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Accurate radio wave prediction models are necessary for the innovation of mobile communication technology and the deployment of wireless sensor networks in railways. The parabolic wave equation (PWE) method is one commonly used method to predict the electromagnetic characteristic of long railway tunnels. However, the advent of novel antennas and technologies (e.g., beam steering, beamforming) has posed new challenges to PWE‐based models such as effective means of taking tilted beam patterns into account. This study addresses such a challenge by using tilted Gaussian beams to embed antennas with oriented patterns or tilted beam directions into PWE‐based models. The proposed approach does not reduce the simulation efficiency of PWE itself. The validity and practicability of the technique are demonstrated by comparing against ray‐tracing as well as experimental measurements in various tunnel environments. [ABSTRACT FROM AUTHOR]

Reconfigurable intelligent surfaces (RISs) have attracted major attention in the last few years, due to their useful characteristics. An RIS is a nearly passive thin surface that can dynamically change the reradiated field and can therefore realize anomalous reflection, refraction, focalization, or other wave transformations for engineering the radio propagation environment or realizing novel surface-type antennas. Evaluating the performance and optimizing the deployment of RISs in wireless networks need physically consistent frameworks that account for the electromagnetic characteristics of dynamic metasurfaces. In this article, we introduce a general macroscopic model for evaluating the scattering from an RIS. The proposed method decomposes the wave reradiated from an RIS into multiple scattering contributions and is aimed at being embedded into ray-based models. Since state-of-the-art ray-based models can already efficiently simulate specular wave reflection, diffraction, and diffuse scattering but not anomalous reradiation, we enhance them with an approach based on Huygens’ principle and propose two possible implementations for it. Multiple reradiation modes can be modeled through the proposed approach using the power conservation principle. We validate the accuracy of the proposed model by benchmarking it against several case studies available in the literature, which are based on analytical models, full-wave simulations, and measurements. [ABSTRACT FROM AUTHOR]

On‐body propagation channels show significant polarization selectivity that has dominant impacts on the on‐body link quality in wireless body area networks. For on‐body relay channels over long distances across the body, the antenna polarization configurations of the relaying nodes are crucial to determine the relay performance, thereby requiring polarization optimization schemes. In this article, narrow band flat‐fading on‐body channels at 2.484 GHz are measured to analyse their polarization distribution above the skin under static postures. The measured on‐body channels show full‐space polarization convergence and dispersion, which are modelled by an extended 3 by 3 channel polarization matrix, and a statistical channel model is also proposed. Multi‐hop polarized on‐body relay channels are analysed on the relay link capacity, which shows polarization dependency between adjacent hop channels when relaying nodes are mounted by linearly polarized antennas. Both regular and iterative polarization selection algorithms are then designed to optimise the antenna polarization configuration of the nodes. Simulations based on the proposed polarization distribution model show significant link capacity increases for two‐hop and tfhree‐hop on‐body relay channels by the optimization algorithms. The results confirm the necessity of proper polarization selection schemes for on‐body relay channels. [ABSTRACT FROM AUTHOR]

In satellite communications, the adverse propagation effects produced by the atmosphere to the signal are compensated by the systems using propagation impairment mitigation techniques, protection by diversity being one of their main categories. Two slant-path propagation experiments have been carried out in Madrid in the Ka- and $Q$ -bands, with the Eutelsat KA-SAT and Alphasat satellites, respectively, with three concurrent years of measurements available: from March 2014 to February 2017. In this paper, results on time diversity and orbital diversity—the latter obtained from a frequency scaling approach— are presented, the first one for both frequency bands and the second for the $Q$ -band. An acceptable overall behavior is obtained by comparing the results with the available models. For both diversity techniques, possible gains are moderate but not negligible due to the climatological conditions of the evaluated site. [ABSTRACT FROM AUTHOR]

This paper proposes a hybrid modeling approach for the prediction of the room-to-room radio propagation channel. The model combines ray tracing (RT) with the propagation graph (PG). The PG vertices are obtained at each room by RT with the assumption that the receive antenna (or transmit antenna) virtually locates on the surface of the separating wall between the two rooms. Rays transmitted from one room to the other through the separating wall are deterministically calculated by Snell’s law of refraction. Predictions by the proposed model are compared with the measurement data from an office-to-office scenario. The results show that the proposed modeling works with the simplest parameter settings, i.e., assuming no propagation from the room containing receive antenna to the room containing transmit antenna, RT applied separately in each room only involves mechanism of line of sight and first-order specular reflection. [ABSTRACT FROM AUTHOR]

