UWB radar imaging based multipath delay prediction for NLOS position estimation

Conventional Time-of-Arrival (ToA) based Ultra-Wideband (UWB) positioning suffers strongly from multipath. Harsh propagation environments or non-line-of-sight (NLOS) situations lead to biased position estimates with high estimation errors. To overcome this problem, we propose a radar imaging based method to predict delays of dominant propagation paths. This is done in a three-step approach: First, a radar image of the environment is created using measured training data. We generate a scattering coefficient map with the large synthetic aperture of distributed and moving antennas. The training data can easily be obtained from channel estimates of a UWB communication system with mobile nodes. Second, the radar image is used to reconstruct path gains and path delays. Thus, the channel response is predicted for arbitrary transmitter and receiver positions. Finally, dominant multipath delays are extracted using WRELAX. The proposed algorithm is validated by anechoic chamber measurements with controlled reflectors. Moreover, an extensive measurement campaign in a laboratory/office environment shows that strong paths can be predicted with nanosecond accuracy in a real world scenario.