Expanding 4.9 GHz Spectrum Use Will Take Time


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In adopting new rules to expand use of the 4.9 GHz spectrum band, the FCC may have stumbled coming out of the starting blocks.

A little history. In 2002, right after 9/11, the FCC designated 50 MHz of the 4.9 GHz (4940-4990 MHz) exclusively for public safety in fixed and mobile applications to support the “protection of life, health and property.” At the time, the agency identified about 90,000 public safety entities (as defined under Part 90 rule) around the country that were eligible to hold 4.9 GHz licenses. This tally included all state and local governments (including municipal utilities) that now are the incumbent users.

To meet their own homeland security initiatives, non-traditional public safety entities and the federal government could negotiate 4.9 GHz band sharing arrangements with eligible Part 90 entities. The 50 MHz swath comprises 18 channels, 10 at 1 MHz (Ch 1-5, Ch 14-18) and 8 at 5 MHz (Ch 6-13). These channels can be aggregated into bandwidths of 5, 10, 15 and up to 20 MHz, the maximum 4.9 GHz channel size. This sizable bandwidth supports numerous wireless broadband applications and is complementary to public safety’s traditional land mobile radio VHF/UHF voice communications. 

Broadband uses include temporary fixed communications and wireless LANs for incident scene management (ad hoc mobile networks) along with several permanent fixed applications: point-to-point (PTP) video surveillance, point-to-multipoint (PMP) broadband device connections and PTP backhaul for both LMR and 700 MHz public safety broadband networks such as FirstNet. (see, Why FirstNet Needs 4.9 GHz)

In its September 30 Order, the FCC cites that “there are only 3,559 licenses currently issued to 2,090 individual licensees” despite nearly 90,000 eligible public safety entities.

With such a low take rate, the FCC Order opens unused spectrum for non-public safety commercial applications on a leased basis. The FCC designates a state-level spectrum sharing process permitting “one statewide 4.9 GHz band licensee per state (the State Lessor) to lease some or all of its spectrum rights to third parties, including commercial, critical infrastructure, and other users, thus making up to 50 MHz of mid-band spectrum available for more intensive use.”

The State of Maryland’s comments supported the 4.9 GHz primary use objective and acknowledged release of unused spectrum for secondary uses. (Note that by rule secondary users cannot interfere with authorized primary users and are not protected from interference from primary users.)

Maryland said it needs relatively few licenses to meet its public safety objectives: six statewide agency licenses, another 27 for Maryland local governments and 13 for non-Maryland jurisdictions in the National Capital Region.

In quantifying the actual number of licenses issued, Maryland pointed out that very few 4.9 GHz licenses “reveal the actual number of PTP and PMP paths or other uses,” suggesting that more of the band is being used than the Commission says. Maryland called for the FCC to modify the Universal Licensing System to register such PTP and PMP use. Further, Maryland argued that establishing the State Lessor role creates for the prime licensee in each state an unnecessary burden that goes beyond their already significant public safety responsibilities.

Maryland called on the FCC to create a national plan for 4.9 GHz spectrum management in coordination with national public safety associations with spectrum planning handled on a regional basis.

The Utilities Telecom Council in its commentary supported expanding eligibility for primary use to critical infrastructure companies such as utilities while opposing secondary use eligibility for commercial users due to congestion and interference problems they might cause.

Federated Wireless, as a spectrum access system administrator, said it supports 4.9 GHz spectrum sharing but that it should be handled in the same way as the 3.5 GHz Citizens Broadband Radio Service licenses are being managed.

The firm called for establishing three user tiers with the SAS coordinating their spectrum usage in any region in the country. The SAS database would also identify and incorporate unregistered PTP and PMP links while protecting band usage among primary users.

Federated Wireless argued that such an approach is more efficient and cost-effective and would lead to more robust development of the band than other FCC approaches. Moreover, Federated Wireless emphasized that the SAS model for CBRS has been tested and accepted by the U.S. Navy and other Department of Defense users and is no longer an “experiment.”

The Public Safety Spectrum Alliance, formed in August in partnership with other associations and public safety leaders, wants to preserve the 4.9 GHz nationwide spectrum for public safety and have it assigned to FirstNet. FirstNet would develop and manage a spectrum plan to “support and protect existing public safety licensees while also allocating a portion of the spectrum for 5G technologies and potentially integrating it with the FirstNet.”

Others commented on the FCC’s approach. We may not have heard the last of the 4.9 GHz saga.

By John Celentano, Inside Towers Business Editor

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