Radio wave Propagation Modelling

This lecture examines the fundamental principles governing electromagnetic wave propagation within the troposphere. It focuses primarily on the characteristics and limitations of Line-of-Sight propagation as the foundational mechanism for direct-path communication. A crucial aspect explored is the concept of the Fresnel Zone, emphasizing its critical role in ensuring reliable signal transmission even under nominally clear path conditions by defining a volume around the direct path that must remain substantially unobstructed. The discussion then advances to the Two-ray Ground-reflection Model, which provides a more realistic analysis than simple Line-of-Sight by accounting for the interference effects between the direct wave and a reflected wave from the ground surface. Evaluating the performance of such Path Loss Models is central, particularly in understanding how path loss varies with distance and identifying the Critical Distance where the dominant propagation mechanism shifts, which directly impacts the predicted attenuation. The influence of these propagation mechanisms and path loss on overall received Signal Quality, including phenomena like fading, forms a key part of the analysis. Finally, the subject addresses the distinct behavior of Surface Waves propagating over conducting media, specifically analyzing their attenuation characteristics and propagation mechanisms across surfaces such as dry soil and seawater.

This research work was aimed at determining the seasonal variation of 5G network signal speed and Signal strength over Abuja, North-Central Nigeria. The research involved the measurement of 5G network signal download and upload speeds, the ping and the Reference Signal Received Power (RSRP) in both rainy season and dry season months of 2024, from July 1 to December 31, 2024. The measurements were taken every hour daily from 8:00 am-6:00 pm in a particular experiment site using Speedtest software and Netmonitor application installed on a laptop computer and Infinix Android phone with a Simard of a particular network service provider in Nigeria. The results showed that there were variations in the speed of the download and the upload of the 5G network as well as the signal strength in the study area hourly and seasonally. It was concluded from the results that the average 5G signal strength was higher in dry season compared to the signal strength in rainy season, given that the average RSRP values in dry season and rainy season were-107.9 dBm and-110.3 dBm respectively. It was recommended that the effect of some atmospheric components like rainfall, pressure, temperature on the 5G network signal over Abuja be investigated in future works as they may have some influences on 5G signal in addition to the ping as discovered in this work. This study will inform the infrastructural development strategies and resource allocations in Abuja and other areas.

The rapid development of 5G communication networks has ushered in a new era of high-speed, low-latency wireless connectivity, as well as the enabling of transformative technologies. However, a crucial aspect of ensuring reliable communication is the accurate modeling of path loss, as it directly impacts signal coverage, interference, and overall network efficiency. This review paper critically assesses the performance of path loss models in mid-band and high-band frequencies and examines their effectiveness in addressing the challenges of 5G deployment. In this paper, we first present the summary of the background, highlighting the increasing demand for high-quality wireless connectivity and the unique characteristics of mid-band (1–6 GHz) and high-band (>6 GHz) frequencies in the 5G spectrum. The methodology comprehensively reviews some of the existing path loss models, considering both empirical and machine learning approaches. We analyze the strengths and weaknesses of these m...

The distribution of trapped energetic electrons inside the Earth's radiation belts is the focus of intense studies aiming at better describing the evolution of the space environment in the presence of various disturbances induced by the solar wind or by an enhanced lightning activity. Such studies are usually performed by means of comparisons with full numerical simulations solving the Fokker‐Planck quasi‐linear diffusion equation for the particle distribution function. Here we present for the first time approximate but realistic analytical solutions for the electron distribution, which are shown to be in good agreement with exact numerical solutions in situations where resonant scattering of energetic electrons by whistler mode hiss, lightning‐generated or chorus waves, is the dominant process. Quiet time distributions are well recovered, as well as the evolution of energized relativistic electron distributions during disturbed geomagnetic conditions. It is further shown that c...

Statistics of amplitudes and obliquity of lower band chorus whistler mode waves have been obtained from Cluster measurements in Earth's outer radiation belt and fitted as functions of L, latitude, magnetic local time, and three geomagnetic activity ranges for Dst∈[+10,−80] nT. Very oblique chorus waves have generally a much smaller average intensity than quasi‐parallel waves, especially on the nightside. Nevertheless, analytical estimates and full numerical calculations of quasi‐linear diffusion rates show that dayside very oblique waves (θ>60°) dominate pitch angle scattering of energetic electrons during moderately disturbed periods. As geomagnetic activity increases, leading to higher wave amplitudes, electron lifetimes are only slightly reduced, due to a decrease of the wave obliquity probably related to Landau damping by stronger incoming fluxes from the plasma sheet. As a result, electron energization by chorus waves for Dst>−80 nT generally occurs in a loss‐dominate...

