The requirements are necessary because the FCC disregarded the established yardstick for protecting GPS in favor of one based on harmful interference. That is, interference that is allowed until it is bad enough that receivers aren’t working right.

In other words: interference is OK up to the point that it isn’t. Once it starts breaking things, you look at how to keep them from breaking.

The globally accepted criterion for protecting GPS has long been a one-decibel (1 dB) degradation of C/N0, the carrier-to-noise power density ratio. This is also called an Interference Protection Criterion or IPC.

This is a way of describing the strength of the GPS signal relative to the surrounding noise. The strength of the GPS signal can naturally vary a bit (the signals come from moving satellites) and the surrounding noise can vary as well. GPS experts use this combined, easy-to-measure criterion to determine how much signal noise you can add and still have receivers work reliably.

Reliability is key. The C/N0 approach includes a bit of margin to allow for the natural fluctuations and challenges that crop up (like heavy tree cover) that impair signal reception. Why? You don’t want an essential or safety-of-life system depending on an unreliable receiver. Positive train control uses GPS to help prevent collisions between moving trains and protect those working alongside the tracks.. There are over 1.5 million drones registered in the United States and GPS-based geofencing automatically keeps them away from airports and collisions with manned aircraft.

GPS is a National Critical Function, according to the Department of Homeland Security, upon which the vast majority of critical infrastructure relies. So, in the same way that civil engineers build in margin to keep drivers safe on a suspension bridge being hit by high winds, spectrum engineers keep people safe by building safety margin into GPS interference measurements.

That margin that will largely disappear under the FCC’ s decision.

It’s What We’ve Done Before

“In determining whether a new service would cause harmful interference to an incumbent service,” the FCC wrote, “we begin with and rely on the Commission’s long-standing definition embodied in our rules: ‘harmful interference’ is ‘[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 ITU] Radio Regulations.’ We apply this definition for evaluating potential for interference with respect to all services and allocations, including those associated with RNSS in the 1559-1610 MHz band where GPS operates.”

The FCC weighed the half dozen tests done by the government and Ligado and decided that the “1 dB C/N₀ degradation metric does not assess whether the actual performance of the GPS devices is affected and, accordingly, does not directly address whether there would be any ‘harmful interference’ as defined by the Commission.”

That decision is particularly important because GPS receivers simply work—until they don’t.

It is well known, said Logan Scott in a 2016 interview, that GPS receivers can give accurate position information even when experiencing serious interference. Scott is a GPS signal expert and consultant specializing in radio frequency signal processing and waveform design for communications, navigation, and other systems.

As long as GPS receivers are tracking satellites, he said, they can provide fairly accurate positioning information right up to the point where the interference causes them to lose their lock on the satellite. Substituting position error for C/ N0 degradation effectively eliminates the safety margin.

“GPS is very much a safety-of-life system,” said Scott. “Margins are important. You don’t want to use the margin up.”

The 1 dB standard is the “most readily identifiable and predictable metric that will ensure a harmful interference level is prevented,” GPS receiver manufacturer Trimble told the FCC staff in April 16 calls. “It is the only reliable mechanism to ensure the adequate protection of GNSS receivers. Alternative metrics, such as key performance indicators, are administratively impractical given the wide diversity of GNSS receivers and applications, and only reveal problems after harmful interference has already occurred, leaving GPS users with inaccurate or misleading information.”

Conditions

Having chosen to lower the bar, the FCC gave Ligado a list of conditions to help prevent problems. It adopted Ligado’s earlier proposal to not use the spectrum closest to the GPS band for terrestrial service. The FCC is also limiting power in the downlink band from 1526-1536 MHz to 9.8 dBW (10 W) with a +/- 45 degree cross-polarized base station antenna. “Based on FAA analysis, the minimum inter-station separation distance shall be 433 meters in a hexagonal grid,” the FCC wrote. The agency mandated other location limitations and out-of-band emission limits as well as reporting and notice requirements.

Ligado is also required to replace or repair federal government devices “that experience or are likely to experience harmful interference from Ligado’s operations.” To enable this they must have a way to exchange information with the government in place at least 30 days before deploying a base station in the downlink band — the short stretch of useable Ligado spectrum closest to GPS where operations pose the greatest risk.

They have to detail base station locations and technical operating parameters to federal agencies prior to commencing operations in that band and work with affected agencies to identify the devices that could be impacted. They also have to develop a program to repair or replace those devices. If a device can’t be fixed or replaced the firm “shall negotiate with the affected government agency to determine an acceptable received power level over the military installation.”

What About Civil Users?

The situation for civil receivers is unclear. Ligado must maintain a toll-free number for the general public to report interference. The company is not only responsible for taking the calls and investigating the reports, it must inform the FCC of interference within an hour. One has to wonder about this arrangement as that puts both Ligado and the FCC in a difficult position of having to address problems that aren’t supposed to arise.

Ligado also has to give six months notice to the GPS receiver manufacturers, letting them know county by county where base stations will be and updating those coverage maps every six months. This suggests that the receiver manufacturers are to have some role in dealing with interference issues even if it’s just answering questions from their customers. It is not at all clear who pays for any repairs or replacements to receivers that are not owned by the government.

Since Ligado has made clear its intention to deploy its wireless service using existing infrastructure, the firm could begin operations pretty quickly. The FCC, however, said in its order that Ligado could not commence operations for at least 90 days.

So there is some time to consider what comes next.  It remains to be seen how well the combination of power limits, advance notice, and corrective mechanisms ordered by the FCC will work to protect GPS.

In fact, the FCC appears to be anticipating some problems.

