting family event, he is unable to attend. However, in view of the importance of this issue, he volunteered to produce a written paper on the topic to help stimulate discussion. Here is a link to that paper.

The paper starts by stating the need for new spectrum to speed economic growth which is important for both our society and for national security. Spectrum allocation should not be viewed as a zero sum game, but it is critical to develop innovative sharing techniques to get the maximum use of this limited resource. Since radar systems are a large user of spectrum and are difficult to share with using conventional approaches, this is a very timely conference.

TDWR

tdwr
The paper then urges FCC and NTIA to be more transparent about ongoing 5 GHz U-NII interference problems with the FAA’s TDWR weather radar. We previously mentioned the mysterious San Juan TDWR case involving interference from an AT&T-operated Motorola unit and which is puzzling based on the public record to date. NTIA has prepared a report on the San Juan case, but it mainly confirms that the DFS function in the AT&T/Motorola unit wasn’t working without explaining why. Another NTIA presentation from last year’s conference confirms that while some cases are caused by nonfunctional DFS, some have been caused by compliant DFS systems used in WISP systems, necessitating an unusual “voluntary” FCC agreement with WISPA to effectively coordinate such systems to prevent such interference. The paper urges FCC and NTIA to explain more what the root causes of these problems are so that future systems can be designed to avoid them.

The main part of the paper advocates joint design of new radar systems with communications experts in order to maximize spectrum sharing and consider financial cost sharing of features that facilitate sharing subject to the radar mission needs. Just as the stealth bomber design involved a unique team of aeronautical engineers and EEs who could trade off flying issues with radar visibility issues, joint design of radar/comm systems may well result in sharing breakthroughs. While current legislation does not allow this type of cost sharing, it is not beyond the reach of new legislation that has been discussed. The paper points out that while full duplex paired spectrum with “24/7 and 1000 ms/ 1 s” time availability has been the norm for commercial systems, the decline of voice minutes and the domination of packetized traffic means that partial time availability, synched with radar rotation, could result in productive access to radar spectrum. While nonmilitary backlobe radio have not improved in 40+ years, advances in radio astronomy antennas indicate that new designs can significantly decrease backlobe levels and facilitate sharing. Such designs are expensive, but cost sharing could address that.

if you are interested, here, again, is the link.

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