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For more than twenty years, Ray Tracing methods have continued to improve on both accuracy and computational time aspects. However, most state-of-the-art image-based ray tracers still rely on a description of the environment that only contains planar surfaces. They are also limited by the number of diffractions they can simulate. We present Min-Path-Tracing (MPT), an alternative to the image method that can handle diffractions seamlessly, while also leveraging the possibility to use different geometries for surfaces or edges, such as parabolic mirrors. MPT uses implicit representations of objects to write the path finding challenge as a minimization problem. We further show that multiple diffractions can be important in some situations, which MPT is capable to simulate without increasing neither the computational nor the implementation complexity., Comment: 5 pages, 6 figures, accepted at EuCAP 2023

In this paper, the impact of interference between multiple phase-coded Frequency Modulated Continuous Wave (FMCW) Dual Function Radar Communication (DFRC) systems is analysed. For the RADAR receiver, interference occurs when another nearby DFRC system is active. For the communication receiver, RADAR echoes from the same DFRC system interfere with the receiver. The performance achieved by interference cancellation at both functions is studied in different scenarios. Finally, stochastic geometry is used to analyse in a two-way automotive scenario which signal component (RADAR or communication) is dominant, in order to evaluate whether the interference should be cancelled at the RADAR receiver based on the communication receiver output or the opposite.

The future communication systems will use higher frequencies, Ka and Q band. For the implementation of fade mitigation techniques, it is important to have representative time series representing the degradations of the received signal for GEO and LEO satellites. This paper presents a model combining numerical weather prediction software WRF and MultiEXCELL rain cells model in order to have more accurate representation of the dynamics of the attenuation for GEO and non-GEO satellite links.

A physical-statistical ray-based model is applied to model the UAV-to-ground radio channel in urban areas. The modeling method relies on simple input data, such as input distribution parameters (e.g. mean building height, building height variance). The physical part of the model being based on ray-tracing, it is also applicable over very wide parameter ranges at a very low computation time thanks to a pre-calculation procedure.

This paper investigates device-to-device (D2D) communications where two nearby users are enabled to communicate directly with each other. A network analysis under Rician fading is proposed to account for a strong line-of-sight (LOS) component typical for this technology. Semi closed-form expressions for the cellular (CC) and underlaid D2D communication outage probabilities are derived relying on stochastic geometry theory. Schemes where D2D communications reuse the uplink (UL) or the downlink (DL) CC bands are compared. The choice between them is shown to strongly depend on the base stations (BS) and user equipments (UE) transmit powers.

This paper analyzes the time correlation properties of vehicle-to-pedestrian (V2P) channels based on measurement campaign carried out at 3.8 GHz. Several propagation conditions and different mobility patterns were investigated. Subsequently, an analytical auto-correlation function (ACF) is proposed and successfully compared to the measurement data.

This paper exploits the Doppler and delay spreads for pedestrian-to-pedestrian (P2P) communications based on a measurement campaign carried out at 3.8 GHz. Several propagation conditions and different mobility patterns were investigated. In particular, the impact of vehicle passing in the vicinity of a P2P links was considered. It was found that the delay spread does not only depends on the propagation environment but also on the body mutual orientation whereas the presence of a moving vehicle in the vicinity of P2P links can have an impact on the Doppler spread.

In this paper we present an indoor channel measurement campaign from 26 to 30 GHz, using a virtual antenna array. On the receiving side a $3\times 3$ spatial grid, moving in the environment, was considered. On the transmitting side we considered a massive virtual array of $21\times 21$ elements. Multipath components were extracted by means of a high resolution algorithm. The results obtained with the full massive array are compared with those obtained with a small sub-array, in order to investigate the effect of array size in channel modeling.

The main contribution of this paper consists in integrating a physically correlated shadowing model of the aggregate interference in a stochastic geometry-based approach. The considered shadowing takes place in a Manhattan urban grid and combines both penetration and corner diffraction when modeling signal transmission from base stations to users. A tractable expression for the network coverage probability is obtained thanks to the framework of stochastic geometry. Our results suggest that the diffracted mechanisms are dominant compared to building penetration. It is also shown that the second order diffracted signal have little impact on the coverage compared to the first order signals.

In recent work, the transmittance between circular apertures was formulated, thanks to the projection of equivalent currents evaluated on the apertures over Zernike polynomials, through a polynomial series of a near-field coefficient which is accurate for large apertures and low-order modes. It was observed that this expansion becomes numerically instable for low relative distances. In this paper, we derive a stable representation which can be calculated at arbitrary distance. In case of identical modes, it reduces to a closed-form expression for which an asymptotic near-field formula is given.

