January 16, 2018
According to the Federal Railroad Administration, there were more than 1,000 train accidents in the United States in 2017. This should come as little surprise to those in the industry, as well as anyone who watches news programs or reads a newspaper. Incidents in New York, Philadelphia, and Washington, D.C. are just three of the accidents that have garnered coverage by the media last year.
What may not be as obvious is that, while accidents continue to be a too-frequent occurrence, the number has decreased since 2014. One reason is the implementation of Positive Train Control (PTC). The advanced communications system that automatically controls train activity to minimize collisions, derailments, and improper movement through track switches is scheduled for full implementation by the end of this year. As shown in figure 1, many of the rail carriers are gearing up to meet that Congressional deadline.
Using an On Board Computer (OBC), PTC systems (figure 2) monitor static and dynamic conditions in real time to alert train engineers of on-coming speed limits or track conditions that require the train to slow down or stop completely depending on the train’s position, direction and speed. If the engineer does not respond correctly or in time, the OBC automatically decelerates the train and can even bring it to a halt within a safe braking distance from the restriction. Even though PTC systems cannot stop train-vehicle accidents at crossings or incidents that occur when people illegally walk on a track, the amount of incidents they can prevent makes them a vital component of modern train systems.
Because of the mission critical nature of PTC, interference-free communications is required. The importance of clear spectrum is evident by a recently completed three-year study conducted by Clifton Weiss & Associates, Inc. (CWA), an engineering consultancy that specializes in electronic communication systems planning, design, and integration. CWA, which provides services that improve transportation and utility systems through technological innovations, leveraged the testing capability of the Anritsu MS27101A Remote Spectrum Monitor™ with Vision™ database software to monitor PTC systems by capturing signals across a wide dynamic range in real time and logging the data for later analysis.
As part of the study, CWA monitored RF signals on an actively operating railway to identify periodic or persistent interferers that would degrade the performance of the railway’s pre-assigned PTC public safety system locations. A challenge under normal circumstances, CWA was given a deadline of less than four months to provide the first detailed report.
Due to the short timeline, three remote spectrum monitoring instruments with LTE connectivity were needed to capture signals across the required frequency range with fast measurement speeds. Database software was also necessary to log the data for analysis and create customized reports.
Using the MS27101A, 9 kHz – 6 GHz, ½-rack Remote Spectrum Monitor web-based automated data capturing hardware and Vision software platform, CWA was able to meet the interference study’s stringent technical requirements. Vision provided complete command and control of all three spectrum monitoring receivers. The software also created a near-real-time and continuous spectrum view while minimizing backhaul data usage, no easy task given the potentially short signal duration in the PTC band.
Each MS27101A used a cellular 4G network via LTE modem. Vision’s customized database presented the spectrum monitoring information correlated to GPS coordinates from each MS27101A. CWA engineers regularly monitored the acquired data, providing monthly reports. They conducted power measurements in signal and guard bands to measure signal activity and minimize spillover. Collecting data 24/7 allowed for periodic occupancy reports generated by Vision’s monitoring system. Figure 3 shows the measurement dashboard and spectrum occupancy statistics.
Anritsu’s remote spectrum monitors and associated software suites were able to monitor, analyze and archive spectral activity, which was critical for maximizing available spectrum resources and minimizing interfering events. Complementing these features were the fast sweep and low noise floor of the MS27101A, which assisted with capturing the necessary signal data and analyzing it in CWA’s short deadline.
For more information about this application, read a complete success story on the project. For more information on spectrum monitoring techniques, as well as Anritsu’s solutions for these environments, visit our Remote Spectrum Monitoring page.