2904666262

The transmission conditions influence on position accuracy in NAYSTAR-GPS system

Krzysztof Ostrowski Supervisor: dr inż. Tomasz Mąka

Abstract

NAVSTAR-GPS positioning system, also known as GPS, is a satellite-based naviga-tion system that is used widely both in civilian and military for positioning, navigation, timing and other position related applications. Positioning systems are based on time delay and freąuency-shift estimation of the incoming signals in the receiver side, in order to compute the user’s location.

Sources of accuracy degradation in satellite-based navigation systems are well-known. While atmospheric-dependent sources (delays that depend on the ionosphere and tro-posphere conditions) can be greatly mitigated by applying available mathematical at-mospheric models, the Doppler freąuency shift and multipath effect need special at-tention to the receiver engineering.

Provided in this thesis software implementation of NAVSTAR-GPS receiver fol-lows the concept of software-defined radio (SDR). In the presented NAVSTAR-GPS receiver design the acąuisition and tracking processes are related to LI carrier C/A codę MATLAB Simulink simulated signal. The purpose of this thesis is to develop the acąuisition and tracking algorithms to extract the navigation data bits from mentio-ned signal and check the bits validity in case of navigation signal fluctuations. Later developments of navigation signal efficiency improvement techniąues are also discussed.

Complete implementation of NAVSTAR-GPS system has been developed in MATLAB Simulink R2008a software taking advance of Embedded MATLAB [Mat]. The receiver tracking algorithm consists of early-late gate for codę tracking and Costas loop for carrier tracking. Acąuisition process implements parallel codę phase search approach and fine freąuency measurements.

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