Get Ready to Share Your Spectrum
By Mark Crosby
Friday, September 23, 2016 | Comments
It wasn’t too many decades ago when trunking technology was introduced in the Part 90 bands. Because trunking systems need not distinguish between the users seeking access to the technology, the basis for retaining 20 or so disparate radio services where spectrum was allocated based on the type of business an applicant was engaged became instantly obsolete. Just in case any readers are too young to remember, there used to be actual separate radio service spectrum allocations for relay press, motion picture, motor carrier and even telephone maintenance business activities.

I remember the arguments from those who predicted end-of-the-world scenarios if the spectrum that was once segregated into multiple pieces for disparate services but used for identical purposes were consolidated into two spectrum pools — one dedicated for business/industrial/land transportation (B/ILT) eligible entities and the other for public-safety entities. In the B/ILT side of the aisle, on certain power, petroleum, railroad and automobile emergency frequencies, the assigned frequency advisory committees (FACs) retained channel concurrence rights, but the primary eligible classes of applicants did not retain exclusive rights to the channels. Same thing for the police, fire and forestry conservation radio services. Twenty, 10 or even five years from now, will maintaining such applicant-based segregation rules continue to make any sense? Will the nation’s policymakers continue to endorse the notion that certain classes of users are still entitled to preferential spectrum access rights when advancing technologies and emerging spectrum management tools make such distinctions essentially irrelevant? I doubt it.

Creating two pools was a good first cut back in the day; prudent spectrum management prevailed, and tremendous spectrum efficiencies resulted. Advancing technology trumped the status quo, and private land mobile radio (PLMR) industry entities benefited significantly. In the future, egged on by ever advancing technologies, coupled with the insatiable demand for spectrum from consumer, business, mission-critical, commercial and government sectors, today’s spectrum landscape status quo will not last either; neither will tomorrow’s. It’s where we are, and fighting to maintain the status quo is more than likely a losing proposition.

Examples of Sharing
A few observations and predictions. First, it is a mistake for any class of incumbents to assume that the spectrum that was once allocated for their use with good intentions will remain allocated for their use under the original terms and conditions forever more. Allocations are no longer forever, if they ever were. Why? Because absent access to new sources of spectrum that do not exist, spectrum sharing is an absolute necessity, even sharing among different types of use scenarios that were once considered impossible to contemplate by incumbent interests.

Broadcasters started having their spectrum repurposed back in the early 1970s, and it is still being reallocated for commercial broadband purposes and white space devices, with use tethered to a database that manages spectrum access. Incumbent interests representing operational fixed users originally opposed the opportunity to share six 173 MHz channels with vehicular repeater systems. The FCC noted there were only 2,000 or so operational fixed systems across the country and determined that the existence of such systems should not prohibit the possibility of enhanced spectrum sharing and efficiencies. To ensure system compatibility, the industry was asked to design and implement engineering-based frequency coordination protocols, a task that was readily accomplished.

Advanced medical body area networks (MBANS) will be sharing the 2.36 – 2.39 GHz band with aeronautical telemetry systems. Does one think for a moment that aeronautical telemetry interests ever conceived of the day when the spectrum allocated for their purposes would be shared with healthcare facilities? There is an MBAN registration requirement prior to initiating the capability, and coordination and concurrence protocols are in place with the Aerospace & Flight Test Radio Coordinating Council (AFTRCC) enabling spectrum sharing. Note that coordination protocols unique to this sharing opportunity were part of a condition imposed by the FCC, but a collaborative effort among the responsible parties resulted in the adoption of appropriate protocols.

The 3.5 – 3.65 GHz band, after incumbents were just getting settled in, was reallocated for a Citizens Broadband Radio Service (CBRS) with new terms of engagement. While the majority of those interested in this band cringed over the name, they nevertheless supported the retooling of the band for greater broadband purposes. As a sign of policies to come, incumbents were asked to confirm their continued use of the band. System administrators that will provide real-time dynamic spectrum access will manage access to the band. Who you are and why you seek access to the wireless capabilities of the CBRS are not necessary.

Apply these cases and others to bands that are still under consideration for enhanced sharing, and what does one see? At 4.9 GHz, public-safety incumbents have argued long and hard to maintain the status quo after 10 years or so with a few minor adjustments, including the demand that historical frequency coordination regimes be applied. A noble effort indeed but I doubt the FCC will be willing to support such an exclusionary access approach and traditional site-based coordination in this band when enhanced access is the objective. It may have at one time been a public-safety primary band but not forever. Incumbent systems will be protected but will be encouraged to collaborate with the new regime. I would anticipate the potential for dynamic spectrum sharing managed by one or more system administrators. In all likelihood, the 5.9 GHz band may witness a similar migration to the new order. The template incorporates greater user access, band retooling to accommodate original incumbents, and advanced spectrum management capabilities to promote real-time dynamic spectrum sharing.

I appreciate and understand that the 900 MHz incumbents, both within and immediately adjacent, are not pleased with the thought that a broadband capability may be enabled in a band originally established in 1985 for site-based B/ILT trunked systems. For amusement and again for the younger readers of this article, the commercial side of this band was originally made available through an FCC-managed lottery, complete with ping-pong balls. No joke. But does anyone think for a minute that the FCC on its own motion will not choose to re-evaluate the state of spectrum efficiency in this band? Has the tact “hell no” been a successful approach by incumbents in any other band identified for a technological upgrade and greater user access? It may work for a while, but not forever.

The future of spectrum? Greater sharing even among disparate uses is inevitable. Spectrum allocations are not cast in concrete, certainly not long term and certainly since advanced spectrum management capabilities have the potential to instantly accommodate all users, even those afforded priority rights.

There will be no single spectrum management approach acceptable to the FCC. Site-based frequency coordination, system registrations and dynamic spectrum access capabilities coupled with sensing and geolocation are all in play depending on the band and its intended uses. Incumbents and proponents for greater spectrum sharing will collaborate to maximize spectrum efficiencies. New technologies will be required to promote spectral coexistence, receiver standards will be considered, and spectrum engineering tools to measure electromagnetic compatibility and propagation characteristics to better evaluate the effects of greater spectrum sharing will also be developed.

The FCC’s recent order that authorized the sharing of 700 MHz and 800 MHz public-safety and 800 MHz B/ILT spectrum and infrastructure by the state of Ohio and FirstEnergy is perhaps a sign of great sharing opportunities to come.

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Since 2004, Mark E. Crosby has served as president and CEO of the Enterprise Wireless Alliance (EWA), a national association representing the interests of business enterprises that rely on wireless communications systems. Crosby is a member of the Commerce Spectrum Management Advisory Committee, which advises the assistant secretary for communications and information at the National Telecommunications and Information Administration (NTIA) on spectrum policy issues and serves as an officer and member of the board of directors of the Land Mobile Communications Council (LMCC). Prior to joining EWA, Crosby was president of Access Spectrum, a company he co-founded in 2000 to pioneer spectrum band management for private wireless licensees deploying voice and data technologies. From 1975 until 2000, Crosby served as president of the Special Industrial Radio Service Association, and following radio service consolidation, the Industrial Telecommunications Association (ITA).

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