3
Additional Matters

The study committee’s statement of task (see Appendix A) contains three primary tasks, which were addressed in the preceding chapters. The statement of task also provides that the committee may address “other related issues the study committee determines relevant.” In the course of its work, the committee has concluded that there are several important issues surrounding the technical and administrative processes used in the long saga that has led to the authorities granted in Federal Communications Commission (FCC) Order 20-48. The following observations are offered with the hope that future proceedings might provide more streamlined and optimized approaches to balancing the desire to protect and enable incumbents while maximizing the economic and operational benefits provided by new entrants into a given spectrum region.

3.1 TOWARD A BETTER MEANS OF ASSESSING HARMFUL INTERFERENCE

It is important to understand why a large number of different communities reached diametrically opposed opinions on the likelihood of “harmful interference” from the Ligado license on Global Positioning System (GPS) and mobile satellite services (MSS) operations. The FCC defines harmful interference as “[i]nterference which endangers the functioning of a radionavigation service or of other safety services or seriously degrades, obstructs, or repeatedly interrupts a radiocommunication service operating in accordance with [the International Telecommunication Union] Radio Regulations.” The committee believes that, because of a lack of a quantifiable definition of harmful interference,

this has led to a 15-year process with respect to Ligado that has tied up spectrum, as well as untold resources of the participants. This issue is being played out to a lesser degree in the case of C-band licensing, and it is reasonable to expect that this issue will come up again in future with respect to GPS and other services.

Although there are different interpretations of test data, these differences arise in no small part from different assumptions about the design and performance of the receivers. Most aspects of the interference analysis have commonly accepted engineering principles: free-space loss, a standard National Telecommunications and Information Administration (NTIA) terrain propagation model, representation of antenna patterns, appropriate stand-off distance, and so on. However, many of the participants had very different, at times unfounded, assumptions about receivers. Some based their analysis on the worst-case device present in the field, some based on the bulk of the GPS receiver population, and others considered what could be the performance of a state-of-the-art receiver. There has been regulatory reluctance to interfere in the marketplace by having government standards for receiver performance (outside of safety communities, such as aviation), and receivers have not historically been part of the regulatory process. However, the committee believes that the FCC, working together with industry and government participants, can come up with measured levels for harmful interference in a given band of spectrum based on the intended usage in that band and based on near past and state-of-the-art receiver performance in the presence of significant adjacent-band power.

Policy makers have a necessary role in protecting existing uses of the spectrum, and not “fossilizing” industries by freezing spectrum usage and therefore precluding future uses. Unfortunately, “refarming,” “repurposing,” or “reallocating” spectrum (in this case, permitting a medium-power terrestrial adjunct) will have impacts for the existing users. As an example, this report identifies where this impact is likely for certain high-cost, high-accuracy civil GPS receivers that were designed prior to the application by Ligado. Regulators must be free to balance the impact on existing users with the benefits of future use. Existing users, however, should be provided some policy guarantees about the use of this equipment and service as they consider the investment. This policy should be broad, and not tied to specific transactions. There is a need for policy that balances existing users and future uses.

In the case of GPS, the committee believes that a sensible criterion for harmful interference could be developed that accounted for position error effects, acquisition and tracking challenges, and continuity of service. Such a criterion might be based on a maximum limit for degradation of C/N₀, and factor the possible effects of out-of-band emissions (OOBE) and adjacent-band signals in a designated frequency range for a reasonably well designed receiver. This analysis would then dictate an adjacent-band power mask that the FCC would guarantee going forward for a given period of time. Given this,

it would then be possible for receiver manufacturers to guarantee acceptable receiver performance for cold-start acquisition, tracking, continuity of service, and positioning, navigation, and timing accuracy. This could be extended to other safety or communications services.

Another advantage of such an approach is that there would be no need to perform tests on large sets of receivers in order to evaluate whether harmful interference was occurring, either by a C/N₀ loss standard, a position accuracy degradation standard, or some suitable combination of the two approaches. An adjacent-band emitter would be guaranteed not to cause harmful interference in compliant GPS receivers as long as it complied with the maximum power limits for both its in-band and its OOBE.

If the FCC were to adopt future guarantees about adjacent-band power masks, the masks could be changed over time as receiver design technology improved. If the promise were, for example, for a 15-year period, then every 5 years a revised future mask guarantee could be published for the coming 15-year future interval over which no mask guarantee had yet been made. This would enable GPS receiver manufacturers to design, build, and sell devices to customers who would have a guaranteed period of service from their products.