In this paper, we consider high-energy electron scattering and nonlinear trapping by oblique whistler waves via the Landau resonance. We use recent spacecraft observations in the radiation belts to construct the whistler wave model. The main purpose of the paper is to provide an estimate of the critical wave amplitude for which the nonlinear wave-particle resonant interaction becomes more important than particle scattering. To this aim, we derive an analytical expression describing the particle scattering by large amplitude whistler waves and compare the corresponding effect with the nonlinear particle acceleration due to trapping. The latter is much more rare but the corresponding change of energy is substantially larger than energy jumps due to scattering. We show that for reasonable wave amplitudes ∼10–100 mV/m of strong whistlers, the nonlinear effects are more important than the linear and nonlinear scattering for electrons with energies ∼10–50 keV. We test the dependencies of ...

Discrete ELF/VLF chorus emissions are the most intense electromagnetic plasma waves observed in the radiation belts and in the outer magnetosphere of the Earth. They are supposed to propagate from the localized source region in the vicinity of the magnetic equator towards magnetic poles roughly along the magnetic field lines. The THEMIS project Electric Field Instrument (EFI) and Search Coil Magnetometer (SCM) measurements were used to determine the spatial scale of the chorus source localization region in the day side of the outer magnetosphere of the Earth. We present simultaneous observations of the same chorus elements registered onboard several THEMIS spacecraft in 2007 when all the spacecraft were on the same orbit. We also performed a case study of discrete chorus emissions captured simultaneously by four THEMIS spacecraft. The discrete chorus elements were observed in the frequency range 0.15 -0.25 of the local electron gyrofrequency that is typical for the outer magnetosphere. We evaluated the Poynting flux and wave vector distribution and have quasi parallel propagation to the local magnetic field. The amplitude and phase correlation analysis of data allowed us to estimate the characteristic spatial correlation scale transversal to the local magnetic field to be in the range of 2800 -3200 km.

In this paper we investigate the resonant interaction of thermal ∼10–100 eV electrons with a burst of electrostatic field that results in electron acceleration to kilovolt energies. This single burst contains a large parallel electric field of one sign and a much smaller, longer‐lasting parallel field of the opposite sign. The Van Allen Probe spacecraft often observes clusters of spatially localized bursts in the Earth's outer radiation belts. These structures propagate mostly away from the geomagnetic equator and share properties of soliton‐like nonlinear electron acoustic waves: a velocity of propagation is about the thermal velocity of cold electrons (∼3000–10,000 km/s), and a spatial scale of electric field localization along the field lines is about the Debye radius of hot electrons (∼5–30 km). We model the nonlinear resonant interaction of these electric field structures and cold background electrons.

We describe a mechanism of resonant electron acceleration by oblique high-amplitude whistler waves under conditions typical for the Earth radiation belts. We use statistics of spacecraft observations of whistlers in the Earth radiation belts to obtain the dependence of the angle θ between the wave-normal and the background magnetic field on magnetic latitude λ. According to this statistics, the angle θ already approaches the resonance cone at λ∼15° and remains close to it up to λ∼30°–40° on the dayside. The parallel component of the electrostatic field of whistler waves often increases around λ∼15° up to one hundred of mV/m. We show that due to this increase of the electric field, the whistler waves can trap electrons into the potential well via wave particle resonant interaction corresponding to Landau resonance. Trapped electrons then move with the wave to higher latitudes where they escape from the resonance. Strong acceleration is favored by adiabatic invariance along the increa...

This paper, based on the results of experimental studies of the influence of forest vegetation on the transmission of digital signals in a radio channel for ZigBee technology, testifies that there is a zone (with a radius of about 50 m), within which the influence of forest on the loss of packet information does not occur, it suggests: 1) an empirical calculation model for the linear attenuation coefficient and its numerical value for the frequency 2.4 GHz is estimated to 𝛼𝛼 𝑚𝑚𝑚𝑚 = 0.5215 dB/m, which is practically close to the value 𝛼𝛼 𝑚𝑚𝑚𝑚 = 0.5 dB/m. as per recommendations ITU-R P.833.6., 2) an empirical expression determining the dependence of the working attenuation of a radio signal in forest vegetation as a function of the operating frequency and the distance between the transmitting and receiving stations. The results of this work can be used to evaluate the effectiveness of radio communication applications on transport in forest area.

