Identification, Friend or Foe (IFF) Modeling

August 24, 2021 by Leslie Provenzano

Identification, Friend or Foe (IFF) is an aircraft identification system designed for command and control. It enables military and civilian Air Traffic Control (ATC) interrogation systems to identify aircraft, vehicles, or forces as friendly and to determine their bearing and range from the interrogator. These systems are necessary to prevent friendly fire and help eliminate casualties by detecting dangers and providing vital insight for decision making.

The US Military, along with NATO, started development on a new secure mode of IFF in the 1990s known as Mode 5. It is used in ATC systems and will replace the current Mark XII waveform. Mode 5 uses modern modulation, coding, and cryptographic techniques to overcome performance and security limitations in the Mark XII waveform. Additionally, Mode 5 systems provide expanded data handling capabilities to securely pass the GPS position coordinates and other extended data. The Mode 5 system also uses interference-reducing techniques, which allow additional data transmissions to be overlaid on existing Air Traffic Control (ATC) system frequencies without significantly increasing interference.

The goal is to provide enhanced performance, security, and expanded data handling capabilities. Therefore, there is a need for comprehensive testing of the new IFF systems and test support equipment prior to the widespread deployment of the technology. On the civilian side, the Federal Aviation Administration (FAA) has mandated the use of Automatic Dependent Surveillance-Broadcast (ADS-B) for civilian ATC systems; therefore, a similar need exists for testing ADS-B systems. It is essential to ensure that the IFF system can operate effectively under a variety of conditions that include high-density and high-volume air traffic scenarios. This requires comprehensive at-scale testing with a large number of multiple aircraft systems generating signals for the live interrogator/receiver.

Deployment of the IFF and ADS-B systems without such comprehensive testing may leave operational flaws undetected until the system has been deployed, leading to potential safety concerns and significant costs to address the deficiencies post-deployment.

IFF Library Overview

To meet these needs, SCALABLE has developed a Live-Virtual-Constructive (LVC) based testing framework called the IFF Library. The IFF Library has the following capabilities:

  • High-fidelity model of Mode 5 IFF communication system including a high-fidelity model of the squitter transmitter and receiver with bit-correct data structures and logic for selected AIMS and MIL-STD messages.
  • Equivalent civilian Automatic Dependent Surveillance-Broadcast (ADS-B) models and ability to mix ADS-B and Mode 5 transmissions.
  • Software Defined Radio (SDR) functionality to synthesize Mode 5 and ADS-B signals on the same channel.
  • An external interface to interoperate with live applications to display tracks generated by the simulated aircraft radios.

Comprehensive testing must be done at scale with a large number of multiple aircraft systems generating signals for the live interrogator/receiver to ensure that the IFF system can operate effectively under a variety of conditions. Deployment of the IFF and ADS-B systems without such comprehensive testing may leave operational flaws undetected until the system has been deployed, leading to potential safety concerns and significant costs to address the deficiencies post-deployment. At the same time, it is cost prohibitive to test these systems with live aircraft at anywhere close to the scale of operations that will mimic peak usage.

SCALABLE has designed and developed a fully functional prototype of the IFF Library (including hardware) solution which includes the following primary components:

  • A scalable Mode 5 model implementation in JSTEN that can operate in real-time and effectively scale to assess scenarios with 1000+ simulated transmitters
  • A software defined radio implementation for the Mode 5 RF injection integrated with the encryption hardware
  • Interfaces to selected SAF tools (e.g., OneSAF) to support dynamic platform position updates and potentially traffic inputs
  • Scenario visualization interface
  • Detailed data collection and test report generation capability

Use Cases

Figure 1 illustrates the concept of operation of the IFF Library.

Figure 1: Modeling an ATC System Using the IFF Library

In this mode, the simulation can be driven by internally defined motion or by external CGF tools (e.g., OneSAF) to realistically simulate the aircraft mobility for a given operational scenario.  ADS-B tracks can also be downloaded from the FAA and replayed in simulation time.  Any message transmissions initiated by the IFF transmitters in the simulation are subjected to realistic RF propagation effects based on platform and environmental characteristics that include aircraft speeds, the antenna type, and orientation, and obstacles due to terrain that exist in the transmission path between the simulated transmitter and a representation of the live receiver in the simulation. The resulting path loss and signal attenuation determine if the message is received at the receiver and the transmission delay it is likely to experience. The messages received successfully at the simulated receiver may optionally be then injected into the live Mode 5 receiver via a coaxial cable connection between the machine running the simulation and the live Mode 5 receiver equipment, or by an actual over-the-air transmission at 1030/1090 MHz via a GNU Radio driven software defined radio hardware such as the Universal Software Radio Peripheral (USRP).

Contact us for a live demo of our IFF capabilities.

SCALABLE has proven communications simulation technology for planning and evaluating advanced large-scale network concepts and architectures. SCALABLE has demonstrated the most advanced emulation-based solutions for cyber training & assessment.