Global Navigation Satellite System (GNSS) receivers need to be robust to operate in harsh conditions. The use of Vector Tracking Loop (VTL) architecture in urban environments has improved receiver tracking in such conditions compared to orthodox receivers utilising Scalar Tracking Loops.

In conventional GNSS receivers, tracking is performed in several independent tracking loops that provide measurements (pseudo ranges, pseudo range rates, carrier Doppler) to a navigation algorithm (Kalman filter), controlling the Position, Velocity, Time (PVT) solution. In VTL, the two tasks of signal tracking and PVT estimations are combined; however, VTL architectures are sensitive to channel contamination and data incest. It is therefore required to combine the benefits of VTL with other sensors.

Within the VTL4AV project, Telespazio UK has designed and developed a Software-Defined Radio (SDR) proof-of-concept, implementing a VTL robust architecture including deep coupling with external sensors. The project has also created a fault detection and isolation strategy to ensure integrity in urban environments, whilst supporting multi-GNSS constellations. The benefits of this robust architecture will be demonstrated in both simulated environments (for satellite failure, multipath, attenuation, etc) and in real environments where urban canyons, masking, interference and multipath can be expected.