In a departure from its original public safety mandate, the 4.9 GHz band is the latest mid-band spectrum being eyed for public and private network use. Escalating demand for high-speed, low latency broadband connectivity is the main reason. In 2002, the FCC allocated 50 MHz of spectrum in the 4.9 GHz (4940-4990 MHz) band for fixed and mobile services, specifically for public safety support. Non-traditional public safety entities such as utilities and federal agencies could negotiate 4.9 GHz band sharing agreements with eligible public safety entities. However, restricting usage to public safety entities was intended to enhance 4.9 GHz transmission reliability and avoid potential interference experienced in other unlicensed, heavily used bands like 5 GHz or 900 MHz.
Key questions: Should 4.9 GHz be shared for non-public safety uses? If so, how should spectrum sharing be managed? The ‘Yes’ argument is that 4.9 GHz band usage has not evolved as originally envisaged and remains underutilized. Commercial wireless operators could leverage part of the 50 MHz bandwidth for mobile data use. New or established entities could manage the spectrum allocations. The ‘No’ argument is that public safety communications, especially for in-building applications, is too important for both first responders and building occupants, to be shared, even on a priority or pre-emptive basis.
AT&T’s FirstNet provides first responders (fire, EMS, police) nationwide with exclusive, interoperable wireless broadband communications (voice, data, video) using 10 MHz blocks in 700 MHz Band 14 (758-768 MHz downlink/788-798 MHz uplink). These frequency bands are adjacent to the existing 6 MHz narrowband channels (769-775 MHz DL/799-805 MHz UL) used for land mobile radio.
Today 4.9 GHz is used mainly for point-to-point microwave backhaul for FirstNet and LMR applications. With 50 MHz bandwidth, new broadband point-to-multipoint use cases are being considered.
End User Input
Several interested parties have tabled their ideas with the FCC. In August, a consortium of industry associations suggested in a letter that multiple 4.9 GHz use cases could be developed for fixed and mobile wireless, microwave, robotics, WiFi, unmanned aircraft systems, and other technologies. The signatories included: American Petroleum Institute, Enterprise Wireless Alliance, Forestry Conservation Communications Association, International Municipal Signal Association, National Sheriffs’ Association, and Utilities Technology Council.
Importantly, the consortium proposed handling 4.9 GHz spectrum management through the FCC’s certified frequency advisory committees already established in the member organizations. Spectrum could be assigned on a first-come, first-served, and non-discriminatory basis to maximize its use for technological innovation while avoiding interference between systems.
Public Safety Perspective
In a separate submission, the Safer Buildings Coalition argues that first responders need broadband wireless connectivity in their public safety communications toolkit. SBC represents public safety agencies, standards organizations, code bodies, wireless carriers, manufacturers, distributors, system integrators, and end-users.
The association suggests that the 4.9 GHz spectrum should remain dedicated to public safety but acknowledges adaptations could be managed. SBC says that excess capacity could be made available for secondary use but requires public safety priority and preemption rules similar to the U.S. military’s priority/preemptive use of 3.5 GHz CBRS. Moreover, SBC emphasizes the FCC, frequency license holders, and the industry must actively collaborate and cooperate to protect the band from harmful RF interference.
SBC’s vision is that 4.9 GHz spectrum be adapted to eliminate in-building ‘wireless dead zones’ that pose a risk to first responders and building occupants during an emergency. There are an estimated 1,000,000 commercial buildings in the U.S. with more than 20,000 square feet and two or more stories, according to the U.S. Energy Information Administration’s latest Commercial Buildings Energy Consumption Survey. Broadband wireless coverage everywhere inside these buildings is a public safety imperative.
First responders must be able to communicate effectively while inside buildings during emergencies. Separate, dedicated spectrum and indoor wireless systems will help eliminate dead zones in underground garages, furnace and utility rooms and elevator shafts, where commercial cellular signals typically do not reach.
Such priority-based service could be managed by a single nationwide band manager such as the established Spectrum Access System role in CBRS, or possibly FirstNet.
John Foley, SBC Managing Director comments, “The conversation about 4.9 GHz is an opportunity to refocus the discussion about the critical nature of wireless connectivity for both the public and public safety, and we look forward to continuing our active role in pushing for innovation, scalability, and the ultimate goal of eliminating all in-building wireless dead zones.”
The industry awaits an FCC decision on the matter, Inside Towers has reported.
By John Celentano, Inside Towers Business Editor
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