“Our analysis should not be construed to say that there is no potential for harmful interference to any GPS device currently in operation or in the marketplace,” the FCC wrote. Indeed, the Commission said it acknowledges that even Ligado-backed testing showed “there is potential for harmful interference to some devices, particularly high-precision devices.”

The agency concluded confidently, however, “that the advance notification and other conditions …which build on commitments that Ligado has made with several GPS device manufacturers, will address any identified potential harmful interference to GPS before (ground-based) network operations commence.”

Only time and potentially painful experience will tell.

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Whether or not GPS really will a actually be protected remains far from clear. Opponents are convinced Ligado’s plans pose a threat to GPS despite the assurances in FCC press releases that the final order will incorporate “stringent conditions to ensure that incumbents would not experience harmful interference.”

They have reason to be doubtful.

Protections?

Some of the key conditions touted in the FCC releases are not new. Ligado several years ago proposed creating a 23 MHz buffer zone or “guard band” between Ligado and GPS frequencies and cutting the Ligado base station power to 9.8 dBW. These measures were taken into account during extensive testing by the Department of Transportation (DOT) in 2016. That testing showed Ligado’s revised plan still posed an interference risk to GPS receivers.

“There is reason for significant concern that the FCC’s approval of the Ligado application could lead to widespread interruptions in essential GPS-dependent services,” said Diana Furchtgott-Roth, DOT’s deputy assistant secretary for research and technology in a statement.

Just reducing power, for example, does not address interference because that depends on a number of other factors.

“A higher density of base stations operating at lower power levels in an area could create the same level of interference as a more limited number of base stations with higher power,” said GPS receiver manufacturer Trimble in a filing posted April 21 by the FCC.

“They (the FCC and Ligado) make a stunningly erroneous claim that by using lower power transmitters, the problem is solved,” said Logan Scott, a GPS signal expert and a consultant specializing in radio frequency signal processing and waveform design for communications, navigation, and other systems. “If they would talk to an engineer, they would learn that cellular service provisioning is a game of flux density. As you lower the transmit power, you need more cellular base stations. To use an analogy from my backyard, I can install one high-flow sprinkler head to cover the entire yard or a bunch of low-flow heads, each covering a small portion. Either way, the grass does not care about anything other than inches of water and we are going to get wet if we run across the yard. Ligado’s core argument that low power will cause no harm is equally wet.”

Garmin, which also makes GPS receivers, pointed out in another new filing that Ligado has failed for years to provide any details about how it intended to deploy its ground structures despite repeated requests.

“A terrestrial wireless broadband system embodies much more than transmit power, and its operation is largely dependent on other deployment parameters such as tower spacing (ISD), antenna height, antenna downtilt, and antenna polarization,” Garmin wrote. “A proposed power level of 9.8 dBW alone is insufficient to fully specify a system that will protect GPS.”

Army Strong

The Defense Department reiterated its opposition in a statement to Inside GNSS Tuesday.

“Each American relies on GPS each day for many things like E-911 to locate citizens in need of emergency assistance, our financial system, to order and receive shipments, to travel for work and leisure, and even use in cellphones,” the statement said.” The military relies on GPS each day for all those reasons as well and additionally to coordinate tactical operations, launch spacecraft, track national security threats, and deliver precision munitions — and this decision by the FCC will put the military and everyone’s use of GPS at risk. That’s why the Department and eight other federal agencies are strongly opposed to this proposal and have asked for denial.”

Whose Yardstick?

One of the key issues is defining what constitutes interference and Ligado has been seeking to change the yardstick.

The GPS community relies on an internationally accepted criterion of a one-decibel (1 dB) degradation of C/N0, the carrier-to-noise power density ratio. This is also described as an Interference Protection Criterion or IPC.

That mouthful of terminology refers to the strength of the signal relative to the surrounding noise. Since the signal strength can naturally change a bit (the signals are coming from moving satellites, for example) and the surrounding noise can vary, GPS experts use this combined, easy-to-measure criterion to determine how noisy things can get and still have receivers work reliably. The IPC includes a bit of margin to allow for the natural fluctuations.

Ligado, however, wants to define interference as when things actually go wrong. According to Ligado interference only occurs when there is a change in key performance indicators — that is when the positioning and timing accuracy as experienced by the user are thrown off. Since interference must only be addressed when something is not working there is arguably little or no safety margin.

“Not only does (the 1 dB standard) have a long and well-established history in both international and domestic regulatory proceedings of protecting GNSS operations from harmful interference,” wrote Trimble, “but it also provides the most readily identifiable and predictable metric that will ensure a harmful interference level is prevented. It is the only reliable mechanism to ensure the adequate protection of GNSS receivers. Alternative metrics, such as key performance indicators, are administratively impractical given the wide diversity of GNSS receivers and applications, and only reveal problems after harmful interference has already occurred, leaving GPS users with inaccurate or misleading information.”

Industry Group

The GPS Innovation Alliance (GPSIA), whose members comprise a number of receiver manufacturers, expressed deep disappointment that the FCC appears to have ignored “the well-documented views of the expert agencies charged with preserving the integrity of GPS, specifically on the critical issue of what constitutes harmful interference to users of Global Navigation Satellite Systems (GNSS), said J. David Grossman, GPSIA’s executive director.

The 1 dB Standard for radiofrequency-based services is critical for GNSS, said Grossman. “GPSIA has consistently advocated for adoption of the 1 dB Standard as the only reliable mechanism that provides the predictability and certainty to ensure the continuation of the GPS success story, with the support of the Department of Defense, the Department of Transportation and numerous other federal agencies.”

