On Sept. 12, 2008, a Union Pacific freight train collided with a Metrolink commuter train in the Chatsworth community of Los Angeles, killing 25 people and injuring 135 others. The Metrolink train had run through a red signal and entered a section of single track for which the Union Pacific train had been given right of way by the dispatcher. Each train was traveling at about 40 mph when they collided.
As a result of the crash and the subsequent investigation into the causes, Congress passed a bill mandating positive train control (PTC). These systems are meant to prevent train-to-train collisions, enforce speed restrictions, provide safety for road and rail workers, and prevent movement through misaligned switches. The bill requires all Class I freight railroads and passenger operators to implement PTC by Dec. 31, 2015.
In addition, the bill requires the interoperability of PTC communications systems, so that a locomotive on any railroad can operate on any other railroad's track using the same control systems. However, the legislation does not mandate the development of an interoperable standards protocol.
A view of the 2008 Chatsworth train crash.
An IEEE PTC Study Group was formed in November 2011 to explore the development of such a protocol. The goal was to build on IEEE 802.15 standards and expand them for transportation. The 802.15.4p Task Group was approved and began developing the baseline protocols in 2012.
Before the formation of 802.15.4p, there were no IEEE 802 wireless standards addressing the critical performance needs of fast-moving vehicles. This new standard supports reliable operation over a narrow channel for vehicles moving up to 600 km/h. It also contemplates operations in new spectrum bands for 802.15.4 specs.
The 15.4p standard enables data rates of up to 1 Mbit/s over frequencies in the VHF, UHF, and SHF bands (specifically 161, 216, 217, 220, 450, 770, 896, 915, 928, 2,450, 4,965, and 5,800 MHz) operating in contiguous or noncontiguous channel bandwidths as narrow as 12.5 kHz and as wide as 2 MHz. The standard uses modulation techniques such as GMSK, C4FM, QPSK, DQPSK, Pi/4 DQPSK, and DSSS DPSK. Depending on frequency band and operating rules, transceivers employing the standard can operate with a range of up to 70 km and TX output power of greater than +30 dBm.
The standard got backing from more than 90 engineers in more than 70 companies, including systems integrators such as Bombardier, Alstom, Siemens, Herzog, Parsons, GE, and Parsons Brinkerhoff. The chip vendors Qualcomm, Freescale, Texas Instruments, Via Technologies, and NXP support the standard, as do regulators in the US and around the world.
The Rail Communications and Control standard was formally approved on March 27, 2014, paving the way for vendors to focus on bringing interoperable communications systems and devices to the rail freight and transit market. Several device vendors are expected to announce the release of compliant products shortly.
On the wireless front, we should expect industrial VHF/UHF, WiFi, 3G/4G cellular, and other radios operating below 6 GHz deployed on locomotives and at wayside stations, base stations, and railyard locations. The more complex of these platforms will be sophisticated software-defined radio and cognitive radio systems meeting the demanding certification requirements of national agencies like the US Federal Communications Commission.
Other hardware platforms expected to support the standard would include network management servers, mobility controllers, Interoperable Train Control Messaging servers, M2M messaging and communications gateway and application servers, routing and switching gear, and a plethora of software and engineering services to manage and support the standard.
Railroads and transit authorities globally use a number of often proprietary systems and protocols for rail communications and control. This presents the most significant challenge for implementing 802.15.4p. Interoperability afforded by adoption of 15.4p enables forward-thinking railroads and transit authorities to provide flexibility and scalability to their networks.
-- William Albano is a Taipei technical and marketing communications representative at Lilee Systems, which helped develop the IEEE 802.15.4p standard.