Aerospace Electronic and Defense Systems: Link 16 from Space over the United States

Global Coordination for Hypersonic Missile Defense

The Department of Defense created SDA in 2019 to build a constellation of missile transport and tracking satellites in low Earth orbit on a rapid timeline, augmenting large spacecraft constellations with hundreds of relatively inexpensive small satellites. These spacecraft constitute what SDA calls its Proliferated Warfighter space architecture and will serve as the foundation for joint and multi-domain command and control capabilities.

Being able to tie the SDA PWSA in with air, ground, and naval tactical assets is important to the SDA concept to track hypersonic missiles from orbit, and coordinate interception using all existing assets. Since most of these assets are already tied in to a Link 16 JTIDS network, this would be the most obvious path. Link 16 has been implemented by most units using a frequency hopping, TDMA architecture, sometimes with stacked nets using CDMA, over tactical areas roughly 2000 NMi square. Even Taiwan, using the PoSheng program, has been using Link 16 compatible radios. Up until this time, satellite gateways have been used to route data beyond the tactical areas.

Why is this a Problem

Link 16 is a military tactical data link used primarily by NATO and allied nations for secure and jam-resistant communication and data exchange between various platforms such as aircraft, ships, and ground forces. It operates in the L-band frequency range (969-1206 MHz), which is also used by civil aeronautical radio systems and Mode S transponders. There is a frequency notch for IFF at 1090 MHz.

Interference between military Link 16 and civil aeronautical radio and Mode S can occur due to several reasons:

Frequency Overlap: Link 16 operates within the same frequency range as some civil aeronautical radio systems and Mode S transponders. If not properly managed, simultaneous transmissions in the same frequency band can lead to interference.
Signal Strength: Link 16 transmissions can be relatively powerful, especially when used between aircraft and ground stations or airborne platforms. If the Link 16 signals are strong, they might overwhelm weaker civil aviation signals, causing interference or degradation of communication or surveillance capabilities.
Spectral Interference: Even if transmissions are not directly overlapping in frequency, adjacent channel interference can still occur if the spectral characteristics of Link 16 transmissions spill over into neighboring frequency bands used by civil aeronautical radio or Mode S systems.
Jamming and Electronic Warfare: In a military context, intentional jamming or electronic warfare activities may be conducted using Link 16 frequencies, which could inadvertently affect nearby civil aviation systems operating in the same band.

To mitigate these potential interference issues, various measures can be taken:

Frequency Management: Regulators and military authorities work together to allocate and manage frequency bands to minimize interference between military and civil users.
Transmit Power Control: Military platforms using Link 16 can adjust their transmit power levels to minimize interference with nearby civil systems.
Antenna Design: Antenna design and placement can be optimized to reduce spillover of Link 16 signals into adjacent frequency bands.
Filtering and Signal Processing: Advanced filtering techniques and signal processing algorithms can be employed to mitigate interference effects.

Overall, while interference between military Link 16 and civil aeronautical radio and Mode S systems is a potential concern, careful frequency management and technological solutions can help minimize its impact and ensure the continued safe and effective operation of both military and civil communication and surveillance systems.

What would it look like?

Interference from military Link 16 transmissions to civilian aviators is a possibility, although it's typically managed through coordination efforts and technical solutions to minimize such occurrences. However, there have been reported instances where interference from military systems, including Link 16, has affected civilian aviation.

Interference from Link 16 or any other military system could manifest in several ways:

Communication Degradation: Civilian pilots or air traffic controllers might experience degraded communication quality or even loss of communication due to interference from Link 16 transmissions. This could result in garbled or unintelligible radio transmissions.
Navigation Disturbance: Interference might also affect navigation systems onboard aircraft, such as GPS receivers, potentially leading to inaccuracies in position reporting or navigation guidance.
Mode S Transponder Malfunctions: Mode S transponders, which are used in civil aviation for aircraft identification and surveillance, could be affected by interference from nearby military transmissions, leading to erratic transponder behavior or loss of Mode S functionality.
Radio Frequency Interference (RFI): Pilots or air traffic controllers might observe unexpected signals or noise on their radio frequencies, which could disrupt normal communication procedures.

If civilian aviators encounter interference believed to be caused by military transmissions, they would typically follow established reporting procedures. These procedures may vary depending on the country and the aviation authority involved, but generally, they would include:

In-Flight Reporting: Pilots experiencing interference would communicate the issue to air traffic control (ATC) via radio communication. They would describe the nature of the interference and any associated effects on their aircraft systems or communication capabilities.
Post-Flight Reporting: After landing, pilots or operators may file a formal report with the appropriate aviation authority detailing the interference incident, including the time, location, and observed effects.
Air Traffic Control Reporting: ATC personnel who receive reports of interference from pilots would likely document the incident and may also escalate the issue to higher authorities for investigation and resolution.
Aviation Authority Notification: Aviation authorities, such as the FAA in the United States or its equivalent in other countries, would be notified of interference incidents, and they would coordinate with relevant military agencies to investigate and address the issue.

It's worth noting that while interference from military systems like Link 16 is possible, it's relatively rare due to the extensive coordination efforts and technical solutions in place to minimize such occurrences. However, when interference does occur, prompt reporting and investigation help ensure that appropriate measures are taken to prevent similar incidents in the future and maintain the safety and integrity of civil aviation operations.