That reliability is vital as GPS is used for all forms of transportation as well as modern emergency response systems, said Furchtgott-Roth. It is essential to effectively guiding police, fire, and other rescue vehicles to where they are needed.

“GPS is the invisible utility we all take for granted, and the Federal government has a duty to public safety to ensure that GPS remains accurate and available,” said Furchtgott-Roth.

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The effort is part of the GPS Testing for Critical Infrastructure or GET-CI program supported by DHS’s Science and Technology Directorate.

GET-CI tests equipment to identify weaknesses and help manufacturers and operators address them. It is one part of a multi-pronged effort to conduct vulnerability and impact assessments, develop mitigations, explore complementary timing technologies and engage with industry through outreach events and meetings.

“Accurate and precise position, navigation, and timing (PNT) information is vital to the nation’s critical infrastructure,” said Bill Bryan, the acting under secretary for science and technology. “S&T established this program to assess GPS vulnerabilities, advance research and development, and to enhance outreach and engagement with industry. The objective is to improve the security and resiliency of critical infrastructure.”

The 2020 GET-CI event will be held later this year. DHS S&T will create a live-sky GPS spoofing environment primarily for testing fixed infrastructure applications. There will also be limited support for ground-based mobile applications.

DHS will pay to host the evaluation event and there will be no registration fees. Participating organizations are responsible, however, for costs associated with personnel traveling to and attending the event, such as transportation, lodging, and other related costs.

The opportunity is open to critical infrastructure owners and operators, commercial GPS receiver manufacturers and civil industry stakeholders. Those interested in participating need to apply by April 24. Respondents who are selected will be asked to enter into a Limited Purpose Cooperative Research and Development Agreement (LP-CRADA) with DHS S&T in order to participate.

More information is available at https://go.usa.gov/xvYvB

Photo: DHS Headquarters while under construction / Courtesy of General Services Administration

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Repeated testing of the plan since it was first proposed by Ligado’s predecessor firm LightSquared in 2010 has shown that supporting terrestrial communications with the frequencies, which are in a band used by satellite systems, could interfere with GPS receivers. That testing included changes made by the firm to ease interference including reducing the amount of power in the signals and forgoing use of frequencies closest to GPS.

The Departments of Defense and Transportation strongly opposed the proposal in a statement released late Friday. “Our Departments — and almost a dozen other federal agencies — are strongly opposed to the Ligado proposal and have asked for its denial.”

“Americans,” they said, “rely on our Global Positioning System (GPS) each day for many things: to locate citizens in need of emergency assistance through our E-911 system, to secure our financial system, to order and receive shipments, to travel by car for work and leisure, to facilitate commercial trucking and construction work, and even to make a simple cellphone call. Our Departments rely on GPS each day for all those reasons as well to coordinate tactical national security operations, launch spacecraft, track threats, and facilitate travel by air and sea. The proposed Ligado decision by the Federal Communications Commission will put all these uses of GPS at risk.”

Boeing told the FCC in calls April 14 that approval of the Ligado plan would require the replacement or retrofitting of INMARSAT receivers on “potentially tens of thousands of in-service aircraft.”

“The conversion process would place a significant burden on the commercial airline industry at a time when the Covid-19 virus is placing substantial financial pressure on airlines,” the firm said in a Friday filing. “The manner in which these expenses will be reimbursed and the time required for this process to be completed must therefore be clearly addressed in any Commission order approving Ligado’s application.”

The FCC news release of the announcement included this language: “In the order approving Ligado’s application, the Commission included stringent conditions to ensure that incumbents would not experience harmful interference.  For example, the Commission mandated that Ligado provide a significant (23 megahertz) guard-band using its own licensed spectrum to separate its terrestrial base station transmissions from neighboring operations in the Radionavigation-Satellite Service allocation.  Moreover, Ligado is required to limit the power levels of its base stations to 9.8 dBW, a reduction of 99.3% from the power levels proposed in Ligado’s 2015 application. The order also requires Ligado to protect adjacent band incumbents by reporting its base station locations and technical operating parameters to potentially affected government and industry stakeholders prior to commencing operations, continuously monitoring the transmit power of its base station sites, and complying with procedures and actions for responding to credible reports of interference, including rapid shutdown of operations where warranted.”

The order approving the request had not been posted as this article went to press.

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When notice of the plan was first officially posted by the FCC in 2010 it appeared pretty clear they were expecting opposition. The firm, then called LightSquared, submitted its request on November 18, 2010. The next day, which happened to be the Friday before Thanksgiving week, the FCC put out its call for comments and gave interested parties just 10 days, instead of the usual 30 days, to respond. Anybody who was focused on family and feasting would have likely missed the deadline.

LightSquared wanted to use ancillary terrestrial components (ATCs) as the basis for a terrestrial network of some 40,000 ground stations. It is hard to overstate the surprise of those managing satellites in the neighboring frequency bands. A terrestrial service with powerful signals in a band where they would be next to signals already weakened by travel from space was a jaw-dropping proposal to many familliar with GPS.

A sharp-eyed member of the GPS community — that is those who provide GPS and those who use GPS — noticed the filing. Experts quickly assessed the plan and the National Telecommunications and Information Administration (NTIA), which coordinated federal use of frequencies, noted the potential for interference in a filing to the FCC in January 2012.  A few weeks later the FCC approved the request, with the proviso that LightSquared not interfere with GPS.

That triggered more rounds of testing and, finally, a letter from the NTIA on Valentine’s Day 2012 that said there “was no practical way to mitigate the potential interference” and that no additional testing was warranted. The FCC withdrew its conditional approval and LightSquared filed for bankruptcy shortly thereafter.