This paper evaluates MIMO radio channel measurements at 3.8 GHz, conducted in various urban microcellular environments in the city of Louvain-la-Neuve, Belgium. Large-scale parameters, such as shadow fading, delay and angular spreads as well as dense multipath power are extracted and compared with values provided by existing models. A joint specular-dense multipath cluster-based model is then parametrized from the experimental data, detailing cluster spread and correlation properties.

Strategies are developed to optimize the downlink performance of a massive MIMO network constrained to a fixed global transmit power and a fixed total number of transmit antennas. Two possible degrees of freedom are analysed : the distribution of the base stations and the beamforming technique. Two different shadowing environments are considered as well. The network performance is evaluated either by means of Monte Carlo simulations, or using analytical expressions derived thanks to stochastic geometry. The results suggest that the coverage probability increases with the numbers of base stations and the cluster size.

This paper evaluates MIMO radio channel measurements at 3.8 GHz, conducted in various urban microcell environments in Louvain-la-Neuve. Large-scale parameters, such as shadow fading, delay and angular spreads, are extracted and compared with values provided by existing models (COST 273, COST 2100 and 3GPP-3D).

To investigate on-body channel space-time correlation characteristics in various walking scenarios, we analyze the correlation properties at 4.2 GHz between two on-body radio links with a transmitter on the heart and receivers on both hands. For that purpose, two different measurement campaigns are exploited. The results show that, depending on the walking scenario, the space-time correlation characteristics can vary from very stationary to not stationary at all. More exactly, the stationarity cases correspond to the scenarios where the subjects walk uniformly and regularly along a straight line with periodic arm swings, whereas the non-stationary behavior arises from random trajectories and irregular arm swings.

A fast method for the radiation analysis of arbitrary oriented planes is presented. It combines an adaptive spectral integration scheme and a recently proposed unequally-spaced fast Laplace transform algorithm [F. Andersson, “Algorithms for Unequally Spaced Fast Laplace Transforms,” Applied Computational Harmonic Analysis, vol. 35, pp. 419–432, 2013]. It is illustrated on the free-space Green's function through an example where an important speed-up factor is evaluated compared to the brute force spectral integration.

Closed-form analytical expressions are derived for the numerical integration of the spectral Green's function with Contour-FFT. Results indicates that a proper uniform grid of spatial points enhances the convergence rate of the truncation error, that the Nyquist-Shannon theorem can be generalized to inverse Laplace transforms on linear path and that the relative error specific to Contour-FFT is a regularized gamma function. Two examples illustrate the modularity of the approach.

The Physical Optics aperture radiation is decomposed into an inhomogeneous plane-wave spectrum, for which a sub-nyquist sampling is achieved, despite a 2-digits accuracy. Validation with a Hertzian dipole and observations are made for large planar surfaces. The Spectral Physical Optics (SPO) seems particularly well-suited for multiple interactions between large facets in complex scattering environnements.

To statistically model time-variant vehicle-to-vehicle (V2V) channels, the dynamic multi-path components (MPCs) are characterized based on suburban measurements conducted at 5.3 GHz. The correlation matrix distance (CMD) is used to determine the size of local wide-sense stationary (WSS) region. Within each WSS time window, MPCs are extracted using wideband spatial spectrum of Bartlett beamformer. A MPC distance (MCD)-based tracking algorithm is used to identify the "birth" and "death" of MPCs over different WSS regions, and the lifetime of MPC is modeled with a truncated Gaussian distribution. Distributions of number of MPCs and their positions are statistically modeled. The MPC characterization considers both angular and delay domain properties as well as the dynamic evolution of MPCs over different WSS regions. The results shows insight into the dynamic behaviors of MPCs in V2V environments, and is useful for the scatterer modeling in the geometry-based stochastic channel modeling.

The polarimetric properties of so-called Dense Multipath Components (DMC) are investigated in various outdoor and indoor environments, relying on broadband measurements and Ray-Tracing (RT) simulations. The ultimate goal is to parameterize a heuristic Diffuse Scattering model to be embedded in RT tools, in order to reproduce the experimentally observed cross-polar discrimination (XPD) characteristics.

In the design of diversity and fast handover schemes for high-speed railways (HSR), a better understanding of the shadow fading cross-correlation properties is required. In this paper, the cross-correlation models of shadow fading in HSR environments are proposed based on a large set of measurements in China. The measurements are conducted using a practically deployed and operative GSM-Railway (GSM-R) system at 930 MHz. It is found that the cross-correlation of shadow fading between two neighboring base stations (BS) dependents on the BS height and the tilt angle of the antenna, and a heuristic Exponential distribution model of cross-correlation is proposed.

