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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.

La movilizacion unitaria de apoyo a los represaliados politicos es un aspecto practicamente sin estudiar, pero de notable relevancia, de la lucha antifranquista. Este articulo pretende ayudar a llenar ese vacio. En un contexto de marcado endurecimiento de la represion, las organizaciones clandestinas y los movimientos sociales de oposicion se dotaron de una herramienta transversal para ayudar a las victimas y denunciar su situacion. Los primeros ejemplos se documentan en 1967 en diferentes localidades, pero es a partir de inicios de 1969 cuando se constituye el principal germen del movimiento: la Comissio de Solidaritat de Barcelona. Este nucleo inicial y mas destacado se extendera en los anos siguientes a otros municipios de Cataluna, primero, y Madrid y otras capitales, mas tarde. A traves del estudio de la documentacion generada por estas nuevas plataformas, asi como de la realizacion de entrevistas a algunos de sus componentes, se constata su importancia como uno de los ejes vertebradores del nuevo tipo de oposicion a la dictadura. Gracias al trabajo de las Comisiones de Solidaridad se consiguio amortiguar el embate represivo al tiempo que deslegitimar al regimen y aglutinar las diferentes sensibilidades presentes en el antifranquismo. Asimismo, no puede obviarse la influencia de esa experiencia en la creacion de organismos unitarios de oposicion durante el franquismo y la transicion. Normal 0 21 false false false CA X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabla normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:8.0pt; mso-para-margin-left:0cm; line-height:107%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri",sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:Calibri; mso-bidi-theme-font:minor-latin; mso-fareast-language:EN-US;}

In this paper, a path loss characterization at millimeter-wave (mmWave) frequencies is performed in a typical indoor office environment. Path loss results were derived from propagation channel measurements collected in the 25–40 GHz frequency band, in both line-of-sight (LOS) and obstructed-LOS (OLOS) propagation conditions. The channel measurements were performed using a frequency-domain channel sounder, which integrates an amplified radio over fiber (RoF) link to avoid the high losses at mmWave. The path loss was analyzed in the 26 GHz, 28 GHz, 33 GHz and 38 GHz frequency bands through the close-in free space reference distance (CI) and the floating-intercept (FI) models. These models take into account the distance dependence of the path loss for a single frequency. Nevertheless, to jointly study the distance and frequency dependence of the path loss, multi-frequency models were considered. The parameters of the ABG (A-alpha, B-beta and G-gamma) and the close-in free space reference distance with frequency path loss exponent (CIF) models were derived from the channel measurements in the whole 25–40 GHz band under the minimum mean square error (MMSE) approach. The results show that, in general, there is some relationship between the model parameters and the frequency. Path loss exponent (PLE) values smaller than the theoretical free space propagation were obtained, showing that there are a waveguide effect and a constructive interference of multipath components (MPCs). Since the measurements were obtained in the same environment and with the same configuration and measurement setup, it is possible to establish realistic comparisons between the model parameters and the propagation behavior at the different frequencies considered. The results provided here allow us to have a better knowledge of the propagation at mmWave frequencies and may be of interest to other researchers in the simulation and performance evaluation of future wireless communication systems in indoor hotspot environments. This work has been funded in part by the MCIN/AEI/10.13039/501100011033/ through the I+D+i Project under Grant PID2020-119173RB-C21 and Grant PID2020-119173RB-C22, and by COLCIENCIAS in Colombia.

In this paper, a comparative analysis between concentrated and distributed massive multiple-input multiple-output channels (C-mMIMO and D-mMIMO respectively), in an indoor environment using ray-tracing (RT) in the 26 GHz band is presented. The comparison is carried out in a realistic scenario consisting of a floor of a large building. The simulations emulated the up-link channel in an indoor cell in the framework of a time division duplex (TDD) - orthogonal frequency division multiplexing (TDD-OFDM) system. Both base stations, concentrated and distributed, were equipped with an array consisting of 100 antennas, and the maximum number of 20 simultaneously active users is considered. The channels are simulated using a well-tested and rigorous RT software. Using RT channel modeling, this work characterizes the up-link channels with both technologies, estimating the coherence bandwidth of the channels and analyzing the achievable capacity, assuming perfect channel state information (CSI). The results show that the D-mMIMO channel outperforms the C-mMIMO one from the point of view of their behavior in broadband as well as in terms of the obtainable capacity. This work was supported by the MCIN/AEI/10.13039/501100011033/ through the I+D+i Project under Grant PID2020-119173RB-C21 and Grant PID2020-119173RB-C22.

