Software Global Position Systems Receiver
Software communication devices utilize the current fast processor speed and analog to digital converting rate to minimize the use of dedicated hardware, and rely on software to implement most of the traditional hardware functions. The software GPS receiver is one of the applications of the so-called software-radio techniques.
In a software based GPS receiver, the only hardware needed are an antenna, radio frequency devices such as amplifiers and/or conversion devices that down convert the radio frequency signals to intermediate frequency signals, and an analog-to-digital converter that outputs digitized samples of the input analog signals. Software running on digital signal processing chips or on general-purpose computers are used to perform all of the remaining functions, including satellite signal acquisition, tracking, ephemeris data processing, and user position calculations. Using software approaches to perform GPS receiver functions offers many advantages over conventional hardware approaches, such as flexibility in design and implementation, hardware independence, ease of upgrade, capability of working with discontinuous signals, and the potential for using sophisticated signal processing programs to work with signals far below normal levels.
I started working in this area in the summer of 2002 as a summer faculty fellow at the Air Force Research Laboratories (AFRL) in Wright Patterson Air Force Base (WPAFB). Currently, I am collaborating with Dr. James Tsui and David Lin of AFRL developing signal processing techniques to mitigate various forms of interference on GPS signals.
Related publications and reports:
1. Morton, Y. T. J., Tsui, J. B. Y., Lin, D. M., Miller, M. M., Schamus,
J., Zhou, Q., and French, M. P., “Assessment and handling of CA code
self-interference during weak GPS signal acquisition”, Proceedings of
the 2003 Institute of Navigation Conference, Portland, OR, Sept. 2003.
2. Liou, L.L, J. B. Tsui, D. M. Lin and J. Schamus, F. van Graas, and Y. T.
J. Morton, “Passive Altimeter Study Using GPS Flight Data,” Proceedings
of the 2003 Institute of Navigation Conference, Portland, OR, Sept. 2003.
3. Morton, Y. T., “Developing a simulation model for accessing Ultra-wide
band interference on software GPS receivers”, Summer Faculty Project
Report, Sensors Directorate, Air Force Research Laboratory, Wright Patterson
Air Force Base, August, 2003.
4. Morton, Y. T., "Interference Identification and Removal for Weak GPS Signal Acquisition", Final Technical Report Submitted to the Sensors Directorate, Air Force Research Laboratory, Wright Patterson Air Force Base, August, 2002.
5. Lin, D. M., Tsui, J.B., Liou, L. L., and Y. T. Morton, "Sensitivity analysis of a stand alone GPS software GPS receiver and an acquisition method", Proceedings of the 2002 Institute of Navigation Conference, Portland, OR, Sept. 2002.