Working the Problem

The coordination of spectrum usage and mitigation of interference issues between military and civil aviation systems typically involves multiple agencies and organizations, both at the national and international levels. Some of the key agencies involved in the United States include:

Department of Defense (DoD): Within the U.S., the DoD is responsible for managing military spectrum usage and ensuring that it complies with regulatory requirements while also meeting operational needs. The Defense Spectrum Organization (DSO) within the DoD oversees spectrum management activities.
Federal Aviation Administration (FAA): The FAA is responsible for regulating civil aviation within the U.S., including the management of radio frequencies used for air traffic control and communication with aircraft. The FAA works closely with the military to coordinate spectrum usage and mitigate interference issues.
National Telecommunications and Information Administration (NTIA): NTIA is responsible for managing federal spectrum use and coordinating spectrum allocations among federal agencies, including the military and civilian users.
National Spectrum Consortium (NSC): The NSC is a collaboration between government, industry, and academia aimed at advancing spectrum technologies and addressing spectrum-related challenges, including interference mitigation.
NATO and International Coordination: Internationally, NATO plays a significant role in coordinating military spectrum usage among member countries. Additionally, international agreements and organizations such as the International Telecommunication Union (ITU) facilitate coordination and allocation of spectrum resources globally.

To address interference issues and ensure effective coordination between military and civil aviation systems, these agencies and organizations undertake various measures:

Spectrum Sharing Agreements: Formal agreements and protocols are established between military and civil aviation authorities to define spectrum allocations, coordinate usage, and mitigate interference.
Technical Solutions: As mentioned earlier, technical solutions such as frequency management, transmit power control, and advanced filtering techniques are implemented to minimize interference effects.
Training and Education: Both military and civil aviation personnel receive training on spectrum management and interference mitigation to ensure awareness and adherence to protocols.

Regarding Alaska and Hawaii, being part of the United States, similar coordination mechanisms and agencies are involved in managing spectrum usage and addressing interference issues. However, due to their unique geographical locations and operational considerations, specific regional arrangements and protocols may exist to address spectrum management challenges in these areas. Additionally, given Alaska's proximity to Russia, there may be additional considerations for coordination with neighboring countries to mitigate cross-border interference issues.

FAA and FCC regulation of Link 16 in CONUS

The FAA and FCC regulations regarding Link 16 usage within the continental US (CONUS) focus on ensuring compatibility and minimizing interference with civilian aviation systems due to the different purposes and frequencies used. Here's a breakdown of their roles:

Federal Aviation Administration (FAA):

Spectrum Management: The FAA allocates radio spectrum for civilian aviation use, including ADS-B and air traffic control radars. They have a vested interest in ensuring military operations using Link 16 don't create undue interference with these systems.
Compatibility Testing: The FAA works with the Department of Defense (DoD) to ensure Link 16 equipment used within CONUS is tested and certified to meet National Telecommunication and Information Administration (NTIA) standards. This certification minimizes the risk of Link 16 transmissions interfering with civilian aviation systems.
Frequency Coordination: While Link 16 typically operates outside of FAA-controlled spectrum, the FAA might be involved in coordinating with the DoD to identify potential areas of overlap or concern, especially in areas with high concentrations of civilian air traffic.

Federal Communications Commission (FCC):

Spectrum Allocation: The FCC plays a broader role in managing the electromagnetic spectrum across various sectors, including civilian aviation and the military. While they don't directly regulate Link 16 usage, they establish the overall spectrum allocation framework that the DoD must adhere to when operating within CONUS.
Enforcement: The FCC enforces regulations regarding spectrum usage to prevent unauthorized transmissions or interference with licensed services. While Link 16 is a military system, the FCC might be involved if there were any reports of Link 16 transmissions causing significant disruptions to civilian aviation communication.

Challenges and Solutions:

Limited Spectrum Availability: As the demand for radio spectrum increases, ensuring compatibility between military and civilian systems becomes more complex. The FAA and DoD are constantly working on solutions like frequency hopping techniques within Link 16 to minimize the chance of interference.
Network Evolution: The military is exploring ways to adapt Link 16 for use with smaller, low-power radios. This could potentially lead to a wider range of Link 16 operations within CONUS, requiring continued collaboration between the FAA and DoD to address potential compatibility issues.

Overall, the FAA and FCC play crucial roles in regulating Link 16 usage within CONUS to ensure it coexists peacefully with civilian aviation communication systems. It's an ongoing effort requiring cooperation and technical solutions from both military and civilian stakeholders.

Spectrum Users

The primary radio service operating in the 960 to 1215 MHz frequency range is the aeronautical radionavigation service (ARNS)

. This service is used for ground-based and airborne systems that control civilian and military aircraft in the National Airspace (NAS).

Here's a breakdown of the key systems using this band:

Distance Measuring Equipment (DME): Provides aircraft with precise information about their slant range from a ground station.
Tactical Air Navigation (TACAN): The military version of DME, offering similar functionality.
Secondary Surveillance Radar (SSR): Also known as Mode S, a ground-based radar system that interrogates aircraft transponders to identify and track their position.
Identification Friend or Foe (IFF): A military system that helps identify friendly aircraft using transponders.

Additional Allocations:

While ARNS is the primary service, there are a couple of additional allocations in this band:

Aeronautical Mobile (Route) Service (AM(R)S): This service allows for communication between aircraft and ground stations, including:
- Automatic Dependent Surveillance-Broadcast (ADS-B): Aircraft broadcast their position and other data for improved air traffic awareness.
- Universal Access Transceiver (UAT): Used for short-range communication between small aircraft.
Limited DoD Use: The Department of Defense (DoD) might operate some communication systems, like the Joint Tactical Information Distribution System (JTIDS), on a coordinated basis within this band.

