Military Embedded Systems

Open architecture COTS form factors: The optimal approach for UAV/UAS applications


August 26, 2010

David French


A broad range of embedded computing form factor options matches diverse airframe size and mission requirements for today?s UAVs and UASs.

“We have just won a war with a lot of heroes flying around in planes. The next war may be fought by airplanes with no men in them at all. It certainly will be fought with planes so far superior to those we have now that there will be no basis for comparison. Take everything you’ve learned about aviation in war, throw it out of the window, and let’s go to work on tomorrow’s aviation. It will be different from anything the world has ever seen,” said Gen Hap Arnold, U.S. Army Air Forces (USAAF), on VJ Day, 1945[1].

Unmanned Aerial Vehicles (UAVs) and Unmanned Aerial Systems (UASs) are proving General Arnold’s visionary thinking, as they emerge as two of today’s most adaptable, in-demand military technologies. These programs offer endurance, efficiency, flexible mission management, attack capability, information collection, and connectivity: valuable attributes that enable military command to effectively and safely multiply forces. The vision for these unmanned systems is to harness their intrinsic benefits for automated, modular, globally connected and sustainable multi-mission purposes that maximize force utilization. The U.S. Air Force’s UAS Flight Plan has predicted a leaner, more adaptable and efficient air force encompassing a broad family of unmanned aircraft that reaches well past the earliest strictly surveillance-based predecessors.

As new UAS applications go beyond mere surveillance to encompass small man-portable vehicles (even micro- and nano-sized), medium “fighter sized” vehicles, large “tanker sized” vehicles, and special vehicles with unique capabilities, there is a significant requirement to expand the embedded computing technology that controls them. This increased diversity in UAS applications and functionality supports the U.S. DoD’s long-term commitment to sophisticated, technology-supported warfare. Making this commitment a reality will challenge future UAS designs to combine multi-mission, ultra-rugged, net-centric, modular, open architecture features capable of carrying any standard payload within their given performance envelope.

Embedded technology advancements and a broad range of COTS form factors have become key enablers of new modular UAS/UAV platforms. The good news is that UAS designers have a wide arsenal of open architecture COTS form factors that will satisfy evolving SWaP, performance, space constraint, extended temperature, and sophisticated signal-processing requirements. Determining the optimal form factor for a particular UAS/UAV design requires a deep level of expertise and an understanding of the advantages and design trade-offs provided by the range of embedded computing alternatives.

Open architecture COTS form factor options

In this maze of embedded design challenges, sticking to a single computing form factor for all UAV/UAS designs is not really a relevant approach. Instead, designers must leverage and evaluate a varied slate of standards-based options. The optimal embedded computing choice meets the desired program and UAS/UAV platform goals by matching the airframe requirements and creating interoperable, COTS-based systems that integrate with the Joint Forces’ worldwide information network. This includes adding capabilities such as payload, networking, and effective data processing, analysis, and dissemination. The demand is rising for net-centric implementations that enable soldiers, military systems, and equipment to share real-time information with higher bandwidth and increased computing performance. So is the need to upgrade embedded computers in existing deployed units.

From the ultra-rugged VPX to small Computers-on-Module (COMs), high-bandwidth MicroTCA, and proven CompactPCI, designers now have a richer and broader variety of proven COTS embedded computing form factor options. Designers can also leverage continued advancements to standards-based technologies to achieve their varied and evolving UAS/UAV platform objectives. Since the landscape of available open architecture form factors covers a wide set of technologies, it is wise to evaluate each on its strengths for a particular application.

VPX for high-speed signal processing

UAS payloads (short-, medium-, or long-range airframes) may include communications, signals intelligence, high-resolution Synthetic Aperture Radar (SAR), imaging systems, or even weaponry. Improved situational awareness is the primary goal, downloading compressed, live video or other information to a portable device on the ground. As a result, image compression and bandwidth demand much of the system designer’s attention. Largely based on its ability to provide high-frequency processing as well as a reliable fabric solution, rugged VPX is emerging as an ideal platform for these data-intensive UAV applications (Figure 1).


Figure 1: Rugged VPX technologies are emerging as an ideal platform for data-intensive UAV applications. Pictured: The Kontron VPX Blade VX6060, with two independently implemented Intel Core i7 processing nodes linked to an Ethernet and PCIe infrastructure.




