R-Mode: An Alternative to Global Navigation Satellite Systems for Terrestrial Navigation at Medium Frequencies

Kurzfassung

Positioning and timing information is fundamental for our daily lives in today’s society. Our society uses this information in many applications such as telecommunication networks, energy grids and general navigation applications. Today this crucial information is mainly derived from the global navigation satellite system. Due to the low signal strength, this signal is prone to jamming and spoofing. Therefore, we need backup systems as countermeasures. R-Mode is such a system under development for use in the maritime domain. We utilize existing transmitter infrastructure to transmit a modified signal that enables ranging, and, if a sufficient number of stations is received, positioning. Our goal in this thesis is to develop a prototype receiver for the modified signals transmitted at medium frequencies. In a first step, we extend the existing descriptions of the Medium Frequency R-Mode system by exploring the different biases introduced in the transmitter chain and propagation. The knowledge is fundamental for our development as any solution needs to mitigate this influence. In a second step, we derive the theoretical lower performance bound of the system, which we use for a coverage prediction for the R-Mode Baltic test-bed. We use the derived bounds further to test the performance of different estimation approaches on the R-Mode signal. Around the estimation, we design a software-defined radio-based receiver that can perform real-time positioning estimation. We characterize different hardware components to ensure the best performance and integration in the developed receiver software. The results are modules that can be freely combined to fit the receiver for a given task. For a prototype, we conducted measurement campaigns to generate real dynamic and static positioning results. During our trials, we delivered the first positioning solution in the far field of the R-Mode transmitter. In the last part of this work, we used our results and experience to suggest further improvement on the signal verifying with simulations