A Downward Compatible Navigation and Communication Integrated Signal Technology

Satellite transmission technology is developing rapidly, and based on the satellite system's broadcast transmission ability, the satellite system's navigation and communication ability has become a hot topic of future development. In earlier research, our team proposed a satellite navigation and communication integrated technology based on spread spectrum broadband signals. The technology can significantly increase the GNSS satellite downlink broadcast rate while ensuring downward compatibility. This paper summarizes the technology and its technical system. The proposed broadcast signal consists of the navigation signal and communication signal. The navigation signal part is precisely the same as the existing GNSS signal and provides the synchronous service for the communication signal based on the original positioning service. Cyclic Code Shift Keying (CCSK) modulation is used for the communication signal. PN codes in the same family as the navigation signal are used for the spread spectrum. The communication and navigation signals are in the same frequency and phase on radio frequency and synchronized on the baseband. In order to avoid the degradation of detection performance and error performance caused by cross-correlation interference between navigation and communication signals, the code phase optimization algorithm is introduced to turn the cross-correlation function into a favorable condition and enhance the detection performance of the pilot channel and communication channel. Because of the discontinuity of the code phase set, the receiver of the signal can use the fuzzy decision algorithm to improve the fault tolerance of the system to phase jitter and synchronization deviation. Because the proposed signal system transmits information by adjusting the signal delay, the signal is susceptible to the multipath effect. To solve this problem, we design the master-slave Rake receiver strategy by taking advantage of the characteristics of the pilot and communication signal in the same frequency and phase. The Rake receiver parameters are determined through the pilot channel and applied to the communication channel. This method has little change to the receiver and can effectively compensate for the multipath effect. It does not need to occupy more frequency points in the spectrum resources and has good compatibility, which is conducive to promoting and utilizing existing GNSS equipment.