Powerful jammers are able to disable consumer-grade global navigation satellite system (GNSS) receivers under normal operating conditions. Conventional anti-jamming techniques based on the time-domain are unable to effectively suppress wide-band interference, such as chirp-like jammer. This paper proposes a novel anti-jamming architecture, combining wavelet packet signal analysis with adaptive filtering theory to mitigate chirp interference. Exploiting the excellent time-frequency resolution of wavelet technologies makes it possible to generate a reference chirp signal, which is basically a “de-noised” jamming signal. The reference jamming signal then is fed into an adaptive predictor to function as a refined jamming signal such that it predicts a replica of the jammer from the received signal. The refined chirp signal is then subtracted from the received signal to realize the aim of anti-jamming. Simulation results demonstrate the effectiveness of the proposed method in combating chirp interference in Galileo receivers. We achieved jamming-to-signal power ratio (JSR) of 50dB with an acquisition probability exceeding 90%, which is superior to many anti-jamming techniques based on the time-domain, such as conventional adaptive notch filters. The proposed method was also implemented in an software-defined GPS receiver for further validation.

With the development of global navigation satellite systems (GNSS), the interference among global navigation satellite systems, known as the radio frequency compatibility problem, has become a matter of great concern to system providers and user communities. The acceptable compatibility threshold should be determined in the radio frequency compatibility assessment process. However, there is no common standard for the acceptable threshold in the radio frequency compatibility assessment. This paper firstly introduces the comprehensive radio frequency compatibility methodology combining the spectral separation coefficient (SSC) and code tracking spectral sensitivity coefficient (CT_SSC). Then, a method for determination of the acceptable compatibility threshold is proposed. The proposed method considers the receiver processing phase including acquisition, code and carrier tracking and data demodulation. Simulations accounting for the interference effects are carried out at each time step and every place on earth. The simulations mainly consider the signals of GPS, Galileo and BeiDou Navigation Satellite System (BDS) in the L1 band. Results show that all of the sole systems are compatible with other GNSS systems with respect to a special receiver configuration used in the simulations.

The auto-correlation function (ACF) of Binary Offset Carrier (BOC) modulated signals has multiple peaks which raise the problem of ambiguity in acquisition and tracking. In this paper, the ACF is split into several sub-correlation functions (SCFs) through dividing the integration period of ACF into several partials. Then a pseudo correlation function (PCF) is constructed from the SCFs through a combination function to eliminate all side-peaks. The unambiguous tracking method based on the PCF achieves better code phase tracking accuracy than the conventional methods in AWGN environment. It only requires half computation cost of Bump-Jumping (BJ) and nearly quarter of Double-Estimator, although offers slightly less accurate tracking than BJ and Double-Estimator in multi-path environment. Moreover, this method suits all kinds of BOC signals without any auxiliary correlators.

A new concept for a navigation and communication satellite system has been proposed. The navigation satellite system that forms the basis of the proposed system has been studied by one of the authors and extended to add a mobile communication function to the system. The satellite system consists of 15 satellites in quasi-geostationary orbit (QGEO) that have a geostationary altitude and high inclination and provide global coverage and positioning capability to the observer through only reception of the range measurement signals generated at the satellites, which are in the same configuration as the satellites in Global Positioning System (GPS), Three satellites out of the 15 satellite are designated to install a subsystem for mobile satellite communication in order to satisfy mobile communication convenience as required in a Future Air Navigation System's (FANS) concept of International Civil Aviation Organization (ICAO). The case studies of 15-satellites constellations demonstrate not only an acceptable positioning accuracy over the whole globe, but also an accuracy distribution weighted on the north pole region as an example of a weighted accuracy distribution. The addition of a mobile communication function suggests a unified system of satellite navigation and communication, which might provide convenience for the civil aviation industry, because the two functions currently depend on different systems.

A new concept for a positioning satellite system based on a new satellite constellation has been studied. The system needs a minimum of four satellites injected into quasi-geostationary orbit (QGEO) with high inclination. Due to the QGEO characteristic, the satellites are orbiting within continuous visibility range of ground control stations (GCS), from which the satellite time is controlled through the link connections of the feeder and the intersatellite communication (ISC). Consideration is made for the required high accuracy and quality checks against malfunction, wherever the satellites may be positioned. The orbit data processing function, another major function, is performed independently of the time control. The case of global coverage attained by twelve satellites has been studied in this paper. When a constellation of satellites for a global navigation satellite system (GNSS) is designed, conditions to obtain a good geometric dilution of precision (GDOP) at all places and times should be considered. Therefore, the satellites will be spread out in wide directions and are in an asymmetrical arrangement when seen by an observer are considered when setting the parameters of the ephemerides of the constellation. Under the restraints of the designed constellation, the GDOP value distribution for a third of the world map with area time parameters is computed and summarized in histograms for the system evaluation.