Towards UWB Self-Positioning Systems for Indoor Environments Based on Electric Field Polarization, Signal Strength and Multiple Antennas

Accurate wireless indoor positioning in non line-of-sight (NLOS) and multipath environments is an open research topic. In order to minimize the effect of such environments on ranging accuracy, self-positioning systems come to play. However, an accurate initial position (IP) estimation of the device to be located has a significant impact. The key challenge is to reliably detect the direct path (DP) from the transmitter to the receiver so as to enable accurate positioning calculations. We believe that studying ultra-wide band (UWB) signals from the electromagnetic (EM) point of view increases the chances of an optimum usage of this new technology. In our approach, electric field polarization together with received signal level will assign the DP a unique signature so that the receiver is able to distinguish it from other reflections. In this way, not only reflections can be mitigated to some extent, but also the DP can be detected even if it is attenuated by an object, in other words, if the direct path is not in line-of-sight (LOS). Combining UWB technology with multiple antennas, i.e., UWB beamforming, is beneficial for several reasons: (1), due to its large bandwidth only UWB allows sufficient resolution in sub-centimeter range for our target applications (e.g. positioning of robots) among all other wireless techniques based on EM waves (J.Y. Lee and R.A. Scholtz, 2002), and (2), UWB beamforming does not suffer from ambiguities (so-called grating lobes) and enables narrowing the main lobe only by widening the antenna separation (F. Anderson, et al, 1991). The main goal of this introductory contribution is to cover the concept of this approach