This paper presents a physics-based macro model that can predict with a high degree of accuracy various experimental data available for the propagation path loss of radio waves in a cellular wireless environment. A theoretical macro model based on the classical Sommerfeld formulation can duplicate various experimental data including that of Okumuraet al.carried out in 1968. It is important to point out that there are also many statistical models but they do not conform to the results of the available experimental data. Specifically, there are separate path loss propagation models available in the literature for waves traveling in urban, suburban, rural environments, and the like. However, no such distinction is made in the results obtained from the theoretical analysis and measured experimental data. Based on the analysis using the macro model developed after Sommerfeld’s classic century-old analytical formulation, one can also explain the origin of slow fading which is due to the interference between the direct wave from the base station antenna and the ground wave emanating from the reflections of the direct wave and occurs only in the near field of the transmitting antenna. The so-called height gain occurs in the far field of a base station antenna deployment which falls generally outside the cell of interest, while in the near field, within the cell, there is a height loss of the field strength for observation points near the ground. A physical realization of the propagation mechanism is illustrated through Vander Pol’s exact transformation of the Sommerfeld integrals for the potential to a spatial semiinfinite volume integral and thus illustrates why buildings, trees, and the like have little effects on the propagation mechanism. [ABSTRACT FROM AUTHOR]

Physics-based wireless propagation modeling and network protocol design have evolved over decades as orthogonal areas in communication systems research. This fragmented approach does not exploit available efficiencies when planning and deploying communication systems. In an attempt to integrate the two areas, we harness the understanding of the underlying physics of electromagnetic propagation to enhance the robustness of network protocol design by deriving physics-based network-level performance metrics. We use ray-tracing and parabolic equation models of 2.4 GHz propagation along tunnel and open-air sections of London Underground to evaluate the performance of a communications-based train control system. For comparison, we consider existing path loss models for tunnel environments and investigate whether they can provide sufficient accuracy to be used for network protocol design. We show that physics-based models lead to reliable predictions at the network level, similar in fidelity to using measured data and unlike using simplified channel models of the path loss exponent type. [ABSTRACT FROM AUTHOR]

It is found that for very low-frequency (VLF) signals, the mode-conversion interference produces a cycle slip during the sunrise or sunset transition at certain distances far away from the transmitter. In this paper, an anisotropic terrestrial waveguide with abrupt effective height change of 20 km geometry has been adopted to investigate the diurnal behaviors of amplitude and phase caused by the night-to-day transition. At the waveguide junction, sequential determinations of transmission and reflection coefficients are determined by the resulting linear equations from field matching. Field calculations across the day-to-night transition are carried out by using a reciprocity theorem correspondingly. This paper illustrates that VLF wave propagation experiences multimode interference in periodic variations in amplitude during sunrise and sunset over a long propagation path. [ABSTRACT FROM AUTHOR]

Antennas, and more generally any equipment under test (EUT) capable of coupling to impinging electromagnetic waves, are well-known sources of power loss in reverberation chambers (RCs). As such, it is fundamental to model their contribution to an RC quality factor. The standard model available in the literature is based on power dissipated in loads connected to an antenna. This letter argues about the inaccuracy of this description, where internal dissipation within an antenna (or EUT), associated to potentially low radiation efficiencies, is neglected. An alternative model is validated by showing its self-consistency in predicting change in loading effects as opposed to the standard model. It is expected to have practical importance for tests performed in the low-frequency range of RCs, where antenna-related dissipation is the dominant loss mechanism, and in particular for EUTs which can be expected to display poor radiation efficiencies. [ABSTRACT FROM AUTHOR]

Fabry–Perot (FP)/leaky-wave antennas fed with multiple sources are analyzed and modeled. A transmission line (TL) approach for a rapid and efficient analysis of such antenna configuration is developed. The method is based on the superposition of the traveling leaky waves excited by each of the applied sources. The field distribution inside the cavity is derived by using a longitudinal TL model which takes into account the interference of the multiple leaky waves excited by the sources. The radiation pattern of the multiple fed antennas is obtained by using the fast Fourier transformation of the field distribution. The propagation constants of the leaky waves, traveling inside the FP cavity, are computed analytically, and the accuracy of the proposed expressions is verified by using the transverse resonance method approach. A novel and accurate closed-form expression for the leaky-wave propagation constant has been derived. A detailed analysis of the antenna properties is carried out by using the model showing how this antenna configuration is suitable for designing very large aperture antennas with very high gain and fairly acceptable bandwidth. A prototype of a multifeed FP antenna has been fabricated by using 3-D printing technology and tested. [ABSTRACT FROM AUTHOR]

