Open standards for the railway computing market
Products that are based on standards make our lives easier. They standardize how we implement solutions in diverse applications, providing us with assurance that the solutions are sustainable and will therefore prevail for many years to come. Developed as open standards, their use and re-use is not restricted in any way. The advantages for users lie above all in low costs. Looking specifically at railway computing, open standards from PICMG facilitate seamless interoperability of system solutions and coexistence of the most heterogeneous applications on a single, modular smart railway platform.
When taking frank stock of all the electronics installed by mobility providers in rail vehicles and on the wayside, one can generally assume to find predominantly closed, proprietary system solutions from individual manufacturers. These fulfill the required international rail transport standards DIN EN 45545 and DIN EN 50155 for continuous operation under extreme temperatures (-40 °C to +85 °C), high humidity and heavy mechanical stress due to shocks and vibrations, or DIN EN 45545 HL3 for fire protection. However, the embedded computing technology used to implement the individual applications that meet these standards has not yet been specified by the industry. With more and more electronics required to develop smart trains and tracks, standardization of railway computer technology is becoming a priority.
For example, hermetically sealed railway electronics are being expanded to include numerous IoT-based solutions for predictive maintenance and wagon tracking. Train cockpits, too, are becoming smarter and smarter, incorporating comprehensive video surveillance of the tracks as well as the entire train and its doors. Passenger comfort requires control of heating and air-conditioning systems, announcements and displays; integration of ever-smarter passenger information and seat management systems; provision of infotainment services and Internet access; as well as smart ticketing and billing systems with walk-by-payment.
Does it really make sense to develop a separate, self-contained system for each of these functions? Wouldn’t it make much more sense to regard the smart train or wagon as a single IT unit with several distributed subsystems to be assembled in a modular way, as required by the operator? Cross-model and cross-manufacturer? Shouldn’t we treat trains today as edge servers that must be managed centrally and also across borders in view of their increasingly autonomous operation? Wouldn’t a completely new approach to railway computing make sense under those circumstances? Might the commercial IT sector and the telecommunications industry, which is developing completely new IT approaches in line with broadband expansion and 5G mobile telephony, provide us with valuable inspiration?
What megatrends can the railway industry benefit from?
Looking at the example of the telecommunications market, there has been a strong and ongoing trend away from dedicated hardware solutions to platforms that use software-defined network (SDN) and network function virtualization (NFV) technologies to flexibly allocate the available computing power. This successfully separates the function from the hardware, thereby also standardizing the underlying hardware platforms. At the same time, these platforms are expected to be convergent to make them interchangeable for different requirements. The goal is a highly agile closed-loop development process that constantly uses information from ongoing operations to develop and optimize the platforms further.
Of course, nobody will want to update systems that require certification every few months – at least not the part that has to be certified. However, the basic concept of increasingly flexible computing platforms through higher abstraction at the software level and the associated high standardization of these platforms – can be a valuable guiding principle for the standardization of railway computing. But to what extent can this megatrend in the IT and data center market be applied to trains? To what extent is it possible to standardize railway IT, making it more flexible, more universally applicable, and more interchangeable? And, how can you succeed in making these platforms truly open? After all, it isn’t possible to simply port telecommunications and data center technologies developed for well-acclimated environments to railway tracks, trains, or wagons, where high shock and vibration resistance is required for extended and rapidly fluctuating temperature ranges. This leads to the question: Which open standards already integrate the appropriate requirements?
A large number of embedded computing standards are used in rail transport today – even in proprietary railway IT systems. There are a multitude of standards for the various individual solutions, whose requirements, specifications, guidelines, and features are documented by a diverse array of standardization committees and consistently implemented by their proponents. They provide a harmonized, stable, and globally recognized framework for the dissemination and use of technologies. These include specifications such as PCI-Express, USB, I2C, and Ethernet as communication buses, as well as M12 connectors for robust physical connectivity. These individual solutions are consistently developed further in the committees created for this purpose. In doing so, attention is also paid to long-term availability with downward compatibility, so that existing solutions can always be replaced by their successors. This ensures long-term availability for trains that remain in service for many decades.
Standards bridge manufacturer boundaries
However, it is a well-known fact that manufacturers have created variants of such standards – either to solve very specific problems, or to distinguish themselves from the competition through vendor lock-in. Not every serial interface is therefore always the same, and the multitude of very specific protocol designs sometimes makes interoperability within a single standard difficult. Converging different programming standards into the European standard EN 61131, which is based on the international standard IEC 61131, ultimately made it possible to unite heterogeneous approaches to solutions, merging them, for example, via object-oriented further development into a new standard for distributed control systems: EN 61499. This example clearly illustrates the polarization between proprietary solutions and open standards. In a society that increasingly aspires to the principles of the sharing economy, which enables the shared use of resources, open source and open standards are becoming a fundamental requirement – also for the further development of railway computing platforms.
