Süß, M: Robust Composite Clock Using Modified Kalman Filteri

Main focus of a global navigation satellite system (GNSS), such as the European System Galileo or the GPS operated by the United States is the generation of a highly stable and robust system time and the determination of the time offsets relative to the system time for each satellite clock. With the application of the so-called clock offset estimates or parameters, pseudo range measurements are corrected to mitigate the time related error of each satellite clock. Evidently, any failure or mal-functioning of the system time affects the synchronization performance. It is therefore a key requirement of a GNSS to generate a robust system time. Conceptually, there are two approaches to be distinguished to establish a system time: the master and the composite clock approach. Contrary to the master clock approach, in which one atomic clock physically defines the system time, a composite clock, studied within this work, establishes its system time as a kind of weighted average out of the participating clock offsets. Using a composite clock, a clock offset affected by an operational event can be excluded from the ensemble defining the average. Within the thesis the design and performance evaluation of an operational composite clock algorithm based on a novel modified Kalman filter is presented.