Regulatory Body:

The International Telecommunication Union (ITU) allocates radio spectrum frequencies for various services globally. In the case of the 960-1215 MHz band, the ITU designates it for worldwide use by the aeronautical radionavigation service.

FCC title 47, up to date as of 3/06/2024. Title 47 was last amended 3/05/2024.

§ 87.479 Harmful interference to radionavigation land stations.

(a) Military or other Government stations have been authorized to establish wide-band systems using frequency-hopping spread spectrum techniques in the 960–1215 MHz band. Authorization for a Joint Tactical Information Distribution Systems (JTIDS) has been permitted on the basis of non-interference to the established aeronautical radionavigation service in this band. In order to accommodate the requirements for the system within the band, restrictions are imposed. Transmissions will be automatically prevented if:

(1) The frequency-hopping mode fails to distribute the JTIDS spectrum uniformly across the band;

(2) The radiated pulse varies from the specified width of 6.4 microseconds ±5%;

(3) The energy radiated within ±7 MHz of 1030 and 1090 MHz exceeds a level of 60 dB below the peak of the JTIDS spectrum as measured in a 300 kHz bandwidth. The JTIDS will be prohibited from transmitting if the time slot duty factor exceeds a 20 percent duty factor for any single user and a 40 percent composite duty factor for all JTIDS emitters in a geographic area.

(b) If radionavigation systems operating in the 960–1215 MHz band experience interference or unexplained loss of equipment performance, the situation must be reported immediately to the nearest office of the FAA, the National Telecommunications and Information Administration, Washington, DC 20504, or the nearest Federal Communications Commission field office. The following information must be provided to the extent available:

(1) Name, call sign and category of station experiencing the interference;

(2) Date and time of occurrence;

(3) Geographical location at time of occurrence;

(4) Frequency interfered with;

(5) Nature of interference; and

(6) Other particulars.

Space Development Agency aims to test Link 16 over the United States this year - ExBulletin

The head of the Space Development Agency said he plans to begin demonstrating Link 16 space-to-ground connectivity over the United States by the end of the year, provided the agency obtains the long-awaited approval from the Federal Aviation Administration.

Link 16 is a military signal commonly used by SDA satellites to connect to ground radios. U.S. forces, NATO, and their international allies rely on the capability of real-time data exchange.

The agency worked with the FAA to obtain permission to test Link 16 over national airspace, but the process took longer than expected.

Primarily, the FAA wants to make sure we have tested compatibility features on our satellites so we can't interfere with any radio navigation aids, SDA Director Derek Tournear said during a Space webinar. News on March 6. This makes sense and we are working with the FAA to put a plan in place to do so.

After launching its first satellites last April, the SDA hoped to be able to quickly validate this capability and integrate it into large-scale Department of Defense exercises, such as Northern Edge, a joint training exercise conducted in the Gulf of 'Alaska.

Instead, the agency opted to conduct initial testing in international waters starting in November. In the initial demonstration, three satellites built by Denver-based York Space Systems transmitted signals from low Earth orbit about 1,200 miles above Earth to an international test site.

The Air Force's 46th Test Squadron supported the mission from the ground.

SDA now has 27 satellites in orbit. These spacecraft are not only equipped to communicate via Link 16, but also have what are called inter-satellite optical links that allow them to share data with each other.

SDA first tested these inter-satellite links in 2021 during a demonstration mission with the Defense Advanced Research Projects Agency called Mandrake. Tournear said the agency began testing this capability with the first batch of satellites it launched and plans to expand it to the entire constellation later this summer.

As the agency works to test and demonstrate the capabilities of its first tranche of satellites, it is also preparing for its next launches, which are expected to begin in September. This mission will kick off a nearly year-long campaign to launch approximately 161 satellites from Vandenberg Space Station in California.

“We plan to have at least one of these launches by the end of this calendar year, and then the rest will be done basically as fast as we can get them through the payload processing facilities,” Tournear said .

Courtney Albon is C4ISRNET's space and emerging technologies reporter. She has covered the U.S. military since 2012, focusing on the Air Force and Space Force. She reported on some of the Department of Defense's most significant acquisition, budget and policy challenges.

Sources

1/ https://Google.com/

2/ https://www.c4isrnet.com/battlefield-tech/space/2024/03/07/space-development-agency-aims-to-test-link-16-over-us-this-year/

For the first time ever, the Space Development Agency has demonstrated the ability to connect satellites in low-Earth orbit (LEO) to ground-based radios using Link 16 tactical data links — a key step to operationalizing the agency’s future constellation of data transport satellites.

During a series of three demonstrations held Nov. 21-27, SDA connected three satellites equipped with Link 16 payloads to terrestrial radios stationed inside the territory of one of the United States’ Five Eyes allies, the agency announced Tuesday. Operators conducted passive and active network entry, acquired fine frequency synchronization and broadcasted several tactical messages, according to a press release.

The satellites used for the demonstration were made by York Space Systems and launched by SDA earlier this year as part of its Tranche 0 transport layer. The constellation of data relay systems is considered the demonstration tranche for SDA’s Proliferated Warfighter Space Architecture (PWSA) — a planned multi-layer configuration of hundreds of LEO satellites that will enable new and augmented capabilities for the military.

The PWSA is considered the backbone to the Pentagon-wide effort known as Joint All-Domain Command and Control (JADC2). The idea is to connect all of the U.S. military’s sensors and shooters under a single network, and SDA’s satellites will play a key role in enabling the rapid collection and dissemination of critical decision-making data.

Link 16 has been an integral part of realizing JADC2, as it is the only common tactical data link used across the United States’ military branches, the NATO alliance and other international allies. By deploying satellites equipped with Link 16 payloads into space, SDA aims to offer beyond-line-of-sight connectivity for warfighters.

