The 10.0-10.5 GHz Spectrum Battle Heats Up

The FCC, in its Proceeding RM-11715 is considering a Petition for Rulemaking from Mimosa Networks to create a new frequency allocation for wireless networks. If granted, this that would allow the licensing of high-power fixed microwave links in the 10.0-10.5 GHz band under Part 90, Subpart Z, using rules similar to those adopted for the 3650-3700 MHz band. As of April 18, the FCC Electronic Comment Filing System shows 241 filings, including the original Petition and FCC releases and the deadline for reply comments has now been extended to April 25, 2014.

In the United States, the 10.0-10.5 GHz band is allocated on a primary basis to the government radiolocation service, and on a secondary basis for non-government radiolocation services and the amateur radio service. As a result, it comes as no surprise that the New America Foundation, Qualcomm and other wireless broadband interests support a new wireless allocation in that portion of the spectrum and the incumbent users, amateur radio operators, are strongly opposed to this.

From what I've read and heard from amateur radio operators, with the possible exception of the 2.4 GHz ham radio spectrum, the 10.0-10.5 GHz band is the most popular amateur radio microwave band. The ARRL distance records show communications at distances more than 1,000 km using tropo propagation, and reports many examples of rain scatter propagation greater than 700 km. The band is also allocated, on a secondary basis, to the amateur satellite service and it is likely to see more use as the cost of launching small satellites ("CubeSats") drops.

In its Petition for Rulemaking, Mimosa states: "In order to guard against interference with both U.S. Government and civilian radar operations, Mimosa proposes the application of Dynamic Frequency Selection restrictions to wireless broadband operations in the band, Further, the application of coordination procedures and requirements provided in Subpart Z will ensure amateur radio operations in the band will not be disrupted. In addition, as a further safeguard, Mimosa proposes a band plan for the 10.0-10.5 GHz band that would protect frequencies in the band that are most often used by amateur radio operators." However, Mimosa does acknowledge that use of the 10-10.5 GHz band by radio amateurs has become increasingly popular during recent years.

Mimosa’s proposed rules don’t include the band plan, but it does appear in an Appendix. Their proposal would divide the band into 20 MHz wide channels with a guard band at 10.0-10.01 GHz and provide an amateur calling band at 10.35-10.37 GHz. The amateur satellite allocation at 10.45-10.5 GHz would also be reserved in the band plan. Under the proposed rules, Part 90 users would be limited to a maximum EIRP of 55 dBW, although there are no minimum antenna gain or pattern performance requirements.

In its comments, Qualcomm states: "The FCC should consider the opportunities that the 10.0-10.5 GHz band can offer to support licensed mobile operations in addition to the backhaul uses Mimosa identifies."

Qualcomm’s proposal continues: "First and foremost, the FCC should determine the extent to which this band can be cleared of incumbents. If the band can be completely cleared in a reasonable time frame, particularly in those areas of the country that are experiencing high demand for mobile broadband data, the FCC should clear the band."

If incumbents can't be cleared from the band Qualcomm says "Authorized Shared Access (ASA)" should be considered. While this approach may work for government users of the band, I can't see how this would work to protect amateur radio operations, which are intermittent and often driven by enhanced propagation, which itself can be difficult to predict.

Amateur radio use is only mentioned once in the Qualcomm comments and that is in a footnote.

The Open Technology Institute (OTI) and Public Knowledge (PK) at the New America Foundation offered these comments about protection of amateur radio operations in the band: "

Although OTI and PK have no view at this time about the efficacy of Mimosa's proposed interference-avoidance mechanisms--or even whether they are necessary--we commend Mimosa for advancing protections that have proven effective in other bands and that could potentially meet the legitimate concerns of band incumbents."

The comments also: "urge the Commission to consider whether small cell and unlicensed use of the band under Part 15 of the Commission's rules would be a compatible and additional use case for this band."

The Wireless Internet Service Providers Association (WISPA) comments give more attention to protection of amateur radio operations than the Qualcomm and OTI/PK comments.

Regarding technical and operating rules, WISPA inquired about minimum antenna performance standards, requirement for features to minimize radiated power to the minimum needed, standards for device certification, power limits and out-of-band emission limits, and the most effective band plan. The organization asked: "Should guard bands and a 'notch' be required to protect amateur radio operations? Do the guard bands proposed by Mimosa provide sufficient interference protection?"

The American Radio Relay League (ARRL), the national association for amateur radio, filed extensive comments opposing the Mimosa Network's Petition. The ARRL argued that the FCC is without authority to make the allocation proposed in the Petition and it therefore must be dismissed. The ARRL noted that in ITU Region 2, 10.0 to 10.5 GHz is allocated on a primary basis to the radiolocation service and on a secondary basis to the Amateur Service. The 10.45 to 10.5 GHz segment is also allocated to the Amateur-Satellite service. International footnote 5.479 also allocates 9975-10025 MHz to the meteorological satellite service on a secondary basis for use by weather radars. The ARRL stated: "There is no mobile for fixed allocation in ITU Region 2."

The ARRL’s comments continued:"Directly relevant to Mimosa's proposal, Footnote US128 very clearly and without equivocation prohibits all non-Federal services in the band 10-10.5 GHz except for the amateur service, the amateur-satellite service, and the non-Federal radiolocation service. [ARRL emphasis]. This United States footnote makes it impossible to grant the relief sought by Mimosa."

The ARRL argued there is no compatibility between wireless broadband operation and Amateur Radio operations at 10 to 10.5 GHz. The organization noted that this would limit amateur radio use to two small segments of the band and stated: "Those exclusions, however, are not in Mimosa's proposal, mandatory."

In the comments, the ARRL noted: "The ‘band plan’ proposed by Mimosa indicates a presupposition that the bulk of the terrestrial use of the 10.0-10.5 GHz band by radio Amateurs occurs in what it misleadingly identifies as the ‘weak-signal sub-band 10.350-10.370 GHz.’ It also urges wireless broadband users to avoid the Amateur Satellite Service segment above 10.45 GHz. The assumption, however, that those two segments are the only ones used actively by radio amateurs or that they are the only segments that require protection from interference is mistaken." Several examples are cited to show there are amateur operations throughout the 10.0-10.5 GHz band--including amateur television repeaters in southern California with inputs near 10.4 GHz--use 27 MHz-wide NTSC FM emissions.

The Comments of David Weinreich, WA2VUJ provide a brief, but excellent, technical argument for denying Mimosa's petition.

You can view the most recent filings, including all of those mentioned here, in the FCC Electronic Comment Filing System Proceeding RM-11715 Details.

Doug Lung

Doug Lung is one of America's foremost authorities on broadcast RF technology. As vice president of Broadcast Technology for NBCUniversal Local, H. Douglas Lung leads NBC and Telemundo-owned stations’ RF and transmission affairs, including microwave, radars, satellite uplinks, and FCC technical filings. Beginning his career in 1976 at KSCI in Los Angeles, Lung has nearly 50 years of experience in broadcast television engineering. Beginning in 1985, he led the engineering department for what was to become the Telemundo network and station group, assisting in the design, construction and installation of the company’s broadcast and cable facilities. Other projects include work on the launch of Hawaii’s first UHF TV station, the rollout and testing of the ATSC mobile-handheld standard, and software development related to the incentive auction TV spectrum repack.
A longtime columnist for TV Technology, Doug is also a regular contributor to IEEE Broadcast Technology. He is the recipient of the 2023 NAB Television Engineering Award. He also received a Tech Leadership Award from TV Tech publisher Future plc in 2021 and is a member of the IEEE Broadcast Technology Society and the Society of Broadcast Engineers.