COM Express: Scalability and flexibility for UAS sensor processing

4Unmanned Aerial System (UAS) sensors are increasing in number and complexity, burying operators and analysts beneath more data than they can handle. In response, UAS engineers need to pack more processing power behind the sensor itself, and Commercial Off-The-Shelf (COTS) vendors are leveraging the low Size, Weight, and Power (SWaP) and flexibility of COM Express to meet their scalability demands.

"We're going to find ourselves, in the not too distant future, swimming in sensors and drowning in data," said now-retired Lieutenant General David A. Deptula, Air Force Deputy Chief of Staff for Intelligence, Surveillance, and Reconnaissance (ISR) at the 2009 GEOINT Symposium. At the time, Deptula was concerned about the deployment of Wide Area Airborne Surveillance (WAAS) sensors that would increase the number of MQ-9 Reaper video feeds from one to ten, creating exponentially more than the 18,000 hours of ISR data being analyzed each month. Today, sensor systems like ARGUS-IS can provide up to 65 simultaneous video feeds and generate 5,000 hours of HD video per day. In other words, the future has arrived.

Although systems like the ARGUS-IS present untold potential for ISR efforts, transmitting and processing that amount of data far exceeds the capability of existing networks and analysis tools. Consequently, there is a desire to add more and more power onboard unmanned vehicles, but each additional sensor processor adds extra SWaP to a resource-limited environment. Quickly evolving sensor technologies also make these processors especially susceptible to , increasing development cost in times of fiscal uncertainty. This has led UAS engineers to pursue SWaP-sensitive and scalable distributed processing solutions for their designs, and COTS vendors are responding with .

"COM Express is ideal in scenarios like point of sensor processing where weight and heat dissipation from the processor are big concerns," says Jeff Porter, Senior Systems Architect at Extreme Engineering Solutions (X-ES) in Madison, WI ( "Especially in unmanned aerospace environments, the SWaP advantages with regards to COM Express are significant if you are doing distributed processing with a single processor solution. The advantage of COM Express is that the mating connector is on the opposite side of where your processor or processors are located, so it allows you to efficiently attach heat transfer mechanisms directly to the die of the processor." The fact that COM Express is designed to limit modules down to their most basic level also reduces thermal, cost, and weight inefficiencies associated with backplane-mounted systems, Porter adds.

"For SWaP-sensitive applications like unmanned vehicles, backplane-based systems such as 6U and 3U drive a lot of extra weight and cost for that backplane interconnect," says Scott Fabini, Product Line Manager at Radisys located in Hillsboro, OR ( "So for a system that is small and light, and field replaceable at the small system level like you will see in unmanned vehicles, COM Express really makes the most sense. In terms of size, the module is the right size for a mobile processor with the full memory capacity that those mobile processors offer along with Ethernet technology, so you can fit it into the palm of your hand and build your solution around it."

The COM Express specification defines four standard form factors that can be connected to an application-specific carrier board through a variety of Pin-out types (Figure 1, Table 1). This not only enables UAS designers to compromise between size, performance, and power, but also allows the processor complex to be swapped out to suit future demands, says Nigel Forrester, Product Marketing Manager at Emerson Network Power Embedded Computing, headquartered in Carlsbad, CA (

Table 1: The COM Express specification currently supports seven different Pin-out types that include standard I/O for multiple applications.

Figure 1: COM Express modules are available in several form factors, ranging from the 55 mm x 84 mm ҍiniӠto 110 mm x 155 mm ҅xtendedӠmodules. Modules in comparably sized form factors (like ҃ompactӠand ҂asicө are even interchangeable, given the selected Pin-out type and position of mounting holes.

"The biggest benefit of the COM Express type of architecture is that it does give you the ability, with a single, designed carrier, to have some flexibility and scalability in the processing capability by taking off one module and plugging in another one," Forrester says (Figure 2). "The key reality is that the most complex bit of most of these designs is the processor and memory complex, and that is effectually what a COM Express module is. It is the very high-speed fabric interfaces between processor and memory and the various standard I/O that you get, and by buying that off-the-shelf, you get a ready-to-go working subsystem that means you can then concentrate on the bits that are custom to your application Рsensors, I/O, and so on."

Scalability defends against silicon, lifecycle obsolescence

The ability to scale processing performance is critical to UAS designs, as it helps meet advancing sensor demands and guards against long-lifecycle obsolescence. Using a modular COM approach, however, the processor complex is separated from the rest of the system with a custom carrier board. This allows engineers to leverage a wide range of processor options using COM Express while mitigating obsolescence and reducing design costs.

"From a UAS perspective, because all military programs take a long time to get to deployment, sometimes that means going through a couple of processor cycles," Forrester says. "We have recently seen a couple of applications for this type of product where the customer started developing using a particular generation processor, built some prototypes, and got some traction, but by the time they got near deployment Intel or Freescale were a generation or two further along. So they actually updated their product to use the latest generation processor architecture for deployment. That again is more easily possible with a COM-type architecture because you are not tied to a single planar board."

