CBRS Really is a “Win-Win”

By: Dave Wright, Policy Director, Spectrum for the Future

This is the bottom-line message from a recent blog post written by Jesse Caulfield, the CEO at Key Bridge Wireless. I try to avoid using corporate buzzwords/phrases, but in this case “win-win” is a succinct way to capture the outcomes of the good-faith collaboration that has occurred in the government/industry collaboration to initially bring the Citizens Broadband Radio Service (CBRS) into existence and to continue improving federal/commercial spectrum sharing – both in CBRS and in other bands.

Jesse points out that as the demands for spectrum continue to grow, both for commercial and government uses, spectrum sharing will become a critical enabler for efficient use of each megahertz. CBRS is the leading example of what is possible, and we should apply the collaboration lessons from CBRS as we move forward. We should also be very careful not to effectively throw away all that we have gained in the area of federal/commercial collaboration by upending the meticulously engineered military protection regime in CBRS with macro cellular power levels.

I couldn’t agree more strongly with Jesse’s assertion that the introduction of macro cellular power (i.e., Category C or D Citizens Broadband Radio Service Devices (CBSD)) into CBRS “would require a complete revisit of CBRS spectrum sharing models to avoid pushing those training areas even farther out.”

While the recent Valo Analytica study on the negative impacts of higher power in CBRS largely focused on the impacts to commercial operations, it also noted that higher power would necessitate a thorough review of the protection regime for the incumbent military systems. Valo noted the following issues that higher power would create in this area:

  • Larger Dynamic Protection Area (DPA) neighborhoods for Category C and D, and possible reassessment of all neighborhood sizes in light of aggregate interference considerations.
  • Expansion of DPAs to greater distances off-shore due to higher-power interferers, in turn necessitating increased sensitivity (and, therefore, more stringent interference protection criteria) of Environmental Sensing Capability (ESC) sensors which will need to detect radars at greater distance.
    • Aggravates the potential impact to all CBRS devices within the ESC “whisper zones.”
  • Consideration of aggregate interference contributions from distant higher-power CBSDs potentially impacting closer, lower-power CBSDs.
    • Can impact the shutdown of closer lower-power devices in the event of incumbent radar activation, via the DPA move list calculation.
    • Can impact power reductions of closer lower-power devices mandated through IAP to protect Fixed Satellite Service (FSS) earth stations, PAL Protection Areas (PPA), and ESC “whisper zones.”

As I noted at last fall’s NTIA Spectrum Symposium, “CBRS is the “poster child” for government-industry collaboration.” And I concluded with, “We need more government/industry spectrum win-wins, not just zero-sum transfers (I win/you lose).”

###