When reverberation chambers are loaded to increase the coherence bandwidth for modulated-signal measurements, a secondary effect is decreased spatial uniformity. We show that an appropriate choice of stirring sequence, consisting of a combination of mode-stirring mechanisms such as paddle and antenna-platform stirring, can mitigate the potential for increased uncertainty. We develop a new mode-stirring sample correlation model for uncertainty due to the stirring sequence. In a comparison with an empirical uncertainty analysis, the model is found to have an agreement within 2.5%. Our analysis is demonstrated for four loading cases in each of three reverberation chambers. The model is used to determine an optimal stirring sequence for a given chamber setup directly from correlations associated with each stirring mechanism. The model can also be understood in terms of the entropy of a measurement and it is shown that maximizing the entropy corresponds to a minimized uncertainty. The method presented here not only provides insight into sources of uncertainty but also allows users to determine an optimal mode-stirring sequence with minimized uncertainty for a given chamber setup. [ABSTRACT FROM AUTHOR]

In the Earth-space link communication system design, rain attenuation must be considered, especially with a frequency above 10 GHz. Therefore, a reliable rain attenuation prediction model is necessary for the design of these systems. Recently, two anomalous behaviors have been reported in existing rain attenuation prediction models. First, predicted rain attenuation results from many models vary nonmonotonically with elevation angles. Second, the rain attenuation predicted by the ITU-R model varies nonmonotonically with a percentage of time or rain rate in low latitudes (between 36° S and 36° N) and low elevation angles (below 25°). To tackle these problems and improve the prediction accuracy, a new rain attenuation model is developed based on the exponential rain cell profile, and a concept of rain rate adjustment factor is proposed. Evaluating performance by utilizing the Recommendation ITU-R P.311-15, the new model provides better prediction results than other existing models. Moreover, the anomalous behaviors are also improved in this model. [ABSTRACT FROM AUTHOR]

A finite-difference time-domain-based technique for evaluating envelope correlation coefficient (ECC) and mean effective gain (MEG) of multiple-input multiple-output (MIMO) antennas operating in real-life nonuniform propagation environment is introduced. The proposed algorithm is based on the formulation of a modified cross correlation Green’s function (CGF), which directly incorporates the specific angular distribution functions and cross-polarization discrimination parameters. Thus, the proposed technique based on modified CGF is able to calculate ECC/MEG for MIMO antennas in nonuniform propagation scenario, directly from the time-domain antenna currents. This avoids the troublesome determination of far-field antenna pattern at each working frequency and the consequent postprocessing, as required in the conventional approach. Numerical examples using thin-wire half-wavelength dipole antennas and printed microstrip-fed slot antennas are provided to show the effectiveness of the proposed technique for characterizing MIMO antennas in nonuniform propagation environment. [ABSTRACT FROM AUTHOR]

Large gateways of future satellite communications (Satcom) systems will likely operate at Q-/V-band frequencies (40–50 GHz) to take advantage of the larger available bandwidth. On the other hand, Q-/V-band Satcom systems suffer from highly variable propagation losses, which must be accurately assessed and modeled. The Alphasat Aldo Paraboni propagation experiment, conceived and realized by the Italian Space Agency (ASI), Rome, Italy, has been running since 2014 to carefully investigate the propagation effects in the Ka- and Q-band and, thus, to support the design of high-throughput systems and propagation impairment mitigation techniques. In the framework of this experiment, ASI deployed two large ground terminals (Cassegrain antenna with 4.2 m diameter) in Tito Scalo (South of Italy) and Spino d’Adda (North of Italy). This contribution investigates the effect of antenna strut elongation on propagation measurements, which causes an additional reduction of 1–2 dB in the received signal during sunny days. [ABSTRACT FROM AUTHOR]

In this paper, we study the feasibility of an opportunistic radar, which exploits the probing signals transmitted during the sector level sweep of the IEEE 802.11ad beamforming training protocol. Several solutions are presented to detect the presence of prospective obstacles and estimate their position, radial velocity, and backscattered signal amplitude, which differ in the amount of prior information as to the transmitted signal and the channel fluctuation. Also, we derive the Cramér–Rao bound as a benchmark for the proposed estimators: The derivation of these bounds is per se relevant, as it generalizes classical results to the case where the echo is not entirely contained in the observation window. Numerical examples are provided to assess performance of the proposed solutions. The results indicate that the close-to-one detection probability is achievable up to 90 m with a probability of false alarm of 1e-4 and Swerling-I target fluctuation; in this region, the target delay is estimated with an accuracy smaller than the symbol interval (corresponding to a range resolution smaller than 10 cm) with probability close to one, while the velocity estimate is generally quite poor as a consequence of the very short duration of the probing signal. [ABSTRACT FROM AUTHOR]

