Connecting Diverse Battlefield Platforms With Link 16: Sponsored Content
Developed during the Cold War to direct U.S. and NATO fighter aircraft against the threat of incoming Soviet aircraft over Western Europe, the Link 16 datalink system is now becoming a ubiquitous situational awareness and command and control tool capable of providing all echelons and services with both theater and tactical battlespace data.
Link 16 originated in the 1970s and ’80s to provide situational awareness, tracking and targeting information from airborne warning and control system (AWACS) aircraft and warships to Air Force F-15 and Navy F-14 interceptors. The system allowed aircraft to see the radar track data of the AWACS’ radar, which had an operating range of 300 miles. An additional benefit of the system was that it allowed data link equipped aircraft to receive the radar tracking data without the need for the tactical aircraft to activate their own radar systems.
Once the system was installed on F-15s and F-14s, the ability to see the extended radar picture was revolutionary.
“I know where everything is in the area. So I’ve got great situational awareness and I can have the AWACS tell me who to go shoot, and the guy next to me sees the same thing, so he knows I’m going to shoot the guy on the right, and he can take the guy on the left and we share our data between us. And everybody knows what’s happening in the air to air battle,” says Pete Camana, Viasat Inc.’s chief technology officer for Tactical Data Links. “All platforms had the same Common Operating Picture (COP).”
In the 1990s, using Link 16 involved not only distributing the COP, but also provided ground or airborne controllers the ability to give aircraft the directional information they needed via their datalinks. The information was not distributed networkwide, instead it was more of a point-to-point operation between command and control platforms and aircraft. But by the 2000s, there was a recognized need for other platforms besides fighters to see and share the air/battlefield picture, says Andy Kessler, Viasat’s vice president and business area director for Viasat’s Next Generation Tactical Data Links.
Link 16 was the only system able to do this, and as coalition operations became more common, data sharing to create a common operating picture became a necessity. “If you wanted to play, if you had a fighter aircraft and wanted to participate [in a coalition operation], it had to have a Link 16 radio. Because if it didn’t it couldn’t be seen, it didn’t have the same picture as everybody else, and was a really disadvantaged unit that wouldn’t be allowed to participate,” says Kessler.
Over the last decade, Viasat introduced systems such as its Small Tactical Terminal (STT) to meet this growing need. Weighing 15 pounds and the size of a loaf of bread, the STT can fit in a variety of platforms. Kessler notes that it was the STT that opened the way to introducing Link 16 into a variety of new platforms, such as helicopters, unmanned aerial vehicles and ground vehicles. Link 16 capable radios have been installed on platforms as small as four-wheel all-terrain vehicles. The recently introduced AN/PRC-161 handheld radio pushes this capability further down to individual dismounted users, he says.
The expansion in the availability of Link 16 systems across platforms was accompanied by a change in how such data sharing networks were put together. Kessler notes that old Link 16 network designs supported as few as 20 or 30 simultaneous users while current state-of-the art networks can theoretically support multiple hundreds or tens of thousands of users across multiple net numbers.
Supporting Network Centric and Coalition Operations
Another factor driving the development and acquisition of new types of Link 16 systems was the Department of Defense’s (DOD’s) shift toward network-centric warfare and operations in the 2000s. This created a need for more nodes across networks to form and coordinate larger communications architectures.
A major part of the DOD’s network centric efforts were programs of records like the Joint Tactical Radio System (JTRS), which was an ambitious effort to connect all the DOD’s nodes—aircraft, ships, ground vehicles, dismounted troops together using a series of related radios operating a variety of waveforms including Link 16. The JTRS program ultimately didn’t succeed, but Kessler notes that it demonstrated the military’s determination to integrate and connect its various platforms.
One of the key technical outgrowths of this period was a significant reduction in the size, weight and power needs for tactical radios, allowing Link 16-equipped radios to be installed in ever-smaller form factors and platforms.
Traditional Link 16 operations provided users on different, mostly airborne, platforms with a theater-wide picture of friendly and enemy forces. The shift has been to support not one, but multiple Link 16 networks across a theater providing operators with both the big picture and smaller, localized tactical pictures for small (especially ground based) units, says Jon Stearn, a Viasat Link 16 technologist.
