Indirect path detection of passive localization based on wireless propagation measurements

An important prerequisite for precision localization is to discern "direct paths" (DP), i.e., paths that suffer a single reflection process on their way from the transmitter to the receiver, from indirect paths (IPs). This paper studies how to distinguish between DPs and IPs purely based on measurements of radio propagation parameters, namely the time of arrival (TOA), direction of departure (DOD), and direction of arrival (DOA). Any combination of two of those parameters allows the computation of a reflection point. We establish rules to decide how large the deviations between these points might be to consider a path an IP. Several different decision rules are discussed and compared. The paper derives closed-form equations for these decision criteria and the resulting performance. Simulation results show that under common localization scenarios employing ultrawideband signals, the proposed algorithms can effectively detect IPs and significantly improve localization accuracy.