Testimony of Mr. Anthony J. Russo

Director
National Coordination Office
Space-Based Positioning, Navigation and Timing

Hearing on "Sustaining GPS for National Security"
Subcommittee on Strategic Forces
U.S. House of Representatives

September 15, 2011

Chairman Turner, Ranking Member Sanchez and distinguished members of the Subcommittee, thank you for this opportunity to speak to you today. The Global Positioning System has grown into a global utility whose multi-use services are integral to U.S. national and homeland security, economic growth, and transportation safety. It is an essential element of the worldwide economic infrastructure. Services dependent on GPS information are now an engine for economic growth, enhancing economic development, and improving both the safety and the quality of life. The system is critical to first responders and a key component to multiple sectors of U.S. critical infrastructure.

The Role of the Space-Based Positioning, Navigation and Timing Executive Committee

Since 1983, the United States has had a multi-use policy in place for GPS. This policy has had strong bipartisan support and each successive administration has strengthened the interagency participation in the program. In 2004, President Bush issued a National Space-Based Positioning, Navigation and Timing (PNT) Policy establishing a Deputy Secretary level Executive Committee to advise and coordinate on policies, programs, requirements, schedules, architectures and budgets to sustain and modernize GPS, systems that augment or enhance GPS, and any backup capabilities. Last year, President Obama signed a comprehensive National Space Policy which left the PNT policy in place, but added emphasis and additional guidance in four key areas related to GPS. The policy outlines six primary goals, all of which are threatened by the proposed LightSquared deployment. These are:

  1. Provide uninterrupted availability of PNT services;
  2. Meet growing national, homeland, economic security, and civil requirements as well as scientific and commercial demands;
  3. Remain the pre-eminent military space-based PNT service;
  4. Provide civil services that exceed or are competitive with foreign space-based PNT services and their augmentation systems;
  5. Remain essential components of internationally accepted positioning, navigation and timing services; and
  6. Promote U.S. technological leadership in applications involving space-based PNT services.

To implement the President's PNT policy goals, the Executive Committee has specific tasks including: "Review proposals and provide recommendations to the Departments and Agencies for international cooperation, as well as spectrum management and protection issues," and its member Departments and Agencies are further tasked to "...seek to protect the radio frequency spectrum used by the Global Positioning System and related space-based augmentations." The Executive Committee is also responsible in this policy to identify impacts to government space systems prior to any reallocation of spectrum for commercial, federal, or shared use.

Because the Air Force develops, builds, launches, operates, maintains and modernizes the GPS constellation, the Deputy Secretary of Defense serves as Co-chair of all Executive Committee meetings and his personnel are integral to all activities performed in support of this Policy. To execute the staff functions of the Executive Committee, and to assist them in ensuring implementation of the President's policy objectives, a National Coordination Office (NCO) was established. The NCO is staffed with representatives from every department or agency with major equities in GPS and includes two Air Force officers with extensive GPS backgrounds.

The National Space-Based Positioning, Navigation and Timing Systems Engineering Forum (NPEF)

The NPEF is an interagency working group that supports the NCO on major technical issues that cross agency boundaries and their reports help form the basis for recommendations made to the Executive Committee. The NPEF is co-chaired by the Air Force's Chief Engineer from the GPS Program Office and the FAA's Ground Segment Lead for Global Navigation Satellite Systems and Space-Based Augmentation Systems. They are assisted by technical representatives and other staff from across the interagency.

On the 26th of January this year, the Federal Communications Commission (FCC) approved a conditional waiver for LightSquared's high power broadband network that the Executive Committee had warned might cause significant interference to government-wide GPS applications. On January 28, 2011, I briefed the Executive Committee's Steering Group, co-chaired by Ms. Takai as DoD's representative, on a plan to evaluate LightSquared's proposal and determine some of the specific impacts. The tasking statement was approved by the interagency and released on February 9, 2011. A copy of this statement is included as an attachment to this testimony. There were several reasons why the Executive Committee chose to do this testing even though they knew the FCC was having LightSquared conduct similar testing:

