Abstract
Previously, we have proposed a pedestrian positioning method that uses vehicles near a pedestrian as anchors, and combines vehicle-to-vehicle (V2V) communication signals and GPS signals for high precision positioning. In this method, pedestrian-vehicle distance and angle of arrival (AoA) are estimated from the channel state information (CSI) of vehicular signals and used in position computation, but the precision of angle estimation is limited due to the small number of antennas that can be mounted on a mobile device. To solve this problem, in this paper, we propose a new method to estimate AoA precisely by jointly using spatial change of CSI at multiple antennas and temporal change of CSI per antenna (caused by pedestrian/vehicle movement), and on this basis improve pedestrian positioning precision. Specifically, a two-dimensional antenna array is constructed from CSI acquired from multiple antennas/timings, and the MUSIC method with spatial smoothing is applied to estimate AoA. 3D ray tracing simulations with real 3D map confirm that the proposed method can effectively improve the precision of angle estimation and reduce positioning error when only a small number of antennas are available at a pedestrian device, and the performance increases with the number of antennas.
Highlights
In outdoor environments, generally position information nications, are being actively studied
OVERVIEW In order to solve the problem of the base methods [11], [12] that the angle estimation precision is limited with a small number of antennas, we propose a new method to improve the angle precision, constructing a virtual two-dimensional antenna array with spatial/temporal axes by jointly using channel state information (CSI) acquired from multiple antennas/receiving timings, and apply it to improve pedestrian positioning precision
Based on our previous methods that exploit V2V communication signals together with GPS signals for pedestrian positioning by estimating pedestrian-vehicle distances/angles, in this paper, we have proposed to further improve the precision of estimating pedestrian-vehicle angles by combining the spatial and temporal changes of CSI
Summary
Technologies for preventing traffic accidents, such as vehicle- sion of pedestrian position. The proposed method jointly exploits spatial change of CSI (N antenna) and temporal change of CSI (M receiving timing) to estimate AoA, and uses it to improve pedestrian positioning precision with a small number of antennas at a pedestrian device. CSI is acquired from an OFDM (Orthogonal Frequency Division Multiplexing, which is used in Wi-Fi and LTE) modulated signal, and indicates the signal strength/ phase of each path in the time/frequency domain (Lower right of Figure 1) [14] For this reason, the strength of each individual LoS/multipath wave can be acquired from CSI if the time resolution of a receiver is high enough to separate paths, and the precision of distance estimation is improved compared with the case where RSSI is used. The propagation distance can be estimated from the time-of-flight, by exploiting CSI information [15], [16]
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