Software defined radio for HA-NDGPS performance improvements

Document Type

Conference Proceeding

Date of Original Version



The Next Generation High-Speed Rail Program is a key element in the Department of Transportation's overall program to encourage the development of higher speed rail in the United States. The main focus is on implementing high-speed rail service in selected congested corridors to achieve a more balanced intermodal transportation system. The Program supports the advancement of high-speed rail, particularly on existing infrastructure, by improving, adapting, and demonstrating potentially more cost-effective technologies which could have wide application in U.S. corridors. Up until 2007 the Federal Railroad Administration was the lead agency of nine federal agencies working to develop the Nationwide Differential Global Positioning System. NDGPS is needed for Positive Train Control and is also an enabling technology for automated railroad surveying systems and accurate rail defect detection. FRA and the other agencies have been exploring new signals that could be added to the NDGPS system to improve the accuracy, integrity, anti-jam capability and overall signal robustness. The development and use of High Accuracy Nationwide DGPS (HA-NDGPS) was identified by the Federal Railroad Administration (FRA) as a necessary capability for positive train control (PTC) and for automated rail survey. Currently the only HA-NDGPS receiver in existence is a modified DGPS beacon receiver, of which only a few prototypes exist. There are also concerns about the receiver's ability to function in the noise environment found on locomotives. These receivers also do not have the ability to collect raw signal data which can be used as a tool to post process and characterize signal quality. Under contract to the FRA, Alion Science and Technology has developed a software-defined receiver for HA-NDGPS experimentation and testing. This Digital Signal Processing (DSP) receiver is a combination of COTS hardware including: analog RF front-end gain and filtering; high-speed A/D data acquisition, and a standard laptop computer running C++ and MatLab ™ receiver code. This new advanced capability receiver has been used to establish a performance baseline of the current HA-NDGPS system. Specifically, in this paper we will report upon the software receiver design and development, the lab simulator built to test the receiver, the performance curves (BER vs SNR) from both lab and field testing, and the characterization and mitigation of the noise environment found on typical locomotives based upon testing in Omaha, NE and in Lancaster, PA.

Publication Title, e.g., Journal

Proceedings of the Institute of Navigation, National Technical Meeting



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