“This is not only the first time Link 16 has been broadcast from space, but the beginning of turning the world’s finest warfighting force into a truly connected beyond line-of-sight joint force” Tournear said.

SDA began work on the tests “within 10 hours” of being cleared by the National Telecommunications Administration (NTIA) to do so, according to a press release.

In October, the agency announced it had received a waiver from NTIA via the International Telecommunication Union (ITU) — the United Nations body responsible for coordinating shared global use of the electromagnetic spectrum — to begin conducting experimental Link 16 demonstrations in international territories.

The agency sought the waiver in order to bypass regulations from the Federal Aviation Administration that prohibits transmitting space-based Link 16 over U.S. territory in order to prevent interference with radios used for the commercial aviation industry. Tournear has acknowledged in the past that the restrictions have delayed testing some of the Tranche 0 transport layer satellites since they were launched earlier this year.

“While the U.S. military and allied partners have used Link 16 aboard aircraft for years, a fully operational PWSA will require the ability to establish bi-directional communication from space to ground,” a Space Development Agency press release stated. “Testing Link 16 from space, first with an international partner and then over international water, represents a compromise position and SDA’s requirement remains to test over U.S. airspace to demonstrate the feasibility of the PWSA and its ability to deliver fire control information to the warfighter over existing tactical data networks.”

The waiver also allows SDA to conduct future demonstrations in international territories, such as those of the Five Eyes alliance that includes the United States, United Kingdom, Canada, Australia and New Zealand. The agency did not disclose the Five Eyes ally that was involved with this month’s demonstrations.

The successful Link 16 demo lays the groundwork for SDA’s first operational tranche of data transport satellites, known as Tranche 1. The agency plans to begin a monthly launch campaign of the birds — which includes 126 data relay satellites, 35 missile warning and missile-tracking satellites and 12 experimental satellites — at the end of 2024.

Demonstration included active and passive Link 16 network entry, transmitting messages to and from low Earth orbit to terrestrial radios

Date: Nov. 28, 2023

WASHINGTON, D.C. – The Space Development Agency (SDA) today announced it successfully demonstrated the first-ever Link 16 network entry through space to ground connection from low Earth orbit (LEO) to a series of receivers using terrestrial radios during three demonstrations held Nov. 21-27, 2023.

Operators working with SDA conducted both passive and active network entry, obtained fine synchronization, and transmitted multiple tactical messages from satellites using L-band radios aboard Tranche 0 (T0) Transport Layer satellites to a ground test site located within the territory of a Five Eyes partner nation.

This success represents a major milestone for T0 of the Proliferated Warfighter Space Architecture (PWSA) and demonstration of a significant new capability for the warfighter. This accomplishment also reflects a leap ahead in the Department of Defense-wide Joint All Domain Command and Control (JADC2) effort, connecting available sensors to available warfighting platforms globally. The PWSA Transport Layer is the backbone of JADC2 in space and will enable delivery of tactical messages, including beyond-line-of-sight scenarios, using Link 16 radios aboard space vehicles.

“I can’t underscore enough the significance of this technical achievement as we demonstrate the feasibility of the Proliferated Warfighter Space Architecture and its ability to deliver space-based capabilities to the warfighter over existing tactical data links,” said SDA’s director, Derek Tournear. “This is not only the first time Link 16 has been broadcast from space, but the beginning of turning the world’s finest warfighting force into a truly connected beyond line-of-sight joint force.”

Link 16 is a tactical datalink communication system used by the United States, NATO, and coalition forces to transmit and exchange real-time situational awareness data among all network participants.

For the initial Link 16 demonstration, SDA used three T0 Transport Layer satellites provided by York Space Systems, Denver, from both of the 2023 T0 launches. The 46th Test Squadron, 96th Test Wing, headquartered at Eglin Air Force Base, Florida, served as the lead developmental test organization for ground operations. The demonstration leveraged prior fixed-site risk reduction testing at the 46th Test Squadron Datalinks Test Lab and with York Space Systems.

The tests began within 10 hours of receiving approval from an allied nation after the National Telecommunications and Information Administration issued a waiver, in accordance with the International Telecommunication Union process, to transmit from space to ground. The waiver also includes permission to conduct future tests over international waters.

Due to current Federal Aviation Administration restrictions that prevent broadcasting Link 16 from space into the U.S. National Airspace System, SDA coordinated with the NTIA to obtain a waiver to transmit to a Five Eyes nation and over international water to meet established PWSA mission criteria.

While the U.S. military and allied partners have used Link 16 aboard aircraft for years, a fully operational PWSA will require the ability to establish bi-directional communication from space to ground. Testing Link 16 from space, first with an international partner and then over international water, represents a compromise position and SDA’s requirement remains to test over U.S. air space to demonstrate the feasibility of the PWSA and its ability to deliver fire control information to the warfighter over existing tactical data networks.

Tranche 0, the warfighter immersion tranche, demonstrates the feasibility of a proliferated architecture in cost, schedule, and scalability toward necessary performance for beyond-line-of-sight targeting and advanced missile detection and tracking. SDA launched the first 10 satellites in April 2023 and the next 13 in September 2023. A third launch carrying the final T0 space vehicles is scheduled for the near future. Once completed, the Tranche 0 constellation will consist of 28 satellites – 19 Transport and eight Tracking satellites, plus one ground-based testbed satellite – forming a resilient constellation in LEO.

