## 1 Introduction
Since the interference brought about by the rapid development of mobile communication systems will have a practical impact on the ability of GNSS to provide high-precision and stable services in the long term, ensuring compatibility between the systems is a prerequisite for the realization of the synergistic development of the integration of air and space as the new generation of mobile communications is constructed and operated. In recent years, scholars at home and abroad have studied ground communication and satellite navigation system interference events, with the use of different interference analysis indicators to determine the impact on the signal. The U.S. terrestrial communication system optical cube system has appeared to have an impact on the navigation performance of GPS systems in the neighboring frequency [5]. For this reason, the U.S. government has analyzed the system's ground modeling, operation scenarios, interference analysis of GPS systems, simulation and testing, and interference elimination measures to ensure the safe operation of the system. [PERSON] et al. used the spectral separation coefficient as an assessment of inter-system coexistence metrics to illustrate the impact of the optical cube system on the signals in the L1 and E1 frequency bands [6; 7]. For the study of the compatibility issue between the two systems, [PERSON] et al. of the Galileo Architecture Support Team of the European Commission used the method of interference coefficients and equivalent carrier-to-noise ratios as metrics for the analysis of inter- and intra-system interference [8]. [PERSON] et al. from the Joint Research Center of the European Commission pointed out that interference from LTE signals may have a significant impact on pseudorange measurements and position calculations of GNSS. In the case of frequency band proximity, strong interference from LTE signals may lead to an increase in pseudorange error, thus affecting position accuracy [9]. On the domestic front, as the BeiDou system has been put into use, compatibility studies between it and mainstream mobile communication systems have been carried out one after another. People began to conduct compatibility studies between S signal and mobile communication systems, and the satellite receiving terminal was tested in different scenarios. The results showed that the 4G signal located at 2555 MHz-2575 MHz would cause the carrier-to-noise ratio of the BeiDou S signal to degrade, resulting in obvious interference effects [10]. [PERSON] et al. used the carrier-to-noise ratio deterioration value as an evaluation index from the link budget point of view and analyzed the neighboring frequency interference caused by 4G to the BeiDou RDSS system. The results indicated that the interference would cause 5 dB-10 dB carrier-to-noise ratio degradation [11]. In 2019, the Beijing Satellite Navigation Center, from the point of view of the RF, proposed a response strategy for the interference of 4G to the BeiDou RDSS [12]. As 5G enters the stage of high-speed development, people begin to study the compatibility of 5G signals with satellite navigation signals. In 2021, [PERSON] et al. of Beijing Satellite Navigation Center analyzed the impact of 5G signals on BeiDou RDSS from the perspective of signals by using the equivalent carrier-to-noise ratio as an evaluation index, and gave the safe distance between the 5G base station and the RDSS receiver to be 40 m under the premise that the communication success rate is at 95% [13]. In 2022, Xi'an University of Posts and Telecommunications analyzed the interference results of 5G signals on BeiDou RDSS from the factors of positioning, communication, and bandwidth, and designed experimental scenarios for testing [14].