"The basic premise of COM Express is that you have application-specific I/Os that separate it from the rapidly changing and complex processor modules, so it allows for easy future upgrades to take advantage of enhancements in performance and power," says Bill Hanrahan, Vice President of Business Development at Sealevel Systems in Liberty, SC ( "People tend to have very specific processors in mind when they are looking at applications like this. It is what they have experience with and it is highly dependent on the Operating System (OS) platform that they are using as well. Most of what we have done has been Intel architecture to-date, but certainly there is a wide variety of processors available out there in COM Express Рthings like Freescale, some of the higher end capabilities from AMD, and VIA now has some processors out there Рthis gives you a wide variety of choices."

"The industry has coalesced around a common set of I/O in the x86 (processor) realm, and I think other architectures are adopting the same I/O so it is becoming increasingly common," Fabini says. "Most of the I/O made available natively through the processor and chipset are available through the board-to-board connector of COM Express without any cabling required. COM Express brings those interfaces down to a carrier board from which a customer can design their custom, application-specific solutions around the brains and the heart, which is the COM Express module. There are no cables coming off to provide supplementary I/O like video and USB because those are all defined in the board-to-board connector of COM Express, which is really an advantage over say a PC/104 where I/O options are more limited."

Figure 2: The Radisys CEQM77 (left) is a HALT and HASS-screened Type 6 "Basic" COM Express module based on 3rd generation Intel Core i7 processor. The Emerson COMX-P40x0-ENP2 Type 6 "Basic" modules (right) are based on extended temperature range Freescale QorIQ processors.

The modularity of COM Express allows developers to select different CPUs Рeven CPUs with different footprints Рwithin the same COM Express form factor, Fabini continues. "A carrier supporting the Type 6 Pin-out and the mounting holes for both the "Basic" and "Compact" form factors Рthe most common form factors Рallows for a solution that can scale between low-power Atom and high-performance Core processor solutions (Sidebar 1). That modularity also helps in terms of product longevity Рa lot of Aerospace and Defense programs have very long product longevity. Because COM Express is an industry standard, you get commonality across even multiple processor generations, so you could upgrade from one processor generation to the next via that modular approach."

Sidebar 1: Software scalability for the edge network

COM architectures for custom COTS

The Department of Defense (DoD) has been pursuing a Modular Open Systems Approach (MOSA) to design and acquisition for some time, but the wide range of sensors on unmanned platforms makes commonality difficult. platforms makes commonality difficult. For example, video sensors can have very different I/O requirements than navigation sensors, and many of them also require I/O that does not come standard off processor chipsets. Because the COM Express carrier board is designed for customization, however, high-speed buses can be used for interface expansion to establish a communication path between the processor and sensors that require non-standard I/O. Not only does this reduce the hardware footprint, but it also allows the flexibility to meet the demands of diverse sensors within a single, configurable system.

"Typically, we would design an interface on the carrier board to the COM module using designs, and the FPGA allows you to combine multiple components into a single package to reduce component count, board size, and complexity, but it also allows you to create hardware control to exactly match the application and make it more efficient," Hanrahan says. "You can configure virtually any kind of I/O onto the carrier board through PCI Express expansion. [A] good example with the flexibility of COM Express: we have recently been working on a new UAS application where there are multiple video sources that need to be processed, and the only way to do that was with a General-Purpose GPU (GPGPU) design. We were able to put that onto a carrier board to be able to handle all of that video processing. That is a high-end, creative way of adding I/O, but there are digital/ inputs, sensor inputs, reed relay outputs, thermocouples, obviously the classic serial ports/Ethernet/USB Рit is really anything that you want or need for a UAS application."

The flexibility of COM Express can also be extended to the system level so that a single platform can accommodate multiple sensors. Engineers at Sealevel have developed COM Express-based systems with configurable I/O slots that accept eight different I/O cards, allowing the units to process data from different sensors within a small footprint (Figure 3).

Figure 3: The small-footprint Relio R2 from Sealevel Systems includes configurable I/O to suit a number of applications.

COTS sensor processing for tomorrow, today

In light of current budget uncertainty, scalable processing has become even more crucial to extracting maximum value from UAS sensors for years to come. While these sensor systems demand a flexible, small form factor compute architecture, military commanders also require technology solutions that provide Quick Reaction Capability (QRC) and comply with DoD acquisition strategies. COM Express offers both the performance and versatility to meet these challenges.

"There is a requirement for MOSA," Hanrahan says. "[Defense agencies] are embracing open standards, and COTS products are here to stay in military applications. The two driving factors are lower overall cost and faster development time. The fact that you have an industry-standard architecture in COM Express guarantees you long-term evolution and the product's available reliability because you have a long-term, wide group of companies building it. That contributes to overall lifecycle management, which is critical for military applications."