2 D Measurement with Single Known Reference Position for Indoor Localization in European UWB Band

In this paper, a hybrid 2D-Measurement technique is presented for the estimation of the remote position of an active reflector unit (Tag), in terms of radial distance and azimuth angle. The technique is based on Interferometry and FMCW multistatic radar system which operates in the European UWB frequency band [6-8.5 GHz]. The measurements have been performed in a real indoor environment for the line-of-sight case with respect to a single known reference position. The estimated root-mean-square errors observed are 2.1cm & 7.1° over [1 1.6] m & [45° 90°], respectively. Introduction The Indoor Localization with an accuracy under a meter-scale is a great challenge. Although, an accuracy of a meter-scale may be interesting to help people to find ways around museums, airports, malls but it is not adequate for many other situations [1]. Most of known techniques are based on radio-signature or time delay measurement which presents an accuracy of more than a meter. Another drawback is that the number of known references/anchors and their positions play an important role in the localization estimation. Generally, it requires at least three known positions for the location [2-3]. The presented system just requires a single known position for 2D localization and it uses a hybrid-technique based on Frequency-of-Arrival (FOA) and FrequencyDifference-of-Arrival (FDOA). The architecture, the technique and the system performance are presented in this paper which is used for the 2D position estimation of a remote active-Tag in a real Indoor Environment for a Line-of-Sight (LOS) case. 1. System Design Consideration and Implementation 1.1. System design and consideration This paper describes a system using two jointly techniques, FMCW multistatic radar and optic’s interferometry techniques, for 2D localization of a remote active-Tag. The main advantages of this system, compared to [1-3] are: only one known reference position is used for location-estimation and simultaneously, the multipath effects can be strongly reduced by shifting the frequency spectrum by the active-Tag (to be localized). This technique requires the measurements of the FOA and FDOA which lead to the computation of radial distance and azimuth-angle as Angle-of-Arrival (AoA), simultaneously. The system design consists of two main subsystems: Localization Base Station & the active-Tag. The schematic of the LBS, allowing the localization of an active-Tag by using FMCW radar technique, is shown in Fig 1. Fig. 1. On the left: Architecture defined for the LBS & active-Tag. It consists of one transmitting antenna (A0) and two receiving antennas (A1 & A2) which are placed closely on the same axis. A linearly swept sinusoidal FMCW signal covering the 6-7 GHz (∆f=1GHz) frequency is generated with a sweep time, Tm=10 msec, and then this signal is up-converted to 7.5-8.5 GHz and finally amplified before being transmitted by the antenna A0 towards the active-Tag. The up-conversion is done with a Local Oscillator (1.5 GHz) and a mixer. Each RF chain of the LBS (two receivers and one transmitter) is connected to a dedicated circular polarized antenna [4-5]. The transmitter antenna is connected to a linearly URSI-France Journées scientifiques 25/26 mars 2014