In spherical near-field (NF) measurements, post-processing techniques based on spatial filtering have been presented as an interesting tool for the mitigation of echoes or stray signals deriving from the environment surrounding the antenna under test (AUT). The spatial filtering is very efficient in measurement scenarios with a stationary AUT. Whenever the AUT is rotating, in order to increase the effectiveness of the echo reduction, the antenna needs to be displaced outside the centre of rotation. Unfortunately, the number of acquisition samples needed to represent the AUT in offset configuration is higher with respect to one needed for the onset configuration. An innovative NF/far-field transformation algorithm for spherical offset measurements which allows to significantly reduce the number of measurement samples has been recently proposed. Such technique has been named translated spherical wave expansion (TSWE) and is based on the definition of new reference systems centred on the AUT rather than on the origin of the measurement sphere. In this study, the authors present the experimental investigation of the TSWE echo reduction properties for offset AUT. [ABSTRACT FROM AUTHOR]

This contribution presents propagation measurements at 60 GHz in indoor non-line of sight scenarios. Besides analysing the measurements, the authors have considered several system aspects, such as bandwidth and directivity in order to investigate the small-scale behaviour of the radio channel after beam-forming. The results show that due to the high resolution in the angular and time domain achievable by large antenna arrays and wideband signals, the fading is significantly reduced and the equivalent transmission channel becomes more sparse and deterministic. These insights represent an essential source of information for future systems design and the ongoing channel modelling activities for systems operating at mm-waves. [ABSTRACT FROM AUTHOR]

The performance of the satellite communication systems employing polarisation diversity or frequency-reuse schemes to improve the spectral efficiency is degraded due to the depolarisation-induced interference originated by raindrops and ice particles present along the Earth-Space propagation path. Two models account for both rain and ice contributions. One predicts the long-term cumulative distribution function (CDF) of cross-polarisation discrimination (XPD). The other predicts the relationship between XPD and co-polar attenuation (CPA) and it was derived considering exclusively data at the V-band. In this study, the former model is improved by considering the individual ice and rain contributions and their combined effects, while the latter is validated against new measurements at the Ka band. New models are then proposed for the XPD-CPA relationships at the Ka-band taking into account both rain and ice contributions and also their combined effects. Finally, the predictions provided by the first model are usually converted to the corresponding XPD-CPA relationship using the long-term first-order statistics of rain attenuation, (incorrectly) considering that the equiprobability hypothesis applies. A new approach for the conversion of the XPD CDF into the corresponding XPD-CPA relationship is presented. [ABSTRACT FROM AUTHOR]

In this paper, an inhomogeneous human body model was presented to investigate the propagation characteristics when the human body was used as an antenna to achieve signal transmission. Specifically, the channel gain of four scenarios, namely, (1) both TX electrode and RX electrode were placed in the air, (2) TX electrode was attached on the human body, and RX electrode was placed in the air, (3) TX electrode was placed in the air, and RX electrode was attached on the human body, (4) both the TX electrode and RX electrode were attached on the human body, were studied through numerical simulation in the frequency range 1 MHz to 90 MHz. Furthermore, the comparisons of input efficiency, accepted efficiency, total efficiency, absorption power of human body, and electric field distribution of different distances of four aforementioned scenarios were explored when the frequency was at 44 MHz. In addition, the influences of different human tissues, electrode position, and the distance between electrode and human body on the propagation characteristics were investigated respectively at 44 MHz. The results showed that the channel gain of Scenario 4 was the maximum when the frequency was from 1 MHz to 90 MHz. The propagation characteristics were almost independent of electrode position when the human body was using as an antenna. However, as the distance between TX electrode and human body increased, the channel gain decreased rapidly. The simulations were verified by experimental measurements. The results showed that the simulations were in agreement with the measurements. [ABSTRACT FROM AUTHOR]

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This paper investigates the quality of communication in wireless networks and connection quality evaluation on the basic parameters of indoor and outdoor applications with produced experimental data. The analysis of the influence of radio waves propagation conditions of in the wireless communication networks were performed at the different types of medium. Comparison of the radio waves propagation indoors and outdoors has been done. Also, the effect of the obstacles of various materials on radio propagation was performed. [ABSTRACT FROM AUTHOR]

