Jose-Victor Rodriguez

Polarized Indoor MIMO Channel Measurements at 2.45 GHz

In this paper, a 4 times 4 indoor multiple-input multiple-output (MIMO) measurement campaign at a frequency of 2.45 GHz is presented. The main contribution of this work is the analysis of the impact of radio-wave polarization in MIMO systems operating at a typical indoor scenario through the calculation-from the measurements carried out-of a great deal of parameters such as the mean path loss, the cross polarization discrimination (XPD), and the RMS delay spread, which are all essential to estimate the performance of real MIMO systems. In this sense, some path loss models-which have been adjusted according to the measurements-are given, taking into account polarization, attenuation through walls, and the effect of T-junctions existing in the considered indoor scenario. Moreover, additional parameters such as the K-factor and statistical distribution, as well as spatial parameters, are discussed.

Wide-band measurements and characterization at 2.1 GHz while entering in a small tunnel

The wide-band complex transfer function and propagation characteristics in a small passageway tunnel for nonline-of-sight are studied in this paper. A two-dimensional wide-band model based on the uniform theory of diffraction (UTD) and geometric optics (GO) is implemented and a network analyzer is used to perform measurements. In order to obtain the power delay profile, a correction factor is used, which adjusts the deviation caused by the windowing and zero padding performed in frequency domain. The UTD model predicts quite well the averaged path loss, power delay profile, root-mean-square (rms) delay spread and coherence bandwidth, even when the curved tunnel is approximated to two straight lines. Furthermore, it is shown that the position of the transmitter is crucial in the performance of the system: the path loss slope and rms delay spread are increased when the inclination of the transmitter is increased. In all cases, the rms delay spread is lower than 40 ns, where the coherence bandwidth decreases to 20 MHz. This parameter is proposed to estimate the excitation zone inside a tunnel.

An improved solution expressed in terms of UTD coefficients for the multiple-building diffraction of plane waves

A new formulation expressed in terms of uniform theory of diffraction (UTD) coefficients for the prediction of the multiple diffraction produced by an array of finitely conducting buildings considering plane-wave incidence is presented. The solution considers the building cross sections to be rectangular as well as the source to be above or level with the buildings height and, due to the fact that only single diffractions over finitely conducting wedges are involved in the calculations, an easier final formulation is achieved. Furthermore, the computing time is reduced over existing solutions especially when the number of buildings is large. The proposed formulation can find application in the development of theoretical models to predict more realistic path loss in urban environments when multiple-building diffraction has to be considered.

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.

MIMO Channel Sounder Based on Two Network Analyzers

Different channel sounders are reported in the literature to measure the multiple-input-multiple-output (MIMO) wireless channel, most of them being dedicated systems. In this paper, a MIMO channel sounder that is based on two network analyzers is presented. The measurement process is totally controlled by a PC via a wireless local area network (WLAN), a local area network (LAN), and a general-purpose interface bus, and they are synchronized by using two global positioning systems (GPSs). The system is restricted to static propagation environments. An advantage of this system is its configurability, thanks to which it is not wireless system dependent. Last, initial measurements in a laboratory of a university at 900 MHz for a 4times4 MIMO system are also presented.

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 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.

A Hybrid UTD-PO Solution for Multiple-Cylinder Diffraction Analysis Assuming Spherical-Wave Incidence

A modified hybrid uniform theory of diffraction-physical optics formulation for the analysis of the multiple diffraction caused by an array of cylinders, assuming spherical-wave incidence, is hereby presented. The solution, validated with numerical data from technical literature, is mathematically less complex and computationally more efficient-particularly for a large number of cylinders-than other existing methods, due to the fact that high-order diffraction terms (slope diffraction) are not considered, without such lack of terms barely entailing any loss in accuracy. Results can be applied in radiowave propagation analysis when multiple diffraction over rounded obstacles has to be considered.

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.