[EN] This study presents an analysis of the capabilities of using multi-user multiple input multiple output (MU-MIMO) in indoor environments at the 3-4 GHz band through an empirical characterisation of the MU-MIMO channel, obtaining a statistical description of the degree to which this specific multi-user channel verifies the condition of 'favourable propagation'. Different metrics have been considered to measure the degree of orthogonality between the channels, such as the orthogonality coefficient or the condition number. In addition, in order to obtain a direct measure of the goodness of the channel in terms of the achievable spectral efficiency, the capacity of the channel has been calculated for different numbers of users and base station antennas and compared with theoretical i.i.d. Rayleigh channels., This work has been supported by the Spanish Ministerio de Economia, Industria y Competitividad under the projects TEC2017-86779-C2-1-R and TEC2017-86779-C2-2-R.

In this paper, an extensive multiple-input multiple-output (MIMO) measurement campaign in a lab environment has been conducted at the 94 GHz band. Using a vector network analyzer (VNA), up-down converters and omnidirectional antennas displaced in virtual arrays, we have obtained an estimation of the distribution parameters for the most usual distributions employed in the small-scale fading modeling, i.e., Rayleigh, Rice, Nakagami-m and α-μ, by using statistical inference techniques. Moreover, in this scenario the best fit distribution to the experimental data is the Weibull distribution, using the Kolmogorov-Smirnov test. However, the α-μ distribution provides

La movilización unitaria de apoyo a los represaliados políticos es un aspecto prácticamente sin estudiar, pero de notable relevancia, de la lucha antifranquista. Este artículo pretende ayudar a llenar ese vacío. En un contexto de marcado endurecimiento de la represión, las organizaciones clandestinas y los movimientos sociales de oposición se dotaron de una herramienta transversal para ayudar a las víctimas y denunciar su situación. Los primeros ejemplos se documentan en 1967 en diferentes localidades, pero es a partir de inicios de 1969 cuando se constituye el principal germen del movimiento: la Comissió de Solidaritat de Barcelona. Este núcleo inicial y más destacado se extenderá en los años siguientes a otros municipios de Cataluña, primero, y Madrid y otras capitales, más tarde. A través del estudio de la documentación generada por estas nuevas plataformas, así como de la realización de entrevistas a algunos de sus componentes, se constata su importancia como uno de los ejes vertebradores del nuevo tipo de oposición a la dictadura. Gracias al trabajo de las Comisiones de Solidaridad se consiguió amortiguar el embate represivo al tiempo que deslegitimar al régimen y aglutinar las diferentes sensibilidades presentes en el antifranquismo. Asimismo, no puede obviarse la influencia de esa experiencia en la creación de organismos unitarios de oposición durante el franquismo y la transición. The united mobilization in support of victims of political reprisals is a virtually unstudied aspect of the fight against the Franco dictatorship, yet it is extremely important. This article aims to help fill that void. Amid markedly increased repression, the underground organizations and social movements of the opposition developed a cross-societal tool to help the victims and to speak out against their situation. The first examples were documented in 1967 in different towns, yet it was not until early 1969 that the main origins of the movement took root: the Comissió de Solidaritat de Barcelona [Solidarity Committee of Barcelona]. This initial and most prominent hub would be extended to other cities in subsequent years, first in Catalonia, and later in Madrid and other capitals. Our study of the documentation generated by these new platforms, combined with interviews with some of their members, confirms the importance of this network as one of the main axes of the new mode of opposition to the dictatorship. The work of the Solidarity Commissions made it possible to mitigate the brunt of repression, while delegitimizing the regime and bringing together the different awareness groups within the anti-Franco movement. Mention must also be made of the influence of this experience on the creation of united opposition platforms during the Franco regime and the transition to democracy.