This paper studies the behavior of the sum-rate of outdoor multi-user multiple input multiple output systems, where a uniform linear array is utilized at the base station (BS), as the number of BS antennas and the number of users increase. Two schemes are studied for the downlink, the zero-forcing and the maximum ratio transmission (MRT). To begin with, the channel matrix is described deterministically using direct scattering theory. Its matrix elements are the Fourier coefficients of functions that have a physical significance, being connected to the geometry of the environment. For the case when the energy is not arriving at the BS from every spatial direction, we prove for the ZF scheme that the achievable sum-rate behavior is sublinear in the number of antennas at the BS. For the MRT scheme, we prove that there is a link between the sum-rate and the distribution of the users in the city. To numerically evaluate the sum-rate for a given city, schematically described by its streets and its buildings, we introduce a model for the Fourier coefficients of the aforementioned functions, which mixes geometrical and statistical ingredients. We randomly distribute high buildings that will act as strong scatterers and look at the influence of their number on the sum-rate. With the ZF scheme, we perform the calculations for the case where the number of BS antennas, MT , is equal to the number of users, MR, and for the case where MT is larger than MR . We observe that the sum-rate first increases linearly with the number of BS antennas, and becomes sublinear after MT reaches a certain value. The threshold depends on the number of high buildings. With the MRT scheme, the calculations confirm the theoretical predictions, and the sum-rate is greater if the users are spread over all of the city. [ABSTRACT FROM PUBLISHER]

This paper describes an extensive propagation channel measurement campaign in a warehouse environment for line-of-sight (LOS) and nonline-of-sight (NLOS) scenarios. The measurement setup employs a vector network analyzer operating in the 2–8-GHz frequency band combined with an $8 \times 8$ virtual multiple-input multiple-output (MIMO) antenna array. We develop a comprehensive statistical propagation channel model based on high-resolution extraction of multipath components and subsequent spatiotemporal clustering analysis. The intracluster direction of departure (DoD), direction of arrival (DoA), and the time of arrival (ToA) are independent, both for the LOS and NLOS scenarios. The intracluster DoD and DoA can be approximated by the Laplace distribution, and the intracluster ToA can be approximated by an exponential mixture distribution. The intercluster analysis, however, shows a dependency between the cluster DoD, DoA, and ToA. To capture this dependency, we separately model the clusters caused by single and multiple bounce scattering along the aisles in the warehouse. The intercluster DoD distribution follows a Laplace distribution, while the cluster DoA conditioned on the DoD is approximated by a Gaussian mixture distribution. The model was validated using the capacity and delay-spread values. [ABSTRACT FROM AUTHOR]

In this paper, measurement results of onbody radio propagation channels at 2.45 GHz and offbody radio propagation channels at 1.9 GHz using dual band and dual mode (DBDM) antenna are presented. The proposed antenna works at two different frequencies with different radiation modes. Experiments are performed first in the chamber and then in an indoor environment. The path loss has been characterized for ten different on-body radio channels at 2.45 GHz. Five off-body radio channels are studied at 1.9 GHz. The path loss was modeled as a function of distance for onbody radio propagation at 2.45 GHz and off-body radio propagation at 1.9 GHz. For on-body propagation, the path loss exponent is noticed to be 2.48 and 2.22 in the camber and sensor laboratory, respectively. For offbody radio propagation case, the path loss exponent is noticed to be 1.27. The proposed antenna shows very good on-body and off-body radio propagation channel performance. [ABSTRACT FROM AUTHOR]

