22,700 research outputs found
Performance Evaluation of Hyperbolic Position Location Technique in Cellular Wireless Networks
This study addresses the wireless geolocation problem that has been an attractive subject for the last few years after Federal Communications Commission (FCC) mandate for wireless service providers to locate emergency 911 users with a high degree of accuracy -within a radius of 125 meters, 67 percent of the time by October 2001. There are a number of different geolocation technologies that have been proposed. These include, Assisted GPS (A-GPS), network-based technologies such as Enhanced Observed Time Difference (E-OTD), Time Difference of Arrival (TDOA), Angle of Arrival (AOA), and Cell of Origin (COO). This research focuses on network based techniques, namely the more prominent TDOA which is also called hyperbolic position location technique. The main problem in time-based positioning systems is solving nonlinear hyperbolic equations derived from set of TDOA estimates. Two algorithms are implemented as a solution to this problem: A closed form solution and a Least Squares (LS) algorithm. Accuracy and computational efficiency performances are compared in a wireless system established using DGPS measurements in Dayton, OH area
Distributed AOA-based source positioning in NLOS with sensor networks
©2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This paper focuses on the problem of positioning a
source using angle-of-arrival measurements taken by a wireless
sensor network in which some of the nodes experience non lineof-sight
(LOS) propagation conditions. In order to mitigate the
errors induced by the nodes in NLOS, we derive an algorithm
that combines the expectation-maximization algorithm with a
weighted least-squares estimation of the source position so that
the nodes in NLOS are eventually identified and discarded.
Moreover, a distributed version of this algorithm based on a
diffusion strategy that iteratively refines the position estimate
while driving the network to a consensus is presented.Peer ReviewedPostprint (author's final draft
Positioning Accuracy Improvement via Distributed Location Estimate in Cooperative Vehicular Networks
The development of cooperative vehicle safety (CVS) applications, such as
collision warnings, turning assistants, and speed advisories, etc., has
received great attention in the past few years. Accurate vehicular localization
is essential to enable these applications. In this study, motivated by the
proliferation of the Global Positioning System (GPS) devices, and the
increasing sophistication of wireless communication technologies in vehicular
networks, we propose a distributed location estimate algorithm to improve the
positioning accuracy via cooperative inter-vehicle distance measurement. In
particular, we compute the inter-vehicle distance based on raw GPS pseudorange
measurements, instead of depending on traditional radio-based ranging
techniques, which usually either suffer from high hardware cost or have
inadequate positioning accuracy. In addition, we improve the estimation of the
vehicles' locations only based on the inaccurate GPS fixes, without using any
anchors with known exact locations. The algorithm is decentralized, which
enhances its practicability in highly dynamic vehicular networks. We have
developed a simulation model to evaluate the performance of the proposed
algorithm, and the results demonstrate that the algorithm can significantly
improve the positioning accuracy.Comment: To appear in Proc. of the 15th International IEEE Conference on
Intelligent Transportation Systems (IEEE ITSC'12
Sub-Nanosecond Time of Flight on Commercial Wi-Fi Cards
Time-of-flight, i.e., the time incurred by a signal to travel from
transmitter to receiver, is perhaps the most intuitive way to measure distances
using wireless signals. It is used in major positioning systems such as GPS,
RADAR, and SONAR. However, attempts at using time-of-flight for indoor
localization have failed to deliver acceptable accuracy due to fundamental
limitations in measuring time on Wi-Fi and other RF consumer technologies.
While the research community has developed alternatives for RF-based indoor
localization that do not require time-of-flight, those approaches have their
own limitations that hamper their use in practice. In particular, many existing
approaches need receivers with large antenna arrays while commercial Wi-Fi
nodes have two or three antennas. Other systems require fingerprinting the
environment to create signal maps. More fundamentally, none of these methods
support indoor positioning between a pair of Wi-Fi devices
without~third~party~support.
In this paper, we present a set of algorithms that measure the time-of-flight
to sub-nanosecond accuracy on commercial Wi-Fi cards. We implement these
algorithms and demonstrate a system that achieves accurate device-to-device
localization, i.e. enables a pair of Wi-Fi devices to locate each other without
any support from the infrastructure, not even the location of the access
points.Comment: 14 page
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