Recent advances in satellite communication technologies in the tropical regions have led to significant increase in the demand for services and applications that require high channel quality for mobile satellite terminals. Determination and quantification of these requirements are important to optimize service quality, particularly in the Malaysian region. Moreover, the tests on current satellite propagation models were carried out at temperate regions whose environmental characteristics are much different from those in Malaysia. This difference renders these propagation models inapplicable and irrelevant to tropical regions in general. This paper presents the link characteristics observations and performance analysis with propagation measurements done in tropical region to provide an accurate database regarding rain and power arches supply (PAs) attenuations in the tropics for mobile scenarios. Hence, an extension for improving the performance assessment and analysis of satellite/t...

Felieton opisuje sukces, jakim było sformułowanie przez Jamesa Maxwella równań opisujących całość zjawisk elektromagnetycznych, oraz wynikające z rozwiązania tych równań istnienie fal elektromagnetycznych. Do tego miejsca można tylko chwalić Maxwella i podziwiać jego dzieło. Ale odkrywca nie mógł się pogodzić z faktem, że fale elektromagnetyczne mogą się rozprzestrzeniać w próżni. To mu się nie mieściło w głowie! Dlatego postulował, że cały Wszechświat wypełniony jest eterem, który miał być nieważką, ale sprężystą substancją w której miały się rozchodzić owe fale. Ten postulat okazał się błędny, ale przez wiele lat zaprzątał uwagę fizyków.

One of the most important factors in evaluating the performance of routing protocols in MANET is the variation in received signal strength known as fading. Different types of routing protocols have been proposed based on the propagation models that neglect the effect of fading. The choice of propagation models have a great impact on performance, so realistic models are necessary to consider the effect of fading as far as an accurate analysis of performance of the routing protocols is concerned. In this paper, comparative analysis of proactive protocol is performed using NS2, in order to study the impact of propagation model with various topologies. The non-fading models such as free space and two ray ground are simulated for comparison. The simulation results show that the propagation models have a great role in routing protocol of MANET.

The International Telecommunication Union (ITU) published well-tested models and data set for the prediction of fading (or attenuation) due to multipath and rain based on measurements on radio links across the globe. In respect of rain attenuation, ITU released ITU-R PN.837-1 recommendation in which ITU split the globe into 15 regions according to precipitation intensity. In this paper, a web application was developed to study the variation of rain attenuation, multipath attenuation, dominant attenuation and the effective fading experiencedbyterrestrial line of sight microwave links in any of the 15 ITU rain zones. The web application do generate tables and graph plots for the variation of the dominant fading and the effective fading with respect to frequency, link percentage availability, path inclination and point refractivity gradient. The web application was developed with PHP scripting language, MySQL database management system and then hosted online using apache web server. Sample computations were carried out for microwave frequencies in rain zone N which can be found in some parts of Nigeria. Rain and multipath attenuation data were obtained from ITU published data.In all, the result obtained in the paper showed that rain attenuation is the dominant fading for higher frequencies whereas, multipath fading do dominate at the lower frequencies. The frequency at which the transition from dominant multipath fading to dominant rain fading is not fixed. Rather, the turning point depends on different link parameter combinations. The results obtained in the paper showed how changes in link parameters like the link's percentage availability, the path's point refractivity index and the path inclination , can affect the frequency at which the dominant fading in a given rain zone transit from multipath fading to rain fading.

Modeling radio signal propagation remains one of the most critical tasks in the planning of wireless communication systems, including wireless sensor networks (WSN). Despite the existence of a considerable number of propagation models, the studies aimed at characterizing the attenuation in the wireless channel are still numerous and relevant. These studies are used in the design and planning of wireless networks deployed in various environments, including those with abundant vegetation. This paper analyzes the performance of three vegetation propagation models, ITU-R, FITU-R, and COST-235, and compares them with path loss measurements conducted in a cassava field in Sincelejo, Colombia. Additionally, we applied four machine learning techniques: linear regression (LR), k-nearest neighbors (K-NN), support vector machine (SVM), and random forest (RF), aiming to enhance prediction accuracy levels. The results show that vegetation models based on traditional approaches are not able to ad...

