A GPS and GLONASS L1 Vector Tracking Software-Defined Receiver
Type of DegreeMaster's Thesis
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Originally designed for military navigation, GPS has exploded into a modern tool used by government, industrial, and commercial sectors. The position and timing services GPS receivers provide have been integrated into electrical power grids, banking and finance markets, wireless communication links, robotics, and several other applications. The increasing demand for navigation has led to the operation of GPS receivers in challenging signal environments that include suburbs, forested areas, and metropolitan cities. In recent years, GPS receivers have also come under attack from commercial jamming and spoofing devices. To assure the integrity of GPS, the ability for receivers to overcome challenging signal environments must be solved. GPS vectorized signal tracking (vector tracking) has been shown to enhance receiver performance by 2 to 6 dB in poor signal environments over traditional tracking methods that rely on loop filters (scalar tracking). Vector tracking operates by coupling a receiver’s signal processor and navigation estimator together, tracking all the satellite broadcasts as one combined signal. This effectively increases a receiver’s robustness to noise. However, as the signal conditions become worse, GPS vector tracking will fail. GLONASS, the Russian Federation’s equivalent to GPS, is another system that can be used for navigation. Today, many receivers use both GPS and GLONASS with scalar processing. Implementing both constellations into a centralized vector tracking filter gives the opportunity of enhanced navigation capability in challenging areas. In this thesis, the development and analysis of a software receiver that uses GPS and GLONASS vector tracking is performed. Simulation results showed the software receiver’s ability to maintain accurate navigation in GPS or GLONASS jamming environments. Experimental results in forests and urban canyons validated the advantages of integrating GPS and GLONASS with vector tracking over traditional loop filter methods. The thesis concludes that GPS and GLONASS vector tracking can outperform GPS vector tracking so long as GLONASS is not significantly degraded by the environment. From these conclusions, several opportunities of research open up to enhance the software receiver further.