Emitter Localization and Visualization (ELVIS): A Backward Ray Tracing Algorithm for Locating Emitters

We present ELVIS, a new approach for localizing a responder (e.g., firefighter) inside a building. We assume that this responder emits rays which undergo multiple reflections with the walls, ceilings and floors of the building. There are K receivers, each of which receives ray(s) from the responder. The receiver estimates the AOA (Angle of arrival), TOA (Time of Arrival) and power of each ray. We assume that the receiver knows the blueprint of the building and the material characteristics of the walls. We show that, based on this information, the receiver can localize the responder to a high degree of accuracy by applying ELVIS, which is based on backward ray tracing. We have compared the performance of ELVIS, using both single and multiple receivers, under a variety of channel and propagation conditions. We find that, the location prediction error depends mostly on the angular resolution of the receiver antennae. One advantage of ELVIS over traditional localization methods is that, if AOA is estimated with high degree of accuracy, a single receiver would be sufficient to do localization in 3D. In this case one could localize 100 percent of the Bell Labs, Crawford Hill building within 9 cm. With degraded accuracy, including fading and noise effects, ±10 degree angular error, and ±10 ns temporal error, one could localize 80 percent of the building within 10 m using multiple receivers.