# Evaluating GNSS Receiver Resilience: A Study on Simulation Environment Repeatability
## 4 Automated Testbed
Testing an older generation receiver allows for a clearer illustration of the advantages of modern interference mitigation techniques and the benefits of utilizing multiple satellite navigation systems. Modules were then mounted onto custom-designed printed circuit boards to provide crucial additional functionalities not typically found in commercial products: the ability to completely remove power from the GNSS module (including disconnecting any NVRAM backup battery) and to issue a reset signal via USB commands. A USB-RS232 TTL integrated circuit facilitated serial communication and control over both the power supply and the reset signals. This setup granted the PC  
Figure 5: Block diagram illustrating the automated measurement system designed to evaluate GNSS receiver performance under intentional jamming. based control software complete authority over the module's state, enabling a true cold start condition for each measurement, ensuring consistent initial conditions across all repetitions. The choice of these low-cost receivers serves to demonstrate the significant impact of jamming, a factor often underestimated by researchers whose primary focus is not GNSS, leading them to consider more expensive, potentially more robust receivers as unnecessary. Furthermore, low-cost variants are prevalent in everyday consumer electronics, from drones to vehicle navigation systems. Utilizing these readily available modules allows for a direct comparison between single-frequency receivers, a comparison that would necessitate a redesign of the jamming scenarios to incorporate additional frequency bands if more expensive, often dual-frequency, receivers were used. To evaluate the receiver response to interference, a comprehensive test involving three receivers subjected to various interference scenarios was conducted using a simulated static GNSS position (46\({}^{\circ}\)02'55.6\({}^{\prime\prime}\) N 14\({}^{\circ}\)30'30.7\({}^{\prime\prime}\) E) with satellite almanacs and ephemerides from June 10, 2024, 12:00 CET. Simulating a static location via a GNSS simulator was a deliberate choice, crucial for the clarity of this research by eliminating additional variables. In dynamic movement scenarios, GNSS modules can leverage external MEMS accelerometers to predict heading and speed, delaying the noticeable impact of jamming. This additional complexity would obscure the core interference effects that this research aims to communicate. Furthermore, static locations represent real-world critical applications, such as reference GNSS networks in geodesy for RTK correction systems and slow-moving objects like shipyard cranes, which require robust operation in jamming-free environments. Each receiver underwent 50 repeated measurements for different interference conditions. Before measurement, the GNSS module's power supply was cycled via program commands to ensure a consistent cold start state, devoid of almanac data, visible satellites, and code synchronization. The simulation began with the playback of the I/Q samples and simultaneous power-up of the GNSS module. The receivers were allowed 180 s to achieve their initial 3D position fix, a duration exceeding their typical acquisition time to provide a safety margin. Following this, NMEA sentences, representing the receiver's output, were recorded at a 1 Hz frequency interval. Figure 6: Photograph of the automated GNSS receiver evaluation system. The setup features a network switch (**top left**) for data communication between a personal computer, a GNSS signal generator, and an RF jammer. A spectrum analyzer (**right**) monitors the generated spectrum and measures the carrier-to-noise density ratio before it reaches the GNSS receiver under test. Subsequently, an external jammer was activated for 100 s (within 280 s of the simulation's start) and then deactivated. The receiver's data recording continued for an additional 80 s after the jammer was turned off.