The authors present a method of performing accurate tracking of low-altitude flying targets in the presence of multipath and refraction effects. The method applies maximum likelihood (ML) beamforming to an array radar having frequency agility in combination with a computational method for predicting interference patterns which are affected by atmospheric refraction. Tracking errors obtained when using the current ML technique under ducting conditions are shown. Then, the proposed method is described and examples of tracking improvement under ducting are given using experimental data in the X-band.

The development of information and communication technology (ICT) in Indonesia is increasing rapidly every year. However, this increase is not comparable to the distribution of technology in remote areas, especially areas with mountainous contours. So it takes a proper backhaul network design to deploy telecommunication services in remote areas. Microwave transmission technology is widely used as a backhaul network in mountainous areas because it can reach areas that are difficult to reach by fiber optic. However, multipath fading becomes a problem in microwave communication, so to solve it, we use the diversity configuration approach. Space diversity configuration is the system most often used, but in more extreme conditions it can use a hybrid diversity configuration which is a combination of space and frequency diversity. In this study, we designed and compared the performance of two types of diversity configurations, namely space and hybrid diversity in cross-mountainous areas u...

Microwave communication is still important to use in the backhaul network of telecommunications systems because it can reach remote areas that are difficult to reach by cable technology. One of the implementations is cross-ocean backhaul communication which is widely applied in the archipelago. So, to reach the remote areas, proper backhaul network planning is required. A point-to-point microwave transmission network can be a solution to reach remote areas of islands separated by oceans. The problem that occurs is that the multipath fading on the ocean route is quite large so that to overcome this we need a diversity technique. There are various diversity configurations such as space, frequency, and a combination of both or Hybrid. Based on the simulation and theoretical calculations, concluded that point-to-point configuration producing the quality of communication below the standards set by the ITU-R (ITU-T G.821). The use of space diversity and hybrid diversity provided a signifi...

This research focuses on evaluation of Vertical Plane Tracing model and application of single knife-edge diffraction theory for NLOS macro-cell propagation prediction. Vertical Plane Tracing model differentiates itself from other models by applying a slope-diffraction model [1]. This slope-diffraction model addresses the transition zone problem existing in the UTD theory [2]. The second model is based on the diffractions at the top edges of the buildings along the streets. Single knife-edge diffraction theory is implemented with a few special additional methods for its propagation prediction. Both of these methods will be evaluated by comparing with measurement results.

Simulations have become remarkably useful in evaluating the performance of new techniques and algorithms in communication networks. This is due to its comparative cost, time and complexity advantage over the analytical and field trial approaches. For large-scale networks, system-level simulators (SLS) are used to assess the performance of the systems. The SLS typically employs statistical channel models to characterize the propagation environment. However, the communication channels can be more accurately modeled using the deterministic ray tracing tools, though at the cost of higher complexity. In this work, we present a novel framework for a hybrid system that integrates both the ray tracer and the SLS. In the hybrid system, the channel strength in terms of the signal-to-noise ratio (SNR) is fed from the ray tracer to the SLS which then uses the values for further tasks such as resource allocation and the consequent performance evaluation. Using metrics such as user throughput and spectral efficiency, our results show that the hybrid system predicts the system performance more accurately than the baseline SLS without ray tracing. The hybrid system will thus facilitate the accurate assessment of the performance of next-generation wireless systems.

Signal under-coverage due to diffraction losses, is fundamentally considered to be responsible for the hues and cries of communities residing behind mountainous topologies in Taraba and Niger State. Performance analyses of these radio tools are rudimentary for technical radio dimensioning and optimization. The epicenter of this study is to predict the depth of diffraction losses and under-coverage in mountainous areas of the study. To achieve this, an Open Source Geographical Resources Analysis Support System (GRASS) and other conventional diffraction models were employed. The result indicated that the transmitted radio signals were received via the mechanism of diffraction, as the mountain was found to obstruct the signal line-of-sight (LOS) and the ensuing effective ellipsoids of the Fresnel Zones in the analysis. Consequently, it was apparent that there was deep under-coverage in all the radio cells of the study location, as illustrated in the maps created with ArcGIS. The depth ...