  1. We needed to include national security assets in the testing. Since all of LightSquared's work needed to be in the public domain, we did not want to expose vulnerabilities of military or intelligence systems. A separate classified annex of the NPEF report was transmitted to FCC via the National Telecommunications and Information Administration (NTIA) and is currently being assessed by their engineers.
  2. We needed to assess certain assets that may be unclassified, but where the results are still very sensitive. Examples of these would be things in law enforcement systems and systems that are in homeland security applications.
  3. We needed to consider system details that may involve proprietary contractor data, including the specific locations of future broadband towers. This information is included in a "For Official Use Only" document that was transmitted to the NTIA, but redacted from the publicly releasable versions.
  4. We needed to consider the entire scope of interference effects. The FCC Conditional Order limited LightSquared's testing scope to only one type of interference effect called overload interference. There are other types of Radio Frequency (RF) interference effects which I will discuss later in this testimony.

The NPEF's test methodology involved modeling, simulation, analysis, bench testing, radiated testing inside an anechoic chamber, and what is called "live sky" testing where LightSquared set up a tower for us outdoors and broadcast a signal as close as they could to what they expect the actual configuration to be. Each of these methods has advantages and limitations and using multiple methods enhances our confidence in the results. I should point out that LightSquared actively supported our efforts. They provided their prototype hardware, including a custom filter for their transmitters, technical specifications, answered numerous engineering questions, and sent personnel to our test sites to review and comment on our test set-up. I would like to take this opportunity to publicly thank LightSquared for their cooperation. It greatly enhanced the fidelity of our results.

I do want to identify some limitations of our testing effort. The most significant is that we had only one LightSquared base station. Since interference effects in these scenarios are normally additive, this is a serious limitation in a planned environment where the LightSquared base stations are so densely enough packed that a given user will likely see effects from multiple towers simultaneously. This also greatly complicates some of the potential mitigation options. A second limiting factor was LightSquared did not have any LightSquared handsets available for us to test. The handsets operate at a different frequency than their base stations, but also close to GPS, but much less powerful. However, we anticipate they will be much more numerous and since they are mobile they could be anywhere and may even be frequently co-located with GPS receivers. Several technical experts on our team consider this to be a very significant problem, but we were not able to explicitly address this issue. A third limiting factor is the inability to fully represent the diversity of the GPS user community. There are more GPS applications than we can count and at the NCO we learn of new applications at the rate of about three per week. Each application is different. Some require extreme position in location; others do not use position at all, but need very precise timing. Some applications require less precision, but need extremely high integrity—in other words they need high confidence the signal they receive is accurate. Still others do not even read the signal's message content; they only care about the phase relationship between the military and civil GPS signals. It was therefore difficult to construct tests that covered all of our diverse users in the time we had available. And a final limiting factor was the extremely compressed time frame.

But despite these limitations, the NPEF completed the job they were asked to do. They were able to look at a wide range of representative receivers against all three phases of LightSquared's proposed deployment plan. In all, 24 different organizations participated in testing more than 75 different receivers in over 50 separate test events. The answer is definitive: LightSquared's proposed system would create harmful interference throughout all three phases of its planned deployment. I have attached an Executive Summary of the publicly releasable results with this testimony. Our tests showed no evidence of out-of-band emissions. In other words, we were able to confirm LightSquared's claim they correctly filter their transmission so that it is not leaking into the GPS band. However, the tests also confirm the presence of other harmful interference effects. These are:

