Radio Wave Propagation Characteristics Research Articles

Simulation and Analysis of 45 GHz Millimeter-wave Propagation Characteristics in Living Room

In this paper, the characteristics of millimeter-wave propagation at 45 GHz in a living room are investigated based on simulation by the method of shooting and bounding ray tracing/image (SBR/IM). Path loss of co-polarization and crosspolarization is compared to verify the accuracy of simulation. The angle of arrival of different polarization is also revealed. Root mean square (RMS) delay spread of co-polarization and cross-polarization is studied. It is shown that the RMS delay of co-polarization is generally higher than that of cross-polarization in this environment. In addition, the influence of furniture on the propagation characteristics of radio waves in the line-of-sight (LOS) environment is discussed.

Performance Evaluation of LoRa 920 MHz Frequency Band in a Hilly Forested Area

Long-range (LoRa) wireless communication technology has been widely used in many Internet-of-Things (IoT) applications in industry and academia. Radio wave propagation characteristics in forested areas are important to ensure communication quality in forest IoT applications. In this study, 920 MHz band propagation characteristics in forested areas and tree canopy openness were investigated in the Takakuma experimental forest in Kagoshima, Japan. The aim was to evaluate the performance of the LoRa 920 MHz band with spreading factor (SF12) in a forested hilly area. The received signal strength indicator (RSSI) was measured as a function of the distance between the transmitter antenna and ground station (GS). To illustrate the effect of canopy openness on radio wave propagation, sky view factor (SVF) and a forest canopy height model were considered at each location of a successfully received RSSI. A positive correlation was found between the RSSI and SVF. It was found that between the GS and transmitter antenna, if the canopy height is above 23 m, the signal diffracted and RSSI fell to −120 to −127 dBm, so the presence of the obstacle height should be considered. Further research is needed to clarify the detailed tree density between the transmitter and ground station to propose an optimal propagation model for a forested environment.

Numerical simulation of lower ionospheric reflection parameters by using International Reference Ionosphere (IRI) model and validation with Very Low Frequency (VLF) radio signal characteristics

Sub-Ionospheric Very Low Frequency (VLF) radio wave propagation characteristics are the major tool to study the lower ionospheric heights mainly D-region. Wait’s 2-component exponential model is a well-known mechanism to understand the basic characteristics of this layer based on VLF remote sensing. This model deals with two major ionospheric parameters, namely, ‘steepness parameter’ (β) and ‘effective reflection height’ (h′). ‘International Reference Ionospheric (IRI)’ is a famous model for the terrestrial ionosphere that provides mostly the altitude profile temperature of the electron and ions globally. In this manuscript, we use such electron density profiles based on IRI outcomes during a quiet ionospheric condition. We choose our VLF reception location ‘Ionospheric and Earthquake Research Center & Optical Observatory’ (IERCOO), Sitapur (Lat 22.5° N, Lon 87.48° E) to compute the electron density from IRI model. By using the Wait’s exponential model with a log-linear fitting of electron density, we compute the β and h′ from their fundamental definition. With an automation technique, we repeat this process several times and generate a complete data set of such parameters for different time of the day during the summer and winter seasons of the year 2016. To get a qualitative comparison with the VLF signal amplitude variation with β and h′, we choose the Indian VLF transmitter VTX of frequency 18.2 kHz (Lat 8.26°N and 77.44°E). By computing similar data sets for other four receiving locations in India, we replicate the VLF signal amplitude profiles using Long Wavelength Propagation Capability (LWPC) model which matches with the observed signal profile satisfactorily.

INTERACTION OF SHORT-WAVE ELECTROMAGNETIC WAVES
 WITH SMALL-SCALE IONOSPHERIC INHOMOGENEITIES 
 OF THE POLAR IONOSPHERE 
 (part II)

The results of a comparative analysis of the data of computational and field experiments reflecting the peculiarities of the impact of small-scale inhomogeneities of electron concentration in the Earth's ionosphere on the characteristics of radio wave propagation during vertical ground-based and satellite sounding of the ionosphere are presented. It has been proved that these inhomogeneities are the cause of noticeable distortions of traces in ionograms. The simulation results confirm the possibility of determining the degree of concentration change in a small-scale inhomogeneous structure from experimental data.

