Radio Propagation Measurement and Channel Modelling: Salous/Radio Propagation Measurement and Channel Modelling
... have a significant contribution to the total received power. The diffraction loss can be predicted by the single and multiple knife-edge diffraction models [30]. Several methods are proposed in literature to calculate the diffraction loss based on the multiple knife-edge diffraction model such as Bullington, Japanese, Epstein-Peterson, and Daygout methods [31]. ...
... The model fitting parameters were tuned by minimizing the squared error between the measured path loss and the model (i.e., least squares criteria). Another path loss model, widely used in literature to model the LoS channel, is the two-ray path loss model [30]. This model considers not only the direct propagation path but also the reflected one from the ground. ...
... The additional increase in the attenuation is due to the blockage of the LoS by the obstacles and the signal is received by diffraction of the electromagnetic waves. According to Huygens principle, the electric field is the sum of the Huygens sources located in the plane above the obstruction [30]. The calculation of the diffraction loss can be done by treating the obstacles as absorbing knife-edges [30]. ...
According to the world health organization, traffic accidents take about 1.35 million
lives and cause more than 50 million injured persons globally each year. Vulnerable
road users (VRUs), i.e., pedestrians, cyclists and motorcyclists, account for almost
half of the road victims. Direct vehicle-to-VRU (V2VRU) communication can prevent
accidents by providing 360◦ awareness and improving detection, localization, and
tracking of both vehicles and VRUs. Having a realistic channel is a prerequisite for
developing a reliable V2VRU communication system. Contrary to vehicle-to-vehicle
(V2V) and vehicle-to-infrastructure (V2I) communications, V2VRU communication
did not attract much attention in research. A dedicated channel model for V2VRU
communication in critical accident scenarios is still missing. In order to remedy this
situation, this thesis aims to provide the first full parametrization for a geometry-
based stochastic channel model (GSCM) for critical urban scenarios. For this
purpose, experimental single-input single-output (SISO) channel measurements
were conducted in both open-field and urban environments. The measurements
were carried out at a carrier frequency of 5.2 GHz which is close to the 5.9 GHz
ITS-G5 band and to the 5.7 GHz industrial, scientific and medical (ISM) band. The
measurements were executed with a bandwidth of 120 MHz taking into account the
most critical accident scenarios involving vehicle and VRUs.
Even though a handful of recent studies addressed the path loss of the vehicle-
to-pedestrian (V2P) channel, little is known about the impact of the pedestrian
mobility, obstruction by parked vehicles, and shadowing by a crowd surrounding the
pedestrian on the received power. In this thesis, these aspects are investigated and
path loss models are proposed. Moreover, the diffraction loss due to the obstruction
of parked vehicles is calculated. The findings on the diffraction loss are then verified by simulations. It is shown that the multiple knife-edge model provides a good
match to the measured diffraction loss.
Note that it is well established in literature that vehicular channels are non-
stationary. Therefore, in order to parameterize a GSCM channel model, the
stationarity distance is required. However, the non-stationarity of the V2VRU
channel has not yet been analyzed in literature. Hence, in this work, the non-
stationarity of the V2VRU channel is investigated and the stationarity distance is
estimated. Furthermore, the time-variant channel impulse response (CIR) in the
urban environment is found to be highly cluttered by diffuse multipath components
(DMCs). To allow for further characterization of the specular multipath components
(SMCs), a novel method is proposed to extract the SMCs from the CIR based on the
density of their neighboring multipath components (MPCs). Further, an algorithm
for tracking SMCs over time based on their delay and magnitude is presented. In
order to gain more insight on the evolution of the radio channel, the locations of
all scatterers in the propagation environment are estimated by employing a joint
delay-Doppler estimation algorithm.
Finally, the thesis proposes a full parametrization for the WINNER-type GSCM.
In particular, the large scale parameters (LSPs) and their correlations are estimated
in the log domain. The results show that the log-normal distribution provides a
good fit to the distributions of the LSPs. Following the parameterization, channel
simulations are performed with the quasi deterministic radio channel generator
(QuaDRiGa) implementation. Thereafter, the GSCM with the proposed parameters
is validated. The channel validation shows that the proposed model provides a very
good representation for the V2VRU propagation channel in the considered scenarios.
The proposed channel model can be used in simulations to develop and evaluate
V2VRU communication and collision avoidance algorithms in critical accident
scenarios.
... B(ν, f ) is obtained following (1.14). S(ν, τ ) is also known as the spreading function and it describes the spreading effect of the radio channel to the transmitted signal in both the delay and Doppler domains [12]. ...
... Wide-Sense-Stationary channels have the property that the channel correlation functions are invariant under a translation in time or space and this means that the fading statistics do not change over a short time interval and that the ACF is independent of the absolute time. Consequently, the ACF is only a function of the time difference ∆t = t − t and not of the absolute time t [12]. Therefore, the ACF of TVCIR (1.15) simplifies to: ...
... The combination of WSS and US yield the Wide-Sense Stationary Uncorrelated Scattering (WSSUS) model which is stationary in time and transmission frequency domains and conversely has independent components in the Doppler frequency (ν) and delay (τ ) dimensions [13]. US and WSS channels are considered to be timefrequency duals; that is a channel which exhibits US in one domain exhibits WSS in the other domain [12]. Considering WSSUS assumptions, the ACFs reduce to [14]: ...