Safe navigation of labour-aiding robots in commercial orchards will rely on accurate and continuous worker localisation. In this work, an ultra-wideband radio-based system localises a worker via trilateration of four range measurements between antennas on a vehicle and an antenna carried on the worker's belt. Performance results are presented from measurements inside 'work zones' around the vehicle, in open space and in an orchard. At walking speed in open space, when body placement allowed full line-of-sight (LOS) between belt and vehicle antennas, position estimate availability was 99.7% and the distance root mean square error (DRMS) was 57.9 cm. Completely blocked LOS resulted in signal outages and unacceptable performance (11.1% availability; 819.7 cm DRMS). In the orchard, full-LOS performance was similar to that in open-space: 99.3% availability and 63.4 cm DRMS error bound. Orchard trees enabled multipath signal propagation, so blocked-LOS performance was far better than in open-space (60.2% availability; 123.6 cm DRMS). Antenna motion effects were studied in open-space and orchard experiments without body interference. Motion introduced non-collocation errors (individual ranges measured at slightly different positions); DRMS error in open space and orchard were 1.6 and 2.2 times larger than respective static errors. In all experiments the 95th percentiles of the errors were almost twice as large as the DRMS errors. Sporadic large errors and signal outages could be addressed by two belt antennas and filtering. The results indicate that radio ranging offers a practicable approach to orchard worker localisation relative to a nearby vehicle operating at slow walking speeds. Highlights· Ultra-wideband vehicle radios localise orchard worker's antenna via range trilateration. · Dynamic error up to 2.2 times the static, due to non-collocated range measurements. · Walking in orchard with antenna Line-of-Sight: 99.3% availability, 63.4 cm RMS error. · Walking in orchard with no Line-of-Sight: 60.2% availability, 123.6 cm RMS error. · 95% error was much larger than RMS; filtering and two belt antennas seem necessary. [ABSTRACT FROM AUTHOR]

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This study presents an improved method of reactive loading for miniaturisation of coupled-line filters. Compared to the previous method, the proposed method requires a reduced number of reactive elements. Moreover, miniaturisation is accomplished with equal reactance. Effectively, this further decreases the number of reactive elements. Therefore apart from improved loss performance because of the reduced number of low-Q lumped elements, low-cost fabrication and simpler design procedure are also achieved while maintaining a similar rate of miniaturisation. A complete set of design equations is provided for both shunt-capacitive and series-inductive loading. The ideal simulation results, which are in excellent agreement with those of conventional counterparts based on λ/4 lines, theoretically validate the method, whereas the experimental results that match the ideal results better than the previous method demonstrate the practicality of the proposed method. [ABSTRACT FROM AUTHOR]

The tremendous growth of low power wireless technologies oriented to smart city applications has conduced to evaluate the propagation aspects under typical communication scenarios in urban environments where in contrast to cellular technologies the transmitter and or the receiver antenna can be deployed at different heights near ground. Thus, the authors introduce a unified empiric parametrised propagation model with validated parameters from the measurements to study the propagation characteristics in near-ground scenarios. The proposed model considers the antenna's height as well as external power losses because of objects that may block the line-of-sight to the receiver. The main results of this research demonstrate that in near-ground wireless links, the wireless range is severely reduced because of diffraction caused by ground. However, in scenarios where the receiver is always higher than the transmitter the diffraction is null and the path loss slope is less than free space, with the consequence of a considerably higher wireless range. The propagation model presented here is a valuable tool for network planning where typical cellular propagation models might not be appropriate. [ABSTRACT FROM AUTHOR]

Presents the table of contents for this issue of the periodical. [ABSTRACT FROM PUBLISHER]

The table of contents for the "IEEE Transactions on Antennas and Propagation" magazine is presented.

The Rician K-factor of the vehicle-to-vehicle (V2V) wireless propagation channel is estimated using a moment-based method on the envelope of measured pulse data. The measurements were carried out under vehicle-to-vehicle wireless communication channel condition with car rooftop antenna heights at one end of the link and very low antenna height at the other end. Data captured from typical urban, suburban and rural areas are analyzed and the K-factor probability density function is generated for each scenario to give an insight into the V2V channel behavior. For all three areas, the majority of K values are found to be within the range of -10 to +10 dB. The K-factor distributions are close to normal with mean values of 1.8, 2.6 and 3 dB respectively for urban, suburban and rural area. [ABSTRACT FROM PUBLISHER]

In a suggested radio propagation experiment using a deep space antenna, accurate calibration of the propagation delay through the Earth's atmosphere is essential. One or two microwave radiometers can be used for this purpose. Differences in precise locations of the radiometer(s) and antenna to be calibrated leave a residual wet path delay value. We computed the Allan Standard Deviation (ASD) of this residual, as well as the one resulting from different pointing positions in the plane of the sky, by simulations. Pointing offsets, e.g., to avoid solar radiation into the radiometer beam, lead in general to an increased ASD. However, for many observation geometries a deliberate pointing offset can compensate for the location differences. In the case studied we found a reduction of the ASD with up to 45% compared to the ASD obtained for a zero pointing offset. The size of the calculated ASD depends strongly on the model parameters used, e.g., the turbulence strength parameter Cn^2, which has a significant natural variation over a year. [ABSTRACT FROM PUBLISHER]

The table of contents for the March 2014 issue of "IEEE Transactions on Antennas and Propagation" is presented.