The united mobilization in support of victims of political reprisals is a virtually unstudied aspect of the fight against the Franco dictatorship, yet it is extremely important. This article aims to help fill that void. Amid markedly increased repression, the underground organizations and social movements of the opposition developed a cross-societal tool to help the victims and to speak out against their situation. The first examples were documented in 1967 in different towns, yet it was not until early 1969 that the main origins of the movement took root: the Comissió de Solidaritat de Barcelona [Solidarity Committee of Barcelona]. This initial and most prominent hub would be extended to other cities in subsequent years, first in Catalonia, and later in Madrid and other capitals. Our study of the documentation generated by these new platforms, combined with interviews with some of their members, confirms the importance of this network as one of the main axes of the new mode of opposition to the dictatorship. The work of the Solidarity Commissions made it possible to mitigate the brunt of repression, while delegitimizing the regime and bringing together the different awareness groups within the anti-Franco movement. Mention must also be made of the influence of this experience on the creation of united opposition platforms during the Franco regime and the transition to democracy. La movilización unitaria de apoyo a los represaliados políticos es un aspecto prácticamente sin estudiar, pero de notable relevancia, de la lucha antifranquista. Este artículo pretende ayudar a llenar ese vacío. En un contexto de marcado endurecimiento de la represión, las organizaciones clandestinas y los movimientos sociales de oposición se dotaron de una herramienta transversal para ayudar a las víctimas y denunciar su situación. Los primeros ejemplos se documentan en 1967 en diferentes localidades, pero es a partir de inicios de 1969 cuando se constituye el principal germen del movimiento: la Comissió de Solidaritat de Barcelona. Este núcleo inicial y más destacado se extenderá en los años siguientes a otros municipios de Cataluña, primero, y Madrid y otras capitales, más tarde. A través del estudio de la documentación generada por estas nuevas plataformas, así como de la realización de entrevistas a algunos de sus componentes, se constata su importancia como uno de los ejes vertebradores del nuevo tipo de oposición a la dictadura. Gracias al trabajo de las Comisiones de Solidaridad se consiguió amortiguar el embate represivo al tiempo que deslegitimar al régimen y aglutinar las diferentes sensibilidades presentes en el antifranquismo. Asimismo, no puede obviarse la influencia de esa experiencia en la creación de organismos unitarios de oposición durante el franquismo y la transición.

In this work, useful measurement results of the propagation channel characteristics in an indoor office environment at 26 GHz are presented. The parameters of both the floating-intercept (FI) and close-in (CI) free space reference distance path loss models have been derived from channel measurements. The time dispersion characteristics have been analyzed in terms of both the root-mean-square (rms) delay spread and the coherence bandwidth. These results allow us to have a better knowledge of the propagation channel characteristics and can be also used to evaluate the performance of fifth generation (5G) networks in indoor office scenarios.

Air-to-air and air-to-ground communication have been used to interchange data between and from/to different flying objects, respectively, supporting a wide range of applications and protocols. Encryption algorithms are used to secure communications, relying often on pseudo random number generators. Emerging physical layer security methods avoid such number generators and their drawbacks. They rely on the multipath characteristics of the wireless signal that is assumed to be unique and determined by the environment surrounding the communication entities. In this work, an algorithm for generating a security key for encrypting communications within a network is evaluated by analysing the air-to-air/-ground radio propagation channel, which is applied to a case of study of two flying objects.

In this work, we have performed an analysis of the coherence time and Doppler spread of the vehicular-to-vehicular (V2V) propagation channel based on channel measurements at 5.9 GHz. The measurements were collected in a highway and urban environment, where the study of the time variability of the received signal is important due to the motion of both terminals, the transmitter (Tx) and receiver (Rx), together with the objects that are around. The results reported here permit us a better understanding of the V2V propagation channel and can be useful to the deployment of the future vehicular networks.

In this work, we present measured and simulated time dispersion results for two indoor scenarios in the 8–12 G Hz frequency band. The simulated results have been obtained with a full 3D ray-tracing model. The comparison between measured and simulated data shows the potential of these models to describe the time dispersion behavior of the propagation channel at high frequencies. The results reported can be useful for the design and deployment of future wireless systems.

