Spectrum Compatibility Analysis Between LEO Navigation Augmentation Signals and GNSS Signals

Taking advantage of low-earth-orbit (LEO) satellites to establish a LEO navigation augmentation system as a supplement to GNSS is an important development direction in the future. At present, the frequency bands for satellite radio navigation allocated by the International Telecommunications Union (ITU) is quite crowded. BDS, GPS, GLONASS and GALILEO are all overlapped in the L-band. If the signal system of the LEO navigation augmentation system is similar to that of GNSS and occupies the same frequency band, this will inevitably bring the problem of spectrum compatibility. The important parameters of spectrum compatibility evaluation are spectrum separation coefficient, code tracking spectrum sensitivity and effective carrier-power-to-noise-density(C/N0) degradation, which does not consider the influence of Doppler frequency offset. However, the Doppler frequency offset of LEO navigation signals is relatively large, which will have a great impact on spectrum compatibility evaluation. Therefore, this paper analyzes the influence of large Doppler frequency offset on spectrum compatibility analysis, and simulates the interference of LEO navigation augmentation signals to GNSS signals in L1/E1/B1 frequency band, in which the Doppler frequency offset between LEO navigation satellites and GNSS satellites arriving at the same receiver at different times is considered. The analysis results show that due to the large Doppler frequency offset between signals, the effective C/N0 degradation of GNSS signals caused by LEO navigation signals is very small, which can be acceptable. By analyzing the spectrum compatibility of LEO navigation augmentation signals and GNSS signals, this paper provides a theoretical basis for the frequency band selection of LEO navigation augmentation system in the future.