In recent years and in the scope of Fifth Generation (5G) and Sixth Generation (6G) technologies, the joint deployment of Massive MIMO (mMIMO) and millimeter waves (mmWave) technologies has shown very promising results in the quest to meet the very high consumer data rate demands. To design real mmWave mMIMO wireless systems and predict their performances under certain conditions, it is imperative to have accurate mmWave mMIMO wireless channel models that capture the key characteristics for different scenarios. Very high gain and directive Transmitting Reconfigurable Intelligent Surface (T-RIS)s with electronic beamscanning capabilities are also expected to be ubiquitous in 5G and 6G wireless communication systems and hence the need to investigate the channel and T-RIS joint effect. This thesis presents different channel characterizations and models for indoor mmWave mMIMO radio propagation channels based on stochastic approaches. Different channel measurement campaigns were carried out in Indoor Laboratory (InLab), Indoor Open Office (InOpOffice), Indoor Mixed Office (InMixOffice), corridors and Indoor Factory (InF) environments. Massive virtual arrays and T-RISs were employed in the channel measurements. Line of Sight (LOS), Obstructed Line of Sight (OLOS) and Non Line of Sight (NLOS) propagation conditions were investigated in these environments. For the large virtual arrays’ measurements, an investigation on the impact of the array size and geometry on the mmWave mMIMO channel characteristics is performed. Spatial channel correlation over the massive array is investigated and Multipath Components (MPCs) are estimated by means of a high resolution detection algorithm. The estimated specular MPCs parameters are then used for further analysis. Dense Multipath Components (DMCs) are quantified. Common MPCs between different sub-arrays of a massive array are identified following a joint temporal, power and angular threshold criterion and their distributions are then analyzed. For the T-RISs’ measurements, an investigation on the T-RISs beamscanning capabilities and the impact of T-RISs beamforming on the indoor mmWave radio channel characteristics is carried out. The T-RISs measurements involve the synthesis of an omnidirectional Power Delay Profile (PDP) in order to extract the critical temporal and spatial characteristics of the MPCs. For the InOpOffice and the InF environments, both the propagation channel and the T-RIS antenna are modelled separately. The T-RIS pattern is then plugged into the propagation channel and the resulting synthesized channel models are compared to the channel models obtained from the actual T-RIS channel measurements. Path loss and delay spread models for the different indoor environments are modelled and discussed. Statistical spatio-temporal channel models are also derived for the different indoor mmWave mMIMO channel measurements (based on the massive arrays as well as the T-RIS).
... MIMO techniques exploit an additional dimension in the propagation channel: spatial diversity that can be characterized by the correlation degree at transmission and at reception side. This correlation degree depends on space between antennas, angle of arrival, angle of departure of the paths, angular spread that are related to the geometric distribution of obstacles in the propagation channel [10]. Variations of the signal polarization influence also the correlation degree in the channel. ...
... For a time-variant channel, the SISO channel can be defined by its impulse response, in the time domain or with the transfer function in the frequency domain [10]. The complex based band impulse response h(t) is generally described with the input signal at the transmitter and with the output signal at the receiver as equation 1.9 [10]. ...
... For a time-variant channel, the SISO channel can be defined by its impulse response, in the time domain or with the transfer function in the frequency domain [10]. The complex based band impulse response h(t) is generally described with the input signal at the transmitter and with the output signal at the receiver as equation 1.9 [10]. ...
With the development of digital technology and the Internet of Things, there is a growing need for transmission rates per user, capacity, security and flexibility of communications systems. This trend isgeneral in all areas of society and particularly in the field of transport. The digitization of services and autonomous and connected mobility require the development of V2X (vehicles for all) communication systems offering increasingly high transmission speeds, capacity and a level of security. Fifth generation (5G) cellular networks promise significant improvements in throughput, capacity, latency and reliability. Thus, thanks to the possibilities of this technology and due to the obsolescence of the current ground-train communication system used in Europe, GSM-R (Global System for Mobile Communication - Railway) will be replaced by FRMCS (Future Railway Communication System). ) which provides for the parallel use of several radio access techniques including 5G. This 5G technology will allow the emergence of new services: remote driving of trains without a driver on board, deployment of automated trains, coupling / decoupling of line trains, etc. Thus, 5G paves the way for the rail networks of the future that are more connected, more automated and, therefore, more available, safer and more respectful of the environment.The development of these new services requires guaranteeing the robustness, reliability and operational safety of the wireless links on which they are based. To do this, it is necessary to be able to assess the various communication systems upstream of their deployment in railway environments representative of those encountered along railways (trenches, urban areas, rural areas, stations, yard areas, tunnels, etc. .) by emulating these environments in channel emulators using channel templates. Representative channel models are obtained with measurements or simulations (Ray tracing/launching).Thus, this thesis work focuses on the implementation of a 4 x 4 MIMO (Multiple-input, Multiple-output) channel sounder in the 1-6 GHz range in order to characterize different railway environments for which models do not exist. not yet. The equipment developed is based on the use of software radio cards and specific software that have been modified. It is a two-part LTE (Long Term Evolution) type telecommunications system: a base station that will be installed alongside the infrastructure, and a mobile station on the train. The radio channel characteristics are measured by calculating the channel estimate via the pilots of an LTE-OFDM symbol. It can be used on the move. The assembly is compact enough to be transported and allow measurements of the channel in any type of environment.In this thesis we describe the different channel models in the literature and we analyze the existing models in the railway sector in order to identify the environments where it will be necessary to carry out measurements. We focus on simple Tapped Delay Line –TDL models. Secondly, we provide a state of the art of the different types of channel sounder and radio channel sounding techniques. This work allowed us to choose the sounder technology developed, namely a system based on the use of reconfigurable SDR (Software Defined Radio) cards and an LTE type signal. We then detail the architecture, principle and implementation of the channel sounder and its validation by simple measurements. This part constitutes the heart of the thesis. Finally, the last chapter is devoted to field measurements. We conclude and give very many perspectives of the work.
... 2) Uniform correlation coefficient model: The uniform coefficient model, [45], is the worst case scenario where the correlation coefficients are defined as ...
... With this in mind, we determine the data rate achievable at the user of interest as shown in (44), where J j in (45) indicates the interference terms in (43). ...
This paper presents a generalized closed-form beamforming technique that can achieve the maximum degrees of freedom in compounded multiple-input multiple-output (MIMO) broadcast channels with mixed classes of multiple-antenna users. The contribution is firstly described within the context of a three-cell network and later extended to the general multi-cell scenario where we also show how to determine the conditions required to align the interference in a subspace that is orthogonal to the one reserved for the desired signals. This is then followed by an analysis of the impact of antenna correlation for different channel state information acquisition models. The proposed scheme is examined under both conventional and Large-scale MIMO systems. It will be shown that the proposed technique enables networks with any combination of user classes to achieve superior performance even under significant antenna correlation, particularly in the case of the Large-scale MIMO systems.