[EN] This work analyzes the characteristics of the small-scale fading distribution in vehicle-to-vehicle (V2V) channels. The analysis is based on a narrowband channelmeasurements campaign at 5.9GHz designed specifically for that purpose.Themeasurements were carried out in highway and urban environments around the city of Valencia, Spain.Theexperimental distribution of the small-scale fading is compared to several analytical distributions traditionally used to model the fast fading in wireless communications, such as Rayleigh, Nakagami-𝑚,Weibull, Rice, and 𝛼-𝜇 distributions. The parameters of the distributions are derived through statistical inference techniques and their goodness-of-fit is evaluated using the Kolmogorov-Smirnov (K-S) test. Our results show that the 𝛼-𝜇 distribution exhibits a better fit compared to the other distributions, making its use interesting to model the small-scale fading in V2V channels., This work has been funded in part by the Programa Estatal de Fomento de la Investigacion Cientifica y Tecnica de Excelencia del Ministerio de Economia y Competitividad, Spain, TEC2013-47360-C3-3-P, and the Departamento Administrativo de Ciencia, Tecnologia e Innovacion COLCIENCIAS en Colombia.

In this letter, we present a path loss characterization of the vehicular-to-vehicular (V2V) propagation channel. We have assumed a path loss model suitable for vehicular ad hoc networks (VANETs) simulators. We have investigated the value of the model parameters, categorizing in line-of-sight (LOS) and non-LOS (NLOS) paths. The model parameters have been derived from extensive narrowband channel measurements at 700 MHz and 5.9 GHz. The measurements have been collected in typical expected V2V communications scenarios, i.e., urban, suburban, rural, and highway, for different road traffic densities, speeds, and driven conditions. The results reported here can be used to simulate and design the future vehicular networks.

In this work, we analyze the applicability of a geometric-based stochastic (GBS) model based on ray-tracing techniques to vehicular-to-vehicular (V2V) intersections. The accuracy and usefulness of the proposed model is analyzed using simulated results and narrowband channel measurements at 5.9 GHz. The results show that these type of models can be a good choice to evaluate communications protocols and system performance of future vehicular networks.

The knowledge of the propagation channel properties is an important issue for a successful design of ultrawideband (UWB) communication systems enabling high data rates in short-range applications. From an indoor measurement campaign carried out in a typical laboratory environment, this paper analyzes the path loss and time-dispersion properties of the UWB channel. Values of the path loss exponent are derived for the direct path and for a Rake receiver structure, examining the maximum multipath diversity gain when an all Rake (ARake) receiver is used. Also, the relationship between time-dispersion parameters and path loss is investigated. The UWB channel transfer function (CTF) was measured in the frequency domain over a channel bandwidth of 7.5GHz in accordance with the UWB frequency range (3.1 10.6GHz)., The authors would like to thank the anonymous reviewer for his constructive suggestions and useful comments which have improved the final quality of the paper. This work has been funded in part by the Spanish Ministerio de Ciencia e Innovacion (TEC-2010-20841-C04-1).

In this work, we investigate the path loss propagation of the vehicular-to-vehicular (V2V) channel when the vehicles are driving in the opposite direction. The investigation is based on narrowband channel measurements at 700 MHz and 5.9 GHz carried out in different environments under real road traffic conditions, i.e., rural, highway, suburban and urban environments. The results show that there is a path loss offset between the forward and reverse directions, which is related to the environment. Also, we provide mean values of the path loss propagation exponent showing that are higher than the values derived when the vehicles are driving in the same direction. These results should be considered for a proper simulation and design of the future V2V communications systems.

Complex correlation multiple-input multiple-output (MIMO) matrices estimated from measurements under realistic propagation conditions occasionally have positive, zero and negative eigenvalues, converting them to indefinite matrices. In this framework, this paper presents a novel correction procedure (CP) based on the alternating projection (AP) method to find the Hermitian and positive definite matrix closest to an estimated indefinite full spatial correlation (FSC) MIMO matrix. This corrected matrix allows the Cholesky factorisation usually used for generation of synthetic MIMO channel samples. The applicability of the CP has been analysed using real data from non-line-of-sight (NLOS) indoor measurements. The results reported in this paper show that a proper selection of the CP parameters has not a sensitive impact on the cumulative distribution function (CDF) of the eigenvalues of the estimated FSC MIMO matrices. This characteristic makes the CP useful for channel characterisation, allowing to assess the performance of a MIMO system. As an example of the CP application, a study of ergodic and outage MIMO capacities for different array configurations is presented .

