Development of a Real-time GNSS Software Receiver for Evaluating RAIM in Multi-constellation

As Global Navigation Satellite System continues to upgrade, there will be an increasing number of satellites and signals. This offers users benefits such as increased availability and improved diversity of signal For safety-of-life users like aviation, higher availability of integrity is the key goal. A technology providing integrity with little or no ground infrastructure overhead is receiver autonomous integrity monitoring (RAIM). As more satellites are visible to the receiver, the redundancies increase and RAIM availability for detecting faults improves. For evaluating RAIM in multi-constellation in a physical receiver, a real-time software receiver is developed using relative low-cost Commercial Off-The-Shelf (COTS) components. The receiver currently supports single frequency and three constellations with Code Division Multiple Access (CDMA) signals including GPS L1 C/A, Galileo El and BeiDou B1. An efficient software architecture are proposed for the real-time purpose. Some issues are addressed when integration multi-constellation. Using the outputs from the receiver, a developed RAIM script computes the protection levels for the receiver position. Several tests are conducted in multiple locations worldwide and the results show the multi-constellation GNSS has improvement on the position solution and protection level. In the end, future path forward dual-frequency Advanced RAIM (ARAIM) is mentioned.