RSSSeveral mission-critical communications groups submitted comments to the FCC’s notice of inquiry (NoI) on ways to expand opportunities for mid-band spectrum between 3.7 and 24 GHz. The groups generally oppose expanded use of the 6 GHz bands for unlicensed and licensed broadband wireless fixed and mobile services.
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The Utilities Technology Council (UTC) and Edison Electric Institute (EEI) said the 6 GHz bands are already heavily used by utilities for mission-critical operations. UTC and EEI believe that the interference mitigation approaches that the FCC is considering would not be effective as a practical matter, particularly in the long term because of increases in the noise floor that would cause interference from the proliferation of unlicensed devices operating in the bands.
However, UTC and EEI support expanding the use of the 4 GHz band by eliminating full-band, full-arc coordination of satellite earth stations. This spectrum could be put to effective use, and there is sufficient information that has already been submitted on the record to show that it is underused, the groups said.
The Association of Public-Safety Communications Officials (APCO) International urged the FCC to consider bands other than 6 GHz to achieve its flexible spectrum use goals to avoid negatively impacting public-safety communications.
The National Public Safety Telecommunications Council (NPSTC) said the NOI points out extensive fixed microwave and fixed satellite use already exists in the 5.925 – 6.425 GHz band. Public-safety microwave systems in the 6 GHz band form complex networks with high levels of reliability required, given their role in supporting public safety’s protection of the public.
The previous reallocation of the 2 GHz microwave bands to emerging technologies funneled additional operations into the 6 GHz band and resulted in increased public-safety reliance on the 6 GHz spectrum. The 2 GHz band history does not engender any confidence in spectrum sharing, NSPTC said.
“There, the commission stated it had underestimated the difficulty of sharing and modified its initial policy of co-primary public-safety use to one that required public-safety relocation out of the band when requested by new licensed PCS entrants,” NPSTC’s comments said.
Southern Company Services relies on point-to- point microwave facilities in various fixed service bands to support the provision of energy services to the public. It is contrary to the public interest to jeopardize fixed systems used for operation of the nation’s critical infrastructure and to impose burdens on those licensees to track down and enforce interference mitigation efforts against mobile service users, whether licensed or unlicensed, Southern said.
“There do not appear to be many viable options for relocating incumbent fixed microwave systems from 6 GHz,” Southern said. “Although fiber would be the preferred medium, it is exponentially more expensive than microwave and is more difficult to restore in the event of outage.
Duke Energy also opposed expanded use of 6 GHz because it would restrict the amount of spectrum available for growth of utility communications systems required to support smart grid and other grid modernization initiatives.
The Lower Colorado River Authority (LCRA), Tucson Electric Power (TEP) and the city of Mesa, Arizona, also said expanding use of the 6 GHz band would directly harm their mission-critical communications operations. Los Angeles County; the city and county of Denver; the city of Kansas City, Missouri; Ozaukee County, Wisconsin; and the Government Wireless Technology and Communications Association (GWTCA) filed joint comments opposing any sharing of the 6 GHz band in which their microwave links exist, citing risk to public safety from interference.
On the other hand, Motorola Solutions said the bands can support innovative next-generation services for a wide variety of broadband users, and it believes that the regulatory framework developed for the 3.5 GHz Citizens Broadband Radio Service (CBRS) serves as a useful model to encourage new uses while protecting incumbents.
“Motorola Solutions strongly supports the utilization of spectrum sharing techniques for opening the 3.7 – 4.2 GHz and 5.9 – 7.1 GHz bands to other uses,” the vendor said. “In particular, we support allowing both fixed and mobile services to operate in the 3.7 – 4.2 GHz band. We believe the band, in conjunction with Spectrum Access Systems (SAS), can be utilized for a wide array of public and private broadband networks, ranging from fixed (e.g., last mile) link services to mobile small cell networks. A multi-tier spectrum sharing approach would best suit a wide range of applications, ensuring the highest spectrum utilization.”
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