In this work, an analysis of the Doppler characteristics for Ultra-Wideband indoor communication is presented. Channel sounding measurements ranging from 3.1 to 10.6 GHz were performed over the course of several days in an occupied office environment, with the help of a network analyzer. Based on these measurements, we analyze the behavior of both the Doppler spread and RMS Doppler spread in the Ultra-Wideband frequency band. Our measurements indicate a frequency-dependent behavior for both parameters, where consistent values could be measured with respect to time of observation.

Sub-band divided ray tracing (RT) has been widely used to reproduce as reliably as possible the ultra-wideband (UWB) radio wave propagation channel in realistic indoor environments. However, its accuracy is strictly limited by the available description of the environment. Moreover, its computational complexity scales with the number of selected subbands and the number of propagation paths. In the present work, our RT tool considers not only deterministic propagation paths but also diffuse scattering components. Based on a low-complexity sub-band divided RT implementation, we propose a calibration method for indoor UWB sub-band divided RT. The method estimates the optimal material parameters, including the dielectric parameters and the scattering parameters, using channel measurements and multiobjective simulated annealing (MOSA). This calibration can improve the accuracy of sub-band divided RT in terms of the power delay profile (PDP) and the root mean square (RMS) delay spread for all test locations including those not considered by the calibration. A measurement campaign is used to verify the calibration technique. © 2014 IEEE.

The land mobile satellite radio channel between a satellite and a mobile terminal in a typical built-up environment is calculated via a constrained geometry-based model, i.e. replacing physical building facades by clusters of equivalent point scatterers. The properties of these scatterers (in terms of power density and angular spreading) are derived from the application of a physical ray-tracing tool including specular as well as dense multipaths in a canonical street canyon scenario. The proposed approach also incorporates a polarimetric model of diffuse multipath scattering.

Traditional cellular solutions are coming under increasing pressure from wireless peer-to-peer (P2P) systems. The growing interest in wireless indoor communication systems has resulted in many investigations on the characteristics of indoor radio propagation channels. In this paper, we investigate narrowband indoor distributed channels based on an experimental campaign in an office environment. We evaluate the fast fading statistics using the second-order scattering fading (SOSF) distribution. It turns out from the measurements that the fading statistics change over time. An approach to model these effects is proposed.

The polarimetric properties of the radio channel, with particular reference to the Dense Multipath Components (DMC), are analyzed in the present work for different types of outdoor and indoor environments, with the aid of measurements and Ray Tracing (RT) simulations. A heuristic Diffuse Scattering model, suitable to be embedded in RT tools, is properly tuned and parameterized to reproduce the cross-polar discrimination (XPD) characteristics of the DMC extracted from measurement data in the above mentioned scenarios.

On-body channel dynamics are primarily affected by body motions, which not only cause dynamic scattering conditions but also modify the geometry of links over time. We experimentally investigate the Doppler spectra of narrowband on-body channels at 2.45 GHz in both anechoic and indoor environments. The body dynamics resulting from the motion are shown to directly affect the Doppler spectrum. An empirical model is proposed to describe the global and/or local Doppler spreads. The fit of a 3-cylinder-based physical model accounting for the arm swinging is also evaluated.

The most important factors impairing the performance of radio-based indoor localization systems are propagation effects like strong reflections or diffuse scattering. To the full extent, these effects can be captured only by time-consuming measurement campaigns. Ray tracing (RT) offers the possibility to predict the radio channel for a certain environment, avoiding the need for measurements. However, it is crucial to include all relevant propagation mechanisms in the RT as well as to validate the obtained results. In this paper, we analyze if sub-band divided RT can yield realistic ultra-wideband channel impulse responses. We use the RT results for performance analysis of multipath-assisted localization, which depends directly upon the above mentioned propagation effects. In particular, it has been shown that the ratio of the signal energies of deterministically reflected paths to interfering diffuse components quantifies the amount of position-related information of deterministic multipath components. Comparison of this ratio to measurement data is thus useful to validate the sub-band divided RT. The results highlight the need for proper modeling of the diffuse multipath, as estimates of this energy ratio using RT are often overly optimistic. However, the obtained localization performance predictions using measurements and RT show general agreement.

This work focuses on the polarimetric properties of radio waves scattered off building walls. Two measurement campaigns, the first in a street canyon scenario and the second in a campus scenario, are used to validate an ad-hoc polarimetric diffuse scattering model, suitable to be embedded in Ray-Tracing (RT) prediction tools. The polarization part of the model relies on a single parameter, K xpol , that sets the polarization coupling between the original polarization and the orthogonal one, caused by a scattering interaction. Results show that between 20% and 30% of the incident field intensity is depolarized, depending on the scenario, in accordance with what found in the experimental parametrization of the model.

