In reply comments filed this week with the FCC, the ARRL reiterated its argument that any decision to authorize unlicensed National Information Infrastructure (U-NII) devices at 5 GHz “should await a full and complete evaluation of interference potential and interference mitigation techniques among the varied and incumbent users.” The Amateur Service has a secondary allocation at 5650-5925 MHz in the US. Earlier this year the FCC released a Notice of Proposed Rule Making (NPRM) in ET Docket 13-49, seeking comments on making available an additional 195 megahertz of spectrum in the 5.35-5.47 GHz and 5.85-5.925 GHz bands for U-NII use. Reply comments are responses to comments already filed in the proceeding.

“The comments of the National Telecommunications & Information Administration (NTIA) indicate that NTIA shares the same concern that ARRL has raised repeatedly in earlier proceedings concerning the 5 GHz band: that the aggregate interference potential of ubiquitous U-NII devices to incumbent radio services…is currently unknown,” the League told the FCC.

U-NII devices use “wideband digital modulation techniques to provide a wide array of high data rate mobile and fixed communications for individuals, businesses, and institutions,” the FCC explained in its NPRM. The FCC was obligated by the Middle Class Tax Relief and Job Creation Act of 2012 (PL 112-96) to begin a proceeding to amend its Part 15 rules to allow unlicensed U-NII devices to operate in the 5.35-5.47 GHz bands. As the ARRL pointed out in its comments, “There is no legislative obligation, however, to make available the 5.85-5.925 GHz band for U-NII use.”

In its earlier comments, the ARRL urged a complete study of interference potential and mitigation techniques be conducted before making the band available to U-NII devices. The study, the League said, should take into consideration the potential interaction between unlicensed U-NII devices and other incumbent services on the band. These include Federal Radiolocation — the primary government user — Fixed Satellite (Earth to space), the Mobile Service and the Amateur Service. “The present allocation status of this band is quite complicated due to the presence of important federal systems, safety-based DSRC [dedicated short-range communications] applications and vehicle-to-roadside systems to detect and avoid hazards in a vehicle’s path,” the ARRL asserted.

The League said it agreed with the comments of the Wi-Fi Alliance that the proceeding “is not the proper vehicle for development of a compatible sharing plan with associated interference-avoidance protocols.” Such an additional overlay of unlicensed, high-use density mobile applications, the ARRL urged in its comments, “requires careful planning.”

The League has suggested “that a full and complete investigation of the sharing concerns be conducted in an open, transparent manner.” ARRL said it wants to see all stakeholders meet to develop compatible sharing protocols before any new rules for the 5 GHz spectrum are put into place.