Brent M. Ledvina

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Since its creation, the Global Positioning System (GPS) has grown from a limited purpose positioning system to a ubiquitous trusted source for positioning, navigation, and timing data. To date, researchers have essentially taken a signal processing approach to GPS security and shown that GPS is vulnerable to jamming and spoofing. In this work, we(More)
A set of efficient algorithms for processing code-division multiple-access spread spectrum signals has been developed. They make use of bit-wise parallelism to process 32 samples simultaneously. These algorithms have been implemented in a real-time global positioning system software receiver. The receiver consists of a radio-frequency front end, a system of(More)
Background theory, a reference design, and demonstration results are given for a Global Navigation Satellite System (GNSS) interference localization system comprising a distributed radio-frequency sensor network that simultaneously locates multiple interference sources by measuring their signals’ time difference of arrival (TDOA) between pairs of nodes in(More)
This article is a review of Global Navigation Satellite Systems for space scientists who are interested in how GNSS signals and observables can be used to understand ionospheric dynamics and, conversely, how ionospheric dynamics affect the operational capabilities of GPS. The most common form of GNSS is the Global Positioning System (GPS); we will first(More)
A dual-frequency civilian GPS receiver has been developed that runs 10 tracking channels in real time using a software correlator. This work is part of an effort to develop a flexible receiver that can use the new GPS L2C CM/CL signals as they become available on L2 without the need for new correlator hardware. The receiver consists of an RF front end, a(More)
Global Positioning System (GPS) is a satellite based navigation system. The GPS system positional accuracy is limited by ionospheric error. Ionospheric delay is a function of Total Electron Content (TEC). Prediction of ionospheric delays is very important for high precision application such as civil aircraft landing and missile guidance application. In this(More)
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