... The received power, which is the interference signal at Drone 2, is shown as follows by applying the two-ray model [15] as shown in Figure 3. ...
... The polarization plane that is vertical to the ground is called a vertical polarization (TM wave), and that which is horizontal is called a horizontal polarization (TE wave). The reflection coefficients for incident vertical and horizontal polarization waves [15] are shown as follows. where ε r denotes the relative dielectric constant of the earth fields, σ denotes conductivity, ε 0 denotes the dielectric constant of free space, and φ denotes grazing angle, where x is defined as follows. ...
In recent years, drones have been used in a wide range of fields, such as agriculture, transportation of goods, and security. Drones equipped with communication facilities are expected to play an active role as base stations in areas where ground base stations are unavailable, such as disaster areas. In addition, asynchronous operation is being considered for local 5G, in order to support all kinds of use cases. In asynchronous operation, cross-link interference between base stations is an issue. This paper attempts to reduce the interference caused by the drone network by introducing circularly polarized antennas against the conventional system using linearly polarized antennas. Numerical analyses are conducted to validate the effectiveness of the proposed system, where Signal-to-Interference Ratios (SIRs) are shown to be improved significantly as the numerical evaluation results. Specifically, for the scenario of only access links, in the region where conventional antenna architecture can only achieve an SIR of less than 20 dB, our proposed system applying circularly polarized antennas can almost realize an SIR of more than 40 dB. Significant improvement can be also observed in the scenario with the existence of backhaul links, where the conventional system had difficulty achieving our system design goal SIR of 16.8 dB, while the proposed antenna architecture could easily attain this goal in most regions of our evaluation ranges.
... Electromagnetic phenomena, such as reflection, diffraction and refraction, are considered in this stage. During the last processing stage, the E-field is calculated for each spatial point of the scenario under consideration, following equation (1) [37]. ...
... It must be pointed out that RL simulation results are uncertain in the near field region of the transmitter antenna. Thus, in order to avoid uncertain results in this area, an exclusion area of 5λ distance have been considered around the transmitter location based on the frequency under analysis [37]. ...
Recently, new wireless communication systems within aircrafts cabins have drawn higher attention due to the growing demand of passenger services and applications and their corresponding requirements and constraints. In this regard, the fifth generation (5G) of wireless communication becomes an attractive and promising alternative to enable aircraft passengers’ comfort and entertainment along the flight, considering its potential benefits in term of high data transfers and low latencies. Nevertheless, general population concern about radio frequency electromagnetic fields (RF-EMF) safety in general and, in particular to the environmental exposure at which we are all exposed in these flights, increases at the same time. Thus, in this work, we present an experimental campaign of measurements for current passengers’ environmental exposure assessment, performed in different real generalizable type of flights and aircrafts’ cabins, in order to provide current RF-EMF exposure insight within these complex heterogeneous environments. In addition, worst-case uplink 5G scenarios, where all 5G cellular handsets of the passengers operate at the same time, have been simulated by means of an in-house developed 3D Ray Launching (3D-RL) deterministic technique. Before takeoff and after landing, critical scenarios with the aircrafts’ doors closed have been selected and assessed considering different types of modeled aircrafts full of passengers, considering 5G frequency range 2 (5G-FR2) operating links. The obtained results show that the operation frequency and the morphology and topology of the aircraft cabin have a great influence in the environmental RF-EMF passengers’ spatial distribution and overall exposure, but not exceeding, even in worst case conditions, the international established regulatory limits.
... Any insights into propagation channels, as well as any channel models, must be based on, or verified by, measurements. Basic channel measurement (or sounding) is based on the transmission of a known signal, (the input to the channels) and the observation of the received signal (the output of the channel), which thus contains information about the channel response [38], [59]. Channel sounders can be classified into narrowband and wideband. ...
... Their main drawbacks include (i) low output power (which can be compensated by external power amplifiers), (ii) high noise figure of the Rx (which can be mitigated by an external low-noise amplifier), and (iii) long measurement duration. The choice of the intermediate frequency (IF) bandwidth allows to trade off, to a certain extent, the received noise power with the duration for a frequency sweep, yet in all practically relevant cases the coherence time of a THz channel, during which the channel can be considered as essentially time-invariant, is shorter than the measurement duration, thus allowing only measurements in quasi-static scenarios [35], [59]. ...
Terahertz (0.1-10 THz) communications are envisioned as a key technology for sixth generation (6G) wireless systems. The study of underlying THz wireless propagation channels provides the foundations for the development of reliable THz communication systems and their applications. This article provides a comprehensive overview of the study of THz wireless channels. First, the three most popular THz channel measurement methodologies, namely, frequency-domain channel measurement based on a vector network analyzer (VNA), time-domain channel measurement based on sliding correlation, and time-domain channel measurement based on THz pulses from time-domain spectroscopy (THz-TDS), are introduced and compared. Current channel measurement systems and measurement campaigns are reviewed. Then, existing channel modeling methodologies are categorized into deterministic, stochastic, and hybrid approaches. State-of-the-art THz channel models are analyzed, and the channel simulators that are based on them are introduced. Next, an in-depth review of channel characteristics in the THz band is presented. Finally, open problems and future research directions for research studies on THz wireless channels for 6G are elaborated.
... Correlator channel sounder is one of the methods used for observing the channel impulse response (CIR) of a wireless channel [1]. This method is popular and use in many spectrum of wireless channel measurements such as in [2]- [6] due to its property and behaviour which are simple and easy to implement together with the capability to capture the channel characteristic. ...
... with x is the transmitted signal with consist of the m-sequence bit, ̂ is the received signal, and L is the length of bit equal to equation (1). Using autocorrelation result, the time delay could be determined from the highest coefficient correlation value. ...