This letter presents the results of a measurements campaign carried out at 2050 MHz with the aim of characterizing the time dispersion of multipath propagation when the transmit and receive antennas are placed near and situated on rooftops or mounted on masts. The measurements were taken in four separate locations within the urban area of Madrid, Spain. From the measured data, the root mean square (RMS) value of the delay spread and the delay interval that characterize the time dispersion propagation of the environment under study are analyzed. An average power delay profile (PDP), representative of the time dispersion, is proposed so as to extrapolate these results to other similar environments. The results can be useful for the designer to develop, analyze, and choose the best echo canceller technique and evaluate its performance in terms of the radio channel time dispersion when iso-frequency repeaters are used to enhance the coverage area and capacity of mobile cellular systems, as it is the case of the evolving third-generation UMTS networks.

In this paper, a semi-deterministic propagation model for predicting short-term fading statistics in urban environments is presented. An approach to include surface scattering into deterministic ray-optical propagation models in urban scenarios is derived. This approach considers the coherent and incoherent components of the scattered signal. A statistical characterisation of the received signal at the received position permits to model the short-term fading for a local area around the mobile position using the Nakagami-m distribution. The parameters of the Nakagami-m distribution are obtained taking into account the real environment from a digital map information of the urban area. Computer simulation results and experimental data are compared.

It is well known that the short-term fading conditions of the received envelope in wireless communications channels can be modelled by means of the Nakagami distribution. The value of the m parameter, also called shape factor , indicates the severity of multipath fading, and is a measure of channel quality, making its estimation necessary in many applications. In this letter, a range of possible values of the m parameter based on the analysis of a measurements campaign in urban scenarios is presented.

This work presents the initial investigations in the indoor W-band radio channel with a Vector Network Analyzer - based channel sounder capable of measuring from 75 GHz to 500 GHz (mm-W and sub mm-W) with converters. Initial measurements of the path loss and time-delay domain channel responses measured in the 75–110 GHz frequency band are presented for transmitter-receiver distances lower than 1 meter.

In this work, we perform a path loss characterization of the vehicular-to-infrastructure (V2I) channel in an urban environment based on a log-distance path loss propagation model. The model parameters have been derived from channel measurements at 700 MHz and 5.9 GHz. The correlation between the path loss exponent and the height of the antenna used in the infrastructure side is investigated. The measurements have been collected in an urban area of Valencia, Spain, under real road traffic conditions.

Fundamento y objetivo El tratamiento del paciente cardiologico varia segun su comorbilidad. El indice de Charlson (ICh) y sus adaptaciones son herramientas utilizadas y contrastadas globalmente que intentan objetivar la comorbilidad de un paciente. El objetivo del presente trabajo es evaluar la influencia de la comorbilidad, cuantificada mediante el ICh, en el ratamiento intrahospitalario y farmacologico prescrito al alta hospitalaria en el infarto de miocardio con o sin elevacion del segmento ST. Pacientes y metodo Se estudio a 955 pacientes consecutivos ingresados en un hospital por infarto de miocardio. Se analizo la comorbilidad obtenida el primer dia del ingreso mediante la aplicacion del ICh, se clasifico a los pacientes en 2 subgrupos de menor o mayor comorbilidad (ICh = 2; ICh > 2) y se determino si habia diferencias entre ambos subgrupos segun el tratamiento intrahospitalario y al alta. Resultados Los pacientes ingresados por infarto agudo de miocardio sin elevacion del ST e ICh superior a 2 recibieron con menor frecuencia bloqueadores beta al alta, mientras que no existen diferencias significativas en el tratamiento con inhibidores de la enzima de conversion de la angiotensina, antagonistas del calcio o estatinas. Ademas, se les practicaron menos procedimientos de revascularizacion y menos ergometrias, mientras que no hubo diferencias en la realizacion de ecocardiogramas. Los pacientes con elevacion del segmento ST e ICh superior a 2 era menos probable que fueran tratados al alta con bloqueadores beta y estatinas, y se les realizaron menos ergometrias y ecocardiogramas, mientras que no hubo diferencias significativas en el tratamiento con inhibidores de la enzima de conversion del la angiotensina, antagonistas del calcio, trombolisis o tratamiento intervencionista (revascularizacion). Conclusiones La comorbilidad presente en el momento del ingreso y cuantificada mediante el ICh condiciona de manera independiente el tratamiento intrahospitalario y el alta de los pacientes con infarto de miocardio. Hay un menor uso de tecnicas invasivas, junto con una menor prescripcion de bloqueadores beta al alta en los pacientes con mayor comorbilidad.

