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Deeply rooted in VME and CompactPCI platforms, military embedded design is undergoing a noticeable shift. Modern warfare initiatives are driving designers to find more bandwidth, while at the same time moving to small form factor systems with high availability and proven ruggedness. With diverse requirements ranging from integrated weapons control to handheld GPS-based radios to real-time sharing of surveillance data, military communications are going network-centric.
The latest systems link individual soldiers to vehicles, aircraft, ships and command centers, and more complex systems also require greater communication bandwidth, broader functionality and smaller footprints. Factor in the need for mobility, flexibility and ruggedness, and designers are recognizing high-end processing in small form factors as a key design factor moving forward. Modern warfare systems must balance these issues with the need for standards-based solutions that can be developed and deployed within specific timeframes and budgets.
Initiatives such as the Army’s FCS (Future Combat Systems), JTRS (Joint Tactical Radio System) and WIN-T (Warfighter Information Network – Tactical) (Figure 1), require significantly greater bandwidth, far beyond technologies found on earlier battlefields and are an ideal fit for the ATCA and MicroTCA platforms. Moving things a step further, recently announced MicroTCA specifications take the extensive knowledge and practices developed with ATCA and AdvancedMC, and apply them to smaller form factor, plug-in systems. High bandwidth in a small form factor, coupled with standards development, proven ruggedness, high availability and multicore support is driving ATCA and its smaller counterpart MicroTCA forward, with MicroTCA especially showing great promise in rugged military system design.
MicroTCA boards and systems are designed to meet NEBS Level 3 requirements, addressing demands such as thermal margins, fire suppression, emissions and the ability to continue working even during a severe earthquake. As a result, standard MicroTCA systems are beyond rugged enough for environments such as ground installations or on certain types of airborne platforms. It’s the further ruggedization of MicroTCA that holds greater interest for the military embedded design community.
A range of standardized rugged implementations of MicroTCA is being driven forward by a committee of the PICMG standards body. These include rugged air-cooled MicroTCA (MTCA.1), hardened MicroTCA for military applications (MTCA.2), and conduction-cooled MicroTCA (MTCA.3); MTCA.1 was in fact ratified very recently. These new standards leverage the ANSI /VITA 47 specification to define environmental requirements. For example, MTCA.1 extends MicroTCA into more rugged military environments as defined by ANSI/VITA 47’s EAC6 environmental class and V2 vibration class.
MTCA.3, now underway with PICMG, defines a conduction-cooled interface that allows AMCs to meet the most extreme thermal, shock and vibration profiles defined in ANSI/VITA 47 (such as performing in conduction-cooled systems with no airflow at all in sealed environments). Designers can anticipate these efforts will link VPX and MicroTCA as competing design options (see sidebar “MicroTCA or VPX?”). Early results show promise and rugged MicroTCA options are already available in advance of these standards.
MicroTCA boards and systems are available for use in high shock and vibration air-cooled environments through use of shock isolation, all soldered components and board locking mechanisms. Similarly, solutions available today provide conduction-cooled MicroTCA through the use of standard AdvancedMCs surrounded by a “clamshell” with wedge locks for thermal dissipation.
James Robles, senior technical fellow for The Boeing Company, explains that “telecommunications architectures like MicroTCA and AdvancedTCA are attractive to Boeing because we know they won’t go away. We like what we see in the NEBS, and of course there is good hardware available on the market.”
MicroTCA in Action
The WIN-T program is intended to be mobile, flexible and rugged enough to maintain the highest levels of situational awareness through all kinds of battlefield conditions; significant portions of the network are in fact using the MicroTCA architecture. MicroTCA offers native support of Internet-protocol-based network topologies, offering designers a powerful solution given the network-centric nature of WIN-T.
From a management perspective, the network on a MicroTCA backplane looks like any LAN found at a typical office since each MicroTCA blade is connected on a standard network. The primary benefit here is simplified software development as compared to other architectures.
In VME or even standard CompactPCI implementations, anything being done to software on one blade can potentially affect software on the other blades. In contrast, MicroTCA’s software development model is less complex; software appears as a simple network and is much more like a PC running software on a desktop. As a result, designers avoid the complicated interconnect issues that require management during the software development phase with VME or CompactPCI architectures.
Test results published by BAE Systems show that MicroTCA is rugged enough for even ground mobile applications (Figures 2 and 3). Findings verified the MicroTCA edge connector sufficiently accommodated the vibration profiles required for the WIN-T JC4ISR radio. Specifically, the connectors never failed, and there was no significant corrosion fretting after the equivalent of a 25-year life cycle.