SDA plans to field the first operational generation of the PWSA, Tranche 1, beginning in late 2024. Tranche 1 will include 126 Transport Layer satellites, 35 Tracking satellites, and 12 tactical demonstration satellites (called T1DES). Tranche 1 will be operated by SDA’s groundbreaking space operations centers based heavily on commercial space operations models.

About the Space Development Agency. As part of the U.S. Space Force, SDA is recognized as DOD’s constructive disruptor for space acquisition. SDA will accelerate delivery of needed space-based capabilities to the joint warfighter to support terrestrial missions through development, fielding, and operation of the Proliferated Warfighter Space Architecture. For more information on SDA, contact OSD.SDA.Outreach@mail.mil or visit https://www.sda.mil.

-End-

York Space Systems announces the first-ever demonstration of Link 16 technology from space on its Tranche 0 (T0) satellites. Photo: York Space Systems

The Space Development Agency (SDA) has successfully demonstrated what it claims is the first-ever Link 16 demonstration in space. The demonstrations took place over the last two weeks with three Tranche 0 Transport Layer satellites provided by York Space Systems, demonstrating network entry through space to ground connection from Low-Earth Orbit (LEO) to a series of receivers using terrestrial radios.

Link 16 is a tactical datalink communication system used by the U.S., NATO, and coalition forces to transmit and exchange real-time situational awareness data.

The SDA said in a Nov. 28 release that operators working with the Agency conducted both passive and active network entry, obtained fine synchronization, and transmitted multiple tactical messages from satellites using L-band radios aboard Tranche 0 Transport Layer satellites to a ground test site located within the territory of a Five Eyes partner nation.

“I can’t underscore enough the significance of this technical achievement as we demonstrate the feasibility of the Proliferated Warfighter Space Architecture and its ability to deliver space-based capabilities to the warfighter over existing tactical data links,” said SDA director Derek Tournear. “This is not only the first time Link 16 has been broadcast from space, but the beginning of turning the world’s finest warfighting force into a truly connected beyond line-of-sight joint force.”

The SDA does not have approval from the Federal Aviation Administration (FAA) to broadcast Link 16 from space into U.S. airspace, so SDA received a waiver from the National Telecommunications and Information Administration (NTIA) to transmit to a Five Eyes nation. The SDA said this is a “compromise position” and the Agency still has a requirement to test over U.S. air space.

The SDA said this accomplishment is also a “leap ahead” in the Department of Defense-wide Joint All Domain Command and Control (JADC2) effort, connecting available sensors to available warfighting platforms globally. The SDA’s PWSA Transport Layer is the backbone of JADC2 in space.

York Space Systems delivered the satellites used in this demonstration, as part of a contract for nine satellites awarded in August 2020. Eight satellites were launched in March 2023 by SpaceX, and one was on a SpaceX launch in September.

“We are proud to maintain our role as the most agile prime contractor to SDA as it revolutionizes rapid, dedicated space support to the combatant commands by deploying the most innovative solutions of state-of-the-art technology,” said Dirk Wallinger, CEO of York. “This accomplishment not only cements our commitment to advancing space technology but also underscores our dedication to providing cutting-edge solutions for the evolving needs of global security.”

York has a number of SDA contracts and is also developing 42 satellites for SDA’s Tranche 1 Transport Layer; 12 experimental satellites as part of the Tranche 1 Demonstration and Experimentation System (T1DES) program; and 62 satellites for Tranche 2 Alpha.

Date: October 26, 2023 | Outlet: Breaking Defense | By: Theresa Hitchens

WASHINGTON — The Space Development Agency (SDA) finally can begin testing Link-16 signals from its Transport Layer of data relay satellites in low Earth orbit, having just received approval from a key international regulatory body — although the agency remains caught up in a long-running Defense Department spat with the Federal Aviation Administration that is preventing use of the venerable military data/communications link over US territory.

“I’m glad to report SDA received approval from the International Telecommunication Union (ITU) for experimental use of Link 16 from space from the radios being flown on the York Tranche 0 Transport satellites. This approval allows SDA to test over international water and over the territory of a Five Eyes ally,” SDA Director told Breaking Defense in an email today.

He did not, however, reveal which of those allies — Australia, Canada, New Zealand and the United Kingdom — are involved.

The ITU, headquartered in Geneva, manages electromagnetic spectrum usage that crosses borders to prevent interference. Individual nations, however, are responsible for allocating frequencies for various domestic uses and ensuring against interference inside their own borders. In the case of the United States, the semi-independent Federal Communications Commission is the chief regulatory body, but coordination of spectrum use among federal agencies is managed by the National Telecommunications and Information Administration.

SDA has already launched 19 Tranche 0 Transport Layer satellites, as the first test birds for its planned mesh network constellation to provide high volume, low latency communications between sensors and shooters across all domains — with the Transport Layer deemed by the Defense Department as the backbone of its planned Joint All Domain Command and Control (JADC2) network-of-networks. York Space Systems and Lockheed Martin won contracts in 2020 to each build 10, but one of the York birds is staying on the ground as a test vehicle.

Tournear explained that “testing Link 16 from space first over international waters and with an international partner, while important, represents a compromise position for SDA and our requirement remains to test over U.S. air space in order to demonstrate the feasibility of the Proliferated Warfighter Space Architecture and its ability to deliver space-based capabilities to the warfighter over existing tactical data links.

“This testing is absolutely critical to SDA’s on-time delivery,” he stressed.

For SDA, schedule is everything — after all its motto is Semper Citius, or always faster. The agency has ambitious plans to put some 400 of its Transport Layer satellites up by the end of 2028, developing and launching new variants, or Tranches, every two years. Further, the SDA acquisition model has been embraced by the Space Force and the Pentagon as the way of the future to keep ahead of China.