The subject of the article is the design and practical implementation of the wireless mesh network. IQRF radio modules were used for the network design. The IQRF ® technique has enabled the construction of a mesh network with the possibility of reconfiguration. The theoretical part contains a description of the IQRF ® hardware solutions used. The practical scope includes the design part, where the configuration of the radio modules was carried out and the parameters of the radio network were set to allow its implementation in various topologies. Then, a wireless network consisting of 10 IQRF modules was launched in the P3 building of the Opole University of Technology. At this stage, configured radio modules were placed in selected rooms on all five floors of the building in order to carry out tests of the radio network constructed in this way. The tests included measuring the packet transmission delay time as well as the received signal strength. Research was carried out for several network topologies.

Recent advances in satellite communication technologies in the tropical regions have led to significant increase in the demand for services and applications that require high channel quality for mobile satellite terminals. Determination and quantification of these requirements are important to optimize service quality, particularly in the Malaysian region. Moreover, the tests on current satellite propagation models were carried out at temperate regions whose environmental characteristics are much different from those in Malaysia. This difference renders these propagation models inapplicable and irrelevant to tropical regions in general. This paper presents the link characteristics observations and performance analysis with propagation measurements done in tropical region to provide an accurate database regarding rain and power arches supply (PAs) attenuations in the tropics for mobile scenarios. Hence, an extension for improving the performance assessment and analysis of satellite/t...

This article makes a comparative analysis of the power intensity levels measured with the Network Cell Info Lite application and the performance of the different Log-Normal, Okumura Hata, COST 231, Wolfish Bertoni and SUI propagation models in the Frequency Band 4G LTE. The study was carried out in 5 LTE coverage cells located in the southern area of ​​the City of Riobamba and the model that best fits each cell is limited using absolute error analysis, obtaining an empirical correction factor for the proposed models. For the analysis of the absolute error, 3 measurement campaigns were carried out with 50 samples where the mean value was obtained. The analysis carried out will be suspended because the Log-Normal model is the one that best fits the Riobamba environment considering that it is a residential area, and that the power levels vary from (-80 dBm to -106 dBm) and that the coverage areas were determined up to 200m.

The aim of this work is to present a preliminary investigation on the propagation of electromagnetic fields generated by wireless technologies inside a nuclear facility or power plant. First, a survey of currently proposed wireless technologies for nuclear facilities and plants has been carried out. Then, for selected scenarios, the electromagnetic field propagation has been studied by means of electromagnetic simulation tools, and the presence of the nuclear environment has been simulated by properly modeling environmental parameters and engineered barriers. The choice of the proper simulation techniques and tools is mandatory in order to simulate the effect of the realistic environment on the propagation. Accordingly, the feasibility of wireless technologies application at nuclear facilities can be assessed on the basis of results achieved from simulated scenarios. The goal is to analyze, for selected scenarios, possible issues due to the propagation of an electromagnetic field in...

Mo untain c li ffs co nstituting knife edges inOu e nce radio wave propagating fro m VH F to mi crowave freq ue nc ies. T he d iffracti o n phenomena ca used by th ese sing le o r multi ple kn ife edges are a do mina nt propagati o n mecha ni sm tha t has to be take n into account in pla nnin g TV , FM ne two rk s, ce llul ar radi o, mi c ro wave ne two rk, e tc., in mo unta in o us regio ns. In orde r to in vesti gate the a bove mec ha ni sm fi e ld stre ngth meas ure me nt s we re co nducted over fi ve do ubl e knife edge path s a nd the measured sig nal levels a re co mpa red w ith several predic ti on tec hniques. T he deviati ons of the predi c ti o n techni q ues and th eir suitabil ity are prese nt ed in thi s paper. It is seen th at o ut of a ll the predic ti o n me thods G iovane ll i's method gives best agree me nt w ith the o bse rved result s.

Prediction of path loss in a wireless system is important to determine its quality of service. Fluctuations and variations of signal strength at higher frequency range in Near Field zone, is a common difficulty to achieve higher data rate. Continuous variation in signal causes decay of strength by the interference of the atmospheric obstructions and hence electric field intensity gradually decreases with the distance. In this paper the behaviour of field strength is explored through AWAS Electromagnetic Code which predicts the rapid variations in electric field intensity irrespective of environment as compare to statistical models which do not capture the variations as per Environment. An adequate and optimum values of these parameters is essential for efficient transmission. The results show that the numerical analysis predicts much lower field strengths which could significantly affect the channel quality.. This investigation is essential to reduce the rapid fluctuations in field strength of the WiMAX.