VPX enables higher performance processing per slot but also higher-speed interconnects between processing and I/O elements using PCIe, 10 GbE, or Serial RapidIO. These interconnects provide 10 Gbps between elements or several hundred GBps in aggregate, depending on the system implementation. Handling the increased signal rates that characterize high-bandwidth, high-performance UAS applications, VPX systems can achieve greater than 5 GBps using a number of different serial fabric technologies. Full-mesh architectures, not available in VMEbus systems, enable system aggregate bandwidth greater than 100 GBps.

The VPX platform builds on VME’s processing capabilities, combining robustness and excellent EMC – fundamental strengths of the VMEbus architecture – with new high-bandwidth serial interconnects for high-speed differential signaling over the backplane. VPX leverages more I/O per slot – for example, taking data in a fast 10 GbE data rate and dispatching it to several processors that manage the workload in parallel – and maximizes higher computing density from available processors and chipsets. This is in contrast to VMEbus platforms primarily using parallel bus technology that provided successive bandwidth improvement over the years, starting with 40 MBps and evolving to today’s 320 MBps.

As an example of VPX’s suitability for applications that require video-streaming capabilities, VPX can be integrated with codecs including ITU-T H.263, H.264 (MPEG-4 part 10), and JPEG2000 to provide very efficient image compression. The H.264 codec is particularly optimized for streaming and offers extremely efficient compression by providing the capability to trade off image quality or compression as the available bandwidth changes. This flexibility makes using VPX with this codec a viable option for supporting UAS video payload applications that can be required to operate over a number of data link options and operational scenarios.

MicroTCA meets rugged, high-bandwidth needs

Range and altitude may be deciding factors in choosing an embedded computing form factor. UAS platforms that need to perform in longer-range missions will typically need to operate at higher altitudes as well (Figure 2). Then there are range and altitude requirements for extended loitering capabilities, too, which all translates into the need for a rugged and reliable form factor in terms of power, weight, and thermal management.


Figure 2: Vertical Takeoff and Landing Tactical UAVs (VTUAVs) can take off and land in rugged or unimproved terrain in close proximity to troop and tactical operations centers. Acting as a communications node within the Joint Tactical Radio System (JTRS), they extend both network effectiveness and flexibility.




A case in point is that a larger airframe may have an avionics bay containing forced-air cooling, where many smaller airframes do not offer that capacity. Rugged air-cooled MicroTCA (MTCA.1), hardened MicroTCA (MTCA.2), and conduction-cooled MicroTCA (MTCA.3) leverage the ANSI/VITA 47 specification to define these types of environmental requirements.

MTCA.1 extends MicroTCA into more rugged military environments as defined by ANSI/VITA 47’s EAC6 environmental class and V2 vibration class. The new MTCA.3 spec is now underway with PICMG and is expected to define a conduction-cooled interface that meets the most extreme thermal, shock, and vibration profiles defined in ANSI/VITA 47 (that is, performing in conduction-cooled systems with no airflow within sealed environments, common to space-constrained UAS applications).

These options highlight MicroTCA as a cost-effective alternative to the ultra-rugged VPX; MicroTCA is characterized by high processing capacity, extremely high communication bandwidth, and high availability designed into a small form factor. A 3U or 4U system, tapping up to 12 compute blades on a single backplane all potentially using a multicore processor, could be integrated with as many as 24 cores in a very small footprint. Designersusing MicroTCA can also leverage as many as 21 high-speed serial connections on the backplane, each delivering bandwidth of 2.5 Gbps. Depending on the airframe or its ground control system, as well as how each system is implemented, an extensive range of MicroTCA-based communications bandwidth capacities is available, ranging from 40 Gbps to >1 Tbps. When contrasted to VPX’s 80 GBps aggregate bandwidth, designers need to additionally understand that VPX also defines a larger quantity of user I/O options not defined in the MicroTCA spec.

CompactPCI: Proven rugged, long-term reliability

CompactPCI also provides notable bandwidth, performance, and cooling options. Its status as a mainstay UAS platform is based on advantages such as its inherent ruggedness, rear I/O, support for the full range of high-speed interfaces, and an extensive range of PCI-compatible software. With improvements in space and energy savings enabled by advancements such as Intel’s 32 nm, Atom-based low-power processors and multicore architectures, many designers consider CompactPCI ideal for a self-contained network implementation managing multiple blades communicating over GbE in a single backplane. Even though CompactPCI is largely limited to 1 GB speeds and parallel PCI – dramatically reduced bandwidth as compared to a VPX backplane – it uses the same 3U/6U mechanics and so can readily accommodate the same rugged environments.