The COST 2100 channel model is a geometry-based stochastic channel model (GSCM) that can reproduce the stochastic properties of multi-link Multiple-Input Mulitple-Output (MIMO) channels over time, frequency and space. By contrast to other popular GSCMs, the COST 2100 approach is generic and flexible, making it suitable to model multi-user or distributed MIMO scenarios. In this paper a concise overview of the COST 2100 channel model is presented. Main concepts are described, together with useful implementation guidelines. Recent developments, including dense multipath components, polarization and multi-link aspects are also discussed.

Compared to classical spatial MIMO wireless systems, cross-polarized MIMO systems are an interesting way to reduce equipment size while still maintaining low inter-antenna correlation. In this paper, the time-variation of the polarization of the received waves is investigated. In this scenario, a theoretical formulation is proposed in order to obtain the parameters of the elliptical polarization, based on the signals received on three perpendicularly polarized antennas. A measurement campaign has been performed in an indoor-to-indoor scenario and at a frequency of 3.6 GHz. Based on these measurements and the proposed theoretical formulation, the time-variation of the parameters describing the polarization ellipse is analyzed and a time-variant statistical model is proposed.

The BuNGee FP7 project is looking at achieving throughput densities substantially higher than available with today‘s systems. The project addresses this goal by a combination of techniques: below-rooftop access base stations and a unique feeding architecture using a combination of licensed in-band and out-of-band license exempt spectrum. Very high capacity feeding hubs with high-order spatial reuse are created using multi-beam antennas and advanced MIMO techniques, using millimeter waves.

A general aim of geometry-based stochastic channel models (GSCMs) is provision of imaginary, but realistic propagation channel responses that can be used as a reference channel in evaluating performance of mobile communication systems. This paper provides an overview of recent development in the GSCMs with particular emphases of 1) structural refinement, 2) parametrization, and 3) validation of the model. The refinement in this paper refers to a multi-link extension of the existing GSCM in the form of ”add-on” such that it fits into various implementation of single-link GSCMs. The model parametrization is a tedious but essential work that guarantees the realistic-ness of the GSCM outputs. Finally, it is also crucial to show validity of the GSCM with specific sets of model parameters such that the GSCM outputs show the intended reality of actual propagation channels. Finally, an example of applying the multi-link extension ”add-on” to the COST273 channel model, being one of the improvements led to to the COST2100 channel model, is given.

In this review paper, a number of recent contributions in the field of multi-link propagation are presented and analyzed, with a particular focus on beyond next generation wireless communication networks. Advances in channel sounding, characterization and modeling are described in three areas: (i) regarding cooperative channel fading statistics, the impact of node mobility is highlighted; (ii) metrics for characterizing the separation between multiple single- and/or multi-antenna channels are detailed; (iii) new geometry-based approaches with multi-link capabilities, including WINNER and COST models, are presented and compared. Finally, a couple of key features not sufficiently included in current models are discussed.

This work models the fast fading characteristics in indoor to indoor and outdoor to indoor channels at 3.8 GHz. Starting from real world measurements, the fast fading characteristics are extracted and properly modeled, taking into account the nodes movement conditions. For static environments, the fast fading is modeled with the well known Ricean distribution. As expected the K-factor depends on the path loss. On the other hand, in mobile environments, the probability density function of the signal envelope is accurately described by the recently developed second-order scattering fading (SOSF) distribution. The SOSF distribution combines the Rayleigh, Ricean and double Rayleigh fading and any linear combinations of these. Our results show that the higher the mobility, the more severe is the fading.

In previous work, it has been observed that the specular and the diffuse component are linked in the angular domain. The idea of adding a diffuse component to each specular cluster has been proposed to model the specular-diffuse channel. In this paper, an approach is proposed to treat the specular and the diffuse measurement data simultaneously, with a clustering algorithm that is applied jointly on the specular and the diffuse component. The output of the clustering algorithm gives clusters that are characterized by their specular and their diffuse component. Measurement results are presented based on double-directional measurements, and parameter values are extracted using the proposed methodology.

Based on multi-node multi-antenna channel measurements in a multi-wall office environment, we estimate the degree of separation between multiple MIMO links by means of two metrics: the correlation matrix distance and the shadowing correlation. Both nomadic and mobile node scenarios are considered and compared. Empirical models are eventually derived. Our analysis reveals that the average separation between two MIMO links sharing a joint transmitter is usually lower in mobile scenarios than in nomadic scenarios, and is strongly related to the spatial correlation of the individual MIMO links. However, there appears to be no relationship between the correlation matrix distance and the shadowing correlation.