Modeling radio signal propagation remains one of the most critical tasks in the planning of wireless communication systems, including wireless sensor networks (WSN). Despite the existence of a considerable number of propagation models, the studies aimed at characterizing the attenuation in the wireless channel are still numerous and relevant. These studies are used in the design and planning of wireless networks deployed in various environments, including those with abundant vegetation. This paper analyzes the performance of three vegetation propagation models, ITU-R, FITU-R, and COST-235, and compares them with path loss measurements conducted in a cassava field in Sincelejo, Colombia. Additionally, we applied four machine learning techniques: linear regression (LR), k-nearest neighbors (K-NN), support vector machine (SVM), and random forest (RF), aiming to enhance prediction accuracy levels. The results show that vegetation models based on traditional approaches are not able to ad...

It is shown that proper representation of transmitting and receiving antennas in indoor environments are decisive for accurate prediction of electromagnetic power transfer parameters using the standard 3D-FDTD method. With the standard Yee method, it is not always possible to precisely describe all the geometrical details of electrically small antennas. A new approach for description of the discone antenna in uniform 3D-FDTD lattice is presented. The calculations are validated by comparing FDTD results with the polyhedral beam-tracing method and experimental data.

An indoor wireless network comprises of multiple devices connected wirelessly in a small geographical area, giving mobility to the connected devices. RF signal associated with wireless networks suffers from many propagation losses. It becomes essential to estimate losses at different locations, in the intended coverage area, to attain the desired performance seamlessly. It helps in the optimal device placement in the wireless networks. In the application, in addition to the propagation losses, there is a need to estimate the loss induced by the presence of smoke and fire, individually, in an indoor environment. This paper first deals with the design of a heatmap generating tool, in MATLAB, which gives the approximate signal strength at different locations on a given floor for a given transmitter. Then the paper discusses the formation of plasma in fast flaming fires and presents the path loss due to it. This path loss is incorporated in the heatmap generating tool and a heatmap is generated for our office ground floor for the case of a flaming fire. The paper also describes a testbed, setup in our office premises, to study the scattering loss caused by smoke particles.

This special issue entitled ''Modeling and Simulation Challenges in Microwave Engineering'' contains invited/ selected articles from The 12th Mediterranean Microwave Symposium (MMS 2012, http://mms.dogus.edu.tr), which was held at Dogus University during September 2-5, 2012 at the same time together with The 6th URSI-Turkey National Assembly and Congress (URSI-Turkey 2012, http://ursi.dogus.edu.tr). Technical programs of MMS 2012 covered a vast array of electromagnetic and microwave topics, including microwave circuit design and applications, the latest breakthroughs in antenna design, wireless communications, exotic materials, biomedical applications, numerical methods, etc. A series of short courses/tutorials were also organized by esteemed experts/scientists (all are IEEE Fellows/Distinguished Lecturers): Prof. Pyotr Ya. UFIMTSEV (father of the PTD and stealth design), Prof. Dr. Constantine BALANIS (world-wide known antenna master), Prof. Dr. Levent GÜ REL (world record holder of electromagnetic solvers with billions of unknowns), Prof. Dr. Shiban K KOUL (worldwide expert on microwave teaching), Prof. Dr. Sembiam RENGARAJAN (master on waveguide slot antennas), and Prof. Dr. Ö zlem Aydın Ç _ IV _ I (European lecturer on MEMS). It was also once in a lifetime opportunity having two keynote speeches on the History of the Diffraction during the opening session with two esteemed scientists. First, Prof. Ufimtsev addressed ''Fifty Year of Physical Theory of Diffraction (PTD).'' Then, Prof. Balanis summarized ''Geometric/Uniform Theory of Diffraction and Its Applications.'' The first article in this issue, entitled ''Fifty Years of Diffraction,'' prepared by Balanis, Sevgi, and Ufimtsev summarizes these keynote speeches. The other articles discuss different modeling and simulation aspects in electromagnetics and microwave engineering. I express my gratitude to all contributing authors.

The paper explores diffraction of acoustic waves at a two-dimensional hard trilateral cylinder with rounded edges. It represents the extension of the physical theory of diffraction (PTD) for finite objects with rounded edges. A first-order PTD approximation is developed. Integral equations are formulated for acoustic fringe waves and solved by method of moments (MoM). Good agreement is observed with the exact solution found by MoM when the object size exceeds a few wavelengths.

