Abstract
In the case of through-the-wall localization of moving targets by ultra wideband (UWB) radars, there are applications in which handheld sensors equipped only with one transmitting and two receiving antennas are applied. Sometimes, the radar using such a small antenna array is not able to localize the target with the required accuracy. With a view to improve through-the-wall target localization, cooperative positioning based on a fusion of data retrieved from two independent radar systems can be used. In this paper, the novel method of the cooperative localization referred to as joining intersections of the ellipses is introduced. This method is based on a geometrical interpretation of target localization where the target position is estimated using a properly created cluster of the ellipse intersections representing potential positions of the target. The performance of the proposed method is compared with the direct calculation method and two alternative methods of cooperative localization using data obtained by measurements with the M-sequence UWB radars. The direct calculation method is applied for the target localization by particular radar systems. As alternative methods of cooperative localization, the arithmetic average of the target coordinates estimated by two single independent UWB radars and the Taylor series method is considered.
Highlights
Localization capability is becoming one of the most attractive features of a wireless sensor network.Ultra wideband (UWB) radar systems as a special kind of wireless sensor network allow one to detect and track authorized or unauthorized moving targets with an advantage in critical environments or under hindered conditions
There are a number of applications where ultra wideband (UWB) radar systems can be very helpful, e.g., for through-the-wall detection and localization of persons during security operations or fire, detection of people trapped in an avalanche or an earthquake, monitoring of critical infrastructures or through-the-wall imaging of building layouts and interiors [2]
The comparison of the target trajectory estimations by the localization methods considered in this paper has shown that the best performance is provided by JIEM (Figure 15)
Summary
Localization capability is becoming one of the most attractive features of a wireless sensor network. The simple arithmetic average of the target coordinates estimated by the particular nodes (MEAN), the least-squares method [11,12,13], the constrained weighted least-squares method [14,15], the spherical-interpolation method [16,17], the Taylor series method [9,12,18] and various methods based on optimization principles [11,19] can be listed In addition to these papers, several interesting contributions (e.g., [20,21,22,23]) devoted predominantly to the target localization by UWB sensor networks based on TOA estimation have been published recently. The monitored area for through-the-wall localization is complex, and the particular TOA can be frequently estimated with a large error These short analyses indicate that the application of modified localization methods developed originally for a general number of nodes (radars) does not have to provide a meaningful improvement of the target positioning accuracy and the robust performance for the target localization by two independent radar systems.
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