  1. Co-channel Interference: Two systems that augment GPS are authorized users in the same frequency band where LightSquared has its license. These are not government systems, but there are government users of these systems, including the Department of Defense. GPS receivers that obtain this augmentation signal are denied at great distances from any LightSquared base station. Filtering out co-channel interference is not feasible since the augmentation signal can be anywhere in that frequency band.
  2. Overload Interference: Contrary to LightSquared's claims that only older or poorly designed receivers would experience desensitization, also known as overload interference, the NPEF testing showed the effect is pervasive and applies to our newest and best-designed military and civil receivers as well as to those in all sectors of the commercial markets. In fact, the high-end receivers are particularly susceptible to this overload interference. These receivers do contain filters to screen out energy from the adjacent band, but these filters were designed for an environment where the neighboring band was assumed quiet, to have relatively low power satellite signals and not the high power terrestrial transmissions now being proposed for the first time. Some GPS receivers can filter out several hundred thousand times the power of an adjacent signal, but the problem is that LightSquared's transmissions are about 5 billion times more powerful than the GPS signal if the tower is about one-half mile away. The scale of the difference between a LightSquared signal and the power of a GPS signal as it reaches the ground is difficult for us to comprehend. Dr. Brad Parkinson from Stanford University uses the analogy it is like looking for a teaspoon of water in Niagara Falls—that is a relative five billion times difference.
  3. Intermodulation Interference: During preliminary tests conducted at Jet Propulsion Laboratories, NASA engineers discovered that the when the two high-power LightSquared transmissions are received by a GPS receiver with sufficient power that the device's electronics start saturating, it creates a third signal inside the device. This third signal is weaker than the original LightSquared transmissions, but still many times more powerful than the GPS signal and washes out the GPS signal. In addition, the frequency of this third signal is almost dead center in the middle of the GPS frequency the GPS receiver is trying to detect and process. This is not unique to the LightSquared deployment and has been seen in other radio frequency transmissions where two high power transmissions are close together in spectrum. NTIA warned as far back as 2002 this might occur in this particular frequency band with reception of terrestrial transmissions. However, actual hardware had not been available until just this year and it was not further characterized. Not all GPS receivers experience this intermodulation effect, but many do and we were able to consistently recreate it in the anechoic chamber at the White Sands Missile Range and in live-sky testing at Holloman Air Force Base. The discovery of this effect surprised LightSquared and they still have offered no solution to the problem other than to say we will not experience it during the first phase of their deployment which involves only one of their two channels.

In the NPEF task statement the engineering team was asked to consider possible mitigations to any problems they discovered. They were asked them to investigate not only things that we might reasonably request from LightSquared, but also to look at changes the GPS community could do that would mitigate harmful interference and still allow LightSquared to execute their business plan. The NPEF spent many hours considering the full range of options such as: reducing power on LightSquared's transmission, increasing GPS's transmitted power, building better GPS receiver filters or asking for exclusion zones around certain sensitive installations that use GPS. Unfortunately, we could not identify any feasible option that would mitigate harmful interference for all, or even most, GPS users, and still allow LightSquared to meet their system requirements. The only suggested option that might work would be moving LightSquared to a different part of the spectrum, and that involves a host of other issues outside the PNT community.

LightSquared's Technical Working Group (TWG)

When the FCC granted the Conditional Waiver, one of the conditions was for the company to fund testing efforts to resolve the interference concerns the Executive Committee and GPS Industry had raised. The FCC Order further directed the creation of a LightSquared-led working group and highly encouraged participation from the U.S. Government. NTIA, in their role as the President's principal advisor on spectrum issues, asked for help in coordinating the government participation in this TWG. We were able to get 10 of our best technical experts from across the interagency community included in the LightSquared Working Group. Due to legal restrictions, these people could not help write the findings/results, but could and did provide technical information about GPS and government operations at every stage of LightSquared's effort. The TWG also included strong representation from across the diverse GPS industry. Altogether, the TWG contained 39 full-time members and 61 part-time technical advisors, split between GPS Industry, LightSquared, and the Government. Like the NPEF, the TWG used an assortment of different techniques culminating in two weeks of "Live-Sky" testing in Las Vegas. There was healthy cross flow of expertise and data sharing between the NPEF and TWG.

The TWG was divided into seven separate sub-groups based on GPS application type. The results were completely consistent with the NPEF results. All seven sub-groups reported significant harmful interference with respect to all three phases of LightSquared's planned deployment. There was no consensus on feasible mitigation options although most of the GPS Industry participants in the subgroups did advocate for moving LightSquared's service to a different part of the spectrum.