To allow testing over national airspace, SDA needs to resolve its dispute with the FAA, which comes under the Department of Transportation and is responsible for commercial aviation safety, over concerns that Link 16 signals being broadcast through space could interfere with the ability of civil aircraft radios to receive air traffic control radar signals. While the Link 16 line-of-sight communications network long has been used by US military forces and NATO allies for communications among air-, sea- and ground-based platforms, it has never been used by satellites.

Moreover, sources from both organizations told Breaking Defense that Link 16 has been a subject of bitter contention between DoD and the FAA for several years. Ubiquitous military Link 16 terminals, such as the Joint Tactical Information Distribution System (JTIDS) and the Multifunctional Information Distribution System (MIDS), use the 960 – 1215 MHz frequency band, as do civil radio-navigation systems. Thus, DoD is required, under a decades-old agreement with FAA, to ensure that all radio equipment using Link 16 has been tested and certified to meet NTIA standards against frequency interference.

And both FAA and DoD sources say the Pentagon has been lackadaisical about doing so. Indeed, a senior FAA official in September 2021 — an excerpt of which was provided to Breaking Defense — called DoD officials on the carpet for allowing “hundreds” of uncertified aircraft to participate in exercises in national airspace. And as Aviation Week first reported, the FAA last January moved to limit DoD access to the Link 16 frequency bands for all military air, sea and land systems.

Tournear, on Oct. 19 during the MilSat Symposium in Mountain View, Calif., admitted that part of the Link 16 stalemate is “on DoD” for being slow to certify the SDA satellite links.

To that end, he said in today’s email, SDA “continues to pursue” a temporary frequency assignment from the FAA, that would allow it to “begin testing with the support of military partners with battle-ready DOD instrumentation and personnel trained in such testing.”

Tournear added that the agency is “actively pursuing” what is called “Electromagnetic Compatibility Features (EMCF) validation” within DoD, required to prove that its Link 16 terminals to meet non-interference standards.

“We have done and will continue to do all that is within our agency’s power to prioritize the completion of the requested testing. In the meantime, SDA has provided significant data to FAA outlining the safety of Link16 during its long history of military use,” he said.

Several government and industry sources close to SDA-FAA discussions have indicated to Breaking Defense that senior Defense and Transportation officials now have weighed in to speed a deal. One government official elaborated that there are two proposed SDA demos on the table, one of which is probably more doable than the other.

“I suspect that SDA will get some relief after they do the full testing and have some mitigations they can use over the US,” said another government source.

From Wikipedia, the free encyclopedia

Link 16 is a military tactical data link network used by NATO members and other nations, as allowed by the MIDS International Program Office (IPO). Its specification is part of the family of Tactical Data Links.

Link 16 enables military aircraft, ships, and ground forces to exchange their tactical picture in near-real time; it also supports the exchange of text messages, imagery, and voice (the latter on two digital channels: 2.4 kbit/s or 16 kbit/s in any combination). It is one of the digital services of the JTIDS / MIDS in NATO's Standardization Agreement STANAG 5516. MIL-STD-6016 is the related United States Department of Defense Link 16 MIL-STD.

Technical characteristics

Link 16 is a TDMA-based secure, jam-resistant, high-speed digital data link that operates in the radio frequency band 960–1,215 MHz, allocated in line with the International Telecommunication Union (ITU) Radio regulations to the aeronautical radionavigation service and to the radionavigation satellite service.

This frequency range limits the exchange of information to users within line-of-sight of one another, although with satellite capabilities and ad hoc protocols, it is nowadays possible to pass Link 16 data over long-haul protocols such as TCP/IP using MIL-STD 3011 (JREAP) or STANAG 5602 (SIMPLE).

It uses the transmission characteristics and protocols, conventions, and fixed-length or variable length message formats defined by MIL-STD 6016 and STANAG 5516 (formerly the JTIDS technical interface design plan). Information is typically passed at one of three data rates: 31.6, 57.6, or 115.2 kilobits per second (kbits/s), although the radios and frequency-hopping spread spectrum (FHSS) waveform itself can support throughput values well over 1 Mbit/s.^[1]

Link 16 information is primarily coded in J-series messages which are binary data words with well-defined meanings. These data words are grouped in functional areas, and allocated to network participation groups (NPG) (virtual networks), most importantly:

PPLI, or Precise Participant Location and Identification (network participation groups 5 and 6),
Surveillance (network participation group 7),
Command (Mission Management/Weapons Coordination) (network participation group 8),
(Aircraft) Control (network participation group 9),
Electronic Warfare & Coordination (network participation group 10).

Development

Link 16 is intended to advance Tactical Data Links (TDLs) as the NATO standard for data link information exchange. Link 16 equipment is located in ground, airborne, and sea-based air defense platforms and selected fighter aircraft. The U.S. industry is now developing a new Link 16 SCA compliant radio MIDS-JTRS which currently is projected to implement nine various tactical waveforms, including Link 16.^{[citation needed]}

The MIDS program, which manage the development of the communication component for Link 16, is managed by the International Program Office located in San Diego, California. In the United States, the lead Air Force command for the MIL-STD-6016 standard, plans, and requirements is the Air Force Global Cyberspace Integration Center at Langley AFB, with JTIDS program execution managed by the 653d Electronic Systems Wing at Hanscom Air Force Base near Boston, Massachusetts. The MIL-STD-6016 Standard configuration management custodian is the Defense Information Systems Agency.

