Multi-Constellation Integrated Navigation Satellite Selection Algorithm Based on Integrity Protection Level
Ershen Wang, Caimiao Sun, Chuanyun Wang, Pingping Qu, Tao Pang, He He, Yufeng Huang, Shenyang Aerospace University, China
Location: Pavilion Ballroom East
Alternate Number 2
With the rapid development of Global Navigation Satellite Systems (GNSS), the use of multi-constellation integrated navigation systems are the inevitable trend of future navigation development. In order to ensure the real-time navigation, the problem faced by navigation receivers has changed from the shortage of satellites to satellite selection. There are many satellite selection strategies for selecting a subset of satellites to use for GNSS positioning, mainly based on satellite elevation angle and geometrical dilution of precision (GDOP) performance. Satellite selection algorithm based on satellite elevation angle is that some satellites whose elevation angle is lower than a certain value are excluded, however, removing the low elevation satellite will significantly increase the vertical dilution of precision. Thereby increasing the vertical protection level of the receiver, which makes it difficult to guarantee navigation integrity. The satellite selection strategy based on GDOP value means that a subset of satellites with the smallest GDOP value is selected from all-view satellites subsets, which ensures GNSS positioning accuracy.
The increase in the number of visible satellites ensures GNSS positioning accuracy, however, the performance of a single GNSS service is already difficult to meet the requirement of professional navigation, navigation integrity is also an important indicator. There are more algorithms to ensure navigation integrity, mainly based on the monitoring and exclusion of faulty satellites, such as Satellite-Based Augmentation Systems (SBAS), Ground-Based Augmentation Systems (GBAS) and Receiver Autonomous Integrity Monitoring (RAIM). However, studies focusing on the selection of a subset of satellites for positioning with respect to integrity are rare.
It is well known that the protection level (PL) is closely related to the integrity. Ideally, when selecting m satellites from n toal satellites in all-view for positioning, the navigation receiver can select a set of satellites for positioning with minimum PL and GDOP value. However, integrity is more difficult to guarantee than accuracy in positioning solution. Therefore, a new satellite selection algorithm is proposed in this paper, which sacrifices part of the positioning accuracy in exchange for higher navigation integrity. The algorithm removes a poorly performing satellite each time through "greedy search" until it has m satellites for positioning, which has the smallest protection level. However, when there are more visible satellites, the algorithm is impractical. Therefore, the algorithm is improved to accommodate more cases of visible satellites. Finally, the theoretical derivations are validated using GPS/BDS observation data, the results indicate that the PL of the satellite subset selected in the proposed satellite selection algorithm is within the alarm limit, meanwhile, the GDOP of the selected satellite subset is also relatively small. This means that satellite selection for positioning can be achieved while weighing the accuracy and integrity.