... Power delay profile (PDP), power angular spectrum (PAS), and Doppler spectrum (DS) are transmission characteristics that illustrate radio channel dispersion in time, angle of arrival (AOA), and frequency domains, respectively [3]. The RMS delay, angular, and Doppler spreads parameters are usually used for the comparative evaluation of the dispersion phenomenon, which is determined based on PDP, PAS, and DS, respectively [4]. ...
In this paper, we present an empirical verification of the method of determining the Doppler spectrum (DS) from the power angular spectrum (PAS). Measurements were made for the frequency of 3.5 GHz, under non-line-of-sight conditions in suburban areas characteristic of a university campus. In the static scenario, the measured PAS was the basis for the determination of DSs, which were compared with the DSs measured in the mobile scenario. The obtained results show that the proposed method gives some approximation to DS determined with the classic methods used so far.
... The prediction error is, then, considered for predicting the actual PL values. Experimental results show that the proposed model outperformed the data-driven model [154] as well as other CWI models on similar setups. ...
With recent advancements in the telecommunication industry and the deployment of 5G networks, radio propagation modeling is considered a fundamental task in planning and optimization. Accurate and efficient models of radio propagation enable the estimation of Path Loss (PL) or Received Signal Strength (RSS), which is used in a variety of practical applications including the construction of radio coverage maps and localization. Traditional PL models use fundamental physics laws and regression-based models, which can be guided with measurements. In general, these methods have small computational complexity and have been highly successful in attaining accurate models for settings with trivial environmental complexity (e.g., clear weather or no clutter). However, attaining high accuracy in radio propagation modeling at complex settings (e.g., an urban setting with many buildings and obstacles) has required ray tracing, which computationally complex. Recently, the wireless community has been studying Machine Learning (ML)-based modeling algorithms to find a middle-ground. ML algorithms have become faster to execute and, more importantly, more radio data measurements have become available with the increased deployment of wireless devices. In this survey, we explore the recent advancements in the use of ML for modeling and predicting radio coverage and PL.
... To avoid an ambiguous autocorrelation result for detecting the impulses, the PRBS should have a good autocorrelation property. Some PRBS types could be selected, such as Maximum Length Sequence (MLS), Barker code, Gold code, and Kasami code (Salous, 2013). ...
The development of a digital high‐frequency (HF) radio communication system requires an ionospheric channel model from the channel impulse response (CIR) measurement. Although the Watterson ionosphere channel model has been available and used for a long time, several CIR measurements have been conducted in all regions of the Earth in an attempt to validate or replace the Watterson channel model with a suitable model for their region. However, only a few CIR measurements were conducted in low‐latitude regions, especially over Indonesia. In this study, we develop the CIR measurement system for the near vertical incidence skywave (NVIS) propagation mode over Java Island based on the software defined radio platform to meet low‐cost and simple operation requirements. The specification of the system is based on the International Telecommunication Union ionospheric channel characteristic document and increased in order to be able to capture higher values. Results from a 1‐week campaign measurement period show the ability of the system to measure the root mean square of time delay within the range of 0.2–1.3 ms and the Doppler shift within the range of 0.7–1.1 Hz in the quiet conditions of the ionosphere. Further measurements will be conducted to obtain a comprehensive ionosphere CIR that is useful for designing the NVIS‐HF digital communication in Indonesia, which is located beneath the crest region of an equatorial ionospheric anomaly.
... This includes multiple different objects, e.g., walls, stairs, cars, ceiling and floor tiles, doors, windows, etc. We determined relative permittivity and conductivity for different building materials, e.g., glass, concrete, etc., from [32] and used these values for WI simulation. Our horn antenna specifications appear in [28]. ...
Millimeter wave (mmWave) communication systems can employ a large amount of spectrum, and can consequently offer large data rates, e.g., multi-Gigabits-per-second. These systems employ directional antennas to enable acceptable link distances. Directional receiver antennas hence rotate in azimuth to capture the strongest received signal in non-line-of-sight (NLOS) regions. In this paper, we present our measurement results for the 90 GHz band for three different scenarios: indoor, outdoor, and an unusual environment: an airport maintenance hangar. We address line-of-sight (LOS), NLOS, mixed, and LOS-to-NLOS transitions. We used a 500 MHz bandwidth chirp signal and estimate parameters for the close-in free space reference distance path loss model using both simulated (ray-tracing software) and measured data. Path loss exponents are 1.6 for outdoor and 1.8 for indoors, smaller than for free space. We also estimate channel delay dispersion, and statistical stationarity distance for some channel transitions. We observed rapid path loss changes in the LOS to NLOS transition regions, 13 dB for indoor and 17 dB for outdoor. Abrupt changes of the strongest-component angle of arrival, up to 60 degrees over a few cm were observed. We also quantify path loss and root-mean square delay spread (RMS DS) for LOS, NLOS and mixed environments in an airport maintenance hangar. This hangar contains various aircraft, and multiple metallic objects whose positions changed over the measurement time. The maximum path loss exponent was 3.14 for these mixed environments. The RMS DS was a maximum of 16.23 ns in the NLOS region. Rotating the receiver antenna to capture the maximum-power signal from a reflecting object decreased the RMS DS by approximately 4 ns (25%). We observed a small minimum stationarity distance, i.e., six wavelengths in NLOS and a large minimum stationarity distance, approximately six hundred wavelengths in LOS.
... The DEA-based approach can efficiently estimate the channel in time-varying environments and alleviate pilot contamination issues in MIMO systems. The method achieves high estimation accuracy with a lower pilot overhead than conventional techniques, making it more efficient for practical applications [16]. ...
The continuous increase in the user demands fornew-generation communication systems, is making the wireless channel more complex and challenging for estimation, developing a simulation model for the channel,and evaluating the performance of different MIMO systems. In this work, a simulation model for multipath fading channels in wireless communication is performed. The model includes a selection of typical Tapped-Delay-Line channel models that can be implemented to reproduce the effects of representative channel distortion and interference. Based on the simulation results, the proposed method exhibits accurate channel estimation performance for frequency-selective fading channels. The proposed work employed LS, MMSE, and ML methods for channel estimation, using 16 and 32 pilots and fixed pilot locations in each frame. Results are obtained for 4x4, 8x8, 16x16, 16x8, and 16x4 MIMO systems and tapped delay line systems.
