The spectrum sharing model that the industry and FCC developed over the course of a few years for the 3.5 GHz Citizens Broadband Radio Services (CBRS) band could easily be adapted for the 4.9 GHz band—and implemented at a faster pace, according to Federated Wireless, which is one of the entities that has been working tirelessly to supply services for the CBRS band.
Under a dynamic spectrum sharing approach, major carriers and others would be able to use the 4.9 GHz band on an as-needed basis without unduly limiting public safety use of the band, according to Federated Wireless. The FCC late last year granted conditional approval to Federated Wireless and several other entities to be Spectrum Access System (SAS) administrators in the 3.5 GHz band.
Meanwhile, the FCC has been seeking comment on ways to increase the use of the 4.9 GHz band while preserving the integrity and security of the band for public safety, which is using the band for things like data and video backhaul, real-time video surveillance and airborne video. Utilities want the rules to be structured so that they, too, can make use of the band for smart grid and other applications often related to public safety.
Early in the process of developing a sharing regime for the 3.5 GHz CBRS band, there was talk that if successful, a similar strategy might be applied to other bands. As the months rolled by and the rules for the CBRS band remained uncertain, talk of that mostly died down. But given its location near the 3.5 GHz band and other factors, the 4.9 GHz band is being targeted for a similar sharing regime.
Federated Wireless says the work being done to make the 3.5 GHz CBRS band a reality can be leveraged and adapted to the 4.9 GHz band to quickly and efficiently expand usage of the band to additional users. In fact, the same kind of three-tiered approach used for CBRS could be applied to the 4.9 GHz band—and public safety users won’t have to worry that they’re going to experience interference.
“Dynamic spectrum sharing access is the only solution that maximizes usage of the band with the least disruption to the incumbent users,” the company said in its filing (PDF).
Potential users of the 4.9 GHz band have often complained about the lack of reasonably priced equipment and cited it as a deterrent to investment, so expanding access to a wider base of users will better stimulate equipment development in the band to the benefit of public safety, critical infrastructure entities and other potential users of the band. Federated said the equipment being developed for CBRS can easily be modified to also work at 4.9 GHz, further reducing the timeframe for a variety of equipment becoming available at a reasonable cost.
The CBRS Alliance introduced the OnGo brand in May to provide a succinct term to identify equipment that works in the CBRS band.
The 3.5 GHz band is being used in other countries for 5G, which is one of the reasons CTIA wanted the FCC to revise its rules around CBRS. One of the main sticking points is the size of the licenses for the licensed portion of the band; the unlicensed portion is expected to get underway sooner if certification processes move along.
Many of the CBRS SAS administrators, which are going through a certification process before the band officially kicks off, are also deploying an Environmental Sensing Capability (ESC) to monitor the spectrum for Navy radar signals; incumbent federal users of the spectrum get the highest protection.
The theory is that if the Department of Defense is comfortable relying on dynamic sharing techniques, the greater public safety community should have confidence that it will work for it as well.