LoRa Base-Station-to-Body Communication With SIMO Front-to-Back Diversity

The LoRa standard is currently widely employed for low-power long-range wireless sensor networks at sub-GHz frequency bands. The longer wavelengths associated with sub-GHz technology provide excellent radiowave propagation characteristics, yielding a much larger coverage than the higher frequency bands. In the case of wearable sensors, the 868 MHz band can be covered by textile substrate-integrated-waveguide antennas of a convenient size. In body-centric communication systems, front-to-back (F/B) diversity is an important asset to mitigate the shadowing of the antennas by the presence of the human body. This article describes a diversity textile-antenna-based LoRa platform with integrated transceivers. Outdoor measurement campaigns are conducted to assess the performance of the wearable LoRa nodes with F/B diversity in an urban radio propagation environment at walking and cycling speeds. These experiments prove that large ranges of 1.5 km can easily and reliably be achieved for off-body LoRa communication links. The results demonstrate a significant performance improvement in terms of packet loss in NLoS situations when comparing single-receiver performance with different spatial receiver diversity applications. In addition, link budget increases up to 5.5 dB, owing to the realized diversity gain.

5G Key Technologies for Smart Railways

Railway communications has attracted significant attention from both academia and industries due to the booming development of railways, especially high-speed railways (HSRs). To be in line with the vision of future smart rail communications, the rail transport industry needs to develop innovative communication network architectures and key technologies that ensure high-quality transmissions for both passengers and railway operations and control systems. Under high mobility and with safety, eco-friendliness, comfort, transparency, predictability, and reliability. Fifth-generation (5G) technologies could be a promising solution to dealing with the design challenges on high reliability and high throughput for HSR communications. Based on our in-depth analysis of smart rail traffic services and communication scenarios, we propose a network slicing architecture for a 5G-based HSR system. With a ray tracing-based analysis of radio wave propagation characteristics and channel models for millimeter wave (mmWave) bands in railway scenarios, we draw important conclusions with regard to appropriate operating frequency bands for HSRs. mymargin Specifically, we have identified significant 5G-based key technologies for HSRs, such as spatial modulation, fast channel estimation, cell-free massive multiple-input-multiple-output (MIMO), mmWave, efficient beamforming, wireless backhaul, ultrareliable low latency communications, and enhanced handover strategies. Based on these technologies, we have developed a complete framework of 5G technologies for smart railways and pointed out exciting future research directions.

Artificial Neural Network Based Path Loss Prediction for Wireless Communication Network

Accurate path loss (PL) prediction is essential for predicting transmitter coverage and optimizing wireless network performance. Traditional PL models are difficult to cope with the development trend of diversity, time-varying and mass wireless channels. In this work, the most widely used multilayer perceptron (MLP) neural network in artificial neural network (ANN) is employed to accurately predict PL. Three types of environmental features are defined and extracted, which describe the propagation environment only by considering limited environmental types instead of complex 3D environment modeling. Principal component analysis (PCA) is used to generate the low-dimensional environmental features, and eliminate redundant information among similar environmental types. Moreover, the information of base station (BS) and the receiver (Rx), including 3D locations, frequency, the transmitted power of BS, the antenna information, the feeder loss, and the received power of all the locations are obtained from the measurements. Different environmental features are combined with the information of BS and Rx to construct seven datasets for PL prediction models based on MLP neural networks. The impacts of the number of neurons in the hidden layer, the number of hidden layers, the number of training samples, and environmental features on PL prediction models are explored by considering the absolute value of mean error (AME), the mean absolute error (MAE), the standard deviation (STD) of error, the correlation coefficient, and the time ratio, respectively. This work aims to understand the propagation characteristics of radio waves, which can provide a theoretical basis for wireless network optimization and communication system design.