... Table VI presents the average of the absolute mean error between simulation and measurements for an increasing number of considered reflections for the eight measurement positions. The differences seen in path loss, rms delay spread, and rms angular spread as a function of considered reflections are significantly lower than those seen at microwave frequencies [25], [66], which highlights the dominance of the LOS path at THz frequencies as anticipated in previous studies when computing the K-factor values [65]. Simulations converge toward measurements when considering four reflections and scattering loss is enabled in the algorithm. ...
Surpassing 100 Gbps data throughput is a key objective and an active area of research for sixth-generation (6G) wireless networks that can only be met by exploiting the TeraHertz (THz) frequency band (0.3 - 10 THz). THz channel modeling faces new challenges given the emerging relevance of scattering and molecular absorption in this frequency range as well as the lack of a reliable library of material properties. In this work, we address these challenges by measuring systematically the dielectric properties of 27 common building and office materials and reporting an in-house three-dimensional ray-launching (3D-RL) algorithm that uses the created material library and accounts for rough surface scattering and atmospheric attenuation. In order to validate the proposed algorithm, a channel sounder measurement campaign has been performed in a typical indoor environment at 300 GHz. Simulations and measurements show good agreement, demonstrating the need for modelling scattering and atmospheric absorption in the THz band. The proposed channel model approach enables scenarios at THz frequencies to be investigated by simulation, providing a relevant knowledge for the development of ultra-high-speed wireless communication systems.
... Power delay profile (PDP), power angular spectrum (PAS), and Doppler spectrum (DS) are transmission characteristics that illustrate radio channel dispersion in time, angle of arrival (AOA), and frequency domains, respectively [3]. The RMS delay, angular, and Doppler spreads parameters are usually used for the comparative evaluation of the dispersion phenomenon, which is determined based on PDP, PAS, and DS, respectively [4]. ...
In this paper, we present an empirical verification of the method of determining the Doppler spectrum (DS) from the power angular spectrum (PAS). Measurements were made for the frequency of 3.5 GHz, under non-line-of-sight conditions in suburban areas characteristic of a university campus. In the static scenario, the measured PAS was the basis for the determination of DSs, which were compared with the DSs measured in the mobile scenario. The obtained results show that the proposed method gives some approximation to DS determined with the classic methods used so far.
... A channel-sounding technique essentially involves the transmission of a known signal from the transmitter through an unknown channel and its reception at the receiver after being corrupted by the channel. The unknown channel is then characterized based on the knowledge of the transmitted and received signal from different perspectives [30]. The channel sounders can be broadly classified as time domain and frequency domain. ...
As the world warms up to the idea of millimeter wave (mmWave) communication and fifth generation (5G) mobile networks, realization slowly dawns that the data rate, latency, throughput, and other performance metrics that are used to assess a new wireless communication technology will not be enough to support the demands of envisioned futuristic applications. Thus there is an eagerness to further climb up the frequency ladder to use the large swathes of available spectrum in the 0.1 - 10 THz band which is expected to act as the key technology enabler to fulfill the requirements of the sixth generation (6G) wireless communication and possibly even beyond. Channel measurement and modeling are crucial to the design and deployment of future wireless communication systems and researchers across the world are putting their best foot forward to accelerate the process. The present article presents comprehensive assimilation of research efforts in the context of THz channel sounding. A detailed overview of the current channel sounding techniques is first introduced followed by their relevance to THz band channel measurement. An in-house novel channel sounder developed for THz band measurement is also briefly introduced in this context. The paper next provides elaborate dissemination of various measurement campaigns in the band of interest followed by the modeling techniques that are available in the literature and are being adopted for the THz band. Post the description of different challenges and future research directions in the context of sounding, measurement, and modeling the article is concluded.
... P ROPAGATION channel model, which characterizes the propagation of radio waves with several channel parameters, is necessary for the design and development of wireless communication systems [1]. Channel parameters, such as path loss, delay, Doppler frequency shift, direction of arrival (DOA), and direction of departure (DOD) are extracted from the channel impulse response (CIR) measured by a channel sounder or simulated by ray-tracing principles [2], [3]. The propagation channel measurements using a channel sounder are exploited to develop various stochastic channel models, such as non-geometrical stochastic channel models, geometry-based stochastic channel models (GSCMs), and hybrid GSCMs. ...
For beyond the fifth-generation (5G) and future wireless communications, spatial consistency that represents the correlation between propagation channel characteristics in close proximity has become one of the major issues in channel modeling to describe channels more realistically in emerging scenarios, such as device-to-device (D2D). In this study, we propose a novel path loss model based on multi-dimensional Gaussian process regression (GPR) that provides spatial consistency to channels in propagation environment by predicting local shadow fading while fitting large-scale path loss from measured data. The proposed model has a special structure consisting of a radial mean function and local shadow fading term, which are modeled by independent Gaussian Processes. In contrast to the log-distance path loss model and other regression-based models, the proposed model trains two functions simultaneously; thus, predicts path loss well by capturing both global tendency and local correlation. Moreover, because the proposed model is based on GPR, it provides uncertainty of the predicted path loss. We validated the performance of the proposed model in terms of prediction accuracy with the measurement datasets from two different indoor environments. Our experiments showed that the proposed model predicts better than the log-distance path loss model, especially when spatial correlation becomes significant. The proposed model can be used to simulate path loss in a general environment after training the measurement data.
... According to the inverse-square law, the received power of a signal at an isotropic receiving antenna with defined aperture, which propagates spherically from a point-like signal source with defined PT, is inversely proportional to the squared radius of the spherical surface, which corresponds to the distance d [6] = [ 4 ] 2 . ...