Unlike much consumer and even industrial electronic equipment, certain GPS receivers are not throw-away devices that users will upgrade each time a new feature is added. High-end GPS receivers can be expensive and represent a major capital investment for some of their users—for example, surveyors, farmers, construction companies, and geodesists. These users cannot afford to buy these devices if they can expect only a 5-year service lifetime. The FCC has stated that it is “the responsibility of the receiver itself to incorporate a reasonable degree of adjacent-channel rejection in its design.”¹ However, this is true only if receiver designers have a reasonable expectation of near-adjacent interference levels. Going forward, the FCC could forewarn GPS receiver manufacturers about what levels of adjacent-channel rejection will be needed in the future so that manufacturers can design, build, and sell suitable receivers.

Such a policy would also benefit new entrants to the use of adjacent bands. They would know exactly what was and was not permissible for at least a 10-year window. They could make proposals for changes to the next 5-year tranche of the allowed adjacent-channel power mask. GPS receiver manufacturers could then debate and negotiate about the next 5-year tranche, and the FCC could make a ruling based on the available technology going forward. Given the minimum 10-year horizon for the impact of any allowed changes, no party would suffer a bad shock.

The MSS band will likely continue to come under increasing pressure for expanded use. A proactive approach to the issues associated with how additional portions of the

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¹ FCC Order 20-48, p. 34.

spectrum can transition from satellite to terrestrial use will help achieve outcomes that are fair to customers, current license holders, and other entities that have an interest in the band for non-MSS use.

3.2 WAYS TO MANAGE POTENTIAL FUTURE CONTROVERSIES

3.2.1 Receiver Standards

Consistent with the discussion in Section 3.1, the root cause of many of the current spectrum controversies arises from receiver designs that are predicated on different environments than would emerge after FCC rulemakings. This is not a simple “yes or no” problem, as there are significant issues with both the lack of standards and the imposition of standards. In many cases, the problem of receiver co-existence may be addressed through private arrangements among the parties, and this should not be precluded by regulatory solutions.

Many spectrum conflicts could be avoided if receivers were better designed and implemented. The natural inclination is that mandating higher levels of receiver performance would therefore resolve many of the spectrum conflicts that have arisen, and thereby would have value to industry and individual consumers. It is not the intent of this report to propose or oppose any specific action by the FCC. A reader of this report might be inclined to perceive that mandatory receiver standards might have precluded this controversy. Therefore, some other factors that should be considered include the following:

• The lifetime of many devices is shorter than the time in which major changes in spectrum are identified, considered and accepted, and then implemented. For example, smart watches, cell phones, and similar consumer equipment may go through many generations during the time it takes to consider even one spectrum usage change.
• The cost of high-performance analog filters is not subject to Moore’s law. The weight, space, and cost of high-performance filters and the power requirements for high dynamic range receiver front ends are significant, and would likely preclude many of the technology products that have created so much social value for consumers and capability for industry.
• Many of the contentious spectrum actions have represented an extreme change in usage. For example, in the MSS and C-Band, the proposed use of the band went from 5 W transmitters, 40,000 km away, to nearby base stations with radiated powers thousands of times higher. While receiver

• standards might have been valuable in these proceedings, implementing receiver standards across all users of the spectrum to deal with changes in utilization on the order of thousands of times more energy would place a heavy burden on all users, in order to simplify a small number of regulatory actions. One must thus distinguish between receiver standards that address operation in the current environment and those that might protect operation in the presence of some future uses that were vastly different in their impact.

One reason the FCC was faced with so much competing and conflicting input from the various communities in this proceeding is the lack of common receiver assumptions, which could provide a common point of departure for analytic efforts. Assumptions about receiver performance would be highly beneficial in focusing the discussion, without impacting the marketplace or equipment cost and performance. There is little point in having proceedings focus on analytic conclusions when there is no common basis for these analyses.

3.2.2 Ensuring Spectrum Succession

Technology, societal needs, and economics change. However, the spectrum management process treats each of its actions as stand-alone and immutable. It is essential that all spectrum decisions recognize that, at some point in time, they will be adjusted or changed completely. Spectrum processes must reflect that the environments will change, impacting both users of the immediate spectrum, and adjacent bands. Issues such as the varying equities inherent in the authorization of the Ligado system or in the controversies surrounding the implication of the 5G rollout on radio altimeters are not outliers and are not unique; they will become commonplace as new uses emerge and compete with older ones. A cohesive policy about rights of current users, the impact of equipment lifetime, business models, and all other considerations is essential, and should be established outside the pressures of any one spectrum decision. One potential means of systematizing this process is outlined in Section 3.1.

It is often U.S. government policy to promote technology succession (analog to digital television; 1G, 2G, 3G, and now 4G and 5G). But current actions supporting the repurposing of spectrum is at best ad hoc, and certainly does not operate on the same timeline as that which the technology is capable of changing. In the cellular world, spectrum has been repurposed between cellular generations by those holding the commercial licenses. Industry has accepted that it is disruptive to some users and that it obsoletes existing and even some high-cost equipment (e.g., cars with 3G cellular connectivity). These are reasonable decisions, weighing the capability of new uses against some disruption to the old ones. Yet, on the government side of spectrum decisions, there have

been vigorous and effective defenses against changes, and a perceived obligation of any changed regime to not impact any of the existing uses. Although the study committee did recognize that at least one commercial piece of equipment might be negatively impacted in some deployments, the vendor has not manufactured equipment with this susceptibility for more than a decade. Yet, the fact that it was once sold (the committee could not determine how many, if any, were still in use) was sufficient for some opponents of the Ligado to justify opposition.