Correlation between Railway Cutting Scenarios Parameters and Wireless Path Loss Exponent

ABSTRACT Due to the particularity of radio wave propagation characteristics in railway scenarios, the relationship between the scenarios and radio wave propagation loss has yet to be studies. In this paper, several common wireless channel path loss models of public network and the path loss measurement data of railway deep cutting scenarios are compared and analyzed, the correlation degree between the structural parameters and the path loss exponent of cutting scenarios is calculated, and the correlation between the parameters of cutting scenarios and ideal cutting scenarios is analyzed. The preliminary conclusion is that the Hata model in open ground environment conforms better to the path loss characteristics of the high-speed railway’s cutting scenario. The width of width sum and the width difference between crown and bottom of cutting scenarios are closely related to the path loss exponent. And the path loss exponent is more reasonable when the cutting scenarios parameters are within a certain range. The research results have some guiding significance for the collaborative work between cutting scenarios construction and wireless network construction.

Effect of the plasma sheath on the propagation of low frequency radio waves

The plasma sheath formed around a hypersonic vehicle traveling through the atmosphere will affect the quality of wireless signals. To fully grasp this effect, it is necessary to comprise the vehicle antennas in the investigations, which is considered in our work. Firstly, the discrete plasma sheath data is generated by using COMSOL. Then, combining the shift-operator Finite-Difference Time-Domain method and numerical methods such as the high-dimensional Lagrange interpolation, an electromagnetic algorithm designed for the discrete plasma sheath data is developed. Based on this, the influence of the plasma sheath on the radio wave propagation is studied under different flight condition. Results show that, due to the influence both of the plasma sheath and of the vehicle antenna, the radio waves exhibit rich propagation behaviors, such as the frequency-band shift and the tail diffraction, etc. Compared with other studies, the results in this paper more approximately reflect the propagation characteristics of radio waves in the hypersonic environment, and can provide a reference for the related applications.

Features of Propagation Characteristics of Ultrahigh Frequency Radio Waves in an Above-Water Duct as Functions of the Duct Parameters and Wavelength

A new numerical method for finding roots of the characteristic equation in problems of radio wave propagation in tropospheric ducts with a piecewise linear profile of the refractive index is proposed. For the selected model of the vertical profile of the refractive index of an surface duct, dynamics of propagation constants of modes and features of the behavior of the attenuation function of the electromagnetic field as functions of the troposphere parameters and the wavelength are studied. The contribution of the whispering gallery modes is also estimated.

Forecasting the conditions of the decameter radio wave propagation in the Аrctic region

In this paper we present the results of studies the distinctive features of the decameter radio wave propagation based on the results of experimental measurements of radio wave propagation characteristics by the ionospheric oblique sounding (IOS) method and numerical simulation. An algorithm for numerical modeling the trajectory and energetic characteristics of the decameter radio wave propagation in the framework of geometric optics is described. The agreement between the simulated and experimental radio propagation parameters (for example, the values of the maximum observed frequencies) is demonstrated. It is proposed to use the developed diagnostic model of the HF radio channel for the purposes of forecasting in areas not provided with IOS stations.

LoRa Mobile-To-Base-Station Channel Characterization in the Antarctic.

Antarctic conditions demand that wireless sensor nodes are operational all year round and that they provide a large communication range of several tens of kilometers. LoRa technology operating in sub-GHz frequency bands implements these wireless links with minimal power consumption. The employed chirp spread spectrum modulation provides a large link budget, combined with the excellent radio-wave propagation characteristics in these bands. In this paper, an experimental wireless link from a mobile vehicle which transmits sensor data to a base station is measured and analyzed in terms of signal-to-noise ratio and packet loss. These measurements confirm the usefulness of LoRa technology for wireless sensor systems in polar regions. By deploying directional antennas at the base station, a range of up to 30 km is covered in case of Line-of-Sight radio propagation in both the 434 and 868 MHz bands. Varying terrain elevation is shown to be the dominating factor influencing the propagation, sometimes causing the Line-of-Sight path to be obstructed. Tropospheric radio propagation effects were not apparent in the measurements.

