Multi-Level Gnss Signal Simulator For Multi-System Gnss Receiver Developing

Since Global Positioning System (GPS) keeps running for over 30 years, higher performance Global Navigation Satellite Systems (GNSS) has become one of the most important demands for navigation and location services. New GNSS systems like Galileo and COMPASS are making their efforts to satisfy the demands of providing higher measurement accuracy, better tracking robustness and lower tracking sensitivity. These improvements can be achieved through new signal structure, more frequency bands, system interoperation and so on. Thereby, Multi-System GNSS receiver developing would become a hard work, including new architectures designed for new system navigation signal acquisition, tracking and data demodulation processes, especially for the global navigation satellite systems which are under construction, such as COMPASS and Galileo.Traditional GNSS signal simulator provides a comprehensive simulation platform for verifying and assessing the Multi-System GNSS receiver before the corresponding new satellites are deployed. But when we need to analyze how the key technical indicators, such as cold/worm/hot start Time to First Fix (TTFF), acquisition sensitivity and tracking sensitivity, are implemented in the signal processing level and information processing level, or testing and validating the solution for Multi-System compatible design, we can get little help from it. Thereby, a Multi-Level GNSS signal simulator providing testing methods for different design levels of the receiver can bring many benefits to the design and development of Multi-System GNSS receiver. Overall, the Multi-Level GNSS signal simulator can test three design levels of receiver, which can be defined as signal processing level, information processing level and system level, respectively. For receiver designers, testing the receiver from different levels can be used to figure out the influence of each processing level caused to the final performance of the receiver, verify the correctness of the processing algorithms in different levels and analyze whether the design goals in different levels are reasonable as well.This paper presents a Multi-Level GNSS signal simulator based on Software Defined Radio (SDR) architecture and PXI bus, which can generate GPS, Galileo and GLONASS navigation signals, even the candidate signals of COMPASS, on the common hardware platform. The designed simulator provides different testing modes for testing different levels of the receiver, and plays an important role in the design and testing of a self-developed Multi-System GNSS receiver.