Based on a narrowband channel measurement campaign, this paper characterizes the path loss in vehicular environments, categorizing between line-of-sight (LOS) and non-LOS (NLOS) propagation conditions at 5.9 GHz. Based on a linear slope model, values of the path loss exponent and the standard deviation of the shadowing are reported in three different environments, i.e., urban with high road traffic density, urban with moderate/low traffic density, and highway. The results presented here can be incorporated in an easy way into vehicular network (VANET) simulators to develop, evaluate and validate new protocols and system architectures configurations under more realistic propagation conditions.

La dictature de Franco a massivement utilise l’emprisonnement pour lutter contre ses dissidents et opposants. Si, tout au long de quatre decennies, la plupart des prisonniers etaient des hommes, les femmes ont elles aussi ete victimes de cette politique d’enfermement. Les femmes incarcerees ont du subir la misere, les privations et l’endoctrinement religieux et ideologique. Pour celles ayant des enfants, leur eloignement force constituait un moyen de chantage pour imposer la conversion aux valeurs du national-catholicisme. En outre, toute femme en liberte ayant un membre de sa famille en prison, etait consideree comme hostile et suspecte de republicanisme, et faisait l’objet d’un controle social strict. Au fil du temps, les conditions de vie en prison se sont ameliorees et le nombre de prisonnieres s’est reduit. Toutefois, la volonte d’endoctrinement religieux et moral est restee pratiquement invariable jusqu’a la fin du regime.

Propagation characteristics in vehicular radio channels are affected by time- and frequency-selective behavior due to the multipath propagation effect and the movements of the transmitter, the receiver as well as the relevant scatterers. Measurements are vital for the understanding of propagation channels. This article provides an overview of existing vehicular channel measurements. The vehicular channel measurement techniques are briefly described and classified. Furthermore, we review the channel metrics such as path-loss, signal fading and Doppler spread based on the available literature and we summarize and discuss some measurements results of the reported parameters to describe the propagation narrowband channel characteristics in vehicular environments.

Traffic accidents have become an important health and social problem due to the enormous number of fatalities and injuries. The total number of deaths and injuries in the European Union (EU), United States of America (USA) and Japan has been steadily reduced over the last decade. This reduction is mainly attributed to the implementation of a set of road safety measures, such as seat-belt use, vehicle crash protection, traffic-calming interventions and traffic law enforcement. However, the number of accidents has remained uniform due to the increasing number of vehicles and total distance driven (Peden et al., 2004). In addition to passive vehicle safety systems, such as airbags, anti-lock braking system (ABS) and electronic stability control (ESP), new active safety systems have been introduced to improve vehicular safety. To this end, the last decade has witnessed the traffic management industry, engage and promote the integration of information and communications technology (wireless, computing and advanced sensor technologies) into both vehicles and the wider transport infrastructure. These proposals have led to the intelligent transportation system (ITS) concept. At present, different ITS applications have been introduced, such as variable message signs (VMS), located at strategic points (e.g., tunnels and merging highways) or spaced at given distances, to inform drivers about traffic and dangerous situations; automated toll collection systems for highways and parkings; and real-time traffic information broadcasted in the FM radio band. Besides this, onboard ITS applications have improved the assistance and protection mechanisms for drivers: navigation systems, rear and front parking radars, and cameras are extensively used in the vehicle. Vehicles now incorporate sophisticated computing systems, with several sensors interconnected. However, short-range sensors employed in emergency systems, such as forward collision warning and lane keeping assist, are insufficient, specially when these sensors need to extend their communication horizon in emergency cases due to the limitation of their operating range to line-of-sight (LOS) conditions (Vlacic et al., 2001). Therefore, there are safety applications for distance emergency situations, such as blind corners and traffic crossing, where large-range vehicular communication systems are required, e.g., operating rages of about 1000 meters, in both LOS and non-LOS (NLOS) conditions (Gallagher & Akatsuka, 2006). Wireless communications systems which can operate with these constraints are known as cooperative systems on the road. In the cooperative system concept, vehicles and infrastructure exchange safety messages to extend the distance horizon and provide more information in real time to drivers. Cooperative systems involve two

This letter presents a characterization of the vertical plane propagation in terms of the satellite elevation angle for different mechanisms of propagation. The effect of blockage by buildings on the received signal level versus the satellite elevation angle at L-band for urban environments is performed using the uniform theory of diffraction (UTD). © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 26: 336–338, 2000.

