Advanced Data Links

The idea of emissions control, or EMCON, is not new. 

Signature management across the electromagnetic spectrum remains a central military planning consideration. It has, however, taken on a new dimension with the introduction of networked, low observable platforms such as the F-22A Raptor and F-35 Lightning II. 

The all-aspect signature management that underpins these platforms’ stealth demands communications and data links that match or exceed the airframe and propulsion signature reduction features built into the aircraft. Yet those same communications must satisfy their voracious appetite for information if they are to best exploit their advanced processing capabilities. 

The joint force relies on tactical data links (TDL) to exchange time-critical data and gain an information advantage and operational edge over an adversary. The reliance on datalinks is not in itself a bad thing. There are, however, operationally significant challenges that must be managed.

Tactical datalinks have vulnerabilities when it comes to preventing or reducing emissions. The ADF, like many of its allies, must constantly remain ahead of competitors who seek to exploit these emissions, either detected or intercepted. As explained in the Sept-Oct 2020 issue of ADBR, Link 22 is a new means of connecting the joint force for beyond line-of-sight (BLOS) operations using the high-frequency media path. This means it could be vulnerable to detection, interception, and then disruption. 

Most adversaries are equipped with tactical mobile jammers and signals intelligence (SIGINT) receivers. The operating frequencies of Link 16 are well-known and, while there are a series of protective measures such as encryption, an adversary could use jammers to disrupt Link 16 data exchange. Furthermore, they could use SIGINT receivers to detect and potentially locate participating platforms by detecting the signals emitted. Therefore, platform survivability is at stake.

This has given rise to the development of new datalink systems that feature signature-reduction while enabling effective communication. Two key approaches to reduce datalink signatures are low probability of detection (LPD) and low probability of intercept (LPI) techniques. 

Some of the simpler methods that support LPD & LPI include dispersing transmitted energy across a frequency band, also known as spread spectrum, and using frequency or time hopping to make jamming more difficult. However, these techniques offer limited protection from detection by advanced SIGINT capabilities. 

Efficiently designed directional antennae operating at lower power output levels can make detection by SIGINT platforms more difficult. However, any reduction in power makes the role of a jammer much easier. Avoiding detection while mitigating the threat of jamming require demand trade-offs between signal strength and directionality. 

NEXT GENERATION AIRCRAFT 
One of the F-35’s most advanced capabilities is its Multifunction Advanced Data Link (MADL). This waveform encompasses LPD & LPI methods and allows the F-35 to both fuse and securely exchange sensor, target, and situational awareness information with other F-35s via what could be described as a directional narrow beam connection. 

Operating in the K-Band, it supports a high data-rate using the D-Series message catalogue. The key component is the Northrop Grumman Communications, Navigation, and Identification (CNI) system which provides a software-defined capability that allows the F-35 to employ a variety of features while maintaining low-observability. 

These features offer an array of capabilities via 27 software-defined cards. This flexibility enables growth in the capability, as it can easily be upgraded to remain apace with advancing technologies. It is currently unknown if any other platform is or will be equipped with MADL.

The F-22A on the other hand is equipped with the unique-to-Raptor Intra-Flight Data Link (IFDL) which has similar capabilities and features to MADL, including LPI and LPD. However, the IFDL is waveform-incompatible with MADL, thus two of the most advanced information processing platforms on the planet cannot exchange information via their advanced datalinks. 

The USAF is conducting a series of test events to improve data exchange interoperability by experimenting with gateways that allow a translation to take place between IFDL and MADL. As positive as this sounds, it seems a sub-optimal approach to ensuring these 5th generation fighter aircraft can exchange data, and thereby maximise their advanced processing while maintaining stealth. 

Both the F-35 and the F-22A are equipped with Link 16, but the Raptor is a receive-only platform and, even if it could transmit, would it really want to? Just like the F-35, operational considerations will influence whether such a stealth asset will give up its unique advantage. Broadcasting on well-known Link 16 frequencies via an omni-directional antenna would quickly reduce operational effectiveness within the order of battle. 

While the F-35, F-22A Raptor, and B-2A Spirit platforms remain pre-eminent when it comes to signature reduction, other nations have developed their own or have stolen stealth know-how and combined it with their own advanced weapons systems. But it remains to be seen if competitors are able to effectively exploit the advanced datalinks that support and protect these individual platforms. 

The challenge for Australia is similar. How does it balance the imperative exchange of data across all platforms without compromising the unique strengths of individual systems? Without the information exchange provided by tactical datalinks across the joint force, the force isn’t joint. 

But the enormous effort and investment in acquiring and generating stealth capabilities may come to nought due to the limitations of legacy platforms. Balancing these competing demands will be a continual challenge, influenced by the operating environment, the objectives to be achieved, the resources and time available, and the acceptable levels of risk. 

These are the same enduring factors that drive all aspects of operations planning, and simply highlight that network management and planning are an integral part of 5th generation operations and force packaging. 

This article appeared in the November/December 2020 issue of ADBR.