Maria-Teresa Martinez-Ingles

Deterministic and Experimental Indoor mmW Channel Modeling

This letter presents an extensive multidimensional analysis of line-of-sight (LOS) experimental data and simulations at 60 GHz over a 9-GHz bandwidth. Numerical versions of the measured multiple-input-multiple-output (MIMO) channel transfer functions were obtained with a ray-tracing engine that includes single-order diffuse scattering. The received power, RMS delay spread (DS), and maximum excess delay (MED) computed from both measured and simulated data indicate that diffuse scattering improves ray-tracing-based modeling. Moreover, the multipath components (MPCs) extracted from both sets of data using the high-resolution estimator RiMAX were statistically compared. The analysis of the results shows that even a raw description of the environment can be used to predict millimeter-wave (mmW) propagation with ray tracing.

On the Importance of Diffuse Scattering Model Parameterization in Indoor Wireless Channels at mm-Wave Frequencies

In this paper, the impact of considering diffuse multipath components at mm-wave frequencies as well as the significance of selecting appropriate diffuse scattering model parameters is shown. Two different diffuse models, namely, the Lambertian model and the directive model, have been parameterized for several materials typically present in indoor environments. These models are formulated to embed the diffuse scattering phenomenon easily into ray tracing tools. The estimation of the parameters has been performed by comparing measurements and simulations using the models. Once the best fitting parameters have been estimated, they are included in the diffuse components simulation section of a general ray tracing tool. This tool has been used to simulate the power delay profile at 60 GHz in an indoor scenario, including single and double bounce diffuse components. Thanks to the estimated model parameters, the wireless channel at the 60-GHz band can be analyzed, including the diffuse scattering phenomenon, without the need for any previous measurement or simulation. Thus, the channel analysis with ray tracing tools, including dense components, becomes easier, faster, and more reliable.

Experimental Investigation of Electromagnetic Reverberation Characteristics as a Function of UWB Frequencies

The electromagnetic reverberation time characteristics of indoor environments are experimentally investigated from 2 to 10 GHz. At a given frequency, the reverberation time is observed to be approximately constant for bandwidths up to 900 MHz (or larger). Moreover, the reverberation time decreases for increasing frequencies. Based on the theory of electromagnetic fields in cavities, a model to predict a rooms quality factor, reverberation time value, and average absorption coefficient is developed for the first time. The validity and robustness of the model is investigated with data obtained for various environments, central frequencies, and bandwidths. As a validation, the model is applied to another room from 2 to 10 GHz and a maximum (resp. average) relative error of 22.30% (resp. 8.80%) was obtained with a rms error of 1.90 ns. Furthermore, good agreement is obtained with results reported in the literature with settings falling into the model range; scenarios for which relative errors smaller than 10% were computed. The results demonstrate that this approach is not only an accurate alternative to the reverberation time measurements and computations in indoor environments from 2 to 10 GHz, but also a viable route to link propagation mechanisms in indoor scenarios with reverberation chambers.

Experimental comparison between centimeter- and millimeter-wave ultrawideband radio channels

This paper analyzes radio wave propagation phenomena at two very different frequency bands: 2–10 GHz (centimeter wave) and 57–66 GHz (millimeter wave (mm-W)). The two frequency bands have been measured using the same equipment and under similar propagation conditions, such as path loss, root-mean-square delay spread, maximum excess delay, and Rician K factor, and their respective correlations compared. Obstructed line of sight situations have also been considered by using metal and cardboard obstructions. The statistical distributions, main specular reflections, and decay factors have been found similar for the two bands. However, the measured path loss, correlation in terms of electrical distances, and the K factor are higher for the millimeter-wave frequency band. Indeed, the importance of propagation mechanism changes from one band to the other, which must be considered in the design of future mm-W systems.

Comparison of a UTD-PO Formulation for Multiple-Plateau Diffraction With Measurements at 62 GHz

A hybrid uniform theory of diffraction-physical optics (UTD-PO) formulation for the analysis of multiple-diffraction of spherical waves by a series of rectangular plateaux is compared with measurements performed at 62 GHz. The comparison shows a solid agreement between predicted and measured results. Therefore, since the array of plateaux under investigation can be considered as a scaled-model of an urban environment, the results support the validity of the proposed UTD-PO formulation in the analysis of urban radiowave propagation.

Experimental Evaluation of an Indoor MIMO-OFDM System at 60 GHz Based on the IEEE802.15.3c Standard

This letter presents an experimental study of an indoor environment regarding the performance of a multiple-input-multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) millimeter-wave system based on the standard IEEE 802.15.3c. Channel matrices are measured with a vector network analyzer, and in a first step, the intrinsic propagation characteristics are analyzed such as the path loss, capacity, and correlation. In a second step, the performance is studied using different space-time coding strategies. Finally, all this analysis is conducted with respect to different configurations of the MIMO antenna elements.

Impact of clustering at mmW band frequencies

In this work different clustering approaches are investigated in the millimeter-wave (mm-W) frequency band from measurements and simulations. Multipath Component (MPC) parameters have been extracted from both measurements and simulations using RiMAX. Following this step, several clustering techniques such as visual inspection, K-means, and multipath component distance (MCD) were implemented and analyzed. We have found that, at mm-W, the number of MPC within a cluster is very small.

Performance of a Novel Automatic Identification Algorithm for the Clustering of Radio Channel Parameters

A multipath component distance (MCD)-based automatic clustering identification algorithm is proposed to group multipath components (MPCs) obtained from radio channels. The developed algorithm iteratively and dynamically assigns the MPCs to the best cluster thanks to the MCD metric. Its performance and robustness are compared with the K-means MCD algorithm using cluster data simulated with four reference scenarios of the WINNER II channel model. The results indicate that K-means MCD is outperformed for all investigated scenarios in spite of its having a lower computational complexity and faster convergence. Moreover, a by-product of the algorithm is an optimal MCD threshold, that is, the characteristic of the cluster statistical properties for a given propagation scenario. This parameter provides a stronger physical link between the MPCs distribution and the propagation scenario. Therefore, it could be introduced in radio channel models with clusterlike features.

Experimental comparison of UWB against mm-Wave indoor radio channel characterization

This paper presents an experimental comparison between two very different frequency bands: 2-10 GHz and 57-66 GHz. A line of sight indoor environment has been selected, and both bands have been measured under the same conditions and equipment; path loss, delay spread and statistical distributions have been properly compared.

UTD-PO Solution for Estimating the Propagation Loss due to the Diffraction at the Top of a Rectangular Obstacle When Illuminated From a Low Source

A new method based on a hybrid uniform theory of diffraction-physical optics (UTD-PO) formulation for the analysis of the propagation loss due to the diffraction that takes place at the top of a rectangular obstacle that is illuminated from a low source (i.e., the transmitter height is smaller than the obstacle height) is presented. The receiver is considered to be located at the shadow boundary of the second wedge of the plateau so that the solution is valid to estimate the mentioned diffraction loss in order to be incorporated into more general propagation models. In such models, for example, both the free space losses and the typical urban final diffraction loss down to street level (occurring at the receiving point due to an eventual final diffracting obstacle) will be considered. In this sense, it should be noted that the proposed formulation is not a general formalism to estimate radiowave propagation over plateaux (as the receiver is not arbitrarily located). The method, which is mathematically less complex than existing techniques, applies Babinets principle, and is validated through the solid agreement obtained with measurements at 60 GHz and the comparison with a method which is based on the evaluation of a Fresnel surface integral.