Choosing the Ideal Components for Rolling Stock Applications

To meet modern needs, train communication systems must improve in three key areas: bandwidth, response time, and reliability. Many rail networks still use basic visual signaling systems that would not be unfamiliar to a locomotive engineer from the 1800s. However, new and emerging technologies now make it possible to create advanced train communication systems. Driven by changing market expectations and advancing technologies, train communication technology is undergoing a remarkable transition. Industry professionals need to be prepared to meet the new challenges brought on by this transition, or risk being caught unprepared.

In this article we explain in detail the fundamentals of creating train communication systems for today, tomorrow, and beyond.

• The Three Main Criteria for Advanced Rolling Stock Applications
• Types of Applications
• Six Fundamental Requirements
• Solutions for Railway Networks of Today and Tomorrow
• Railway Networks of the Future Can Be Built Today

The Three Main Criteria for Advanced Rolling Stock Applications

Train communication systems must do more to meet the new demands on railway communications systems, such as providing more bandwidth, faster response time, and more reliability—whether for intra-train, train-to-ground, or trackside networks.

Ample Bandwidth

The contemporary traveler expects a higher level of convenience, safety, and service. To fulfill these high expectations train operators now use telephony and data systems for real-time surveillance and modern passenger infotainment systems to deliver rich entertainment and information content to passengers, including news, weather, games, and even Internet access. In addition, with enough bandwidth it becomes possible to use one train control network for voice, video, and other operational data.

Fast Response Time

The old-fashioned method of train control relied on human operators who were given directions through a combination of radio, visual signals, and track circuits; however, this method had a slow response time. For safety reasons, tracks were divided into long "segments" or "blocks," with only one train allowed on a block at a time to prevent accidents.

The introduction of Communication-based Train Control (CBTC) technology improved the efficiency of train operations by allowing operators to reduce the length of the blocks without compromising safety. However, the efficacy of a CBTC system is highly contingent on the communication response time. With real-time response, the CBTC can safely and efficiently maximize the number of trains on the track at the same time.

Reliability

As operators take advantage of the new capabilities of advanced train communication systems, more and more train systems depend on reliable communications, and next-generation communication systems need to be reliable enough to shoulder these new responsibilities. In particular, communications must be sufficiently resilient to overcome the unique hazards of rolling stock operations: weather, shock, vibration, and electromagnetic interference. The EN50155 and EN50121-1/-4 European standards are useful and important benchmarks for confirming that communications devices are sufficiently robust for both onboard and trackside applications.

Types of Applications

WLAN:

Wireless technology frees operators from the limitations and complications of cabling a communication system, which is a particularly arduous task for an application with as many moving parts as a train system. Of all currently available wireless technology solutions, WLAN stands out as the solution with the best balance of capabilities and costs:

Mobility Control Unit:

This system includes a display panel to allow the conductor to monitor vehicle status. A powerful computing platform is used to connect various devices, such as analog/digital I/O units, GPS modules, audio devices, and wireless modules. Fast hand-over times from access point to access point enable immediate status updates to better control the railway system and keep passengers well-informed in all phases of the journey.

Passenger Information System:

This system needs a powerful computing unit to quickly display information on connected displays, and uses an industrial switch for reliable communications with the Ethernet network. This system can be further expanded with passenger entertainment features.

Network Video Recorder:

A reliable network video recording system is responsible for performing efficient and real-time video monitoring. An industrial-grade PoE switch makes it easier to install VoIP phones and IP cameras on the platform when a power supply is not readily available. The nodes at the front and rear of the train require a higher level of performance in order to support NVR playback. Embedded computers with built-in storage expansion can perform the task of video recording in the individual train carriages.