With the digitalization of transportation new use cases for digital information services are emerging. For example, prioritization of road users at traffic signals, especially emergency vehicles, is a desired goal. Requirements for the necessary communication link between road user and C-ITS station are often inadequately met. In particular, increasing communication distances while minimizing latencies are key requirements for timely influencing the control of traffic light signal programs. This paper presents the automotive application of a fast-switchable antenna array with targeted transmission direction selection and high antenna gain. In addition to antenna design requirements, theoretical analyses to increase transmission distance are performed using radio propagation simulation. Furthermore, practical evaluation is performed both in laboratory and test field environment using continuous wave and C-ITS service measurements. An automatic switching of antenna sectors based on geolocation is implemented and discussed from a scientific point of view. As a result, using an adaptive antenna array in traffic telematics environments is proposed to provide more robust communication links and increase the radio transmission distance.
... From channel sounding to channel models Channel measurements by channel sounding deliver an image of the propagation properties of electromagnetic waves at a particular frequency. The term "channel sounding" comes from sonar technology, where short acoustic pulses are sent out from a ship or submarine and the reflections are recorded in the time domain [70]. This provides a viable image of the surroundings. ...
The prospect of offering large contiguous frequency bands to meet the demand for extremely high data transfer rates in the Tbit/s range is making terahertz (THz) waves a key research area for the next generation of wireless communications (6G).
This white paper offers an overview of the fundamentals of THz waves and their properties for various applications with a focus on 6G based communications.
In this white paper you will learn more about:
- Key performance requirements and research areas of 6G
- THz based communication and sensing
- Generation of THz radiation
- High-frequency semiconductor technologies
- Channel propagation measurements
https://bit.ly/3zZEV14
... Besides the theoretical characterization of V2X channels, empirical data are also needed to gain insights into the behavior of realistic channels [16], [38]- [41]. Empirical data are obtained following a specific channel sounding principle, e.g., continuous-wave (CW), direct pulse, or correlationbased [42], [43]. The selection of the sounding principle depends on the channel characteristics that need to be analyzed. ...
This paper describes the implementation of a Doppler spectrum measurement platform for narrowband frequency-dispersive vehicle-to-vehicle (V2V) channels. The platform is based on a continuous-wave (CW) channel sounding approach widely used for path-loss and large-scale fading measurements, but whose effectiveness to measure the Doppler spectrum of V2V channels is not equally known. This channel sounding method is implemented using general-purpose hardware in a configuration that is easy to replicate and that enables a partial characterization of frequency-dispersive V2V channels at a fraction of the cost of a dedicated channel sounder. The platform was assessed in a series of field experiments that collected empirical data of the instantaneous Doppler spectrum, the mean Doppler shift, the Doppler spread, the path-loss profile, and the large-scale fading distribution of V2V channels under realistic driving conditions. These experiments were conducted in a highway scenario near San Luis Potosí, México, at two different carrier frequencies, one at 760MHz and the other at 2,500MHz. The transmitting and receiving vehicles were moving in the same direction at varying speeds, ranging from 20 to 130km/h and dictated by the unpredictable traffic conditions. The obtained results demonstrate that the presented measurement platform enables the spectral characterization of narrowband V2V channels and the identification of their Doppler signatures in relevant road-safety scenarios, such as those involving overtaking maneuvers and rapid vehicles approaching the transmitter and receiver in the opposite direction.
... The frequency (f)-and distance (d)-dependant empirical modeling of the path loss PL [dB], assuming free space propagation is given as follows [17]: ...
Intelligent infrastructure, currently often consisting of C-ITS stations and prospectively supplemented by 5G, is a key-enabler for application-oriented and area-wide realization of highly automated and connected driving. For this, radio coverage along the routes must be ensured, leading to high demands on location- and radio-specific planning and parameterization of roadside units (RSU). Hence, this paper presents efficient planning, measurement and evaluation methods for RSU coverage outlining, allowing economically efficient and technically secured planning of intelligent infrastructure. Necessary scientific technical steps are showcased along a 3.5 km testbed for automated and connected driving in rural environments. First, a radio propagation simulation based on a 3D environment model and its electro-magnetic properties is performed, allowing the examination and optimization of RSU quantity as well as site and antenna selection. Additionally, the necessary calibration of simulation results based on continuous wave (CW) and C-ITS service measurements in both lab-based and real-world scenarios is presented.
... The sliding correlator is a popular technique that is used for wireless digital channel sounder systems. This sliding correlator approach is known for its simplicity yet lower hardware implementation cost compare with Vector Network Analyzer(VNA) (Salous, 2013). Furthermore, the Software Defined Radio (SDR) platform nowadays is more accessible to hobbyists and radio engineers thanks to its flexibility and reusability when the hardware subsystem is implemented in the software domain as a result of the rapidly evolving capabilities of digital electronics. ...
Observation of wireless channel using channel sounder method is needed in order to obtain the channel characteristics in the form of delay spread (Tm) and doppler spread (fD) parameters for optimizing the design of digital communication systems. This also applies to the ionosphere channels which are known to have dynamic properties in the time and place domains. The Sliding Correlator Channel Sounder technique known as a popular technique due to the advantage in the low level of complexity and relatively low cost. Similar to the advantages of the sliding correlator technique, Software Define Radio (SDR) device is one of the popular inexpensive platforms for implementing the communication system into the real world. The implementation of the sliding correlator channel sounder technique in the SDR platform will increase the advantages of the ionosphere channel measurement system that needed as an effort to obtain the dynamic of ionospheric channel characteristic information. However, the process of implementing a sliding correlator channel sounder system into the SDR device requires precise calculations to guarantee the designed system able to works according to the specifications of the SDR device and also meet the system performance targets. This paper discusses the design of a sliding correlator channel sounder system for observing the characteristics of ionosphere channels using SDR devices. The system design starts with the process of calculating the clock frequency generator bit (fchirp) based on the system performance target which refers to the recommendation of the ionospheric channel characteristics based on ITU-R F.1487 documents. Parallel with the calculation of the fchirp, the calculation of the Pseudo Noise (PN) bit length (L) based on the Dynamic Range (DR) value that meets with the specifications of the SDR hardware also carried out. Based on the obtained fchirp and L values, the calculation of other sliding correlator channel sounder parameters is performed with a limitation of a hardware specification and the target system performance. MATLAB simulation results show that the expected system performance can be met. This systems can also be realized significantly through the results of real signal transmission experiments conducted in a closed room laboratory
Este estudo aborda a influência de variações de características geométricas e constitutivas em filtros de microstrip lines na sua resposta em frequência, permitindo a sua análise em função das variações de cada parâmetro. Dessa maneira, obtendo indicações de possíveis modificações para criação de novos filtros e modificações de já existentes para diferentes aplicações em circuitos de rádio frequência.