In multiple-input multiple-output (MIMO) systems, the propagation channels can be characterized by their spatial structure, described by the (complex-valued) channel correlation. Accordingly, also interference in MIMO systems is likely to occur in a spatially structured, correlated way. We discuss that structured spatial interference affects mutual information under interference, depending on the eigenspace alignment between the channel of the desired signal and the channel carrying the interference. Intuitively, worst-case interference occurs, when the channels from the intended signal and the interference show a similar spatial structure. In contrast, least hurtful interference is encountered when these channels are maximally non-aligned. In this paper, we develop an analytical channel model generating multi-user MIMO channels with a given degree of severity of interference, described by the alignment of the channels' eigenspaces. Using radio channel measurements, we parameterize our model to reflect realistic scenarios.

We experimentally characterize nomadic peer-to-peer channels in a multi-wall indoor office environment. In particular, we derived models of path-loss, shadowing and fading statistics at 3.8 GHz in fixed scenarios, and compare them with existing results. Highlights of the paper include a multi-wall path-loss model, the separation between obstruction, nomadic, and dynamic shadowing, a dynamic shadowing correlation model, as well as a multi-link analysis of MIMO links.

in UndeterminedThe radio channels between nodes of an indoor peer-to-peer network show specific fast fading characteristics. Depending on the mobility and on the scattering properties of the environment, different kinds of fading distributions can occur: Ricean fading between static nodes, but also Rayleigh or even double-Rayleigh fading between mobile nodes. We investigate fast fading in indoor peer-to-peer networks based on radio channel measurements. It turns out that the fading statistics change over time. While the predominant fading mechanism is a combination of Rayleigh and double-Rayleigh fading, Ricean fading also occasionally occurs. On top of that, indoors, the statistics of the fast fading change over time even for small-motions of the nodes, since the propagation environment is inhomogeneous. We comprehensively model these effects using a hidden Markov model, parameterized from our measurements. The model is validated, revealing a convincing fit between the model and the measurements.

In this paper, we focus on the stationarity of the scatterer contributions in highly time-variant wideband Car-to-Car (C2C) channels. To do so, these scatterer contributions were first extracted using a high-resolution algorithm and the corresponding time-variant stationarity intervals were estimated using the Correlation Matrix Distance (CMD).

In this paper, we developed an analytical model of vertically polarized on-body propagation to describe the body scattering interference to the on-body channels. The 3-D dimension scattering from the trunk and arms by a point source are considered. Measurements results in an anechoic chamber at 2.45 GHz are also presented to validate the model.

In this paper we describe a testbed for impulse radio ultra wideband based ranging and positioning. We show the characteristics of the generated, transmitted and received pulses. We consider both the maximum likelihood estimator and a threshold-based estimator for the estimation of the time of arrival. We measure the variances for ranging and positioning and compare them to the Cramer-Rao lower bounds for range and position estimation. We discuss the impact of both false multipath component detection and false sidelobe detection on the estimation accuracy. The obtained variances are close to the Cramer-Rao lower bounds when the mainlobe of the first multi-path component is detected. In realistic multipath environments we can use a threshold-based time of arrival estimator in order to detect the first multipath component which may be missed by the maximum likelihood estimator. We show also that the errors on positioning due to false multipath component and sidelobe detection can be highly mitigated by increasing the number of receivers. For a radiated energy of 8.1 pJ and a distance of 5 meters between the transmit and receive antennas, the obtained accuracy is in the order of one centimeter.

The polarimetric characteristics of the signal back scattered from a building wall are studied in this paper with the aid of MIMO measurements and Ray Tracing simulation. A very simple environment with a single building amid an open area is considered to reduce complexity and better isolate the different kinds of back-scattered contributions: specular reflection, diffractions, diffuse scattering. A high degree of crosspolarization coupling, largely due to diffused scattering phenomena, is generally observed. Moreover the diffuse component represents about 30% of the total backscattered power even in such a simple topology.

Compared to classical spatial MIMO wireless systems, cross-polarized MIMO systems are an interesting way to reduce equipment size while reducing the inter-antenna correlation. Cross-Polar Discrimination (XPD) and Co-Polar Ratio (CPR) are two important parameters describing multi-polarized channels. In this paper, the behavior of these parameters is investigated for different observation scales. A measurement campaign has been performed in both Outdoor-to-Indoor and Indoor-to-Indoor scenarios, at a frequency of 3.5GHz. Small-scale variations of XPD and CPR are analyzed in different spatial positions. The distance-related and large-scale variations of XPD and CPR are also investigated and a model is deduced.