The advantages are obvious. OpenStand – the movement dedicated to promoting a proven set of principles that establish the modern paradigm for standards – has summarized the advantages of truly open standards in 10 points:
•Address broad market needs
•Streamline development and implementation
•Embody diverse perspectives
•Leverage proprietary knowledge
•Open new markets and applications
•Serve as building blocks for innovation
•Encourage market competition
•Drive interoperability and scalability
•Drive global innovation and advancement
In addition, there are factors that are commonly associated with modular standards – such as multiple variants, greater flexibility and more optimization options, efficient use of existing resources, plus lower and manageable risks, including protection against obsolescence – as well as supplier neutrality, which naturally applies to every standard. All of this shows that it is quite complex to describe all the advantages of standardization comprehensively and not every argument is equally important for everyone. What is plain, however, is that open standards are clearly preferable to proprietary solutions. (Figure 1.)
Embedded computing platform standards
The worldwide standardization of embedded computing platforms is currently driven mainly by three standardization committees: VITA, SGET, and PICMG.
1. VITA standards: VME and VPX
VITA is the oldest standardization body. It essentially maintains the VME and VPX standards, which are used almost exclusively in the military and defense sector, with some minor exceptions in research and industrial automation. Solutions based on these standards are therefore comparatively expensive, which is why they have rarely been used in the rail transport sector. However, there are some applications in this area, and despite a lack of native support by current processor technologies, compatible high-performance boards are still available today, such as the MEN-A25 6U VMEbus board with Intel Xeon D-1519 processor. Another advantage is the fact that the VME standard has been standardized by the IEC as ANSI/IEEE 1014 -1987. Nonetheless, the standards of the other two standardization bodies offer a somewhat simpler development path, since all these standards use the PCI Express bus for generic expansion options, which in turn is an essential basis of embedded processor technology and is therefore natively supported by all processors.
2.SGET standards: Qseven and SMARC
The SGET standards, Qseven and SMARC, are still relatively new and often target mobile applications where credit card sized modules are deployed. While in principle suitable for use in rail transport, the specifications still have to prove their stability when it comes to long-term availability. For example, SMARC, which is currently considered the more promising of the SGET specifications for new applications, has experienced a leap from version 1.0 to 2.0 that does not offer unlimited backward compatibility for existing applications. In addition, the modules are not designed to withstand the extreme temperature changes in rail transport, which is why developers of railway applications cannot currently find a fully compatible standard computing platform within SGET.
3.PICMG standards: CompactPCI Serial and COM Express
PICMG, on the other hand, offers a broad basis for standardized railway computing platforms with CompactPCI Serial and the basic COM Express specification, which is rail-compatible by adding the proposed open VITA standard 59 extension drafted by MEN Mikro Elektronik to the PICMG specifications. CompactPCI Serial is a specification for the development of system platforms which, thanks to its modular design, enables a diverse range of systems with commercial off-the-shelf (COTS) standard boards, system chassis, and flexibly connectable backplanes. It is already used in numerous railway applications and offers all the basics for deployment as a central edge computing instance in trains, wagons, and in the station (Figure 2). There are countless standard components for designing such systems, and even some boards are available today that can be flexibly adapted with suitable FPGA implementations for the different railway interface standards (including SIL). The standard itself has been established for many years and is currently experiencing a boost in demand.
Reasons for this include:
•IIoT and edge computing trends
•Hardware consolidation on a single platform
•The trends toward hardware virtualization
•Demand for convergent platforms to enable closed loop engineering
Rugged COM Express adds a specification to the list of rail-compatible open standards that is suitable for smaller systems designed for installation in trains and wagons away from the central railway edge computing platforms. Modules of this standard are high-performance systems which, despite their high performance and a thermal design power output of up to around 50 W, can be cooled completely passively and, thanks to the cooling concept, can also withstand sudden extreme temperature changes and the associated thermal stress without problem. Rugged COM Express solves the mechanical and thermal design for extreme temperature changes by combining the PICMG COM Express standard with the standard draft VITA 59. This illustrates a clear advantage of open standards: They can be freely combined to generate new added value.
Demand for Rugged COM Express modules is booming as the mobile computing market produces an extremely high demand for autonomous vehicles. Yole Développement, for example, predicts an increase in camera technologies for autonomous robotic vehicles, at a compound annual growth rate of around 140%, to $900 million in 2023. Such systems require an extremely powerful CPU and GPU for situational awareness and other system performance, and the railway market needs smart machine vision, too. So, these open standards already offer almost everything railway IT engineers need for their system platforms today.
Mini modules suitable for railway applications
What is still missing from open standards for the railway market is a small form factor computer-on-module that has been specified by an independent standardization committee for 100% EMC compliance and thermal shock resistance – for example, based on the PICMG COM Express Mini specification.
There’s clearly more work for the standardization community to do. In addition, not every board or system is designed for certification with standards such as SIL. It is therefore still necessary to check the railway-specific requirements. Nevertheless, there are various manufacturers on the market who offer embedded computing platforms based on open standards for mobility providers, rail network operators, train and wagon manufacturers, and their suppliers; and who also support all current IT megatrends. Proprietary solutions are therefore no longer acceptable.