Abstract
Ground-based pseudolite systems have some limitations, such as low vertical accuracy, multipath effects and near-far problems. These problems are not significant in airborne-based pseudolite systems. However, the monitoring of pseudolite positions is required because of the mobility of the platforms on which the pseudolites are mounted, and this causes performance degradation. To address these pseudolite system limitations, we propose an airborne relay-based regional positioning system that consists of a master station, reference stations, airborne relays and a user. In the proposed system, navigation signals are generated from the reference stations located on the ground and are relayed via the airborne relays. Unlike in conventional airborne-based systems, the user in the proposed system sequentially estimates both the locations of airborne relays and his/her own position. Therefore, a delay due to monitoring does not occur, and the accuracy is not affected by the movement of airborne relays. We conducted several simulations to evaluate the performance of the proposed system. Based on the simulation results, we demonstrated that the proposed system guarantees a higher accuracy than airborne-based pseudolite systems, and it is feasible despite the existence of clock offsets among reference stations.
Highlights
The need for location information has been increasing on account of the growth of the location-based service industry
We assumed that the position change of airborne relays, which results from the propagation time difference of navigation signals, during relay, is negligible
To demonstrate the feasibility of the proposed positioning algorithm, we evaluated the performance of the proposed system if reference station clock offsets occurred
Summary
The need for location information has been increasing on account of the growth of the location-based service industry. A positioning concept was proposed that employs multiple ground-based pseudolites, which are transmitters of GNSS-like signals, and provides navigation signals through these pseudolites [3]. The near-far problem occurs, because the received power level of the pseudolite signals can vary over a large range [7] As another approach, the airborne-based pseudolite positioning system has been studied in conjunction with the ground-based system. The Chinese Area Positioning System (CAPS) was proposed [13] It differs from other positioning systems in that its navigation signals are generated from a ground station and delivered to users through communication satellites. The user sequentially estimates the airborne relay positions and his/her own position using the relayed signals Owing to these structural and procedural characteristics, the proposed system has advantages over the pseudolite-based positioning system and CAPS.
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