LightSquared emerged from bankruptcy in 2015. Newly renamed as Ligado Networks, the company devised a modified plan to work through the interference. That set the stage for another five-year battle over testing and how to define interference.

In the aftermath of the LightSquared decision the government agreed to do more testing and lay out a roadmap of what would be possible for firms that wanted to operate in the bands near GPS. Money for that was finally scraped together and that testing got underway in 2016, four years after the idea was originally proposed.

That testing, called Adjacent Band Compatibility Assessment, tested a number of frequencies including some that had been proposed for use by Ligado and described the power limits and distances that would be required to protect the wide range of receivers tested. Ligado opposed the Assessment from the start, insisting that the results of their own tests — and their own criteria for determining when there was interference should be used. Ligado wanted a standard that used degradation in receiver accuracy and not the internationally accepted standard for GPS interference. That standard is a one-decibel (1 dB) decrease in C/N0, the carrier-to-noise power density ratio.

As it turns out the results of the ABC Assessment, which showed that signals like those proposed by Ligado could cause interference, sat on a shelf for more than two years before they and an analysis by the National Space-Based PNT Systems Engineering Forum (NPEF) were sent to the FCC in December 2019. It appears the FCC has had less than half a year, and a chaotic year at that, to officially weigh the results of the most recent GPS interference testing.

“The Final Report of the Adjacent Band Compatibility Assessment is submitted as part of footnote 7, along with the National Space-Based PNT Systems Engineering Forum (NPEF) Gap Analysis Final Report, in the December 6, 2019 NTIA letter to the docket (attached).  All Assessment data is contained in the report’s Appendices,” said a U.S. Department of Transportation spokesperson. “The Reports and technical data were not submitted separately to the (FCC) Docket.”

“The FAA results for certified avionics are included in the DOT ABC report indicating that 9.8 dBW (10 W) is the level to protect certified avionics (with all of the caveats of the distance from the transmitter this applies to — drawn as a cylinder in Figure ES-4 (of ) the report), but not other categories of receivers,” the spokesperson said.

“However,” they added, “based on the results of the DOT testing and analysis of the other categories of receivers, the transmitter power level that can be tolerated by certified aviation may cause interference with, or degradation to, most other categories of GPS/GNSS receivers including those used for General Aviation and drones.”

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The Federal Communications Commission announced April 16 that Chairman Ajit Pai is circulating a draft proposal within the Commission that would approve a plan by Ligado Networks to use frequencies neighboring those used by GPS for a 5G terrestrial service.

“After many years of consideration, it is time for the FCC to make a decision and bring this proceeding to a close,” said Chairman Pai in a statement. “We have compiled an extensive record, which confirms that it is in the public interest to grant Ligado’s application while imposing stringent conditions to prevent harmful interference. The draft order that I have presented to my colleagues would make more efficient use of underused spectrum and promote the deployment of 5G and Internet of Things services.”

Extensive testing has shown that the firm’s plan to repurpose frequencies allocated for satellite use to also support a ground-based 5G service would interfere with GPS receivers — hampering, in particular, the operation of high-precision receivers.

Pai said that he appreciated the concerns that had been raised by certain federal agencies but it was the Commission’s duty to make an independent determination.

“Based on the painstaking technical analysis done by our expert staff,” he said, “I am convinced that the conditions outlined in this draft order would permit Ligado to move forward without causing harmful interference. For example, the draft order would authorize downlink operations at a power level that represents a greater than 99% reduction from what Ligado proposed in its 2015 application.”

The order, the announcement said, “would require Ligado to protect adjacent band incumbents by reporting its base station locations and technical operating parameters to potentially affected government and industry stakeholders prior to commencing operations, continuously monitoring the transmit power of its base station sites, and complying with procedures and actions for responding to credible reports of interference, including rapid shutdown of operations where warranted.”

“The Chairman’s action is difficult to believe and accept,” said Dana Goward president, of the Resilient Navigation & Timing Foundation. “He says he is acting based upon ‘painstaking technical analysis by our technical staff.’ Given the eight-year and very contentious history of this issue and widespread national and economic security concerns, it is inconceivable that this analysis was not shared with the public for open and transparent discussion prior to him putting it to a vote.”

The announcement comes on the heels of a letter from a bi-partisan trio of leaders from the House and Senate Armed Services Committiees asking the president to help stop approval which they said threatened the usability of civil and military GPS receivers across the United States and could further hurt the economy.

Senators Jim Inhofe (R-Oklahoma) and Jack Reed (D-Rhode Island), chairman and ranking member of the Senate Armed Services Committee, and Rep. Mac Thornberry (R-Texas), ranking member of the House Armed Services Committee appealed directly to President Donald Trump to use his influence to prevent the FCC from allowing Ligado Networks to change how it uses its spectrum.

“Ligado’s planned usage will likely harm military capabilities, particularly for the U.S. Space Force, and have major impact on the national economy,” the congressmen wrote. The timing could not be worse, they said to allow what “is fundamentally a bad deal for America’s national and economic security.”

Underscoring the potential impact on businesses the lawmakers noted that the GPS satellite signals enable much of daily American life.

“These GPS satellites quietly power our economy,” they said, “by providing free precise timing and navigation to our financial and banking sector, agriculture, our logistics and tourism companies, our power grid and cell phone businesses, commercial aviation, space launch and space operations, weather, construction and mining vehicle guidance, as well as surveying and mapping.”

