Signal Design and Compatibility Assessment for LEO Navigation Augmentation System

With the booming development of low earth orbit (LEO) satellite constellations, improving the global navigation satellite system (GNSS) performance based on LEO satellites is attracting more and more research attention. To shorten the convergence time of precise point positioning (PPP) with the help of the LEO navigation augmentation system, the dedicated LEO navigation augmentation signals need to be broadcasted, and the signals need to meet some special design requirements. This paper takes the GNSS L1 and L5 frequency bands as examples to design the LEO navigation augmentation signals. From the perspective of reducing interference to GNSS signals, the carrier frequency of the LEO navigation augmentation signal is selected, and the modulation type is designed. In order to support both high-precision measurement and high data rate, it is proposed that the LEO navigation signal consists of a measurement component and a data component with a high data rate. These two signal components are combined into one composite signal using the multiplexing code shift keying (MCSK) method. On this basis, compatibility between LEO navigation augmentation signals and GNSS signals is evaluated. The impact of LEO navigation augmentation signals on GNSS signals is further analyzed.