Satellite Selection for Multi-Constellation SBAS

Abstract

The incorporation of multiple constellations into satellite based augmentation systems (SBAS) may lead to cases where there are more corrected satellites in view than a receiver has tracking channels. This paper addresses two related topics: identifying the most important satellites to track in order to provide availability; and identifying a recommended number of channels. Previously, the SBAS minimum operational performance standards (MOPS) specified a minimum number of channels required for the user receiver. It is possible to obtain significantly worse availability with this minimum number than with the all-in-view solution when employing a poor satellite selection algorithm. Alternatively, it is possible to achieve high availability with fewer than the minimum number of channels and a very good selection algorithm. This paper describes example selection methods that achieve high availability. It further describes a method to specify performance instead of a minimum hardware channel capacity. This form of specification allows for greater flexibility in receiver design. Manufacturers would be allowed to choose between more channels combined with a simpler algorithm versus fewer channels and a more sophisticated algorithm.

Satellite selection in the context of an operational GBAS

“…Instead, the results and implications apply to any kind of satellite selection in GBAS. As the used algorithm in this work, we utilize our previously presented optimization method with slight modifications on the selection criteria in line with Walter et al Using an exhaustive search instead could change some of the results slightly, but as Gerbeth et al showed the heuristic algorithm to differ by well below 1% on average, we decided on a heuristic approach for the reason of inapplicable computation times otherwise.…”

“…When a GBAS ground station makes a selection of satellites to broadcast corrections for, these factors should be considered instead of just selecting the satellites that lead to the best performance at a given epoch right at the ground station's location. While the topic of satellite selection in general has been largely covered very recently, this work is not limited to a specific selection algorithm but valid for any kind of selection. The objective is rather to show that satellite selection in GBAS is not largely affected by operational implications that cannot be avoided.…”

Assessment of Satellite Selection Methods under DFMC SBAS Augmentation for LPV-200 Approach Operations

“…• "Downdate" method: as defined in [2], activated every epoch; • "Elevation" method: the N highest satellites are selected every epoch, where N is the maximum number of satellites a receiver can process; • "Slow Elevation" method: the free channels are allocated to the highest non-tracked satellites, a channel being set free when the elevation of the tracked satellite falls below 5°; • "Slow Random" method: the free channels are allocated randomly to satellites with elevation higher than 5°, a channel being set free when the elevation of the tracked satellite falls below 5°. After the re-allocation of a channel, the satellite acquisition is modelled in two steps:…”

Fixed Subset Selection to Reduce Advanced RAIM Complexity

“…There are several methods to reduce ARAIM complexity. One way consists in performing satellite selection: the receiver only uses a subset of all the satellites that are in view [2], [3]. This approach reduces the overall receiver computational load for any GNSS based system, and reduces the number of subsets for ARAIM.…”