Integrated 32 nm processor technology along with multicore performance benefits mean CompactPCI systems can enable new and more compute-intensive applications such as UAVs and UASs, characterized by extreme conditions, round-the-clock performance, and high-speed processing. Multicore processor technologies and power-aware designs are enabling higher overall performance within the same or lower thermal and power envelope, essentially extending the life of existing form factor standards such as CompactPCI and delivering options for upgrading and extending the life of currently deployed systems. Existing systems could trim 10 CompactPCI 2.16 single-core boards down to just two dual- or quad-core boards. Multiple quad-core boards can be implemented when ultra-high performance is required for extremely data hungry applications common to UASs. And low-power CompactPCI boards achieve suitable performance-to-power ratios based on passive cooling for convection-cooled and forced-airflow applications (Table 1).


Table 1: Performance-to-power ratios have improved, even within the past five years. In the same Thermal Design Power (TDP) envelope, designers can now get a 24x performance increase using processors capable of operating in extended-temperature environments.

(Click graphic to zoom by 1.9x)




Computer-On-Modules: Power and performance for constrained spaces

The small UAS class of airframes represents profound technological advancements in air warfare, with proven utility and capability during the earliest phases of Operation Iraqi Freedom. Providing not only the commander but individual service members with lifesaving situational awareness, full-motion video is perhaps the most important mission of these small but imperative UAV devices.

Based on the compact Intel Atom solution, these COMs balance performance with the ability to satisfy SWaP requirements critical to these small and extremely energy-efficient UAS devices. For instance, the 45nm Intel Atom processor architecture achieves fast performance (with clock speeds between 1.1 GHz and 1.6 GHz) in a sub W thermal power envelope. It features a power-optimized front side bus of up to 533 MHz for faster data transfer. This in turn enables the development of energy-saving, high-end graphics devices such as those in UAVs or UASs without leaving the safe and proven development path of COMs as an established and future-proof industry standard. Available now, COMs that integrate Intel Core i7 advancements deliver even greater design flexibility in terms of performance and onboard features. Performance-per-watt is as good as it gets, with virtually no performance trade-offs via the enhanced I/O capabilities.

Overall, Core i7-based platforms incorporate a more efficient two-chip solution for better signal integrity and minimized board space, in turn enabling higher performance in smaller, power-constrained portable designs. For visually demanding UAV/UAS applications such as compute- and graphics-intensive imaging or persistent surveillance applications, this technology also delivers significantly enhanced integrated graphics capabilities and data flow performance.

Planning ahead

The U.S. Air Force’s Flight Plan states that “standards and interoperability are keys to the Joint Forces gaining Information Superiority in today’s network enabled environment.”[2] These goals mandate a common set of airframes within a family of systems, all based on standard interfaces and interoperable plug-and-play payloads that are tailored to support one or more of the Joint Forces’ priorities. This strategy represents a major shift that is significant for military embedded designers. No longer a platform-centricmodel, achieving success means designers must address not only how the system works but also how it integrates with the Joint Forces’ worldwide information network.

With assorted and extensive application requirements that continue to evolve, designers of UASs/UAVs are wise to take an open architecture COTS form factor approach such as VPX, MicroTCA, CompactPCI, or COMs. These can deliver advancements in greater compute density, low power consumption, small footprint, enhanced thermal management, increased I/O bandwidth, and optimized processing architectures. The result: Designers have a wealth of options for proven modular systems that meet their design and platform objectives.

David French is Director of Military and Aerospace Business Development at Kontron. He has more than 25 years of experience in the embedded computing industry across multiple market verticals with significant experience in defense and aerospace electronics. David has worked in both engineering and sales/business development capacities. He holds a BSEE from San Diego State University and an MSEE from Rensselaer Polytechnic Institute. He can be contacted at [email protected].

Kontron 858-677-0877


[1] Words on War: Military Quotes from Ancient Times to the Present, by Jay Shafritz, Prentice Hall, New York, 1990, pg. 104.

[2] USAF Flight Plan,, page 56.


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