Link 16 is an encrypted, jam-resistant Tactical Data Link (TDL) network used by U.S. and NATO Allies to create situational awareness among dispersed battle elements by sharing information, over a common communication link. This enables the command and control centers to create Common Operating Pictures (COP), which allows friendly forces to electronically observe the battlespace, identify threats, and acquire targets.

Link 16 communications are used to transfer real-time combat data, voice communications, imagery, and relative navigation information in the battlefield. This network uses JTIDS-compatible communication terminals to transmit and receive data messages. Via Link 16 network, messages can be broadcasted simultaneously to as many users as needed. Link 16 is a nodeless network i.e., it does not depend on any one terminal to act as a node, instead all Link 16-capable terminals act as nodes.

This Tactical Data Link (TDL) network was developed by ViaSat Inc. and Data Link Solutions (DLS) LLC to improve interoperability and support joint operations of land, sea, and air forces.

The main application of Link 16 is as an air and missile defense command and control system. This network is being used by various countries for national air defense, linking their sea- and land-based vessels, ground-based sensors, and surface-to-air missile systems. This helps them to protect their airspace by identifying threats and neutralizing them. This link network has been credited by the US Air Force as a key factor for saving lives in multiple contested environments, owing to the high degree of situational awareness the network provides.

Link 16 uses Time Division Multiple Access (TDMA) techniques to provide multiple, simultaneous communication paths through different networks by assigning each user with a unique time duration slot. The network can be used to broadcast messages between two users or from a single user to multiple users at a time. It is referred to as a nodeless network i.e. a single Link 16 terminal does not act as the node for other terminals and thus, every terminal act as a node in the network.

Link 16 data links operate in the radio frequency (RF) band from 960 to 1215 MHz as allocated by the International Telecommunications Union (ITU) radio regulations. It supports data exchange by supporting any of the three data rates: 31.6, 57.6, or 115.2 Kbps. However, by incorporating more advanced high-performance radio architectures along with physical layer techniques such as frequency hopping spread spectrum (FHSS), Link 16 network can deliver data rates of more than 1 Mbps. It supports up to 128 time slots per second, 127 networks, and is appropriately assigned among the JTIDS radio units.

The information exchanged within the Link 16 network is typically coded based on J-series messages, a set of message formats that use binary data words with well-defined meanings. The J-series messages include network management-related information such as communication control, time slot reallocation, radio relay control, connection status, network time update, acknowledgement, and route establishment. Depending on the situational scenario, the data words are grouped under different functional areas and allocated to different network participation groups (NPGs) that include:

Precise Participant Location and Identification
Real-Time Surveillance
Airborne Communications Control
Mission Management, and
Electronic Warfare and Coordination

The Link 16 network consists of multiple terminals that are located in various ground, marine, and air defense vehicles. These terminals are military-grade radio equipment designed according to the IPO office in San Diego, California. Different governing bodies formulate policies, standards, plans, and requirements for radio equipment to be used by land, sea, or airborne platforms. For instance, in the US, the lead Air Force command for the MIL-STD-6016 military standard is the Air Force Global Cyberspace Integration Center located in Boston, Massachusetts.

Types of Link 16 Network

A Link 16 network consists of three types of communication modes that determine which network type is suitable for the intended network member. All members of the network should select the same mode so that all the nodes can communicate with each other. Mode 1 refers to the normal mode of Link 16 where the network nodes or members use FHSS technique to hop between different frequencies within the 960-1215 MHz band to transmit and receive tactical messages. This hopping mechanism allows multiple Link 16 networks to transmit and receive over the channel. This type of network is called a Multi-Net. In Modes 2 and 4, members can exchange messages without using frequency hopping scheme. Modes 2 and 4 allow only a single network to share messages at a time. This type of network is called a Single-Net. Mode 3 exists and is a valid mode, but not used in practical applications.

Single Net: A Single Net indicates that each network member in a network has the same net number, security scheme, and the same frequency. Each network member is allocated a single time slot during which the messages can be sent and received. In this network, the nodes cannot perform frequency hopping as only a single frequency is used by the nodes of this network. A typical Single Net Link 16 network is shown in the figure given below.

Single Net Link 16 Network, Image Credit: Link 16 Model Architecture for Multiple Nets Simulation, IEEE

Multi Net: In a multi-net, different networks are available for different cluster platforms and each network contain its unique security authentication scheme, frequency band, and frequency hopping patterns (as there are multiple bands). This topology is used to isolate several NPGs that share the time slot across different networks, thereby eliminating or significantly reducing interference among multiple users. Frequency hopping pattern technique along with other signal processing techniques together improve the network performance of Link 16. A multi net design of Link 16 is shown in the figure given below.

Multi Net Link 16 Network, Image Credit: Link 16 Model Architecture for Multiple Nets Simulation, IEEE

Architecture of the Link 16 Network

The architecture of Link 16 defines the protocol stack that combines different network layers, algorithms used to organize the messages, encode, decode and perform various other operations to transmit and receive the messages over the tactical link effectively.

Components of Link 16 Network, Image Credit: Link 16 Model Architecture for Multiple Nets Simulation, IEEE

The protocol stack architecture for Link 16 is similar to other networking protocols (for example, OSI model) that are developed for computer networking applications. Initially, the application layer present is responsible for generating the desired tactical messages along with added security authentication schemes. The network layer receives these messages and simultaneously checks the optimal routes for the packets, and also determines whether other nodes in the network are active. The packets are accordingly addressed in this layer and then sent to the data link layer – which encodes, decodes and organizes the data as frames. It is also responsible for handling the messages to and from the physical layer and determines how nodes recover from potential interference that may occur during communication. The physical layer is the final layer of the Link 16 network and performs other signal processing-related functionalities such as channel coding and modulation of the message. The propagation delay is nothing but the wireless channel via which the message signals propagate to and from multiple nodes in the network. When the node/nodes on the other end receive the packet, they perform the reverse operation of decoding and organizing the message as shown in the above figure.

