Until recently, the United States has taken a decidedly old-fashion approach to running its rail systems. Most of the country’s signaling, switching, and train operation has been handled manually, leading to inefficiencies and unnecessary hazards. The Metrolink commuter train accident in 2008 highlighted just how dangerous manual controls could be, prompting Congress to pass the U.S. Rail Safety Improvement Act of 2008. This act mandated that approximately 73,000 miles of rail and transit infrastructure would have PTC systems in place by 2015.
PTC is a computerized system for monitoring and controlling the movement of trains. The top priority is collision avoidance, but PTC systems can also automatically regulate the speed of trains in response to rail conditions, on-board equipment malfunctions, temporary speed restrictions, and other safety considerations. While the Federal Railroad Administration envisions a National Differential Global Positioning System (NDGPS) to enable seamless train tracking and control, to date the infrastructure is still a patchwork of legacy systems and disparate approaches.
SDR vs. the Tower of Babel
One company trying to address that shortcoming is Santa Clara based Lilee Systems. Lilee’s unique software defined radio (SDR) technology and Intel®-based hardware provides complete end-to-end wireless mobility management, enabling trains moving cross country, for example, to interact intelligently with a wide range of legacy safety systems along the way.
According to Jon Adams, Lilee’s VP of Strategic Development, “There are many components to Positive Train Control. We do the onboard radios, the onboard networking processors, the wayside radios and messaging processors, and the back office mobile IP abstraction. It’s all standards-based and high security. Every train, every piece of equipment in the field—whether it’s fixed or moving—has a fixed IP address, so it becomes straightforward to manage your assets.”
Why resort to something as complex as SDR to handle what would seem to be a relatively straightforward problem? “The answer has less to do with technology than with FCC regulatory domains,” Adams explained. “If you look at the 217-222 MHz band (Figure 1), which is where much of the industry has decided it’s going to put their PTC systems, it’s under four different parts of the FCC [regulations]: it’s under Part 80, which is Maritime Mobile; it’s under Part 90, which is Business/Industrial; it’s under Part 95, which is Citizens Band; and it’s under Part 97, which is the Amateur Radio Service. You can’t operate under the Amateur Radio Service, but you can operate under the other three parts.”
Figure 1: The U.S. radio spectrum from 217-222 MHz is multi-layered.
“The challenge,” continued Adams, “is even if you build a radio that’s flexible in frequency, it still needs to meet the special requirements of whichever part in which it’s operating. But in those parts they don’t specify modulation type, data rates, coding, or other things. So having a fixed radio means you can only service one segment of a pretty small market. But a software defined radio enables you to throw a virtual switch and suddenly you’re completely compliant with Part 80 and are at 16 kbps; or you’re completely compliant with Part 90 and you’re at 9600 baud. That’s why we took the SDR approach.”
Intel Inside (and Outside) the Train
How do Lilee’s solutions leverage Intel technology? “If you look inside our Lilee Mobility Controllers—that go in the back office—or our Wayside Messaging Servers you’ll find an x86 Intel processor that’s running the whole application space. It’s a very robust architecture, and we chose it because it’s so well supported by operating systems and by the customer base. You need to look at the cost of maintaining a platform, and we felt that the Intel architecture really does help to mitigate the unknowns.”
Figure 2: Lilee's LMC-5500 Mobility Controllers provide the backbone for an integrated PTC system.
Lilee’s LMC-5500 Series Mobility Controllers (Figure 2) provide radio device management with roaming control and enable a conduit between the remote network and the back office servers. LMC-series controllers are built around the Intel® Core™2 Quad Processor Q9400 (6M Cache, 2.66 GHz, 1333 MHz FSB) and the Intel® 3210 Chipset with 82801I9B I/O Controller Hub (ICH9). SDR radios within the network establish tunnels with the LMC-5000 to allow mobile radios to move across different segments of the network without having to be aware of the underlying network topology changes.
Lilee’s Intel® AtomTM-based WMS-2000 Connectivity and Application Controllers enable back office visibility of wayside status and alarm messages, providing an interoperable gateway for PTC and legacy train control systems.
One rail system that has completely committed to Lilee’s approach to PTC is Southern California’s Metrolink. “Metrolink is the commuter heavy rail link in Southern California with 219 miles of right of way with over 200 wayside locations for signals and switches where they need to talk to a train,” concluded Adams. “Lilee’s WMS-2000 messaging server is in every one of those. These units manage all the communications from the back office network to the train. In the back office Lilee LMC-5000 mobility controllers extract the IP address so the back office can always send a message to any particular device throughout their entire system.”
While engineers will continue to drive Metrolink’s trains, PTC backup systems are in place to insure against temporary distractions ever again leading to disastrous consequences.
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Lilee Systems is a general member of the Intel® Intelligent Systems Alliance. Lilee Systems is dedicated to delivering the highest quality, most reliable products and solutions for mobile connectivity across multiple market areas including railway.
Roving Reporter (Intel® contractor), Intel® Intelligent Systems Alliance
Editor/Publisher, Low-Power Design
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