Multi-Constellation T-RAIM: an Experimental Evaluation

Time-Receiver Autonomous Integrity Monitoring (T-RAIM) algorithms assess the reliability of the timing solution provided by a Global Navigation Satellite System (GNSS) timing receiver. Timing receivers process GNSS observables under the assumption that their antenna is static or that their position is known. In this way, additional redundancy is obtained with respect to the standard Receiver Autonomous Integrity Monitoring (RAIM) framework. This paper describes a potential T-RAIM approach developed in a multi-constellation context. Measurements from several GNSS constellations provide increased redundancy at the cost of an increased system complexity. In this respect, timing receivers have to take into account Inter-System (IS) biases and drifts between different GNSS time scales. Several configurations are considered and compared. The benefits brought by multi-constellation T-RAIM are demonstrated using real GPS and Galileo measurements collected in a harsh propagation environment.