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[EN] In this paper, the maximum achievable throughput is analyzed in the intra-wagon channel when multiple-input single-output (MISO) and orthogonal frequency division multiplexing (OFDM), MISO-OFDM, techniques are used. This analysis is performed from real wideband propagation channel measurements at 28 and 37 GHz, two potential frequency bands to deploy the future fifth-generation (5G) wireless communications networks. Four different scenarios in terms of the access point (AP) and user equipment (UE) positions inside the wagon have been considered, using 4 and 8 antennas at the AP. The performance of both quasi-orthogonal space-time block code (QSTBC), combined with Hadamard matrices, and transmit beamforming techniques is studied and evaluated from simulation results. The simulation results take into account the signal-to-noise ratio (SNR) and the antenna correlation for each antenna array configuration at the AP. These results provide useful insight to better understand the intra-wagon channel properties and deploy the future 5G wireless networks in this particular scenario at mmWave frequencies, where high-data-rates are expected to support different types of digital applications., This work was supported in part by the Ministerio de Economia y Competitividad MINECO, Spain, under Grant TEC2016-78028C3-2-P and Grant TEC2017-86779-C2-2-R and in part by the European FEDER Funds.

A hybrid uniform theory of diffraction-physical optics (UTD-PO) formulation for the analysis of the multiple-diffraction (MD) that takes place over rectangular-shaped obstacles (plateaus) when the latter are illuminated from a low source is presented. The solution, which is based on Babinet’s principle, has been validated with measurements taken at 60 GHz on a scaled model of the environment under study and with additional measurements performed by other authors. Moreover, the proposed approach has been compared with the wide-angle Fourier split-step parabolic equation method, with the UTD-PO formulation showing better accuracy against the experimental data, especially when the distance between the transmitter and the receiver is increased. Furthermore, the main advantage of the proposed solution is that due to recursion, the calculations imply only single diffractions, thereby avoiding the need of higher order diffraction terms in the diffraction coefficients. The results and findings of this communication are particularly applicable to the planning of microcellular mobile communication systems when the transmitting antenna is located below the height of the surrounding buildings.

Two uniform theories of diffraction or physical optics (UTD-PO) formulations for the analysis of the multiple-diffraction of millimeter plane waves which is caused by both trees and buildings, in vegetated residential areas, are hereby presented. The two solutions consider the buildings, modeled as knife-edges and rectangular sections (a more complex and realistic shape), respectively, and the influence of the tree canopies—assumed to be higher than the average rooftop height—is taken into account by considering the proper attenuation factors and phasors into the building diffraction phenomenon. The formulations have been validated through comparison with solutions previously published by other authors, and the main advantage of the proposed models is that, thanks to their recursion, only single diffractions are involved in the calculations. This way, the need of higher order diffraction terms in the diffraction coefficients is avoided, thereby lowering the computational effort. The results, focused on the 5G millimeter-wave (mmWave) candidate bands, can be applied in the planning of forthcoming mobile communication systems.

A study of the impact of the diffuse scattering phenomenon when calculating radio wave multiple-plateau diffraction losses at millimeter-wave (mm-wave) frequencies is hereby presented. In this sense, measurements of the total attenuation caused by a series of either rough or polished brick blocks are properly compared with the theoretical multiple-diffraction losses of an array of ideally smooth brick blocks predicted by a hybrid uniform theory of diffraction-physical optics (UTD-PO) formulation. The results show the influence of diffuse scattering phenomena when it comes to calculating radio wave multiple-plateau diffraction attenuation and can be applied to the obtaining of more realistic mm-wave propagation models when multiple diffraction over rectangular obstacles with irregular (rough) surfaces has to be considered.

