Technology trends and ruggedized MicroTCAStory
May 30, 2007
It is likely that ruggedized MicroTCA's target market requirements will be beyond the scope of a single specification. It is also very possible that the committee will develop a series of distinct but interrelated specifications.
Debates about what COTS does or does not mean abound, but it is clear that open standards play an important role in the thinking of military electronic systems architects. VMEbus began this trend, and military applications are now probably the largest VME product consumers. VME’s longstanding use is certainly a testament to the strength of the underlying technology, but it is also evidence of the inertia in the military market and its long adoption and procurement cycles.
That is changing though. One important reason is that silicon suppliers outside of a few specialists are not very interested in the military market as it is dwarfed economically by the commercial communications and consumer electronics markets. You currently cannot buy a military-qualified Pentium processor, and you likely never will. As a result, equipment designers must, at a minimum, use the silicon developed for the less environmentally demanding commercial markets. This is not necessarily a bad thing because the high volumes represented by desktop silicon offer the best possible bang for the buck, although obsolescence issues often blunt the advantages.
Perhaps the most important technology shift occurring is the move from parallel data buses to switched serial interconnects. Virtually every desktop PC sold today has PCI Express, which replaces the older PCI bus. It is faster, uses fewer interconnecting traces and connector pins, and can be made much more reliable. In a parallel bus such as VME or CompactPCI, any board can bring the entire system down. The board-to-board isolation provided by switched serial interconnects makes very robust and fault-tolerant architectures that continue to operate in the event of a possible failure, and this is of interest to military designers.
The concept of availability instead of simple Mean Time Between Failure (MTBF) has long been an integral part of core telecommunication equipment, and it is being embraced by military designers. System management, where all of the hardware and software resources of a system can be locally and externally monitored and controlled, is also a core telecommunication concept generating military equipment designers’ interest.
Standards for systems based on switched serial interconnects are becoming mainstream. The PICMG 2.16 specification – which provides for a switched Ethernet fabric on the backplane – was the first, followed by VITA 41 and now VITA 46, among others. The most comprehensive and sophisticated standard now is AdvancedTCA, which appears to be the most widely adopted open computer standard ever developed for nonconsumer applications. While designed for central office telecommunication applications, AdvancedTCA is already being used by military designers, as Lockheed Martin’s recently announced Wideband Data System (WDS) demonstrated. WDS uses a mix of commercially available AdvancedTCA gear and LM custom boards. The system is capable of routing more than 10 million 2 KB packets every second.
Out of AdvancedTCA came a requirement for a new, managed, fabric-based and hot-swappable mezzanine specification, which led to the development of the Advanced Mezzanine Card (AdvancedMC). Before too long, it became quite evident that AdvancedMCs were powerful enough to function as system boards when plugged directly into a backplane, and that concept led to the development of MicroTCA.
MicroTCA, originally developed for the telecommunication market, is garnering intense military designer interest. In an effort to respond to this and to expand MicroTCA’s applicability for other markets, PICMG recently formed a new technical subcommittee to develop a ruggedized version for extreme environmental and mobile military applications. The group’s goals are ambitious and include:
- Commercial and military applications
- Military airborne, shipboard, and ground mobile equipment
- Telco industry customer premise equipment
- Forced air and conduction-cooled rugged form factors
- Higher level of shock and vibration per IEC60721-3-3 Class 3M4 or 3M7 and possibly ANSI/VITA 47
- Machine industry – rotating machine mounted, no fans, vibration
- Transport industry – railway, truck, ship, aircraft mounted
- Telco industry – remote access such as roadside or pole mounted, no fans
- Traffic control – roadside, no fans
- Security – remote access, no fans
Known as rugged MicroTCA, this is primarily a thermal and mechanical design effort, and MicroTCA’s basic system architecture will be retained. A basic premise is to reuse existing AdvancedMC modules, but with the addition of conduction cooling for many target markets. The conduction-cooled mechanics will increase the solution’s robustness, improving shock, vibration, and extended-temperature performance. A range of liquid cooling solutions will also be developed for extreme environments.
It is likely that ruggedized MicroTCA’s target market requirements will be beyond the scope of a single specification. It is also very possible that the committee will develop a series of distinct but interrelated specifications. The committee understands this and is defining various markets’ specific requirements before the engineering begins.
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