Similarly, Dr. W. Joel D. Johnson, software defined radio (SDR) digital transceiver program lead at Harris Government Communications Systems Division, explains that Harris Corporation has successfully used MicroTCA for radios that will be used in the harshest of environments, albeit with modifications such as conduction-cooling and a new connector.
Where MicroTCA Fits
VME and CompactPCI have long been mainstay military design platforms, typically offering 6U architectures with some amount of redundancy and a medium level of bandwidth. Many onboard vetronic, navtronic and avionic applications do not require high-bandwidth communication between blades or vehicles, and VME and CompactPCI architectures are highly viable solutions–320 Mbytes/s for VME64. But with a limited number of gigabit Ethernet connections on the backplane, these architectures do not support the bandwidth required for more communication-intensive applications. Switched-fabric extensions to these architectures (VITA 31, VITA 41 and PICMG 2.16) do offer more bandwidth, but the required 6U form factor is just not conducive to smaller designs.
MicroTCA, ratified in July 2006 as PICMG MCTA.0, addresses these issues with high processing capacity, extremely high communication bandwidth and high availability in a small 2U form factor. VME and CompactPCI implementations offer just two serial connections on the backplane; MicroTCA offers as many as 21 high-speed serial connections, each providing as much as 2.5 gigabits per second bandwidth.
This is all packed into a 2U board, meaning MicroTCA requires less space to achieve greater bandwidth–advantageous for military initiatives seeking continued improvements in Size, Weight and Power (SWaP). MicroTCA was initially developed for air-cooled, less rugged applications, but its NEBS Level 3 rating meant it could handle greater shock and vibration from the outset. And with the ratification of MTCA.1, standard-compliant COTS MicroTCA can now be used for all but the most rugged air-cooled applications.
SWaP continues to be a top military issue, but many applications require computing bandwidth and high availability that just cannot be sacrificed as a design trade-off. In these instances, MicroTCA has a small form factor advantage over both VME and CompactPCI, including their derivatives VITA 31, VITA 41 and PICMG 2.16. MicroTCA blades are smaller and use less power, yet they can still deliver more communication bandwidth and higher computational abilities by using multiple processors on a single backplane. VME or CompactPCI designs can match this performance in 6U, but fall short when modified to 3U. And at 2U x 3-6 HP x 183.5 mm, MicroTCA may be one of the larger small form factors, but is still more compact than 3U VME or CompactPCI.
Multicore and More
MicroTCA means small size and high bandwidth for both communications and computing. Its extensive computing resources come from up to 12 compute blades on a single backplane, which can extend dramatically if each blade in a single 2U system uses a multicore processor. When a system grows to 3U or perhaps 4U, it could be operating today with as many as 24 cores. At that, it would still maintain a very small footprint, which may be what designers consider the most powerful and unique advantage of MicroTCA. A broad scope of communication bandwidth capabilities is realistic (ranging from 40 Gbits/s to more than 1Terabit/s) because actual bandwidth depends on the implementation. The Kontron OM6120 (Figure 4), for example, is a compact 5U system for up to twelve AMCs. Accommodating a high number of multicore Processor AMCs gives designers a wide range of options in communication power.
Earlier military systems did not always require high availability. Today, however, maximum system uptime is an overriding requirement for integrated battlefield management. To accommodate this effectively, MicroTCA offers a means to monitor the health of a system and then “heal” it in the field. Through an Intelligent Platform Management Interface (IPMI), users are notified when the system is running below peak performance. As temperature thresholds change, fans speeds can be throttled up and down automatically. If a board fails, the system can remain up and running while it is removed and replaced. Along with hot swap and full redundancy, IMPI-based health monitoring prevents any single point of failure in the system.
Suited for Diverse Military Needs
Modern military’s diversity of application requirements has tremendous impact on system design in terms of redundancy, system management, processing power, form factors, housing and usage of fabrics. With the recent passage of MTCA.1, the rugged air-cooled standard, MicroTCA fulfills many practical demands on system design for a variety of applications, and is quickly gaining traction in mil/aero apps such as communication systems, sonar and radar.
MicroTCA can be a powerful design option in this scenario, offering the high bandwidth, increased computing power and small form factor required for communication-centric implementations. Rugged enough to handle high-end computational demands under environmental extremes, these standards-compliant offerings will soon go still further in handling even the harshest of environments. This combination of industry testing, increased acceptance and standards body work is fueling MicroTCA’s rapid movement as a military design choice from command centers to shelters to the battlefield.