Evaluation of cooperative automated driving applications requires the capability of simulating the vehicle and traffic dynamics as well as the communications with a level of accuracy that most of the current tools still lack. In this paper, we explore the use of game engines in hybrid traffic-network simulators. We describe and validate a novel framework based on this approach: Veneris. Our framework is made of a traffic simulator, implemented on the top of the Unity game engine, which includes a realistic vehicle model and a set of driving and lane change behaviors adapted to a 3D environment that reproduces real-world traffic dynamics; a ray-launching propagation simulator on graphics-processing-unit (GPU), called Opal, and a set of modules, which enable bidirectional coupling with the OMNET++ network simulator. The more relevant and novel mechanisms of Veneris are introduced, but further implementation details can be checked on the source code provided in our repository. We discuss the validation tests we have performed and show how it provides accurate results in three key areas: 1) the fidelity of the vehicle dynamics; 2) the recreation of realistic traffic flows, and; 3) the accuracy of the propagation simulation. In addition, the general results of the expected performance are provided.

The smart grid (SG) represents the present and the future of electric power grids. Wireless networks (WNs) are a key technology for this updating process, empowering electric networks to be easily managed in a flexible and cost-effective way. However, as with any wireless technology and especially in a harsh multipath environment such as the SG, reckoning with an extensive channel characterization is crucial. This paper presents an exhaustive characterization of two representative scenarios, both in the transport and distribution segment of an SG: a 400-kV outdoor substation and a main power room. The 2.4-GHz ISM band—in which most wireless communication technologies applied to SG operate—is examined in depth to characterize the radio-propagation phenomena. Large and small-scale fading, RMS delay, coherence bandwidth, and electromagnetic interferences are studied under different line-of-sight, polarizations, and frequency conditions to derive empirical models allowing to estimate the aforementioned parameters in other SGs of a similar nature. Finally, to further evaluate and compare our channel characterization, a WN was simulated in a substation to examine the channel modeling impact on its suitable design and operation.

The World Radiocommunication Conference 2015 (WRC-15) identified a number of frequency bands between 24 and 86 GHz as candidate frequencies for future cellular networks. In this article, an extensive review of propagation characteristics and challenges related to the use of millimeter wave (mm-wave) in future wireless systems is presented. Reference to existing path-loss models including atmospheric and material attenuation in recommendations of the International Telecommunication Union (ITU) in Geneva, Switzerland, is given, and the need for new multidimensional models and measurements is identified. A description of state-of-the-art mm-wave channel sounders for single and multiple antenna measurements is followed by a discussion of the most recent deterministic, semideterministic, and stochastic propagation and channel models. Finally, standardization issues are outlined with recommendations for future research.

An experimental characterization of the off-body propagation channel for the ultrawideband (UWB) band from 3.1 GHz to 8 GHz for body area networks (BAN) is presented in this letter. The channel is evaluated in terms of path loss (PL) and Root Mean Square (RMS) delay spread. Channel statistics from measurements carried out considering subjects of different gender in standing still position under line-of-sight (LOS) conditions are compared to the ones without the presence of the body to evaluate the variation on the statistics of the channel in presence of a human body. It is observed a high variation on the path loss and the RMS delay spread parameters for the same attachment position of the receiver antenna on the body of the subjects and a dependence of the statistics with the number of received multipath components (MPC) because of the shadowing effect of the body., This work was supported in part by MINECO, Spain (TEC2013-47360-C3-2-P), and in part by the European FEDER funds.

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.

The calculation of the E-plane radiation pattern of corrugated E-plane rectangular horn antennas in which the corrugations have a cylindrical shape is hereby performed through a method based on a hybrid uniform theory of diffraction-physical optics (UTD-PO) formulation. The proposed method is successfully validated through comparison with the application of an electric field integral equation (EFIE) solved by the method of moments (MoM), with the UTD-PO analysis showing more computational efficiency than the EFIE and other numerical techniques based on the full discretization of the geometry. On the other hand, the use of cylindrical corrugations instead of the traditional rectangular-shaped corrugations is analyzed and, in view of the results, the former may offer a series of advantages in comparison to the latter, such as narrower main lobes as well as better fabrication-related aspects.

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 Babinet's 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.

