Pulsed-RF Ultrawideband Ranging for the GLANSER GPS-Denied Emergency Responder Navigation System

All inertial-only locator systems contain some level of drift that causes the error in the position estimate to grow. A number of techniques have been proposed to minimize this drift however without some external means to periodically establish an absolute correction, the position error continues to increase with time, motions exhibited, and distance traveled. Typically, this external position update is provided by GPS however, in GPS-denied environments, it must be obtained from RF range measurements relative to other devices at known positions. However, as with all RF ranging systems, the ranging signals are susceptible to multi-path reflections, signal fading, and interference resulting in lost signals or signals with significant errors. The GLANSER system is developing a number of strategies to mitigate these issues ensuring the navigation system is able to accurately and robustly blend the ranging radio solution even in the presence of significant signal distortion. In this paper we review the GLANSER navigation architecture with a focus on the mobile and anchor ranging radio operations in the context of the impact of merging the range measurement errors with the navigation solution. We will discuss the importance of multipath resistance and therefore high bandwidth/minimum pulse width in our RF aiding solution. We will follow this with mitigation strategies we have developed to maximize the distance, scalability, and utility of the ranging measurements to minimize the effects of navigator drift. Our early baseline test results will be reviewed with emphasis on ranging radio performance metrics such as through-wall distance, ranging accuracy, and update rate. Finally, we will describe how these advancements will be integrated and utilized to meet the rigorous objectives of emergency responder tracking systems.