At the tactical level, these smaller units will mostly want to receive data in a point-to-point, line-of-sight manner for their specific mission. However, for forces that are more geographically dispersed, they might receive their theater/tactical information via other means, Camana explains. This also provides commanders with flexibility and options to manage bandwidth and to reuse any free spectrum on the network’s nodes and to transmit that information via gateways or satellite links.
Managing Bandwidth
This flexibility also addresses one of the limitations of Link 16, in that it has limited bandwidth which can lead to congestion on “Net Zero”—the overarching theater network. This is a valid concern, one which drove investment in advances like multi-netting and dynamic network management, Kessler explains. These developments also allow up to 127 (at the theoretical maximum) different nets to exist simultaneously in time and space with over 90 percent of this capacity never being used in normal operating networks. This duality—network congestion on Net Zero while also having a huge potential of untapped capacity—is one of the challenges when thinking about Link 16 applications, he says.
“One of the big thrusts that a lot of people are now starting to understand is the opportunity to utilize that unused networkwide capacity on those different net numbers, while at the same time dealing with what is a real congestion problem on Net Zero,” Kessler adds.
At the smaller tactical levels, Link 16 does what it did for AWACS-directed fighters in the 1980s and ’90s—it allows everyone on the network to see all the other Link 16-enabled platforms. In modern applications, this allows an infantry commander on the ground to directly communicate, computer-to-computer with an overhead aircraft, as well as communicate with other ground forces in a resilient manner as part of a communications PACE (Primary, Alternate, Contingency, and Emergency) plan. This kind of direct communication helps to eliminate any misunderstandings that might arise from traditional voice-only messaging in the confusion of a military engagement.
Link 16 is also very resilient to jamming and can operate in a heavily contested RF environment, something that wasn’t feasible with other communications networks, Stearn says.
A great advantage of Link 16 is forward and backwards interoperability. For example, Kessler notes that AN/PRC-161 handheld Link 16 radio operators can use an Android tablet to directly transmit tactical data to an overhead aircraft’s computer via the datalink.
“Once you get it [Link 16], you’re a player and part of the club, you get that [tactical] information for free. Not only are you able to subscribe to the information that’s there, but you’re able to publish information that’s consumed for free by those other platforms. It’s an X-squared effect: not only are things better for me because of what I know, things are better for me because of what everybody else knows about me,” Kessler says.
Another aspect Link 16 shares with the new generation of military waveforms is its inherent low probability of intercept (LPI) and low probability of detection (LPD) capability, which allows platforms using it to operate and survive in harsh electromagnetic environments through its jam resistance. Some of the receiver processing techniques being fielded on software defined radios using these new waveforms are also applicable to Link 16, Camana says.
LPI can be achieved by using a directional antenna and Link 16 can also be power controlled, which hasn’t been the traditional approach to using the system, notes Camana. However, many of the concepts being considered for new military waveforms also apply to Link 16, making the system backwards interoperable with all or most of the platforms currently in the military’s inventory, he says.
“Can we do everything on Link 16 that the most advanced theoretical waveforms can do? No. But can we realize 80 or 90 percent of what they’re doing with the Link 16 waveform? Yes. And we get the multiplier of being forwards and backwards compatible, and having the power of the network,” explains Camana.
Growing Use Across Platforms
One of the challenges Link 16 currently faces is that it isn’t a program of record itself, says Stearn. But he adds that it’s part of many platform implementations and is being included on a growing number of military radio programs.
Link 16 also has features such as dynamic network and bandwidth management that make it attractive to communications programs. This is especially important as the DOD moves away from single, monolithic theater Link 16 networks to smaller networks and nodes covering less geography that may need to interact with neighboring networks when necessary.
“There’s lot of features in Link 16 that have not been traditionally used but are there for use. And as we get even more users, it makes more sense to use them,” Stearn says.
For more information on Viasat’s advanced Link 16 capabilities, please visit www.viasat.com/link-16
