Identification of the Absence of Direct Path in Indoor Localization Systems

Ultra-wideband (UWB) indoor positioning systems based on time of arrival (TOA) techniques are considered to be the high precision alternatives to those employing received signal strength (RSS) or angle of arrival (AOA) due to their superior time-domain resolution. However, the performance of such systems may easily be degraded by the blockage of the direct path (DP) and occurrence undetected direct path (UDP) condition. By erroneous detection of the other multipath components (MPCs) as DP, which is the indicator of the true distance between the transmitter and the receiver, substantial errors will be introduced into the system. The real challenge is to be able to identify the class of the receiver location, therefore, to remedy the ranging measurement in UDP condition. In this paper we propose a methodology to identify and mitigate the UDP conditions, which can substantially improve the overall indoor positioning accuracy.