A comparison of the presence of cylindrical against rectangular obstacles in radio wave multiple-diffraction analysis is performed both theoretically - through hybrid formulations based on the uniform theory of diffraction (UTD) and physical optics (PO) - and experimentally - through measurements performed at 60 GHz. The results can be applied to the analysis of multiple diffraction in the mm-wave band when propagation over periodic obstacle patterns - either rounded or flat - has to be considered.

A uniform theory of diffraction (UTD)-physical optics (PO) formulation for multiple-cylinder diffraction analysis is compared with measurements performed at 60 GHz. Thus, the influence of the variation of parameters, such as: the number of cylinders considered, the radius of curvature, the distance from the transmitter to the array of rounded obstacles, and the polarization is analyzed both theoretically and experimentally. The good agreement shown between the predicted and measured results validates such a theoretical solution for the analysis of radiowave propagation when multiple-diffraction over cylindrical surfaces has to be considered.

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.

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.

The ultrawideband (UWB) propagation channel is analyzed by means of measurements carried out in the 2-5 GHz frequency band in an office environment for different scenarios. Measurements were performed for different polarizations on the transmitting and receiving arrays so the effect of the signal polarization can be also taken into account in the analysis. The main contribution of this paper is not only the analysis of path loss and RMS delay spread in a bandwidth of 3 GHz, but also the influence of frequency on such parameters. The relationship between the path loss for copolar configurations and the cross-polarization discrimination (XPD), both in space and frequency domain, is also addressed.

It has been previously shown that communications in tunnel environments can be improved by using multiple-input-multiple-output (MIMO) techniques, despite the small angular spread of the rays. However, narrowband transmission was always assumed to fulfill the flat channel hypothesis. The objective of this letter is to generalize these previous works to the case of a wideband communication, i.e., when the transmission bandwidth is much larger than the coherence bandwidth of the channel. Performances of MIMO combined with orthogonal frequency division multiplexing (MIMO-OFDM) are studied in terms of bit error rate and considering either space-time coding or spatial multiplexing. Transfer matrices of the channel measured in a straight arched tunnel are introduced in the software used for simulating the communication link.

This letter studies the possible application of MIMO polarization diversity in road/railway tunnels. By means of an extensive measurement campaign extending from 2.8 to 5 GHz, different linear array architectures were studied, considering different polarizations within each array. Channel capacity was calculated assuming either a constant signal-to-noise ratio (SNR), whatever the array architecture, or a fixed transmitted power. Interpretation of the results is based on the spatial correlation between the incident electric fields on the array elements and also on the variation of the SNR in the case of a fixed transmitted power.

A measurement campaign performed at 1.8 GHz in an urban environment of the city of Cartagena, Spain, is presented. The measurement procedure and data analysis are properly described. The experimental results are then compared with various urban propagation models in order to study their validity in predicting radio signal losses. The analysis shows that different considerations assumed in the models such as the type of wave incidence that is impinging over the series of buildings (plane or spherical) as well as the number of the latter existing across the different propagation paths can be significant in order to obtain more precise and realistic predictions of signal losses.

A hybrid uniform theory of diffraction-physical optics (UTD-PO) solution for the analysis of the multiple-diffraction of spherical waves caused by an array of obstacles, which have been modeled by different shapes, is hereby presented. The formulation, validated with measurements from technical literature, does not need to incorporate high-order diffraction terms (slope diffraction) thanks to a recursive relation, therefore producing an easier, faster solution-when compared with other methods-that, at the same time, achieves accurate results. Such results can be applied in radiowave propagation analysis when multiple-diffraction over obstacles with quite different shapes has to be considered.

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.

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.

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.

We develop a modal approach for analyzing multiple-input-multiple-output (MIMO) wireless channel propagation in a tunnel with lossy walls. We use parametric methods to study the effects of the number of modes and of the separation among antennas. We evaluate the performance of the MIMO channel in terms of capacity as a function of range and tunnel size.