Radio communications or wireless systems are an essential technology in modern railways. In Chap. 4, we addressed wired communications systems, so in this chapter we focus on wireless systems.
The lack of an accessible comprehensive reliable dataset of material properties at terahertz (THz) frequencies is a significant roadblock for the development of accurate propagation models for THz wireless systems. To fill this gap, we extract the complex permittivity of 75 different home and commercial furnishings categorized into fabric, leather, plastic, stone, tile and wood from quasi-optical measurements. Given that quasi-optical transmission measurement standards are not developed yet, we utilize both vector network analysis and time-domain spectroscopy under collimated and focused beam illumination to highlight the differences and the challenges that precise material extraction faces at THz, and to compute average complex permittivities with confidence intervals.
Parking lots, as one of the most significant vehicle-to-vehicle (V2V) communication scenarios, have rarely been studied for their millimeter-wave (mmWave) V2V channel characteristics. This paper presents the 41 GHz mmWave channel measurements and analysis results in open and underground parking lot scenarios for the first time. A large number of channel measurement data are obtained, including received signal strength indications (RSSIs) and channel impulse responses (CIRs) at different distances and different arrival angles for three cases. By clustering the power delay profile (PDP), cluster parameters such as cluster number, inter-cluster duration, cluster arrival rate and decay factor are obtained. The channel non-stationarity and consistency are revealed and discussed by various methods and from different perspectives. Large- and small-scale fading characteristics parameters, such as path loss, shadow fading, root-mean-square delay spread (RMS-DS), angle spread (AS), fade depth, and Ricean K factor are analyzed and discussed. The mmWave V2V channel characteristics of three cases are compared and analyzed. The measurement and modeling results fill the gaps of mmWave V2V channel measurements in open and underground parking lot scenarios and provide valuable suggestions for the design and modeling of mmWave V2V communication systems.
The E-band millimeter-wave (mm-wave), i.e., at the 71-76 and 81-86 GHz frequency bands, has a potential of providing tens of Gigabits-per-second (Gbps) data rates in long-range transmissions. It is thus considered a candidate technology for building wireless backhauls, particularly to provide high-speed and low-cost connectivity in remote areas. In order to study E-band long-range propagation properties that are crucial for backhaul communications, we have developed a channel sounding system that operates at 74 GHz, supports a signal bandwidth of 1 GHz and covers a range of more than 25 km. Using the system, we performed channel measurements in across-lake, desert and sea environments, all having line-of-sight (LOS) propagation conditions and around 12-km link distances. Based on the multi-environment measurements, we characterize E-band pathloss, fading, polarization and multipath effects, which are of primary importance for system design. The results show that E-band pathloss, mainly affected by atmospheric humidity, is considerably different in the diverse environments. Vertically-polarized propagation has significantly lower attenuation than horizontally-polarized. The commonly-used ITU-R models fail to predict E-band long-range pathloss for lack of polarization modeling. Severe fading was observed in a very short time and should be considered in link budget. The cross-polarization ratios (XPR) are relatively high, indicating a possibility of using polarized multiple-input multiple-output (MIMO) to boost data rates. No significant multipath was observed, however, severe fading implies that strong and unresolvable scattering or refraction exists around the LOS path. The research reveals the feasibility of E-band backhaul communications in those remote environments, and the results contribute to future system design as well as channel modeling.
Vehicular environments are characterized by a high mobility, which alongside with the presence of abundant dynamic scatterers, lead to vehicular communication channels to be intrinsically non-stationary. In this sense, the quasi-stationary regions (QSRs) can assess the degree of non-stationarity within a determined scenario, and ultimately assist geometrical models to increase channel sampling intervals or to develop more efficient hybrid stochastic-geometric channel models. In this work, the channel QSRs in a vehicular communication (V2X) generic high-dense urban environment at millimeter wave (mmWave) frequencies (28 GHz) have been analyzed using different approaches, such as the extended channel response into a Doppler-delay domain or the shadow fading spatial auto-correlation function (SF ACF) methodology. Then, the QSRs have been used as sampling distance in an in-house developed three-dimensional ray-launching (3D-RL) algorithm as an acceleration approach. The time variant channel features have been extracted and compared with the full resolution approach, obtaining consistent results when considering the QSR sampling distances, while decreasing by 83.30% the simulation computational time for the Doppler-delay approach, and 92.86% for the SF ACF method.
As fixed wireless access (FWA) is still envisioned as a reasonable way to achieve communications links, foliage attenuation becomes an important wireless channel impairment in the millimeter-wave bandwidth. Foliage is modeled in the radiative transfer equation as a medium of random scatterers. However, other phenomena in the wireless channel may also occur. In this work, vegetation attenuation measurements are presented for a single tree alley for 26–32 GHz. The results show that vegetation loss increases significantly after the second tree in the alley. Measurement-based foliage losses are compared with model-based, and new tuning parameters are proposed for models.
Maritime environments cause inaccurate prediction of received signal strength (RSS) by occurring the fading. In this letter, we propose a two-stage model consisting of a ray trajectory-based model and a feedforward neural network. Two independent models ensemble to predict RSS, considering both large- and small-scale fading caused by maritime environments. The proposed model accurately predicts RSS compared with other machine learning models.
В статье рассматривается метод оценки импульсной характеристики канала связи на основе сигнально-кодовых конструкций (СКК), сформированных с помощью ортогонального субполосного базиса. Ортогональный базис состоит из собственных векторов субполосной матрицы, рассчитанной для заданного диапазона частот с минимальным уровнем внеполосного излучения. Для ортогонального базиса отбираются собственные вектора, собственные числа которых близки или равны единице. Оценка импульсной характеристики канала основана на решении системы линейных уравнений, где передаваемая информация заведомо известна. Метрикой эффективности предложенного метода выступает среднеквадратическое отклонение между полученной оценкой и применяемым искажением.