“These satellites contribute $1 billion to the economy every single day,” they wrote — noting that that was based on a conservative estimate. The GPS satellite signals “are necessary for trillions of dollars in financial transactions in the stock markets. The functions provided by our GPS satellites will be all the more important to enable a rapid economic recovery from the effects of COVID-19. Ligado’s plan would hinder GPS functions for the entire American economy.”

Photo: FCC Commissioners. Courtesy FCC.

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Their conclusions were summarized in a memo that sat stalled in an office of the Department of Commerce (DOC) for nearly two months before rumors that regulators might quietly approve Ligado’s plan created so much pressure that it appears to have shaken the memo loose. The memo could be the last element needed in the decision making process on the controversial request.

At the center of the debate is a proposal to take frequencies allocated primarily for use by satellites and allow them to be used for broadband communications. Extensive testing has shown that the proposal, even in a dialed-back form, would cause interference to GPS receivers. Those receivers are used for navigation and positioning but also for super-accurate timing that enables the synchronization of mobile communications and internet traffic as well a financial transactions and other networked systems like the power grid and the cloud. GPS signals are so important that they are now considered to be an essential element of the nation’s critical infrastructure.

Yes. There’s Interference.

“The Air Force has shown — and Ligado itself has conceded — that the proposed Ligado (previously LightSquared) license modification threatens disruption of GPS,” wrote Thu Luu, the Air Force’s executive agent for GPS. A proposal by the Virginia-based firm to address any problems by replacing government GPS receivers that are affected by its network “is a tacit admission that there would be interference,” she said.

Ligado did not immediately respond to a request for comment.

The February 14 memo focuses on military applications and was co-signed by representatives of the Army, Navy and the U.S. Coast Guard. It also underscores the civil GPS applications the Pentagon relies upon and was co-signed by the Departments of Commerce, Energy, Homeland Security, Interior, Justice and Transportation as well as the Federal Aviation Administration, NASA and National Science Foundation.

The memo was “endorsed by the interagency,” said Deputy Secretary of Defense David Norquist. The interagency reflects the civil and defense agencies that work together to support GPS specifically and position, navigation and timing capabilities in general. In a March 24 letter Norquist urged the National Telecommunications and Information Administration (NTIA) within DOC — which manages federal frequencies, and had failed to forward the memo — to “expeditiously” send the February memo to the Federal Communications Commission, which has been weighing the Ligado’s proposal since 2010, when the firm was called LightSquared.

Rumors had surfaced in Washington just before the Easter weekend suggesting FCC Chairman Ajit Pai was poised to immediately approve Ligado’s request. Though the rumors did not track with FCC procedure and nothing indicating a decision has yet emerged, it is not unusual for government agencies to make contentious moves at a time when fewer people will be watching.

The memo and the March 24 letter — plus a March 12 letter signed by Dana Deasy, DOD’s chief information officer and Under Secretary of Defense for Research and Engineering Michael Griffin asking that the memo be conveyed to the FCC — were finally sent to Pai on Friday April 10 by Douglas Kinkoph, NTIA associate administrator and acting assistant secretary for communications and information; then posted by NITA late that evening.

Kinkoph noted in his letter to Pai that the process for authorizing the request from Ligado would be complete only “‘once the Commission, after consultation with NTIA, concludes that the harmful interference concerns have been resolved.'” That, Kinkoph pointed out, was the criteria set by the FCC itself in the 2011 Report and Order on the matter issued by the FCC’s International Bureau. “We believe the Commission cannot reasonably reach such a conclusion,” wrote Kinkoph.

The 13 agencies signing the February memo comprise the majority of the members of the Interdepartment Radio Advisory Committee (IRAC), which gives technical input to NTIA. The February memo could be seen as the feedback from the IRAC that Pai was reportedly seeking this fall.

On Friday Rep. Peter A. DeFazio (D-Mass.), chairman of the Committee on Transportation and Infrastructure, and Rep. John Garamendi (D-Calif.), set up what appears to have been a backup plan should the NTIA have failed to respond or respond fully to DOD’s send-the-memo requests.

The lawmakers wrote on April 10 to Secretary of Transportation Elaine Chao, asking her to convey to Pai copies of DOT’s correspondence regarding Ligado with the NTIA, FCC, DOD, the National Economic Council. They also ask her to send correspondence with Commerce (of which, as noted, the NTIA is a part) and specifically with DOC’s National Institute of Standards and Technology.

DOD and DOT co-chair the National Executive Committee for Space-Based Positioning, Navigation, and Timing (PNT), which coordinates GPS matters across the full government as part of the interagency process. DOT also conducted key interference testing that looked at the power levels GPS receivers could withstand whatever the source — including from Ligado-like signals. DeFazio and Garamendi zeroed in on testing and data, asking DOT to send any studies and analyses by the IRAC regardless of their state of formal approval as well as correspondence signed by multiple agencies and/or departments, regardless of whether it has been transmitted formally to the FCC.

Broad Impact

Thu underscored that the mitigation proposal by Ligado only covers those receivers owned by the government and would leave out many high-value federal uses of civil GPS receivers not owned by the government. DOD makes use of civil GPS receivers in non-combat environments, such as surveying, flight training, training, exercises, other national security events and scientific applications. Like their civilian counterparts, DOD surveyors and construction units often rely on high-precision GPS receivers that are exceedingly sensitive to interference from signals at nearby frequencies.

The military receivers that could be impacted also go well beyond those used directly by DOD, said Thu. For example, NASA uses high-precision military GPS receivers for its launch anomaly monitoring and destruct systems and Homeland Security and the border patrol use military GPS receivers in unmanned surveillance aircraft. Some law enforcement and intelligence agencies use military GPS in drones and the State Department’s diplomatic security service also uses military GPS receivers.

