WPI Precision Personnel Location System: Rapid Deployment Antenna System and Sensor Fusion for 3D Precision Location

An RF-based system is being developed for tracking of first responders and other personnel in indoor environments. The system assumes no existing infrastructure, no pre-characterization of the area of operation and is designed for spectral compliance and rapid deployment. The RF 3D location system, based on a recently developed multicarrier signal fusion algorithm, has previously demonstrated submeter positioning accuracy of a transmitter, even in difficult indoor environments with high multi-path, with all receivers placed outside the building. However, the current version of the system requires a set of 12 to 16 antennas be distributed outside three to four sides of the building in order to obtain the necessary diversity of information necessary to precisely resolve 3D location. This is undesirable as a practical application of a Precision Personnel Location (PPL) system requires rapid deployment of any antenna nodes at a time when almost all manpower at the fire scene is dedicated to rapid and safe entry into the building and fire suppression activities. Thus, the act of antenna deployment must be extremely fast, easy and forgiving. This paper reports on the development and evaluation outcomes of an approach that permits 3D location based upon deployment of two antenna arrays on any one face of the building. The positioning performance of the PPL system with the new antenna system will be compared to performance from the previous incarnation of the PPL system with widely distributed antennas. In the case of the new antenna system, outcomes will be shown for both the cases of Bayesian inference based upon additional sensor information and without this sensor information. The previously described[1], [2], [3], [4], [5] WPI PPL system has demonstrated 3D accuracies of better than 1 m in indoor tests. We will show that the new version of the system does not perform at the level of precision as that with a diverse antenna distribution, however, at a level sufficient to still significantly aid in search and rescue missions. INTRODUCTION: WPI PRECISION PERSONNEL LOCATOR SYSTEM The Worcester Polytechnic Institute(WPI) Precision Personnel Location(PPL) system, being developed at WPI, is an RF based system for locating first responders inside of a building. More specifically, the goal is to have a system that is accurate within +/one meter, portable, rugged, and rapidly deployable with no site preparation or on-site calibration procedures[2]. In recent years, the system has been expanded to consider fire, police, military, and even robotic vehicles in both urban and wilderness settings. ION ITM 2010, Session A4: Urban Indoor Navigation Technology, January 25-27, 2010, San Diego, CA 1 Figure 1 is an artist’s rendition of the PPL concept. The locator units worn by personnel emit a Multi-Carrier WideBand(MC-WB) signal that is received by multiple antennas located outdoors, around the building at known positions. The receiving antennas are connected to our transceiver units, which send the spectrum of the received signal to a central computer through a wireless network. The computer processes the data from all of the received antennas, and calculates the location of the firefighter based on the time-differenceof-arrival(TDOA) like algorithm involving a signal fusion approach. Fig. 1. PPL concept illustration. The goal of the WPI precision personnel location project is development of a system appropriate for use by first responders incorporating no pre-installed infrastructure, rapid deployability, medium (not ultra-wide) bandwidth, flexible and spectrally compliant signals, and low cost personnel tags[2]. Previous papers have described: development and performance of new signal processing and location techniques for the amelioration of the extreme multi-path conditions such as found in typical commercial and industrial structures[1], [2], [3], [4], [5], which usually frustrate all attempts to achieve precision location; incorporation of physiological monitoring sensors and real time display; automated solution of outdoor sensor positions for rapid deployment; synchronization technology for wirelessly connected transceiver nodes[6]. This paper describes a next generation of the PPL fast-deployment antenna system and requisite sensor and algorithmic support for solution of 3D indoor location from antennas located on only a single side of a building. An approach has been developed in which signals are captured from antennas mounted on two extension ladders that can be transported easily by fire truck and then quickly extended and leaned against a building face. However, due to the poor geometry this presents for 3D precision location within the context of the present TDOA-like multicarrier solution technique and especially when challenged within the high multipath indoor environment, large errors in the direction perpendicular to the antenna plane are experienced. To ameliorate this degradation of location precision, a new data fusion system has been developed that uses Bayesian inference to introduce additional, not necessarily precise or low variance information, to obtain a refined global solution. The flexible Bayesian inference engine allows additional information to be obtained from sources as diverse as low-cost inertial sensors and simple radio ranging sensors. The following sections will describe the current WPI location algorithm(σART), pure RF signal based tests of both the unrestricted and rapid deployments, additional sensor information introduced in this paper, and the results of the rapid deployment system information fused with these additional sources of information.