On the use of ray tracing for performance prediction of UWB indoor localization systems

Abstract

The most important factors impairing the performance of radio-based indoor localization systems are propagation effects like strong reflections or diffuse scattering. To the full extent, these effects can be captured only by time-consuming measurement campaigns. Ray tracing (RT) offers the possibility to predict the radio channel for a certain environment, avoiding the need for measurements. However, it is crucial to include all relevant propagation mechanisms in the RT as well as to validate the obtained results. In this paper, we analyze if sub-band divided RT can yield realistic ultra-wideband channel impulse responses. We use the RT results for performance analysis of multipath-assisted localization, which depends directly upon the above mentioned propagation effects. In particular, it has been shown that the ratio of the signal energies of deterministically reflected paths to interfering diffuse components quantifies the amount of position-related information of deterministic multipath components. Comparison of this ratio to measurement data is thus useful to validate the sub-band divided RT. The results highlight the need for proper modeling of the diffuse multipath, as estimates of this energy ratio using RT are often overly optimistic. However, the obtained localization performance predictions using measurements and RT show general agreement.

Low-complexity sub-band divided ray tracing for UWB indoor channels

“…In order to simplify the expressions, we omit the arguments θ {·} and φ {·} in the related formulas. • In [7], [13], it is assumed that the dielectric permittivity ε r and conductivity σ for one material are independent of the frequencies within the entire bandwidth of interest, because it is difficult to estimate how these values vary with the frequency. However, the effective permittivity of the material…”

A Sub-Band Divided Ray Tracing Algorithm Using the DPS Subspace in UWB Indoor Scenarios

“…It is known that measurement campaigns used for the performance prediction of UWB indoor localization systems are usually time-consuming and tedious to perform. SDRT offers the possibility to predict the radio channel for a certain environment, avoiding the need for measurements when evaluating indoor localization algorithms [4]. However, the computational complexity of SDRT is proportional to the number of the propagation paths and to the number of sub-bands.…”

Calibration of indoor UWB sub-band divided ray tracing using multiobjective simulated annealing

“…Then the corresponding calculation for other subbands can be derived directly according to the physical properties of the propagation mechanisms. It is worth mentioning that distinguishing how the dielectric properties vary with frequencies is very difficult, so that it is assumed that the dielectric properties ε r and σ do not depend on the frequency within the entire UWB bandwidth [4], [13]. With the complex electric field η {·} (f c,i ) of the propagation path at the center frequency f c,i of the i−th subband is obtained, the resulting complex electric field η {·} (f c,i ′ ) at all other center frequency f c,i ′ can be calculated [7].…”

“…Rhode & Schwarz ZVA-24 vector network analyzer (VNA) was used to measure the frequency-domain UWB channel at N f = 7501 frequency points over the frequency range from f L = 3.1GHz to f H = 10.6GHz in the Signal Processing and Speech Communication laboratory at Graz University of Technology [4]. The significant blocks are concrete walls, glass windows and metal pillars [16].…”

“…For all these reasons the approximation of the input material parameters lead to a mismatch between the simulation results of RT and empiric measurements [4]. Therefore, it is necessary to implement a calibration algorithm for these RT parameters to improve the prediction accuracy of RT.…”