3.2.3 Administrative Process

In the course of its information gathering, the committee inquired of the FCC witnesses why, given the objections they raised regarding some positions provided in FCC filings, the FCC apparently did not consider introducing less rigorous protections than were asked for (yet more rigorous than are currently in the ruling). The FCC response was that they could not do so because no one had filed those specific requests. FCC regulatory decisions have both a policy component and a technical fact-finding one. The process appeared to the committee to be resolving questions of fact—for example, will Ligado interfere with GPS?—through administrative and/or procedural processes rather than a technical one. Although the committee is keenly aware of the constraints inherent in the Administrative Procedure Act,² it is the committee’s opinion that selecting from specific filings may not be an appropriate technique to answer questions of fact. This proceeding might have had a more accepted outcome if the FCC was in a position to provide its own positions on factual questions. Parties have an interest in filing the most polarized positions that still might pass a “reasonableness” test. Limiting the FCC to picking between these positions is not amenable to the necessary good science for some of the questions in this proceeding.

3.2.4 Economic Mitigation

The FCC order established a process and responsibility for claims of interference to U.S. government equipment, and the mitigation of these issues through Ligado-funded replacements. Putting aside the question of whether there will be interference to GPS equipment, there are no clear policies for what rights equipment owners have with regard to future spectrum regulatory changes. What is the lifetime for any mitigation responsibility? What is the responsibility for receiver performance? How is any such responsibility addressed administratively? These are not issues that should be addressed on a case-by-case basis, but they should have some overarching policy support in advance of the resolution of specific issues.

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² U.S. Congress, 1946, “Administrative Procedure Act (5 USC Subchapter II), §§ 551–559, Washington, DC.

The committee anticipates that spectrum repurposing will be increasingly necessary to support new technology and to support the continuing modernization of the U.S. economy, industry base, and other societal needs. Different FCC actions have had different impacts on incumbent uses. In some cases, such as the C-band auction, existing users were largely made whole through a variety of mechanisms, primarily based on auction proceeds as a responsibility of auction winners. In the Ligado proceeding, U.S. Department of Defense users were promised to be made whole, while there was little consideration for commercial equipment owners. Clearly, this lack of a “safety net” for existing users drove some of the opposition to the FCC actions.

Clearer understanding of the obligations of advocates for spectrum regulatory change, and of the rights of existing users, might go a long way to reduce much of the contention in similar proceedings in the future. Because much of U.S. spectrum policy is based on market principles of “highest and best use,” it is important that the process provide a well-defined mechanism to identify and address the economic and other externalities of these uses.

3.2.5 Toward a More Collaborative Model of the Spectrum Process

The previous section discussed the inherent limitations of resolving spectrum issues through a process more akin to litigation than to engineering judgment. A similar issue arises from the separation of spectrum management responsibilities in the United States between federal and non-federal spectrum. This isolation of decision making may have been appropriate at some point in the past, when non-federal spectrum issues were dominated by broadcast, and federal spectrum issues were dominated by channel assignments for military operations. But today, there is little isolation between these domains. The federal government is a major user of commercial services and has a strong interest in the operation of these services.

A useful step to meeting the U.S. government objectives (as compared to the individual objectives of the FCC and the NTIA) would be to jointly study and test the impact of proposed regimes. Criteria would be agreed in advance, experiments agreed by all parties to be the relevant and inclusive cases. The government has very good engineers; they need to be given a chance to work out how to create the results that would enable policy makers to understand the options in meeting these two objectives simultaneously.

The committee believes that consideration of major changes in spectrum usage that impact both communities should have a higher level of coordination between the agencies, so that engineering and analysis is jointly directed. It is much easier to set criteria and determine the adequacy of proposed testing before the results are available. This interagency coordination would be above and beyond that provided in the legally

mandated process, and it would work to create harmony in how U.S. national interests in spectrum policy are executed, even as disagreements are resolved.

It is important to note that many commercial spectrum rights issues have been resolved directly between the parties through some negotiated framework, which presumably balances the costs and risks to the participating parties. The FCC has greatly encouraged this process in the past, as regulators do not have to choose “winners and losers”; presumably, market forces resolve the issue. This did not happen during the previous LightSquared era, nor in the current Ligado proceeding, as agencies’ processes defined the proceedings and those processes make different trades between benefits and risks. These trades are inherently negotiable decisions, and negotiation should be both accepted and encouraged, instead of endless reiteration of the same issues through successive cycles of argument.