Studies on Propagation Characteristics of Radio Waves for Wireless Networks in Underground Coal Mines

Communication systems relying on wireless technology can significantly improve the safety and production in underground mines; however, their unreliable operation in such high-stress environments is a significant obstacle to achieving this. Underground mine tunnels offers several distinctive features that are quite different from regular rail/road tunnels. While several studies have been performed on electromagnetic (EM) wave propagation in tunnel environments, there is limited understanding of the inter-working of tunnel dimension with long range tilt variations (a typically feature of coal mines) on the propagation characteristics of wireless radio waves. In this paper, we study and describe a new hybrid multimode model for wireless communication applications in underground coal mines; and analyze it with respect to significant parameters such as operating frequency, mine tunnel size, transmitter–receiver position, electrical parameters and antenna gain. The characterization results suggest that the mine tunnel size and transmitter–receiver position affects the signal behavior significantly. However, the electrical parameters have almost negligible effects on the propagation.

Sharing Spectrum UE LTE and Air-Traffic Control Radars in 800 MHz Band

The need to ensure LTE network coverage in sparsely populated and rural areas of Europe (ITU Region 1) has led to a massive use of 800 MHz band (band 20) with its good characteristics of radio wave propagation in LTE networks. However, the frequency band of 800 MHz called “digital dividend” in Region 1 is used on a primary basis not only by the terrestrial mobile service but also by air-traffic control radars (ATCR) that can lead to the creation of harmful interferences at the receivers’ input of ATCR. Such scenarios of mutual interferences became possible after granting licenses for LTE-800 frequencies to operators in such countries as Azerbaijan, Kazakhstan, Russia and other CIS countries, so this problem should be solved by operators at the deployment of LTE-800 networks in airports and areas close to them. So far, for such scenarios the ITU and CEPT have not formulated criteria for interference protection. The proposed protection criteria for receivers of ATCR from user devices’ interferences of LTE-800 networks were tested by experimental studies and can provide a solution to the electromagnetic compatibility (EMC) problem in a complex electromagnetic environment of modern airports and cross-order coordination of 800 MHz frequency bands in Region 1.

LF Radio Wave Prediction at Short Ranges With High Propagation Angles Over Irregular Terrain

Propagation characteristics of low-frequency radio waves at short ranges and with high propagation angles are analyzed by the finite-difference time-domain and one-way/two-way parabolic equation (PE) methods. Both narrow-angle (NA) and wide-angle (WA) PE expressions are considered. It is observed that the NAPE method is hard to be applied in the region where the propagation angle is above 15°, whereas the WAPE method can obtain a higher accuracy so long as the earth surface slope is not very big. If the terrain slope changes dramatically, results of the two-way WAPE are more reliable with an interference pattern. However, diffraction effects of the waves over the mountain are not given full consideration.

Analysis of the transmission characteristics of radio waves in inhomogeneous weakly ionized dusty plasma sheath based on high order SO-DGTD

Based on high order hierarchical basis function and the ideal of shift operator, shift operator discontinuous Galerkin time domain (SO-DGTD) technique for dealing with weakly ionized dusty plasma electromagnetic problems is proposed. Lagrange interpolation is used to transform the metallic blunt cone aircraft with weakly ionized dusty plasma sheath from geometric model built by COMSOL to electromagnetic computational model. In the case of two-dimensional transverse magnetic (TM) wave, the electromagnetic wave propagation in weakly ionized dusty plasma sheath is calculated by SO-DGTD technique. And then, the influence of dust particle concentration and dust radius on the radio wave transmission is analyzed, and the radio wave propagation characteristics pass through the sheath is compared with the flight speed and height change.

圃場における無線センサネットワークのための920 MHz帯電波伝搬特性評価

圃場における無線センサネットワーク（WSN: Wireless Sensor Network）の構築は，これを設置する圃場の電波伝搬特性を把握して行うことが重要である．圃場では送受信アンテナ間の農作物やビニールハウスといった様々な要因により電波伝搬特性に影響が現れることが考えられる．また，地面や金属製支柱等での電波の反射によるマルチパス波によってアンテナ設置位置の微小な違いが受信信号強度（RSSI: Received Signal Strength Indicator）に大きく影響を与えることや，農作物の風による揺れなどがRSSIの時間変動を生じさせることが考えられる．そこで本論文では，WSNで使用される920 MHz帯無線通信を用いてソルガムが生育している圃場内，ビニールハウス内，基地局－圃場間という3つの環境において，電波伝搬特性としてRSSIを測定する．測定結果に対して統計的な解析を行うことで距離減衰特性やRSSIのばらつきについても考慮して評価を行う．解析結果から，通信路上に作物や地面が存在するような環境における，RSSI減衰の程度を確認する．また，送受信アンテナ付近や通信路上に金属が存在する環境や，通信路上に作物が存在するような環境におけるRSSIのばらつきの程度を確認する．