The integration of wideband and multiple-input multiple-output (MIMO) radio technologies represents a powerful tool for different wireless communication standards. In the test process of these systems, new strategies for MIMO channel modelling and characterisation are necessary in order to investigate how the frequency band and the bandwidth affect the system performance. In this paper, a MIMO channel experimental characterisation based on full spatial correlation (FSC) MIMO matrices estimated from frequency domain measurements is presented. Measurements performed between 2 and 12 GHz in a stationary office scenario in both line-of-sight (LOS) and non-line-of-sight (NLOS) conditions are considered. Results show frequency dependency on the experimental MIMO channel characteristics under a high SNR regime, equal electric separation between array elements and isolation of the path loss effect. The ergodic and 1% outage capacities were reduced while the central frequency increases for different array configurations. Remarkable changes on the magnitude of the spatial correlation coefficients and on the MIMO system eigenvalues were observed for different band frequencies.

The spectral efficiency of MIMO (multiple input multiple output) channels is limited by both the spatial correlation and rank deficiency of the channel. Precedent studies have focused less attention in how the frequency band affects these channel properties. In this paper, the results derived from an extensive measurement campaign performed between 2 and 12 GHz in an office scenario, show frequency band dependence on the MIMO channel capacity. Increasing the number of antenna elements under these correlated channels for different frequencies, we found frequency band dependence on both the ergodic and the 10% outage capacities. Taking into account the isolation of the path loss, a high SNR regime, equal electric separation between array elements, and the WSS (wide sense stationary) channel condition, remarkable changes on the magnitude spatial correlation coefficients and on the MIMO system eigenvalues were observed for different frequencies in line-of-sight (LOS) and non-line-of-sight (NLOS).

In this paper, a characterization of the UWB mobile radio channel time dispersion is presented. The results provided were obtained from a measurement campaign carried out in a typical indoor office scenario in the band from 3.1 to 10.6 GHz. Time dispersion metrics as delay spread, coherence bandwidth, delay interval and delay window, in both line-of-sight (LOS) and non-line-of-sight (NLOS) conditions are provided.

In this paper, the influence of the frequency band on the multiple-input multiple-output (MIMO) channel capacity in an office environment is researched. This study is based on an extensive measurement campaign between 2 and 12 GHz in line-of-sight (LOS) and non-line-of-sight (NLOS) conditions.

In this paper an efficient scheduling mechanism for wireless local area networks (WLAN) is proposed. This innovative scheme, named hybrid HCCA-EDCA centralised scheme (HHE-CS), is based on the hybrid coordination function (HCF) protocol introduced by the IEEE 802.11e standard. The HHE-CS aims at satisfying the user quality of service (QoS) demands for real time (RT) services with variable bit rate while maximising the throughput of best effort users. This paper proves conclusively that an adequate allocation of downlink and uplink traffic between EDCA and HCCA increases system performance as compared with more traditional schemes in which all best effort traffic is exclusively delivered by a distributed mechanism like EDCA.

The spectral efficiency of MIMO (multiple input multiple output) channels is limited by both the spatial correlation and the rank deficiency of the channel. Earlier studies have focused less attention on how the frequency band affects these channel properties. In this paper, the results derived from an extensive measurement campaign performed at 4 frequency bands between 2 and 12 GHz in an office scenario, show a frequency band dependence on the MIMO channel capacity. Increasing the number of antenna elements under these correlated channels, we found a frequency band dependence on the ergodic, 10% and 1% outage capacities. Taking into account the path loss effect isolation, high SNR regime, equal electric separation between array elements, and stationary conditions in the measurements, remarkable changes on the spectral efficiency were observed for different frequency bands in line-of-sight (LOS) and non-line-of-sight (NLOS) propagation conditions.

A more general expression for the multiple building diffraction attenuation function using both GTD and PO techniques is presented. The bounds of applicability of the result are derived, assuming that the base station antenna may be located at any distance from the first building, as well as having to be sufficiently below it so that the other buildings lie outside the transition region of the first building. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 18: 335–337, 1998.

