Event-Based Communication Strategies for Collaborative Inertial Radio SLAM

Event-based communication strategies for vehicles navigating by aiding their inertial navigation systems (INSs) with terrestrial signals of opportunity (SOPs) are developed. The following problem is considered. Multiple navigating vehicles with access to global navigation satellite system (GNSS) signals are aiding their on-board INSs with GNSS pseudoranges. While navigating, vehicle-mounted receivers draw pseudorange measurements from terrestrial SOPs with unknown emitter positions and unknown and unsynchronized clocks. The vehicles share INS data and SOP pseudoranges to collaboratively estimate the SOPs' states through an extended Kalman filter (EKF). After some time, GNSS signals become unavailable, at which point the navigating vehicles use shared INS and SOP information to continue navigating in a collaborative inertial radio simultaneous localization and mapping (CIRSLAM) framework. Two event-based communication strategies to share this information are developed, where instead of sharing information at a fixed-rate when measurements become available, information is only shared whenever any vehicle's position error could violate a user-specified position error threshold with some desired probability. Simulation results are presented demonstrating the tradeoff between localization performance and the accumulated transmitted data when the event-based transmission scheme is employed versus sharing data at the fixed-rate. Experimental results are presented demonstrating two unmanned aerial vehicles (UAVs) navigating in a CIRSLAM framework with SOP pseudoranges drawn from terrestrial cellular towers. The event-based communication scheme reduced the cumulative communicated data by 86.6% compared to a fixed-rate scheme, while maintaining the specified error constraint.