Six Fundamental Requirements

There are many manufacturers of video control units, passenger information systems, mobility control units, and IP network video recorders. However, only a few manufacturers produce products that are resilient enough to overcome the harsh environments of rolling stock applications: weather, shock, vibration, and electromagnetic interference. You should look evaluate devices based on these six fundamental criteria:

1. High and Efficient System Performance

High and efficient performance is crucial to the entire communication system. Usually, a computer with a Core 2 Duo CPU and 2 GB of system memory is required since several applications are often run on one or more computers.

2. Wide Operating Temperature Range

Implemented on moving vehicles, the devices and computers are placed in various field sites where the temperature can be extremely hot or cold. Devices and computers used in rolling stock applications are required to meet EN50155 standards, which regulate operating temperature ranges for different classes.

3. Reliable Large-capacity Storage

While storage requirements are low for traditional rolling stock applications, modern rolling stock applications now demand more and more storage capacity. This is particularly true of NVR applications, which require continuous recording and/or playback. Implementing large-capacity hard disk drives is a challenge because they are highly susceptible to the shock and vibration found on moving vehicles, and consequently can be easily damaged. Because of this, some suppliers have turned to using an SSD (solid state disk) for better hard disk performance and anti-vibration/anti-shock protection; however, using SSDs is a high-cost solution. An alternative is to look for products that are specially designed with advanced hardware installation to reduce vibration and shock. In this way, inexpensive off-the-shelf hard disks can be used on moving objects to provide a cost-effective and reliable storage solution.

4. Multiple and Reliable Connection Interfaces

The main purpose of these computers is to connect various control units on the vehicles; therefore, versatile interfaces, such as serial ports, LAN ports, and digital input/output channels are necessary. To ensure secure connections, some interfaces should use M12 connectors. In addition, because multiple display options are necessary for many applications, especially field site monitoring and surveillance, these computers should also offer VGA, DVI, or LVDS display connections.

5. Power Requirements

This is another key requirement for computers used in rolling stock applications, particularly since a sudden change of voltage could occur when the moving vehicle starts or brakes. This is why it is standard for computers used in rolling stock applications to come embedded with a 24/48/72/100 VDC power input with a 30% tolerance.

6. Easy-to-Use Platform

Because of the many applications that are used, the computers must provide an easy-to-use platform so that programmers can quickly apply related applications to the entire system. Windows XP Embedded, Windows XP, Windows 7, and the open Linux platform are considered to be the most user-friendly programming environments by many programmers.

Solutions for Railway Networks of Today and Tomorrow

Moxa offers a complete suite of communication solutions that includes Ethernet switches, embedded computers, and IP cameras with EN50155 and EN50121-1/-4 certification to provide assurance that the products are suitable for harsh railway environments, and Moxa's rugged wireless devices help bring it all together. Moxa's outdoor wireless AP/bridge/client products feature fast Turbo Roaming technology as well as the dependability provided by dual independent RF modules, power redundancy, and a weatherproof, dustproof, wide operating temperature design.

These highly rugged features and turbo roaming technology provide railway operators with the perfect combination for formidable railway applications. With two outdoor wireless AP/bridge/client units in each wayside cabinet, a railway company can replace trackside cabling and its attendant maintenance headaches with dual redundant RF links. The outdoor wireless AP/bridge/client units connect to a solar-powered switch that supports an IP camera and a third wireless device, and another outdoor wireless AP/bridge/client acts as a local wireless AP. As described, this system can give station staff in the field convenient wireless access to system maintenance tools. With the addition of even more advanced technology, these advanced, rugged components can also provide the foundation for a future train communications network, complete with fast train-to-ground WLAN communications.

Railway Networks of the Future Can Be Built Today

The future of railway communications is coming, and operators need to be ready. Moxa offers a full suite of industrial rolling stock products with fast Turbo Roaming, wide operating temperature, weatherproofing, dual RF redundancy, as well EN50155 and EN50121-1/-4 certifications to build future-proof systems that possess the bandwidth, response time, and reliability required for railway applications.

See how railway operators are already taking advantage of Moxa's products at www.moxa.com/event/vertical_markets/railway.

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