Iñigo Cuiñas

Measurement and Analysis of Propagation Mechanisms at 40 GHz: Viability of Site Shielding Forced by Obstacles

Mitigation of interference among adjacent radio systems is a topic of growing interest as the spectrum occupation increases. Site-shielding techniques appear as a method of improving millimeter-wave wireless communication system design, allowing frequency reuse and reducing cochannel interference. The viability of applying such techniques to systems operating in frequency bands around 40 GHz is the aim of this paper. Several propagation mechanisms are experimentally studied, including transmission across building obstacles, depolarization, reflection, and diffraction. The performance of some theoretical models of the different scattering mechanisms has been compared with measurement results. The measuring and processing procedures have also been improved. Values of the dielectric parameters of the materials in this frequency band have been obtained and are given in this paper. The attenuation results indicate that various materials, such as mortar, brick, and concrete walls, that present large values of attenuation in decibels per centimeter, can be used to shield base stations, reducing the frequency reuse distance in radio cellular networks. It can also be concluded that there is a significant diffracted field in the shadow region of brick corners.

Measuring, modeling, and characterizing of indoor radio channel at 5.8 GHz

Wide-band indoor radio channel characterization for broadband radio access networks and unlicensed national information infrastructure has been performed at 5.8 GHz, and results are given in this paper. Delay spreads of 8.8 and 17.2 ns and coherence bandwidths of 9.6 and 4 MHz have been found for line-of-sight (LoS) and obstructed line-of-sight (OLoS) situations, respectively. Results have been compared with predictions made using a ray-tracing tool. To get accurate predictions, a good description of the electromagnetic properties of the obstacles present in the environment is needed. Several experiments were made in order to characterize the electromagnetic parameters of six typical building materials. Transmission and reflection coefficients were measured using the free-space technique. A multiple successive internal reflection model was used to estimate the permittivity and conductivity by comparing the measured and predicted values of the coefficients. Several samples of each material were measured, and the results vary from sample to sample. This variation has been characterized by the calculation of confidence bands for the parameters. The influence of both the dielectric parameters and the order of reflections considered in the ray-tracing tool has been analyzed. The effect is reduced on narrow-band predictions but is more important on wide-band parameters as the delay spread. It is shown that the measured delay spread cumulative distribution function falls within the band predicted using the measured maximum and minimum values of permittivity.

PROPAGATION ANALYSIS AND DEPLOYMENT OF A WIRELESS SENSOR NETWORK IN A FOREST

A complete study for the deployment of a wireless sensor network in a forest based on ZigBee is presented in this paper. First, due to the lack of propagation models for peer to peer networks in forests, propagation experiments were carried out to determine the propagation model. This model was then used for planning and deploying an actual wireless sensor network. The performance of the network was compared with the expected theoretical behavior to extract some conclusions that are presented in the paper. Finally, some general conclusions, as an estimation of the minimum number of routers necessary to cover a given area, are extracted from the experiments and presented in the paper.

Building material characterization from complex transmissivity measurements at 5.8 GHz

An improvement of the well-known internal multireflection model of transmission coefficients is proposed in order to obtain better agreement with complex measured data. The reason for the introduced changes is explained. To obtain the data, measurements were performed at 5.8 GHz using a vector network analyzer, which provided information on the amplitude and phase of the transmission coefficient. By comparing the model and measurements, both the real and imaginary parts of the material complex permittivity were estimated for four different building materials.

Permittivity and Conductivity Measurements of Building Materials at 5.8 GHz and 41.5 GHz

The results of various experiments performed to characterize electromagnetic properties of typical building materials at BRAN (Broadband Radio Access Networks) and MVDS (Multipoint Video Distribution System) bands are presented and compared. Transmission and reflection coefficients were measured as functions of the angle of incidence, using a wideband sounder based on the swept frequency technique. A high precision angular positioning system was built and used in co-ordination with the measurement equipment.The dielectric constants (εr) were estimated by comparing values predicted with a multiple successive internal reflection model and measured transmission and reflection coefficients. It has been found that the variation of the dielectric constant value with the frequency does not necessarily follow the same trend for different materials. For example, the measured εr for plasterboard presents an increment withfrequency (2.02 at 5.8 GHz, 2.5 at 41.5 GHz – measured by theauthors –, 2.58 at 59.5 GHz, and 2.81 at 60.2 GHz – given byliterature –), while the values for glass follow a wanderingpattern (6.06 at 5.8 GHz, 5–10 at 10 GHz, 3.41 at 41.5 GHz, 7.51at 57.6 GHz, and 5.29 at 60.2 GHz). Moreover, the measuredεr for a brick wall at 5.8 GHz (3.58) shows differenceswith values reported at 2 GHz (4.44).