The space-time wireless communications systems will use the advantages of the MIMO (multiple input multiple output) channels. Precedent studies have focused less attention on the eigen/capacity analysis with correlated channels under different frequencies for indoor environments. The results derived from a frequency measurement campaign performed between 2 and 4 GHz, show frequency band dependence on the MIMO channel correlation matrix. Increasing the number of antenna elements under those correlated cases, we found that it does not offer linear increases at both the ergodic and the 10% outage capacities. In this paper, we assume that the channel is unknown at the transmitter and perfectly known at the receiver. Under the WSS (wide sense stationary) channel condition and guaranteeing a high SNR (signal to noise ratio) level, in LOS (line-of-sight) and N-LOS (non-LOS) conditions, remarkable changes on the capacity probability distribution function shape and on the cumulative distribution function of the MIMO system eigenvalues were observed.

In this paper the time dispersion behaviour of the ultra-wideband radio channel from 0.3 up to 3 GHz is analysed. The results given have been extracted from a measurement campaign carried out in the Mobile Communications Group laboratory, in the iTEAM Research Institute, of the Technical University of Valencia. The measured power delay profiles revealed the presence of two clusters of contributions in LOS conditions, the first one with a noticeable decreasing trend, and the second one with a slight trend, and only one cluster in NLOS conditions, with a similar trend to the second cluster of LOS profiles. Time dispersion parameters as delay spread, delay interval, delay window and coherence bandwidth are analysed. The results provided revealed that the channel time dispersion is higher in NLOS locations.

In this paper the impact of the soft handover micro diversity gain on the UMTS system performance is investigated. First, by means of link layer simulations the micro diversity gain is measured in terms of reduction of the average Eb/N0 requirement. After modelling this effect, by some system level simulations we show the high influence of this usually neglected gain in the overall performance of UMTS, demonstrating that in downlink soft handover improves not only the quality of service but also the overall system capacity.

This paper aims at providing not only a detailed analysis of the channel estimation based on the correlation method in UMTS but also a new simple model of the channel estimation error. With the only knowledge of the Eb/N0 perceived in each finger and the use of a negative exponential distribution function the channel estimation can be easily simulated. Thanks to this model it is possible to simplify the link level simulations reducing the computational burden. The given model could also be used to increase or decrease the error in a controlled way to evaluate the influence of channel estimation in the final performance of the system and to determine the necessity of a possible improvement in such technique

In this paper, downlink performance of WCDMA system with site selection diversity transmission power control (SSDT) during soft handover mode is analysed. Signal to interference ratio (SIR) power control techniques are modelled and used in simulations. The study is focused on finding the optimum soft handover margin in terms of maximum system capacity under E/sub b//N/sub 0/ quality requirements. The capacity and resources allocated (number of codes required) using SSDT is compared to usual soft handover technique.

In this paper, a semi-deterministic propagation model for the prediction of short-term fading statistics in urban mobile cellular systems is presented. The model is based on digital map information and is also used to predict coverage areas. The short-term fading is modelled by the Nakagami distribution, where the two parameters defining the distribution for a local area around the mobile position can be obtained from the available digital map information of the urban area. Computer simulation results and measurement campaigns are compared, showing that the best approximation to the probability density function of the short-term fading in mobile urban channels is a Nakagami distribution.

A 26-year-old man was admitted to our hemodynamic laboratory because of an anterior AMI and post myocardial infarction angina. He is an active smoker (10 cigarettes/day) and consumes inhaled cocaine during weekends (the last consumption of cocaine was 1 week ago). No others risk factors were recorded. Initial electrocardiogram shows sinus rhythm and anterior QS complex (V1–V3) with anterolateral ST segment elevation (V1–V5, D1 and aVL). Creatine-kinase isoenzyme MB and Troponin I were elevated at arrival. Upon admission, the patient was normotensive but with signs of pulmonary congestion. Ventriculography showed anterolateral and apical hypokinesia with an ejection fraction of 21%. Coronariography revealed a massive thrombosis and distal vasoconstriction of the left anterior descending coronary artery. Circumflex and right coronary artery were angiographically normals (Fig. 1). Recombinant tissue plasminogen activator was started by intracoronary infusion (50 mg) with additional 50 mg via systemic. Clinical evolution was satisfactory without new

A novel procedure based on the alternating projection method to adjust experimental shadowing cross-correlation (SCC) matrices is proposed. Given an SCC matrix derived from any experimental model, this procedure finds the nearest diagonalisable correlation matrix. This adjustment allows a proper simulation of shadowing samples, since it produces correlation matrices for which Cholesky factorisation is feasible. Simulation results using this procedure for three different SCC models are compared and discussed.