RTC Magazine

Originally targeting small to mid-size telecom systems, the MicroTCA architecture is generating interest for other applications that utilize a network-centric structure, including military, medical and industrial systems. These and other diverse applications now seek to leverage the performance, management functions and high-availability features of MicroTCA while reducing cost and design time. To better address this broader range of market requirements, including the need to operate in harsh environments, MicroTCA has begun embracing ruggedized construction so that its designs can thrive outside of the central office.

The ability to connect to a network for control and data exchange is a key attribute for a growing number of system designs. Medical systems, for example, are evolving to support decentralized diagnostic activity that allows a doctor in one location to utilize a diagnostic tool such as an MRI on a patient in another location. Imaging, fluid analysis, bio-signal monitoring and a host of other medical equipment types are beginning to incorporate wireless and wired network interfaces to become part of an entire medical system that links doctors to remote patients.

Industrial systems are also adopting such a network-centric approach. Automated factory equipment and robotic systems utilize network architectures for communications and control both within a factory and between locations. The availability of wide area networking interfaces even allows equipment in diverse locations to exchange information to create a virtual factory that functions as an integrated system.

The need for Command, Control, Communications, Computers, Intelligence, Surveillance and Reconnaissance (C4ISR) activity to function across a wide operational front is prompting development of network-centric systems in military applications. Network interfaces allow the images and data from unmanned aerial vehicles (UAVs) to flow directly to the field operatives that can benefit most from the information. Networking is also at the core of the Future Combat Systems (FCS) under development that would allow coordination of military activity in the field down to the level of a single individual.

Other network-centric applications abound in commercial activity. Point-of-sale terminals use networks to support retail sales by providing financial transactions and inventory updates for the retailer. Information kiosks provide consumers with up-to-date and interactively customized price and availability information.

On top of this trend toward network-centric system design in other application areas, telecommunications is seeing a move away from traditional equipment installations. Network edge functions such as cellular access points are moving out of the central office and into field settings such as pole-mounted installations. Other edge equipment is moving into enterprise settings such as equipment closets.

Appeal Outside Telecom

For all these diverse applications, the MicroTCA architecture holds tremendous appeal because of its many useful attributes. For one, MicroTCA provides fine-grained modularity and scalability that simplifies the evolution of system function and growth in system capacity. Designers assembling a system can mix and match Advanced Mezzanine Card (AMC) modules, the architecture’s functional building blocks, at will. Because AMC modules have a standard backplane interface, users can upgrade system functions or increase capacity simply by changing or adding modules as needed. This ability is particularly valuable in medical system design because it preserves the system’s overall FDA certification, reducing the re-certification effort for a design upgrade to address only the new module.

Another useful attribute of the MicroTCA architecture is its support for compact system design. The mezzanine-card heritage of AMC modules means they are reasonably small while still offering a high compute density in terms of MIPS per watt per square inch (Figure 1). The chassis design targets back-to-back installations, giving MicroTCA systems a shallower depth than classic thin servers or other system platforms. The specification is open as to configuration, however, allowing from two to twelve modules in a chassis to support a range of trade-offs between size and capacity.

System management functions form a part of the MicroTCA specification, so the monitoring and control of system elements down to the module level is a built-in attribute. This control includes support for hot-swap and remote disabling of modules and other system elements so that redundancy for load-sharing and fail-over fault responses is easy to implement. MicroTCA systems thus offer built-in high availability and short repair time attributes that have been cost-prohibitive for system developers building systems from scratch.

All the elements needed for a MicroTCA-based system are available as commercial off-the-shelf items. Base system hardware elements, including card cages, fans, power supplies and full system enclosures, are available from a number of vendors. Stock AMC modules include a range of processors, a wide variety of I/O interfaces, and many other functions. Developers can thus create entire MicroTCA system prototypes from tested and validated components, providing an out-of-the-box experience to immediately begin software and system development. Foundation system software is also available off-the-shelf for MicroTCA systems. Such software includes a real-time Linux operating system, full system management software, and high-availability system middleware through the Open Software Availability Forum. The wide variety of applications, customers and vendors for each individual element in a MicroTCA system ensures ready availability and low cost due to economies of scale.

Full-System COTS

These many useful attributes mean that developers utilizing the MicroTCA architecture have most of their work already done. Hardware design is reduced to selecting an appropriate combination of stock system elements and occasionally designing an AMC module to address unique requirements. Even then, the specifications cover most of the design details, freeing developers to concentrate on their specific needs. Software design is also significantly reduced, requiring only applications programming within the overall system software. For a growing number of network-centric applications, then, MicroTCA represents an opportunity to develop compact, high-performance, high-reliability designs quickly and inexpensively.

The one area where MicroTCA specifications may not adequately address a wide diversity of application needs, however, is in the operating environment. The current specification, PICMG MicroTCA.0, provides a baseline for commercial and telecom applications based on the NEBS and ETS Class 3.1 standard. This calls for an operating environment with a temperature between +5°C and +40°C, allowing for short-term excursions as low as -5°C or as high as +55°C. The specification also calls for designs to be resistant to earthquake (NEBS GR-63 Zone 4), to 0.5g vibration from 2 to 200 Hz, and to sinusoidal shock at 7g for 11 msec (IEC 61587-1 Class DL1). These specifications reflect the need to survive normal shipping and handling and rack-mounted installation in a small, closed, climate-controlled concrete building: the central office. The many applications now considering the MicroTCA architecture, however, have different needs for mechanical ruggedness and operating environment.

