Enhanced 911 is a first line of assistance for practically every emergency situation, and many cell phone users today expect the same results from an emergency call no matter where they are-whether on the side of the road, in the woods, or in a building. It is a vital part of our nation's emergency response and disaster preparedness system. In the context of 911 service, demand for providing reliable and accurate mobile station (MS) location estimation has become a high priority and has gained momentum in recent years. A major challenge in mobile station location estimation is locating an emergency caller within desired accuracy in an adverse environment where nonline-of-site (NLOS) propagation exists. This paper develops a methodology to improve the accuracy of mobile station location estimation in an NLOS environment. A unique feature of this methodology development, compared to other approaches in the literature, is the application of the systems engineering process. While there are many definitions, systems engineering as applied here is an approach and process for developing the preferred solution to a set of requirements. The methodology consists of two stages. In the first stage, a series of time-of-arrival range measurements are made from each base station (BS) to the MS. Binary hypothesis testing on the standard deviation of the range measurements at a given BS is used to determine if the measures are taken under NLOS conditions. Then, if possible, any BS deemed to be NLOS is eliminated from the estimation in the second stage, in which the selected time measurements of several BSs are combined through least squares to estimate the location of the mobile station. Based on a simulation study, the methodology appears to have the potential to significantly improve the accuracy of location estimates in certain situations.Index Terms-Constrained least squares, least squares, lineof-site (LOS), mobile station location estimation, non-line-of-site (NLOS), root mean square error, systems engineering, vee model.
currently a full time faculty of the College of Aeronautics, have over 25 years of experience in systems design/development, and engineering systems that include telecommunication systems and networks, Radio communications, air defenses systems, avionics systems, and Airborne Warning and Control System (AWACS). Dr. Rahdar developed proficiency with systems engineering principles, process, and practices. He is an expert in taking systems from inception through design, development, and production. His skills are included but not limited to operations research, analytical/statistical analysis, trade studies, new product introduction including gates and design reviews processes, risk and opportunity management, reliability, availability & maintainability, and safety analysis, and complex project management Dr. Ghazal Barari, Embry Riddle Aeronautical UniversityGhazal Barari received her PhD in mechanical engineering from University of Central Florida. Her research was focused on combustion modeling of promising biofuels in order to find a suitable substitute for fossil fuels. She started her career as a tenure track assistant professor in the college of engineering at Embry Riddle Aeronautical University at Prescott, Arizona where she was teaching mechanical and aerospace engineering Fluid mechanics and Thermodynamics courses. She joined ERAU-Worldwide College of Engineering as an assistant professor in 2018.
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