In this work two different implementations of multiple-inputmultiple-output (MIMO) indoor systems are studied: distributed systems (DS) and conventional systems (CS). First a theoretical 3D ray tracing approach, and later an experimental study using a MIMO channel sounder based on a multiport network analyzer (MNA), are used to respectively predict and to measure the MIMO channel response. Results show that, when using DS, capacities are similar to an independent and identically distributed (i.i.d.) fading channel, and they are higher than those obtained by CS, too. They also reveal that ray tracing accurately predicts the results obtained in the measurements for both implementations.

A hybrid uniform theory of diffraction (UTD)-physical optics (PO) formulation for the analysis of the multiple diffraction which takes place in urban environments where a cylindrical hill, either smooth or with buildings located on its surface, causes shadowing of the transmitter from the receiver (a non-line-of-sight situation) is presented, thus furthering a previous study published by the authors, in which the hill is modeled as a wedge. The mentioned UTD-PO solution, which is validated by numerical results from technical literature, is of a good computational efficiency, while at the same time increasing the versatility over other methods for the analysis of the same scenarios, since the presented hybrid formulation allows for the study of the above-mentioned environment when the urban area consists of a small number of buildings.

Two microcellular environments, which are the regular and chaflane street corners, are compared using a ray-launching engine based on the uniform theory of diffraction and geometric optics. This paper includes a study on the signal-to-noise ratio (SNR), K factor, correlation, and multiple-input multiple-output capacity. Two situations, which are the line-of-sight (LoS) and the non-LoS (NLoS), are distinguished and studied separately. In NLoS, the influence of the SNR is higher than the effect of the correlation. However, in LoS, the SNR is comparable in both environments, and correlation determines capacity

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 building's 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.

Channel sounding techniques are used to investigate and compare two micro-cellular environments: regular and chaflane street corners, at four different frequencies using a network analyzer. Parameters are extracted from the power delay profile, which is obtained as the inverse Fourier of the measured frequency response. It is shown that, for line of sight (LoS), delay spread (DS) decreases 10 ns in regular corners and 5 ns in chaflane when frequency varies from 450 to 2400 MHz. For non line of sight (NLoS), RMS DS is around 60 ns in both environments. Frequency correlation is higher in chaflanes than in regular street corners and correlation decreases when the distance in frequency increases. Tapped delay line models are obtained at each frequency in each environment for LoS and NLoS. Finally, for LoS, the coherence bandwidth is bigger in chaflanes than in regular street corners, and it is also observed that it grows as frequency increases. However, for NLoS, the bandwidth remains steady around 4 MHz.

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.

In this paper, a multiple-input multiple-output (MIMO) time-domain channel sounder based on code-division multiplexed signals is presented. This measurement system is formed by commercial and multipurpose equipment such as a base-band pulse generator, a wideband I/Q modulator, and a digital store oscilloscope. Apart from its measurement speed, the main advantages of this proposal are its low cost and the re-utilizable capability of the equipment. The implementation of the channel sounder is described and the MIMO transfer matrix, H(τ), is computed in an indoor environment.

An annular slot antenna suitable for pattern diversity in wideband applications is presented. Pattern diversity is obtained by feeding the antenna simultaneously with two microstrip lines printed on the back of the substrate, which generate orthogonal radiation patterns. Two shorts placed at 45° degrees between the microstrip lines and in the opposite direction ensure an isolation above 15 dB according to measurements. The antenna operates in the range of frequencies from 3 GHz to 12 GHz (1:4 bandwidth) and covers many different standards (Wireless-LAN, HIPERLAN2, WIMAX, UWB). Simulations and measurements for return loss, isolation and radiation patterns are presented. Furthermore, measurements have been carried out in a real multipath environment in order to evaluate pattern diversity performance. Results of measurements of the correlation coefficient and diversity gain over the entire operating bandwidth show that the antenna is suitable for antenna diversity systems. © 2006 IEEE., This work was supported by the Spanish Ministerio de Ciencia y Tecnologia under project TEC2010-20841-C04-01.