“It would be untenable for the United States to pursue an initiative that undermines these capabilities,” wrote Thu, “and it would be exceptionally detrimental to national security.”

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At this point in 2020, there is an irresistible temptation to compare all potential crises—like the loss of GPS position, navigation and timing (PNT)—to the ballooning emergency of the coronavirus. The affect of both contagion and signal loss could remain local, as with jamming from personal devices in the case of PNT. Or it could become truly global with economic impact escalating sharply.

One could also insist that, in both cases, we have lost opportunities to strengthen the U.S. against catastrophe. With pathogens, it’s arguably harder to know which risk to tackle first. That is not the case with satellite navigation.

We have long had a reasonably good idea of what to do, or at least some very good ideas on where to start, but the opportunity for easier fixes has largely disappeared due to inaction. That’s alarming, given how long the navigation community has labored to avoid calamity. The George W. Bush administration called for a backup and improved resistance to interference when it issued National Security Policy Directive-39. Sixteen years ago.

The last 12 months, however, have seen movement toward real change that could genuinely bring the U.S. closer to a PNT backup, more resilient receivers and better-prepared users. Stimulated by hourly updates on how bad things can get in another realm, these steps toward disaster-resistant PNT could actually get us somewhere.

A PNT Backup

The organization closest to concrete results is the U.S. Department of Transportation (DOT), which recently awarded contracts to support testing of a variety of PNT technologies. The contracts to 11 different firms stem from a Congressionally-ordered effort to create a backup for the broad range of PNT capabilities needed in the U.S.

The many technologies chosen for testing reflect the fact that the nation’s use of PNT has evolved well past the point of needing simply a backup for GPS, said Karen Van Dyke, director of DOT’s office of PNT and spectrum.

“Knowing the diverse nature of the critical infrastructure sectors that rely on positioning, navigation and/or timing, it’s unlikely there is one solution that can meet everyone’s needs,” she said, adding that “even GPS itself can’t meet all of the needs, particularly indoors and underground—some of the more impeded environments.”

The testing was mandated in the Fiscal Year 2018 Defense Authorization bill, which also allocated $10 million to implement the plan. Not long thereafter, Congress appropriated another $5 million to move things along and in December 2018 directed DOT to establish a backup system for GPS timing.

Lawmakers wrote clearly what they wanted in the authorization language, setting requirements that were summarized neatly by DOT Deputy Assistant Secretary for Research and Technology Diana Furchtgott-Roth. The system is, “to the maximum intent possible, required to be terrestrial, wireless, have wide area coverage, be difficult to disrupt and capable of expansion to provide positioning and navigation services.”

“We might not be able to do all those things,” she told attendees at the Institute of Navigation’s ION GNSS+ meeting in September, “but we are very much going to try our best possible.”

As of press time, the testing was set to begin the week of March 9 at NASA Langley Research Center in Hampton, Virginia, and continue the following week at Joint Base Cape Cod in at Buzzards Bay, Massachusetts. The Departments of Transportation, Defense (DOD) and Homeland Security (DHS) devised the testing specifics jointly with input from the other member agencies in the Space-Based PNT Executive Committee. Van Dyke stressed that her group has been working with the agencies on the committee so that they are all comfortable with what the results show and with the report that will be sent to Congress.

Furchtgott-Roth is expected to decide sometime in August what kind of PNT backup she’ll recommend in that report. Given the broad use of PNT, she is expected to suggest a system of systems incorporating different technologies. “We are seeking the best solutions to ensure that America has a combination of PNT systems that, when used together, will be difficult to disrupt,” she stated.

DOT’s report is to include a timeline, funding requirements and lessons learned from the testing. The test results on equipment performance may also be folded into efforts underway at DHS to make clearer the distinctions between more- and less-resilient receivers and other equipment.

Tougher Receivers

The good news is that GPS users, specifically users involved with critical infrastructure (CI), are now more attuned to what could happen if the GPS signal they rely on—say for synchronization—became unavailable or untrustworthy.

“In recent years, the agency (DHS) has made some fairly good progress in raising awareness of this issue: of GPS vulnerabilities, of spoofing and also data spoofing,” said Ernest Wong, PNT technical manager in DHS’s Science and Technology Directorate. More manufacturers are releasing more resilient equipment and competing based on the hardiness of their new models. Many of them cite the 2017 DHS document Best Practices for Improving the Operation and Development of GPS Equipment Used by Critical Infrastructure, he said, when talking about their equipment. (That document is available on the first page of gps.gov).

But Best Practices, while a good initial step, is not a standards document or any type of requirements document, said Wong. “The question remains; when someone says that their equipment is resilient, what does it mean? What’s it resilient against? What does it protect against? What are its capabilities?”

This lack of standards makes it harder for companies that build more resilient equipment to differentiate their hardware. As a result, less capable receivers are more likely to find their way into important CI systems.

To address this, DHS is developing the Conformance Framework, a sort of consensus vocabulary for talking about PNT equipment based on levels of resilience.

Though still very much a work in progress, the overall concept is to define the types of expected behaviors for resistant receivers at different levels, Wong told Inside GNSS. Level 1 receivers, for example, will likely be defined as being capable of robust recovery from a threat; equipment with Level 4 resilience should be able to operate through threats. The definition of the levels and the language in the framework will incorporate four core functions: prevention, detection (internal state), response and recovery.