Applications of Link 16

Airborne Platforms: Link 16 network is currently used in several defense platforms in the land, sea, and air. For airborne purposes, popular aircrafts and fighter airplanes such as the B-2 Spirit, F/A-18 Hornet, F-22 Raptor, and F-35 Lightning II use Link 16 terminals on-board to communicate between them and with other gateways that extend the network to friendly forces beyond the contested region.

Maritime: Link 16 is being used in various US carrier ships, French carrier, Royal Navy ships, Japan maritime, MILGEM project class, and Swedish authorities.

Ground-based Platforms: VESTA (verification, evaluation, simulation, training, and analysis) is a minivan that mounts a radio station on top of it. This radio station supports Link 16 capabilities, which allows it to communicate with military platforms in the battlefield.

Read about other link networks - Link 11 and Link 22.

Implementation of Link-16 based Tactical Data Link System Using Software-Defined Radio

J. Suryana and D. Candra,

2019 International Conference on Electrical Engineering and Informatics (ICEEI), Bandung, Indonesia, 2019, pp. 555-559, doi: 10.1109/ICEEI47359.2019.8988856.

URL: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=8988856&isnumber=8988782

Abstract:

Frequency-hopping and direct sequence are techniques of spread spectrum of Link-16 that have good anti-jamming ability. With good anti-jamming ability, this tactical data link is used by US Navy and NATO military for secure communication.

The purposes of this research are to create a Link-16 frequency-hopping system based on software-defined radio and implement it by transmitting some of text.

This research use LabVIEW to design the system. USRP, 1 GHz antennas, and gigabit ethernet switch are used to implement this system.

Published in: 2019 International Conference on Electrical Engineering and Informatics (ICEEI)

Date of Conference: 09-10 July 2019

Date Added to IEEE Xplore: 10 February 2020

ISBN Information:

ISSN Information:

DOI: 10.1109/ICEEI47359.2019.8988856

Conference Location: Bandung, Indonesia

SECTION I.

Introduction

Link-16 is a tactical data link used by military to secure their communication. It provides two levels of security, information security and transmission security. Information security, Link-16 uses Reed-Solomon coding, matrix interleaver, and CCSK, while in transmission security, Link-16 uses the FHSS technique, which is a spread spectrum technique that is widely used in several fields, such as bluetooth and CDMA. Software-defined radio (SDR) provides some or all function embedded in hardware move into software. Therefore, SDR now is widely used because it's flexibility.

The ability of Link-16 to prevent jamming and the flexibility of SDR have become the backround of this research. The objective of this research areto design both of transmitter and receiver of Link-16 secure communication system and implement by take some of text to transmit on it. LabVIEW is used to design this system. The system includes reed solomon coding, interleaver, cyclic code-shift keying (CCSK), MSK modulation/demodulation, and frequency-hopping.

SECTION II.

Secure Communication of Link-16

A. Link-16

Link-16 is a tactical data link currently used by the United States Navy, the Joint Services, and the forces of North Atlantic Treaty Organization (NATO). Link-16 provides tactical communication that is safe and resilient to interference both on land, sea, and air. Link-16 uses Joint Tactical Information Distribution System (JTIDS) as the communication terminal to form the desired radio frequency (RF) signal [1]. Link-16 is the overall name of the data link system, whereas JTIDS is the communication component of the data link [2]. Or in other words, JTIDS is part of Link-16.

Fig. 1

Link-16 and JTIDS [3]

m(t)	is the data sequence,
Ts	is the duration of data symbols,
p(t)	is a PN spreading sequence,
fc	is the carrier signal frequency,
Θ	is the carrier signal phase angle at t=0.

Friday, March 8, 2024

Link 16 from Space over the United States

Global Coordination for Hypersonic Missile Defense

Why is this a Problem

What would it look like?

Working the Problem

FAA and FCC regulation of Link 16 in CONUS

Spectrum Users

FCC title 47, up to date as of 3/06/2024. Title 47 was last amended 3/05/2024.

§ 87.479 Harmful interference to radionavigation land stations.

Space Development Agency aims to test Link 16 over the United States this year - ExBulletin

Space Development Agency completes first space-to-ground Link 16 transmission

Space Development Agency Successfully Completes Space to Ground Transmission from Link 16 Tactical Data Network – Space Development Agency

SDA Demonstrates Link 16 in Space With York Space Systems

SDA gets OK to begin limited testing of data satellites Link 16 nodes – Space Development Agency

Link 16

Technical characteristics

Development

What is Link 16? - everything RF

Implementation of Link-16 based Tactical Data Link System Using Software-Defined Radio

Introduction

Secure Communication of Link-16

A. Link-16

B. JTIDS Design of Link-16

Spread Spectrum

A. Direct Sequence Spread Spectrum

B. Frequency-Hopping Spread Spectrum

Simulation and Implementation Results

Conclusion

Modeling and Simulation of Link-16 System in Network Simulator 2

Introduction

Related Work

The Structure of NS-2

The Layer Protocol Model of Link-16

A. Application Layer

B. Transport Layer

C. Network Layer

D. Data Link Layer

1) IFqs

2) MAC

E. Physical Layer

The Experiment and Results

A. The Methodology

B. The Processing

C. The Results

Conclusion

Open References:

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