Multipath Assisted Positioning using a Single Antenna with Angle of Arrival Estimations

Abstract

This paper presents and extends the idea of multipath assisted positioning, named Channel-SLAM. Generally, multipath reception degrades the accuracy of the positioning device as long as the receiver is based on standard methods. Strategies to mitigate multipath effects on range estimates are in general based on the estimation of the channel impulse response (CIR). All these methods have in common that they determine the CIR in order to remove the influence on the estimate of the line-of-sight (LoS) path delay. In contrast, Channel-SLAM uses the multipath propagation of the wireless signal to allow positioning in cases of insufficient number of transmitters or increase the accuracy otherwise. Channel-SLAM treats multipath components (MPCs) as signals from virtual transmitters (VTs) which are time synchronized to the physical transmitter and fixed in their position. To use the information of the MPCs, Channel-SLAM estimates the user position and the position of the VTs simultaneously and does not require any prior information such as room-layout or a database for fingerprinting. For Channel-SLAM it is essential to get angle of arrival (AoA) information for each MPC in order to estimate the VT position. However, obtaining AoA information in mobile receivers like smartphones is difficult in most of the cases. Hence, this paper estimates the AoA during the receiver movement using only a single receive antenna by a phase difference calculation, i.e. the Doppler-Shift, of the complex amplitude of a MPC at consecutive time steps. To improve further the accuracy of Channel-SLAM, additionally an inertial measurement unit (IMU) is fused to obtain heading information of the moving receiver. The derived algorithm is evaluated based on measurements where only one physical transmitter was used.