Changing Paradigms

In the early days of GPS, people did not worry about corruption of the signals or build receivers to handle such problems, said Jim Platt of DHS’s Cybersecurity and Infrastructure Security Agency (CISA).

“This Conformance Framework,” said Platt, “is really a step forward in changing that paradigm from building GPS receivers as just radios to recognizing the fact that these GPS receivers are really computers that are ingesting GPS signals, processing that information and then passing information on to other systems. Therefore we have to start differentiating what level, what types of receivers are used in what type of applications. More critical applications need receivers with additional security built into them, with better software assurance—and those are some of the things that the Conformance Framework will look to help define.”

Focus on Timing

The initial focus is on GNSS-based timing equipment, Wong told the November meeting of the National Space-Based PNT Advisory Board. This is “primarily to address the most pressing PNT attack surface in critical infrastructure,” Wong said.

The working group hammering out the framework’s definitions includes a number of key equipment manufacturers, CI owners, CI operators and other industry stakeholders. DOT and the Federal Aviation Administration are also members to ensure that the framework is extendable to positioning and navigation. DHS would like more critical infrastructure owners and operators to participate, Wong said, asking that anyone interested in getting involved should email gps4critical-infrastructure@hq.dhs.gov.

The definitions the group comes up with must be non-prescriptive; that is, they define an outcome but not the technology that achieves that outcome. They also must be signal-agnostic so they remain relevant as additional
signals—from, for example, a new backup system—come online.

“The reason why we try to make this source-agnostic is we do view that simply adding an additional PNT source to your device doesn’t automatically make it more resilient,” said Wong. “It depends on how you implement it. If you don’t implement it securely, it could just be an additional attack surface.”

The agency plans to release guidance documentation for the framework this spring and begin the time-consuming standards development process sometime next calendar year. Choosing a standards development organization (SDO) and reducing the time to finalize standards could be real challenges.

“I think the key thing here,” Wong said, “is going to be we may need to go to different SDOs for different sectors because different sectors do have different standard requirements.”

DHS is also working with the Army to suss out vulnerabilities in CI equipment through a program called GET-CI or GPS Equipment Testing for Critical Infrastructure. GET-CI will again offer testing opportunities this year to both manufacturers and CI owners/operators

“We’ve only had two events so far, and the objectives of those first two were really more discovery,” Wong told Inside GNSS. He added that he felt they’d get a much better sense this year of how good current equipment performance really is, because a number of new products have come on the market.

Smarter Buyers

Having more information about receivers isn’t helpful if you don’t know what you need. An Executive Order released by the White House on February 12 aims to address that by having the Department of Commerce—specifically DOC’s National Institute of Standards and Technology (NIST)—develop user profiles.

NIST is to profile the different ways PNT is used and where the vulnerabilities lie. The profiles are meant to help CI owners/operators better understand their level of PNT dependency when using specific applications and their ability to tolerate signal disruptions—all of which can be used to build resiliency based on how the equipment is being used.

“If you’ve developed your PNT profile and you say that timing is critical to my operations, I would probably want to choose a PNT receiver that is higher on the Conformance Framework scale because it’s supporting a critical operation,” Platt said. Eventually certified equipment or adherence to particular industry standards may become part of what is expected for CI operators with certain profiles, but that is something for the future. In the meantime, NIST has the job of developing the profiles because it’s already done something similar for cybersecurity.

“The idea,” said Platt, “is to build off the things that we’ve learned in the cybersecurity profiles so that we can build PNT profiles that are specific to applications. We would envision that there would be a profile application for telecommunications users, there would be a profile for IT users, there would be a profile potentially for aviation users.”

DHS, meanwhile is supposed to look at the infrastructure directly and develop a testing plan to determine just how vulnerable CI systems and assets are to PNT disruption and manipulation.

Those test results will be used to update the profiles, which are to be reviewed every two years, and the Federal Radionavigation Plan. The FRP is the foundational policy and planning document governing ground- and space-based radionavigation systems. This includes GPS and any new backup systems and PNT augmentations like those supporting air traffic control.

“It’s not that you develop a profile for a particular sector just once and then you’re done,” said Van Dyke. “It’s a starting point and then you continue to update them. As you pointed out, technology is changing rapidly. The applications that use the technology also are evolving quite quickly. And so it’s a process, and that process will need to continually be updated.”

In addition to the profiles and testing, the Departments of Transportation, Energy, and Security have six months to develop plans “to engage with critical infrastructure owners or operators to evaluate the responsible use of PNT services.” By the end of a year they are to verify those plans by completing pilot projects. Those pilots on responsible use could become very important.

A Plan with Teeth

It’s one thing to freshen up profiles, policy and planning tools. It’s another thing to get the owners and operators of critical infrastructure to update what could be very expensive equipment. To encourage key stakeholders to stay abreast of changes, the administration has adopted a specific policy of fostering “the responsible use of PNT services by critical infrastructure owners and operators.”

“Responsible” in this case means “the deliberate, risk-informed use of PNT services, including their acquisition, integration, and deployment, such that disruption or manipulation of PNT services minimally affects national security, the economy, public health, and the critical functions of the Federal Government.”

That last line is key, because that’s where the “ouch” could come from for those CI owners and operators who don’t keep up.

The profiles are based on “responsible use of PNT” which, according to the executive order, includes alignment with the standards, guidelines, and sector-specific requirements “selected for a particular system to address the potential disruption or manipulation of PNT services.”

Once the profiles are available, sector-specific federal agencies are to work with DHS to develop contracting language requiring that responsible use by PNT-dependent suppliers. Want to sell the Pentagon computer services? Better check what the profile says about updating timing receivers. Hoping to supply electricity to a federal lab? See what the profile says about protecting energy distribution.

