Indirect Path Detection Based on Wireless Propagation Measurements

An important prerequisite for precise localization, such as in radar systems, is to discern "direct paths" (DP), i.e., multipath components (MPCs) where the signal propagates directly between the target and the localization system nodes (transmitters or receivers), from indirect paths (IPs). This paper describes how to distinguish between DPs and IPs purely based on measurements of observable propagation parameters, namely the time of arrival (TOA), direction of departure (DOD), and direction of arrival (DOA). Any combination of two of those parameters allow the computation of a reflection point, and - in the absence of noise - the points computed from the different combinations are consistent in the case of a DP. In the presence of noise, the computed points deviate from each other, and we establish rules for how large this deviation 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. The situations when the proposed decision rules do not work well are also studied. Simulation results show that under common localization scenarios employing ultrawideband signals, the proposed algorithms can effectively detect IPs and significantly improve localization accuracy.