Ground-based pseudolite positioning systems are valuable in environments where global positioning system (GPS) is not available. To mitigate near-far effect, pseudolite positioning systems often use pulsed signals instead of GPS-like continuous signals. The simple pulse scheme without slot-permutation cannot preserve the spectrum shape of the original un-pulsed signal, and this may result in false frequency-lock in the receiver. Complicated pseudorandom pulse schemes are often used to avoid false frequency-lock, which increases acquisition and tracking complexity. The synchronisation method presented in this study can acquire and track pulsed signals without false frequency-lock under the pulse scheme without slot-permutation, which enables the use of this pulse scheme in pseudolite positioning systems and is useful for reducing complexity of transmitter and receiver. Simulation results show that the presented method can track code phase, carrier phase and Doppler frequency accurately and correctly.

Navigation Signal based on Compound Carrier (NSCC), is proposed as the potential future global navigation satellite system (GNSS) signal modulation scheme. NSCC, a kind of multi-carrier (MC) signal, is generated by superposition and multi-parameter adjustment of sub-carriers. Therefore, a judious choice of parameter configation is needed. The main objective of this paper is to investigate the performance of the NSCC which is influenced by these parameters and to demonstrate its structure characteristics and superiority, employing a comprehensive evaluation system. The results show that the proposed NSCC signal processes full spectral efficiency and limited out of band (OOB) emissions, satisfying the demands of crowed frequency resources. It also presents better performance in terms of spectral separation coefficients (SSCs), tracking accuracy, multipath mitigation capability and anti-jamming reduction compared with the legacy navigation signals. NSCC modulation represents a serious candidate for navigation satellite augmentation systems, especially for signals applied in challenging environments.

As the Global Navigation Satellite System (GNSS) is widely used in all walks of life, the signal structure of satellite navigation is open, and the vulnerability to spoofing attacks is also becoming increasingly prominent, which will seriously affect the credibility of navigation, positioning, and timing (PNT) services. Satellite navigation signal authentication technology is an emerging technical means of improving civil signal anti-spoofing on the satellite navigation system side, and it is also an important development direction and research focus of the GNSS. China plans to carry out the design and development of the next-generation Beidou navigation satellite system (BDS), and one of its core goals is to provide more secure and credible PNT services. This paper first expounds on the principles and technical architecture of satellite navigation signal authentication, then clarifies the development history of satellite navigation signal authentication, and finally proposes the BDS authentication service system architecture. It will provide technical support for the construction and development of the follow-up Beidou authentication service.