“DHS,” Platt said, “has been tasked to develop contract language that could support, or could be used to ensure, that those systems that are highly dependent on PNT—and I say dependent, not just use PNT—but those systems that are dependent on precision PNT are applying the appropriate risk management processes so that we understand what risk is being accepted with PNT and how any risk is being either mitigated or accepted. … If you’re going to provide a service to the federal government, you will have to ensure that you are following the PNT profiles as developed by NIST.” Firms that can show that they meet the new requirements will have a leg up on competitors that are not able to adopt or demonstrate that they can meet those requirements, said Platt.

The profiles won’t be developed in a vaccum, said Platt. NIST will go out and work with the service providers. “This won’t be a surprise to any of them.”

Platt added that, as DHS has spoken with companies and highlighted the importance of timing data, “the light bulb has come on and (the companies) say ‘Oh, there are ways that we can mitigate this—potential disruptions to GPS or other PNT services—that are just good business practices.’ ”

“We realize that there is not going to be a wholesale replacement of receivers out there once we come out with the Conformance Framework or even an industry standard, whatever SDO that we go with. But that doesn’t stop manufacturers from taking a look at their overall operating systems and determining that there are potential risks in the system that they can mitigate through other means. And then … as additional equipment becomes available, there’s also a parallel effort to create additional demand within the owners and operators for more secure and resilient equipment. As they do their lifecycle replacements, the older equipment is replaced with newer equipment.”

Ultimately, this is about more secure and resilient critical infrastructure, Platt said, with more secure and resilient PNT being a subset of that.

“We shouldn’t expect that this should be solved overnight,” said Platt, “but we do see being able to make significant incremental improvements over the next couple of years.”

The post Progress Logged on Strengthening and Backing Up PNT appeared first on Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design.

Originally scheduled for late April 2020 on a SpaceX Falcon 9 rocket, the launch is now projected to go up no earlier than June 30. The schedule will be re-evaluated in May, SMC said in a statement.

“We do not make this decision lightly, however, given our GPS constellation remains strong, we have the opportunity to make a deliberate decision to maintain our mission assurance posture, without introducing additional health risk to personnel or mission risk to the launch,” said Lt. Gen. John F. Thompson, SMC commander and program executive officer for space.

The current constellation is healthy, SMC said, with 31 satellites on orbit, allowing the team to take this strategic pause without gaps in coverage or capability.

GPS III-3 brings the third modernized GPS III satellite to the operational GPS mission, and the team remains ready to execute. GPS III will bring three times better accuracy and up to eight times improved anti-jamming capability than its predecessor.

“The GPS system supports vital U.S. and allied operations worldwide, unabated. As the COVID-19 pandemic is a threat to national security, likewise, rescheduling the launch is in the interest of national security,” said Gen. Thompson. “We have to get it right the first time, and protecting our people is just as important as cost, schedule, and performance.”

SMC still plans to complete the next three GPS launches in 2020.

Photo of a SpaceX Falcon 9 rocket launch courtesy of Space and Missile Systems Center.

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“Analysis of the data has begun,” the U.S. Department of Transportation said in a statement sent to Inside GNSS, “and USDOT expects the analysis phase to remain on schedule for completion in May.”

A recommendation on what the backup system will look like is supposed to be submitted in a report to Congress. That recommendation is expected to comprise several systems including some that can send signals inside buildings.

“Knowing the diverse nature of the critical infrastructure sectors that rely on positioning, navigation and/or timing, it’s unlikely there is one solution that can meet everyone’s needs,” Karen Van Dyke, director of DOT’s office of positioning, navigation and timing (PNT) and spectrum told Inside GNSS earlier this year. “Even GPS itself can’t meet all of the needs, particularly indoors and underground—some of the more impeded environments.”

“The results from the demonstration are planned to be briefed to the National Space-Based PNT Executive Committee (EXCOM), co-chaired by the deputy secretaries of Transportation and Defense, in August 2020 for a decision on the way forward,” DOT said.

The new system is supposed to be terrestrial, wireless, have wide area coverage, be difficult to disrupt and capable of expansion to provide positioning and navigation services.

[Inside GNSS has published three online stories detailing technology from some of the 11 firms selected by the Department of Transportation (DOT) in August 2019 to demonstrate GPS backup technologies that could be used to back up services provided by GPS should GPS signals be jammed, spoofed or unavailable.  See NEON, Echo Ridge and Seven Solutions.]

“We might not be able to do all those things,” DOT Deputy Assistant Secretary for Research and Technology Diana Furchtgott-Roth told attendees at the Institute of Navigation’s ION GNSS+ meeting in September, “but we are very much going to try our best possible.”

The testing is part of a congressionally mandated and funded effort to come up with a back up for the GPS system. Because GPS signals have become integrated into so many aspects of modern life—including the computer systems and networks that keep communication and financial networks running smoothly—DOT chose a variety of technologies from 11 different firms to weave into a cohesive web of positioning, timing and navigation information.

The testing began the week of March 9 at NASA’s Langley Research Center and continued the following week at Joint Base Cape Cod in at Buzzards Bay, Massachusetts.

Though the U.S. started feeling the impact of the coronavirus well before that, DOT was able to finish the tests as anticipated.

“Data collection was completed on time, thanks to the collaborative work of the USDOT/Volpe Center, NASA/Langley, Joint Base Cape Cod, U.S. Coast Guard and the technology vendor teams,” DOT said.

Top photo of NASA’s Langley Research Center courtesy of NASA.

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