Efficient 2.5-D FEM-Based Scattering Analysis of the Human Body for RF Sensing

Abstract

Model training for Device-Free Localization (DFL) and Radio-Frequency (RF) sensing heavily relies on large-scale datasets, which are difficult, expensive, and time-consuming to obtain through measurements. This paper proposes a fast 2.5-dimensional Finite Element Method (2.5-D FEM) for computing the scattering fields of a Body of Revolution (BoR) human model under the excitation of a z-directed dipole. The proposed method can evaluate the effect of human micro-movements through the statistical characteristics of the Received Signal Strength Indicator (RSSI). The numerical accuracy and the practical applicability of the proposed method are validated through comparisons with full-wave simulations and indoor RF sensing experiments. The simulation results show agreement with the experimental measurements, demonstrating that the method is a reliable tool for evaluating micro-movement-induced statistical variations. The proposed method provides a practical and efficient means for generating large-scale, labeled RF training datasets, thereby accelerating the development of indoor localization tools as well as the calibration and tuning of tomographic reconstruction methods.

Figures (9)

• Figure 1: Schematic of the human body under the excitation of a $z$-directed dipole, including an illustrative 2.5-D FEM mesh with labeled material regions (the mesh is shown for illustration only, a finer mesh is employed in the computations).
• Figure 2: A sketch of the images used for the equivalent electric and magnetic currents.
• Figure 3: Normalized directivity at 2.43 GHz in $\phi=0$ plane for $z$-directed electric dipole in the presence of a dielectric cylinder ($\epsilon_r = 52.7 -j12.76$) and a PEC ground plane. The dipole is located at $\mathbf{r}_s = (1, 0, 0.15)$ m, the cylinder has height $h_c = 0.2$ m and radius $r_c = 0.1$ m. Comparison between 2.5-D FEM in this work and Feko$^\text{TM}$ simulations.
• Figure 4: (a) Top-view schematic diagram of the indoor DFL scenario. The gray rectangular region indicates the test area for antennas and human targets. Twenty antennas are deployed as transmitters/receivers, and five human positions are marked. The room entrance is in the lower right corner, where no antennas are deployed. (b) Illustration of the indoor DFL test scenario as seen from the room entrance. The Rx/Tx deployment is marked by red crosses. Human body positions are reported in dashed white lines. The RF acquisition setup is sketched on the lower right part of this figure.
• Figure 5: Scattered (left) and total (right) $E_z$ fields on the $\rho,z$ plane of the simulated human body, shown of Fig. \ref{['fig.body']}, that is modeled by the Cole-Cole muscle model (\ref{['eq:cole']}) at 2.43 GHz, Tx = 7, and $p = 1$. The figure refers to the $\phi=\phi_s$ plane, and the source is located at the right in the figure.