Due to their perfect periodic autocorrelation property, Zadoff–Chu sequences are often used as stimulus signals in the measurement of radio channel responses. In this letter, the cross‐correlation of a linear shift‐invariant system's response to a Zadoff–Chu sequence is derived for the case that a multiplicative perturbation such as phase noise is present at its output. The perturbation signal is shown to incur a spurious discrete Fourier transform, thus degrading the correlation's peak to sidelobe ratio. The implications for the performance limits of channel measurement systems are discussed.
This work contains measurements and characterization of 5 GHz mobile radio channel along indoor and indoor to outdoor paths using a novel narrowband propagation measurement system. This system consists of a vector signal analyzer and highly stable oscillators. The stability and precision of the system permit post-processing the baseband complex received signals in order to analyze the channel characteristics. We have performed narrowband measurements on the 5.41 GHz mobile radio channel in four different scenarios: indoor with line of sight, indoor through walls, indoor through different floors and indoor to outdoor considering in-building penetration. The data collected has been processed for estimating the path loss, fading statistics and Doppler power spectrum for each scenario. We show that the processing permits the extraction of information about the scattering environment. The results permit characterizing the 5 GHz mobile radio channel for future spectrum sharing designs, as well as for network planning and capacity planning for Wi-Fi and cellular applications in this band.
This work shows a methodology to determine the sample size required to define a propagation model adjusted to a specific and uncharacterized jungle region, based on the Longley Rice (L-R) propagation model. The analysis is performed in the HF frequency band and using high performance military tactical communication equipment. Initially, a simulation of the telecommunications system to be implemented were developed using the Radio Mobile platform. Subsequently, through the field measurements done insitu, we estimated the interval of confidence to get an accurate model and the data size to get such interval. The research includes a set of meteorological measurements to validate and characterize the environment under which the optimization is going to be applied. The results obtained yields a set of protocols for determining propagation models to be used on voice, video and data transmission in hostile and uncharacterized areas.
The existence of the ionosphere as an electrically charged region in the atmosphere was suggested way back in 1839 by Friedrich Gauss. However, it was not until the 1920s that Edward Appleton proved that signals could be received without line of sight anywhere on the planet when emitting in high‐frequency ranges and by means of the ionosphere. The study of the ionosphere has widely attracted the interest of communication researchers due to its complexity regarding time and frequency dispersion. In this chapter, the techniques to characterize the ionospheric HF channel are reviewed. Also, the outcomes of the most relevant research projects working on that issue are provided. This chapter also gives the calculations required to conduct the study of channel availability, signal‐to‐noise ratio, multipath delay spread, and Doppler spread. Finally, the outcomes of these calculations are provided for a real case study involving a 12 760‐km long‐haul link from Antarctica to Europe.
Sparse scatterer identification with atomic norm minimization (ANM) techniques in the delay-Doppler domain is investigated for a vehicle-to-infrastructure millimeter wave propagation channel. First, a two-dimensional ANM is formulated for jointly estimating the time-delays and Doppler frequencies associated with individual multipath components (MPCs) from short-time Fourier transformed measurements. The two-dimensional ANM is formulated as a semi-definite program and promotes sparsity in the delay-Doppler domain. The numerical complexity of the two-dimensional ANM limits the problem size which results in processing limitations on the time-frequency sample matrix size. Subsequently, a decoupled form of ANM is used together with a matrix pencil, allowing a larger sample matrix size. Simulations show that spatial clusters of a point-scatterers with small cluster spread are suitable to model specular reflection which result in significant MPCs and the successful extraction of their delay-Doppler parameters. The decoupled ANM is applied to vehicle-to-infrastructure channel sounder measurements in a sub-urban street in Vienna at 62 GHz. The obtained results show that the decoupled ANM successfully extracts the delay-Doppler parameters in high resolution for the channel’s significant MPCs.
The Global Positioning System (GPS) is currently the most widely spread and most used Global Navigation Satellite System (GNSS). Numerous industries and people rely daily on the system’s ability to determine their position as well as to synchronize time with the atomic clock carried onboard the satellites. It is now more important than ever for GNSS to operate securely and reliably, to ensure the safety of its users. However, in this chapter, it is highlighted that this might not always be the case, as attackers constantly find new ways to exploit the GNSS features and pose an imminent threat to the system’s reliability. GNSS receivers are especially vulnerable to three types of malicious attacks, in particular blocking, jamming and spoofing. In this chapter, a thorough research was conducted for the operation of both GNSS receivers and spoofing devices. A literature review based on the current available studies and research for detection and mitigation measures, was made. Then a new spoofing detection method is proposed and the principles and the research that was based on are analysed. Experimental data and results were gathered along with data extracted from simulated spoofed signals. The results from both the experiment and the simulation are reviewed, compared and discussed. Finally, based on those results conclusions are drawn.
Wireless communication technologies play a key role to support the implementation of Power grid Internet of Things (PIoT). An in-depth knowledge of the radio channel is vital to the application of wireless communication technologies in PIoT. This article investigates the radio channel measurements and characterization for PIoT substation scenarios. A novel channel sounder is designed for achieving omnidirectional measurements and phased array antennas-based directional measurements, and a directional multipath components extraction algorithm is proposed. The channel sounding system is verified and is used to perform a series of 3.35-GHz omnidirectional and directional channel measurements in four substation scenarios, involving a 10-kV switch room, a 110-kV GIS room, a semi-indoor 110-kV substation, and an outdoor 220-kV substation. Based on the measured channel impulse response data, both large-scale and small-scale fading characteristics of substation channels are extracted and analyzed. Empirical models of path loss, shadow fading, Rician
K
-factor and root-mean-square (RMS) delay spread are proposed. In addition, results of RMS angle spread (AS) of departure and RMS AS of arrival are presented. These results will provide useful reference for the deployment and optimization of wireless communication networks in PIoT substation scenarios.
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