Presents the cover/table of contents for this issue of the periodical. [ABSTRACT FROM PUBLISHER]

Presents the table of contents for this issue of the periodical. [ABSTRACT FROM PUBLISHER]

The design of efficient positioning algorithms in navigation satellite systems, like GNSS, operating in land mobile environments demands for detailed models of the radio channel. On the one hand, the models need to accurately describe scattering and shadowing/obstruction caused by vegetation. On the other hand, they have to incorporate the steady change in the propagation constellation due to the receiver displacement. In this paper we propose a model of the non-stationary radio channel in a scenario where a mobile receiver drives past a scattering volume, such as a ball or a cuboid, while the transmitter is elevated, like in satellite positioning applications. Such a volume may represent the canopy of a single tree, the canopies of trees in a grove, or a small forest. Scattering by the volume is characterized by means of multiple point-source scatterers that are assumed to form a marked spatial point process. The system functions of the radio channel are given. An integral form of the time-frequency correlation function of the component in the system functions contributed by the scattering volume is obtained as a direct consequence of Campbell's Theorem. Furthermore, a closed-form approximation of this integral form is derived for time lags corresponding to displacements along the receiver trajectory for which the plane wave assumption holds. The approximation takes into account the steady change in the propagation constellation. The proposed model is validated by means of Monte Carlo simulations and by comparing its prediction capabilities with experimental data in a scenario where a mobile receiver drives past a roadside tree. A good agreement is observed, despite the simplicity of the model. [ABSTRACT FROM PUBLISHER]

Presents the cover/table of contents for this issue of the periodical. [ABSTRACT FROM PUBLISHER]

The on-body channel was characterised at various points on the human torso in an anechoic chamber using a pair of wireless sensor modules. The performance of wireless IEEE 802.15.4 sensor nodes operating in the 2.45 GHz ISM frequency band (2.40–2.4835 GHz) is presented over each of the 16 different channels. It is shown that the response at individual carrier frequencies is dependent not only on the initial antenna response, as determined by the on-body measurement in isolation, but also on the overall system performance. Measurement results are also compared with those from the conventional technique using a Vector Network Analyzer. [ABSTRACT FROM PUBLISHER]

Evolution of an oscillatory wide-band pulse in a sparse medium composed of randomly distributed, uncorrelated, discrete scatterers (such as atmospheric clouds, dust, or other aerosols) is studied. The frequency-dependent (dispersive) losses are evaluated by taking into account energy absorption in the medium constituents as well as scattering itself. A reduced, algebraic attenuation of the pulse energy is observed, provided the pulse contains a significant frequency content in the region of strongly varying medium dispersive properties. These frequencies can be provided by pulse carrier frequency selection, short rise and fall times of the pulse, or pulse chirping. It is shown that different types of algebraic attenuation, over the range of penetration depth corresponding to several orders of mean-free path, can be present depending on the inter-relations between characteristic frequencies of the pulse spectrum and the medium dispersive properties. A simple analytical model is constructed that captures relevant features of the propagating pulse energy decay, as well as ranges of penetration depths, and hence may serve as a useful tool in designing and analyzing various scenarios of wide-band pulse propagation in dispersive media in the context of, e.g., signal transmission, imaging, or target detection. [ABSTRACT FROM PUBLISHER]

The effects of carrier frequency, antenna height and season on a broadband wireless access (BWA) system deployed in a rural area at 825 MHz and 3535 MHz are studied in this paper. With the aid of digital terrain information, both large scale and small scale fading effects present in the rural channel are discussed. Our investigation found that the frequency dependence of a wireless channel varies strongly with the environment. Also, the effects of the antenna height in rural areas of irregular terrains vary with the available clearance above the clutters in the regions. This paper uses extensive measurement campaigns to quantify these effects in winter and spring using a BWA system (IEEE 802.16e) deployed in Hetzwege/Abbendorf, Germany. In the study of small scale fading, the variations of the fading distributions of the wireless channel due to season changes are derived and the corresponding multipath propagations are discussed in this paper. [ABSTRACT FROM PUBLISHER]