Estimate of aDregion ionospheric electron density profile from MF radio wave observations by the S-310-37 rocket

The S-310-37 rocket, launched at 11:20 (JST) on 16 January 2007, was equipped with a radio receiver to observe the medium-frequency (MF) radio wave propagation characteristics in the ionosphere. The radio receiver measured the intensity and the waveform of the radio wave at 873 kHz from the NHK Kumamoto broadcasting station. The polarized mode waves' intensity characteristics were obtained by analyzing the observed waveform. In this study, the S-310-37 rocket-observed polarized mode waves' propagation characteristics are analyzed in order to estimate the electron density profile in the ionospheric D region. These observations become better measurement approach because the electron density profile in the ionospheric D region is difficult to be observed by other equipment such as a Langmuir probe. A Langmuir probe can measure in the ionospheric D region; however, the absolute values may be off by the influence of wake effects around the sounding rocket. It is demonstrated that the propagation characteristics of the polarized mode waves can be successfully used to derive the electron density profile in the ionospheric D region.

PROPAGATION CHARACTERIZATION OF IMPLANTABLE ANTENNA AT UWB FREQUENCY – A REVIEW

A technology of wireless body area network (WBAN) was invented in order to enhance the quality of healthcare management as well as to determine faster disease prevention. However, to obtain the real-time data of images and videos from inside the human body, an implantable device is required. Currently, the Medical Implant Communication System (MICS) is used, but, this system has limited data rate which is a narrow-band of 402 – 405 MHz. Thus, this study on Ultra Wideband (UWB) for implanted device is conducted as UWB offers a wide transmission bandwidth as well as high data rate. Knowledge of radio wave propagation behaviour inside human body is needed to perform the implantation. Past researches related to this topic are limited and those conducted focused only on the human torso. This paper aims to provide a better understanding on the characteristics of radio wave propagation inside the human body by using an implantable device at UWB frequency. It is also hoped that this study could be used as reference for future research on this subject.

Modeling of long‐path propagation characteristics of VLF radio waves as observed from Indian Antarctic station Maitri

AbstractPropagation of very low frequency (VLF) radio signal through the Earth‐ionosphere waveguide depends strongly on the plasma properties of the ionospheric D layer. Solar extreme ultraviolet radiation plays the central role in controlling physical and chemical properties of the lower ionospheric layers and hence determining the propagation characteristics of a VLF signal. The nature of interference among different propagating modes varies widely with the length of the propagation path. For a very long path, exposure of solar radiation and thus the degree of ionization vary by a large amount along the path. This influences the VLF signal profile by modulating the sky wave propagation. To understand the propagation characteristics over such a long path, we need a thorough investigation of the chemical reactions of the lower ionosphere which is lacking in the literature. Study of radio signal characteristics in the Antarctic region during summer period in the Southern Hemisphere gives us a unique opportunity to explore such a possibility. In addition, there is an extra feature in this path—the presence of solar radiation and hence the D region for the whole day during summer in at least some sections of the path. In this paper, we present long‐distance propagation characteristics of VLF signals transmitted from VTX (18.2 kHz) and NWC (19.8 kHz) transmitters recorded at the Indian permanent station Maitri (latitude 70° S, longitude 114° E) in 2007–2008. A very stable diurnal variation of the signal has been obtained with no signature of nighttime fluctuation due the presence of 24 h of sunlight. Using ion production and recombination profiles by solar irradiance and incorporating D region ion chemistry processes, we calculate the electron density profile at different heights. Using this profile in the Long Wavelength Propagation Capability code, we are able to reproduce the amplitude of VLF signal.