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Inter-satellite link technology is one of hot issues in current satellite navigation field and construction of inter-satellite link system cannot be completed without the cooperation and supports of ground anchor stations. In this paper, with respect to time synchronization issue which is of great importance in the construction of anchor stations for inter-satellite link, key technological issues such as time system design for anchor station, method of synchronization with standard time, clock error of anchor station and the determination of its precision have been deeply discussed and studied. On the base of relevant studies, a complete design method and solution of time synchronization system for anchor station has been proposed herein, thereby offering solution ideas and technological supports for resolving key problems encountered during the construction of anchor stations for inter-satellite link in China. The anchor station time system proposed in this paper can better ensure the time difference between ground station and BDT is less than 1us and the time synchronization precision of anchor station is less than 5ns, thereby guaranteeing the reliability of anchor station acting as Pseudolite being connected to inter-satellite link while offering further reference for subsequent testings and development of inter-satellite link.

Since the overall distribution of users in the sea area is sparse, it will appear densely in a local angle domain. Specifically, the 3D massive MIMO antenna system are established, which are with the ability to distinguish users in the same horizontal direction as well as vertical direction. According to this, a joint user scheduling and beam selection scheme based on the automatic identification system (AIS) is proposed to solve the problems that of the interference cancellation for the users in the angle domain. In particular, the proposed scheme divides the beam according to the users' location information. Furthermore, we select the user with the highest priority in the beam to form a set of the users in serving, in the meanwhile, the greedy algorithm is used to schedule the user combination to achieve the greatest sum rate. By means of the numerical results, it is shown that the proposed scheme can be used to schedule and serve users in the case of crowded angle domain, and the scheme can obtain near-optimal sum rate.

The method of common-view is characterized by higher precision, good convenience in use, and cheap instrument. A new time synchronous method for multiple users system by common-view technology is presented based on the GEO Positioning System (GEOPS). And the GEOPS common-view theory is studied for which is different from the other GNSS system. This paper introduces the working process and the time service pattern of the GEOPS. In the GEOPS, the pseudo- range found by the receiver through testing is actually the measurement of the whole link from the main control station and through the satellite to the receiver. Due to the different distances between the main control station and each satellite, this measurement has to be done using the upload delay correction by the main control station. The upload delay adopts a polynomial model and the polynomial parameters are demodulated from the navigation message to calculate the delay correction value during the adjustment. In accordance with these characteristics of GEOPS, we propose the GEOPS common-view theory. The format parameters of GEOPS common-view and data calculating method are presented. The time synchronization system, the error analysis and the applied plan of GEOPS common-view technology are introduced. Index Terms-GEOPS; multipel users system; time synchronization; common-view

Since the research on compatibility is becoming a worldwide “hot spot”, decision has been made to improve the anti-jamming performance between satellite systems. Nowadays, primarily been driven, amongst other motivations, by the desire to ameliorate the compatibility performance of GNSS, speculation has continued on the possibility of further optimization. Of special interests is the inter-system interference that one satellite navigation system will suffer due to another satellite navigation system. This paper reports our recent studies in seeking methods for analyzing the inter-system interference.

System integrated clock (SIC) plays an important role in implementing the high-accuracy constellation automatic time synchronization and information exchange. In the establishment of SIC, error and noise are unavoidably introduced. In the paper, various error sources in the process are analyzed at first, and then an error-reduction method under the model of two-way plus common view time comparison is put forward and analyzed. Theory research and simulation experiment show that the constellation time synchronization error is below 10 seconds.