An experimental study of the time reversal (TR) technique is presented in a single-input–single-output configuration over the frequency range of 2–12 GHz. A special emphasis of this work is to investigate and compare impulse response (IR) and TR characteristics for omnidirectional biconical and directional spiral antennas over realistic indoor ultrawideband (UWB) channels in both line-of-sight (LOS) and non-line-of-sight (NLOS) environments. We discuss the effects of channel multipath dispersion and antenna frequency-dependant delay distortions on the received responses in both time and frequency domains. The effectiveness of TR for waveform compression is characterized by computing root mean square delay spread and peak-to-average power ratio. Our study suggests that the effectiveness of time reversal is subject to a tradeoff between competing effects—namely, compensation of spectral phase variation (which leads to compression) and aggravation of spectral amplitude structure (which opposes compression). Although TR is a powerful technique for compensation of phase distortions associated with broadband frequency-independent antennas (as shown in LOS experiments with spiral antennas), it shows only modest performance in compressing time spread associated with multipath delays. [ABSTRACT FROM PUBLISHER]

The table of contents for the June 2012 issue of "IEEE Transactions on Antennas and Propagation" is presented.

In ultra-wideband (UWB) wireless propagation channels, each multipath component (MPC) can exhibit delay dispersion or, equivalently, frequency dependence; even more, this dispersion can be different for different MPCs. While this effect is understood to have important implications for UWB system design, extraction of the frequency-dependence parameters from measurements has been lacking. This paper will provide both the theoretical tools for the parameter extraction, and provide experimental results of such parameters in UWB indoor channels. We first develop a method that extracts a single MPC. Based on the image principle, the method identifies locations and intensity of radio sources including both original and image sources (corresponding to MPCs) by a distributed antenna array. We show that the method provides spatial resolution better than 0.5 m and is robust against possible measurement errors. Having applied the method to the measured channels in indoor line-of-sight scenarios, we track the detected image sources over (partially overlapping) frequency subbands to obtain frequency dependent properties of their intensity and location. The variation of the source intensity over the frequency was found to be significant. Furthermore, the locations of the image sources can vary as the frequency changes. Comparison of the results with models that do not describe varying per-path frequency dependence revealed noticeable difference in the shape of the CIRs, and as a result, in the delay spread and the number of significant delay bins for Rake reception. [ABSTRACT FROM PUBLISHER]

Linear-/circular-polarization designs of the dual-/wide-band cylindrical dielectric resonator antennas (DRAs) are presented. The HEM111 and HEM113 modes of the cylindrical DRA are utilized to design the dual-mode cylindrical DRA. A wideband antenna can be obtained by merging the two resonant modes. To facilitate the designs, new engineering formulas that determine the dimensions of the dual-mode cylindrical DRA are found for the first time. They are obtained by using the covariance matrix adaptation evolutionary strategy (CMA-ES). Design examples for the dual-/wide-band cylindrical DRAs are given for both the linearly and circularly polarized cases. Ansoft HFSS was used to simulate the DRAs and the simulations were verified with our measurements. Good agreement between the measured and simulated results is observed. [ABSTRACT FROM PUBLISHER]

Although acoustic waves are the most versatile and widely used physical layer technology for underwater wireless communication networks (UWCNs), they are adversely affected by ambient noise, multipath propagation, and fading. The large propagation delays, low bandwidth, and high bit error rates of the underwater acoustic channel hinder communication as well. These operational limits call for complementary technologies or communication alternatives when the acoustic channel is severely degraded. Magnetic induction (MI) is a promising technique for UWCNs that is not affected by large propagation delays, multipath propagation, and fading. In this paper, the MI communication channel has been modeled. Its propagation characteristics have been compared to the electromagnetic and acoustic communication systems through theoretical analysis and numerical evaluations. The results prove the feasibility of MI communication in underwater environments. The MI waveguide technique is developed to reduce path loss. The communication range between source and destination is considerably extended to hundreds of meters in fresh water due to its superior bit error rate performance. [ABSTRACT FROM PUBLISHER]

The table of contents for the June 2012 issue of "IEEE Transactions on Antennas and Propagation" is presented.

An efficient propagation prediction model is presented. The modeling is subdivided into three phases; preprocessing, tracing rays, and postprocessing. Information obtained from the relations between the facet pairs is employed in the preprocessing. Heuristic removal of double tracing of rays shared among adjacent tubes halves the tube tracing time. For the prediction of the E-field over a surface, an accurate geometrical approach is proposed and a backtracking calculation method is tailored. Also, the multiple counting shortcoming is resolved in SBR and, single and double diffraction are modeled. The method directly functions on three dimensional geometry of the problem and considers all chains of interactions up to the second order successive diffractions. Finally, the applicability and reliability of the method is verified by comparison of results with a numerical method and measurements. [ABSTRACT FROM PUBLISHER]