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By Eur Ing Paul Parkinson, Senior Systems Architect, Wind River


The expanded development and diverse mission operations of unmanned air vehicles (UAV) has exposed information security (InfoSec) and communication security (ComSec) concerns that are not easily addressed in traditional federated or currently deployed integrated modular avionics (IMA) systems. The need to operate military UAVs in civil airspace communicating over unclassified links to foreign air traffic control systems and keep sensitive and/or classified information separated without increasing space, weight, and power (SWaP) poses challenges to UAV systems architecture. In this paper the MILS (multiple independent levels of security) software architecture is discussed in relation to how it can fulfil these disparate UAV system design requirements.

The Advent of Unmanned Systems

In recent years, there has been very rapid growth in the development and deployment of UAVs. These unmanned systems are being used in a very diverse range of roles, from urban reconnaissance to high-altitude, long-endurance (HALE) operations. In many cases, program developments have been driven primarily by operational requirements to deploy systems in environments deemed to be too hazardous or too hostile for human operators. However, the development of these unmanned systems has not overcome the technical challenges to fulfil these operational requirements along with producing additional tangible benefits.

UAVs do not need to be encumbered by life-support systems for a human operator, often enabling the design to be physically smaller and lighter than a manned vehicle. In the case of military UAVs, this can contribute toward a reduced radar cross-section (RCS) resulting in a lower probability of intercept (LPI) by hostile forces. This can also reduce the need to use stealth, supersonic, or hypersonic capabilities currently used for high-altitude spy planes (such as the U-2, SR-71, and successor aircraft).

UAVs are also capable of performing much longer, extended missions than those restricted by the limits of an individual human operator. This is because they provide the ability to coordinate operation through a number of remote operators working in shifts. This capability provides military planners with the ability to have increased loiter time on target, which can be invaluable for a changing situation on the ground.

There is also the additional benefit that military UAVs can be used in theaters that present a higher risk of intercept than would be acceptable for manned aircraft, including airborne reconnaissance to provide invaluable battlefield intelligence. They can even be used as active decoys, penetrating deep into enemy territory in offensive air operations1. Armed combat variants are now being deployed (usually referred to as unmanned combat air vehicles or UCAVs).

Modular Avionics in the Extreme

Aircraft systems are becoming more and more complex in order to implement more and more advanced functionality. As a result, the software content in these systems continues to grow at an astonishing rate. For example, in the 1980s, the software content in the avionics systems of military fast jets was around 100,000 source lines of code (SLOC), and this has increased significantly in recent years. It has been estimated that the F-35 Lightning II will have around 7 million SLOC.

The increasing complexity of these systems has required an increase in system performance and therefore the physical footprint in terms of SWaP. However, there are pressing requirements to reduce the physical footprint of systems within aircraft and especially within UAVs due to their physical size constraints. So a significant increase in processing density is essential.

This problem is being addressed through the adoption of IMA. This architecture comprises common computing platforms that can host multiple applications co

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