Global BeiDou Navigation Satellite System Research Articles

Time division inter‐satellite link topology generation problem: Modeling and solution

SummaryIn this paper, we study the time‐division inter‐satellite link topology generation (TDILTG) problem for the well‐known Chinese BeiDou Global Navigation Satellite System. The TDILTG problem consists in generating a time‐division topology of the inter‐satellite link network for the navigation satellite system to spread systematic data to all satellites via a few source satellites with the purpose of minimizing the time required to spread the data. We propose a mathematical model to formulate the TDILTG problem and study its 2 lower bounds through a thorough analysis of the problem characteristics. We also present a deterministic constructive (DC) algorithm to solve this problem approximately but very quickly, with a time complexity of O(n3), where n is the number of satellites. Extensive experimental studies on a wide range of randomly generated instances show that the proposed DC algorithm is able to obtain the optimal solutions for most tested instances in less than 1 second. Meanwhile, we also validate that the DC algorithm performs well when the problem scale is large. Furthermore, we provide insights of the effects of different instance parameters on the final results.

Monitoring and evaluation algorithm of GNSS signal in space availability

In civil aviation and other navigation application fields, the availability of Global Navigation Satellite System (GNSS) in Signal in Space (SIS) is a key indicator to evaluate the performance. In this paper, the SIS availability of Global Positioning System (GPS) and BeiDou Navigation Satellite System (BDS) are evaluated and analyzed. The model of satellite availability algorithm is constructed based on the Markov process, with its reliability investigated. Moreover, the evaluation algorithm of constellation availability is developed. Based on the evaluation models, the performance of GPS SIS and BDS SIS is evaluated by using the measured data, respectively. Combined with the availability standard of GPS Standard Positioning Service (SPS) performance standards and BDS Signal In Space Interface Control Document (Version 2.0), the proposed evaluation models of SIS availability are effective and the performance of GPS SIS and BDS SIS conform the availability of performance standards, respectively. Meanwhile, the results are instructive for the study of the availability performance monitoring and the evaluation of global BDS.

Influence of the time‐delay of correction for BDS and GPS combined real‐time differential positioning

Real-time differential (RTD) positioning can achieve a real-time metre-lever positioning based on the differential correction data from a nearby reference station. However, the time-delay of correction data is generally unavoidable when receiving it from the reference station in real-time. Multi-global navigation satellite system combined positioning has the advantages of improving the positioning availability, continuity and accuracy; however, it remains unknown whether it can effectively overcome the time-delay of differential correction in RTD positioning. This Letter focus on the tolerance of time-delay for differential correction in BeiDou global navigation satellite system (BDS) and global positioning system (GPS) combined RTD positioning. Based on a set of static data and a set of dynamic data, the performances of BDS standalone, GPS standalone and BDS and GPS combined RTD positioning by 15 kinds of time-delay of the differential correction data were studied and compared. The numerical results show that, BDS and GPS combined RTD positioning can tolerate longer time-delay of the corrections than BDS or GPS standalone positioning for the same requested positioning accuracy.