LightSquared's New Plan

On June 30, 2011, LightSquared submitted their TWG report acknowledging the harmful interference their system would create. Simultaneously LightSquared submitted a totally independent "Recommendations" report outlining a proposed 3-part solution. The LightSquared recommended solution was not reviewed or evaluated by the TWG and all ten of the government participants in the TWG disagree with assertions it makes about the TWG results. However, the Recommendations paper is a serious and constructive proposal and will be fully considered by the FCC.

  1. First they agreed to re-order the phasing of their system deployment. LightSquared now proposes initially deploying with the lower frequency of their two channels—the channel that would be furthest away from the border of GPS. The new proposal for deployment phasing would decrease—but not eliminate the number and extent of initial impacts to GPS devices impacted and provide more time to implement any necessary mitigation methods.
    1. At this time we, do not know what the impacts of this initial channel transmission (referred to as the "10 MHz Low" phase) are. This configuration was not one of the ones tested by the NPEF because it was not proposed until after the NPEF completed testing. The NPEF informally collected a few data points in what they called an "initial exploratory evaluation," but this is insufficient for a conclusion and an additional six months of study was recommended.
    2. The TWG itself did not evaluate LightSquared's 3-part proposal and the "10 MHz Low" phase was not part of the original test plan. At the very end of their testing period, the TWG sub-groups were able to collect some data on a 10 MHz low transmission. However, there is no consensus in the TWG report regarding harmful interference, except in the High Precision area, where 31 of 33 High Precision receivers failed in this configuration. All seven TWG subgroups recommend further study on this issue.
  2. LightSquared also agreed to reduce their power to a maximum of roughly 1500 watts per tower for initial deployment. This is significantly less than authorized by the FCC. However, it is exactly what LightSquared told the Departments and Agencies their planned operating power was at the beginning of the TWG and NPEF efforts and it is this level the NPEF based much of its analysis on. LightSquared was unable to reach this power level during much of the live sky testing at Holloman and in Las Vegas, so many of the NPEF test data points were taken at reduced power levels.
  3. LightSquared proposed a "standstill" for operating their second, higher frequency channel. The exact time they would need to use this second channel was undefined. However, LightSquared testified to Congress they were seeking a glide path to using it within 2-3 years and their CEO recently announced LightSquared would reach their full capacity by 2014. Additionally, the LightSquared recommendations document clarifies that:

    "LightSquared intends ultimately to deploy a network using a full complement of terrestrial frequencies operating at appropriate power levels, in order to provide LTE capacity and service levels to its customers, it will delay incorporating into its terrestrial network the upper 10 MHz of its frequencies in which transmissions may jeopardize legacy GPS usage." 1 [Emphasis Added]

    Any necessary mitigation measures would therefore need to be in place by that date. The TWG Report states that many High Precision GPS receiver applications may need as much as 10 or 15 years to design, test, and field receiver changes.

Summary

The extensive and comprehensive testing done by LightSquared, the NPEF and the GPS Industry conclusively demonstrates harmful interference from LightSquared's intended deployment of their high-power terrestrial broadband system and should not be allowed to commence commercial operations until the identified problems are resolved to the satisfaction of the FCC.

The Administration believes that we must protect existing GPS users from disruption of the services they depend on today and ensure that innovative new GPS applications can be developed in the future. At the same time, recognizing the President's instruction to identify 500 MHz of new spectrum for innovative new mobile broadband services, we will continue our efforts at more efficient use of spectrum. Therefore, in the short run, we will participate in the further testing required to establish whether there are any mitigation strategies that can enable LSQ operation in the lower 10MHz of the band. We also encourage commercial entities with interests to work with Lightsquared toward a possible resolution, though any proposed mitigation must be subjected to full testing. The challenge of meeting the President's goal also depends on long-term actions by Federal agencies in the area of research and development, procurement practices that encourage spectrally-efficient applications, and new policy development.

Further study is needed on alternative concepts, including the most recent LightSquared proposal. The National Coordination Office will assist as directed by the Space-Based PNT Executive Committee in any follow-on efforts. I thank you for this opportunity to speak on this issue of such strategic importance to this Nation and to over a billion world-wide users. I look forward to your questions.

Footnotes

  1. LightSquared Recommendation Paper filed with FCC 29 June 2011
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