Military and aerospace applications, which have the strictest mechanical and environmental requirements, can illustrate the correspondence and divergence between MicroTCA specifications and application needs. Military systems today need to rapidly move from design to deployment in order to address continual changes in theaters of operation. The MicroTCA architecture addresses that need in several ways. The availability of complete off-the-shelf systems supports an early start to software development, typically the pacing item in system design. Wide stock availability also supports rapid production and deployment of finished systems. Because all system elements are based on standards, including custom module designs, design re-use becomes virtually automatic and can speed the development of follow-on projects.

Military and aerospace systems also have a need for rapid and simple field maintenance so that systems can be quickly repaired or upgraded and returned to operation. The module-level hot-swap feature inherent in MicroTCA systems reduces system repair or upgrade to a quick module exchange, possibly even while the system continues functioning uninterrupted. The same feature allows rapid expansion of system capability if needed.

Addressing Harsh Environments

Where MicroTCA does not meet mil-aero requirements is in system tolerance to harsh operating conditions. Depending on the category of equipment, requirements (MIL-STD-810-F) for operating temperature go from a baseline of 0° to +55°C to as extreme as -40° to +125°C. Shock immunity requirements range from 20g to 40g and random vibration immunity specifications can range from about 2g to 12g.

The existing MicroTCA specifications thus fall far short of addressing even the baseline environmental requirements for military systems. Similarly, though to a lesser extent, MicroTCA environmental standards don’t quite reflect the needs of desktop office equipment that might get dropped, machinery that must operate in a hot, vibrating factory space, or outdoor, pole-mounted systems. But that is about to change.

Recognizing the growing interest in MicroTCA outside of the telecom industry, a MicroTCA Ruggedization Special Interest Group (SIG) arose within PICMG to stimulate development of additional standards that address non-telecom application requirements. As a result, PICMG is in the midst of creating two new specifications for rugged MicroTCA systems. The specification for an air-cooled rugged MicroTCA system, PICMG MicroTCA.1, is scheduled for release to the industry in late 2008. A conduction-cooled rugged MicroTCA specification, PICMG MicroTCA.2, is under active development.

The air-cooled rugged MicroTCA.1 standard targets systems that need an extended temperature range for outdoor and uncontrolled environments and high levels of shock and vibration resistance for operation in mobile applications such as ships and around heavy rotating machinery. The standard is based on the IEC specification IEC 61587-1 and calls for operation in an ambient temperature range of -40° to +70°C (Class C3) with vibration resistance to 3g and shock resistance to 25g (Class DL3), as shown in Table 1. The MicroTCA.1 standard also foresees growth potential for future increases in shock and vibration resistance.

Maximizing Baseline Compatibility

One of the goals in developing the standard was to meet ruggedization requirements with minimal modifications to existing designs that followed the baseline standard. To address increased shock and vibration resistance, for instance, the new standard calls for supplementing the baseline AMC module connector system with a locking device that prevents modules from disengaging. PICMG has conducted extensive environmental testing to establish that the augmented connector system will meet or exceed the target shock and vibration resistance. Designers can address the increased temperature ranges by using extended temperature components or chassis-level heaters.

The rugged MicroTCA.2 standard under development aims to address the extended temperature range and higher levels of vibration and shock resistance needed in many military applications, focused primarily on conduction-cooled applications. PICMG is basing its shock and vibration resistance targets on the standards of ANSI/VITA 47, itself derived from MIL-STD-810-F. It is seeking to address as many environmental classes as possible consistent with maintaining maximum compatibility of baseline and ruggedized designs. One approach under consideration is the addition of a conduction frame to baseline AMC module designs to add rigidity and provide a conduction path to side walls of the sub-rack using wedge locks. As with the air-cooled standard, PICMG will conduct environmental testing to establish the performance of designs based on the standard before its release.

With the imminent release of the air-cooled MicroTCA.1 and the development of the conduction-cooled MicroTCA.2 specifications, application developers outside of telecom now have even more motivation to embrace the MicroTCA architecture, and they can begin right away. Suitable MicroTCA platforms have already begun to emerge that developers can use to get started. Emerson Network Power, for instance, has proven the applicability of MicroTCA to outside applications with its Centellis 1000 platform’s design win for Hypercom’s point-of-sale transaction network products. For more rugged applications, Hybricon has created the Air Transport Rack chassis (Figure 2) that employs locking bars and frame isolation to address military-type shock and vibration requirements along with airflow designs to support operation to +55°C at altitudes to 10,000 feet using telco-grade AMC modules.

These examples help demonstrate that the MicroTCA architecture has applicability well beyond its first target. By providing a full off-the-shelf system design, the architecture promises to shorten design cycles and lower development costs in systems ranging from medical diagnostic equipment to field military gear. Economies gained by widespread market adoption will undoubtedly make MicroTCA a significant and true Commercial Off-the-Shelf embedded technology with tremendous impact. The emergence of ruggedized specifications is now removing the last impediment to tackling tough applications beyond telecom using MicroTCA.

Emerson Network Power
Tempe, AZ.
(602) 438-5720.
[www.EmersonNetworkPower.com].