Urban wide-band measurement of the UMTS electromagnetic environment

Measurements of impulsive noise in the universal mobile telecommunications system (UMTS) electromagnetic environment in urban areas have been conducted and its effect on the UMTS system is analyzed. An impulsive noise-measurement system for the UMTS frequency band has been designed and built, which meets and improves the main features of classical equipments used to measure noise, offering inphase and quadrature outputs simultaneously. This measurement system was carefully calibrated before a measurement campaign was conducted in an urban environment to get impulsive noise statistics. Results show that noise pulses may have high power, long duration, and high repetition rate, so the performance of UMTS could be significantly reduced.

Square Loop and Slot Frequency Selective Surfaces Study for Equivalent Circuit Model Optimization

This paper presents a parametric study of square loop and square slot frequency selective surfaces (FSSs) aimed at their equivalent circuit (EC) model optimization. Consideration was given to their physical attributes, i.e., the unit cell dimensions and spacing, substrate thickness and dielectric properties, for several frequencies and plane wave incident angles. Correlation analysis and evaluation of the influence of physical related input parameters on the FSS performance are presented. Subsequent optimization factor for the square loop classical EC model is analyzed, and a novel EC model formulation for the square slot FSS is proposed. The performance of the proposed EC model was assessed against results obtained from appropriate electromagnetic (EM) simulations, based on a root-mean-square error (RMSE) criteria. Results demonstrate the validity of the optimized EC model, in which good estimations of the frequency response of FSS structures were obtained. Significant reduction of the resonant frequency offsets, in the order of 650 (from 910 to 260) and 460 (770 to 310) MHz, was obtained for square loops and square slots, respectively. The models were further validated against measurements performed on two physical FSS prototypes inside an anechoic chamber at 2.4 GHz. Relatively good agreement was obtained between measurements of real FSS prototypes and results obtained with the EC model. Finally, this work is sought to provide the necessary refinement of elementary models for further studies with more complex and novel FSS structures.

Peer to Peer Wireless Propagation Measurements and Path-Loss Modeling in Vegetated Environments

The use of wireless networks is continuously increasing, as well as extending to new purposes and new environments, mainly outdoor oriented and some of them at vegetation media. Although there are multiple propagation studies at wireless network frequency bands within vegetation scenarios, most of them are focused on classical base station to mobile terminal configuration. The main aim of this research is to provide a propagation study for the three most commonly used wireless network frequencies: 2.4, 3.5 and 5.8 GHz in a peer to peer configured system, where both, the transmitter and the receiver are located at the same low heights, within vegetation media, including forests and meadows.

A Complete Traceability System for a Wine Supply Chain Using Radio-Frequency Identification and Wireless Sensor Networks [Wireless Corner]

Radio-frequency identification (RFID) technology provides an effective tool for managing traceability along food supply chains. This is because it allows automatic digital registration of data, and therefore reduces errors and enables the availability of information on demand. A complete traceability system can be developed in the wine production sector by joining this technology with the use of wireless sensor networks for monitoring at the vineyards. A proposal of such a merged solution for a winery in Spain has been designed, deployed in an actual environment, and evaluated. It was shown that the system could provide a competitive advantage to the company by improving visibility of the processes performed and the associated control over product quality. Much emphasis has been placed on minimizing the impact of the new system in the current activities.

Modelling and Measuring Reflection Due to Flat Dielectric Surfaces at 5.8 GHz

Indoor radio channel planning tools implement different models to simulate propagation mechanisms such as transmission or reflection. The specular reflection formulation is commonly used instead of more complete scattering models. This happens because its coding is less complicated and the software runs faster than when considering reflection in all directions, not yet specular. In this paper, results from measurements are presented, consisting of the effect of constructive walls on an oblique incident wave. These experimental outcomes are modelled by means reflection pattern computations. Physical optics scattering model is used in its classical formulation, and it is then modified to take into account antenna pattern effects in the measurements. The comparison between measurements and simulations is also presented, showing good agreement. Measurements show that low reflective walls produce reflections in several directions across the incidence region. In these situations, the use of algorithms that compute reflection pattern, instead of just specular reflection coefficients, will lead to better agreement with actual results