To cater large number of mobile users along with new applications and gadgets, higher speed and capacity is required in the networks. To overcome this hunger 3GPP has introduced a new high speed and lower latency radio access technology called as Long Term Evolution. This is the fourth generation technology as specified by 3GPP standards which can support from 1.4MHz to 20MHz channel bandwidth along with peak of 100Mbps and 50Mbps in Uplink. In this study we have selected some part of Khatai district of Baku City of Azerbaijan to plan and design a LTE network by providing simulations of coverage by signal level and coverage by signalto-noise-ratio.

Signed… v Acknowledgements Above all, my sincere appreciation goes the Almighty God for granting me the gift of life and good health for the completion of this work. Secondly, my profound gratitude and appreciation goes to my supervisor, Professor Thomas J. Afullo for his guidance, suggestions and criticisms during the undertaking of this research.

A new type of electron-scale coherent structure, referred to as electron vortex magnetic holes, was identified recently in the Earth's magnetosheath turbulent plasma. These electron-scale magnetic holes are characterized by magnetic field strength depression, electron density enhancement, temperature and temperature anisotropy increase (significant increase in perpendicular temperature and decrease in parallel temperature), and an electron vortex formed by the trapped electrons. The strong increase of electron temperature indicates that these magnetic holes have strong connection with the energization of electrons. Here, using high time resolution in-situ measurements from the MMS mission, it is further shown that electron-scale whistler waves coexist with electron-scale magnetic holes. These whistler waves were found not propagating from remote regions, but generated locally due to electron temperature anisotropy (Te⊥ /Te||) inside the magnetic holes. This study provides new insights into the electron-scale plasma dynamics in turbulent plasmas.

In this paper, development of Differential Fade Depth with Path Length Adjustment (DFD-PLA) algorithm for calculating the optimal path length for fixed point terrestrial line of sight microwave communication link is presented. The optimal path length for such link is defined as the path length at which the maximum fade depth is equal to the available fade margin the communication system can accommodate at the given set of link parameters. The DFD-PLA algorithm involved iterative adjustment of the path length based on the difference between the effective maximum fade depth and the available fade margin the system can accommodate. Sample 12GHz microwave link is analyzed and the results show that after 28 cycle the algorithm converged when path length, free space path loss and maximum fade depth in the link dropped from their initial to optimal values of 19.9903 km to 5.8726 Km, 140.40 dB to 129.40 dB and 104.04 dB to 30.56 dB respectively.

Presently space exploration missions involve the usage of upto maximum of two rover systems. A single rover system requires the investment of more time in exploration and mission completion. A dire necessity to look for alternative energy sources and other resources, the pursuit of knowledge and search for the existence of extra terrestrial life, are the motivations for humans to undertake such missions on a large scale in the near future. Communication between individual rovers and the Lander along with their tracking and positioning is a challenging task and we explore an indigeneous way of overcoming this problem. An Enhanced AODV with dynamic routing is implemented to overcome the constraints of Destination Sequenced Distance Vector(DSDV) and latency of Ad-hoc On Demand Vector(AODV). A more viable approach for tracking and positioning is using spread spectrum technique and triangulation method. This papers brings out an indigenous way of overcoming these problems using MANETs by combining the advantages of both AODV and DSDV, thus increasing the performance of the system.

Irregular terrains covered with forest vegetation represent a challenging scenario for radio planning. A case of particular interest is the one where a forest-covered high hill or mountain is interposed to the link, for which typical diffraction loss models usually apply as good approximations, even disregarding the vegetation influence. Pragmatic approaches to incorporate the forest contribution, such as adding a clutter height, usually improve accuracy a little further. In this scope, this paper assesses the performance of some models based on the Uniform Theory of Diffraction (UTD) for RF path loss prediction in such ridges. Special attention goes to a hybrid model in which the forest is a uniform layer over a wedge that represents the ridge, and its influence is incorporated into the diffraction coefficient. The path loss predictions are compared with measurements from a mountainous region of the USA, and the statistical adherence of the models to the measured data is discussed. Overall, the slightly better performance of the models which incorporate the vegetation influence was confirmed, the hybrid model performing the best for frequencies below 910 MHz.

This paper presents the results of measurements and simulations of the characteristics of 900 MHz band radio propagation channels in a tunnel environment. The simulations were made using the FDTD method (with companion UPML) and measurements made use of the swept frequency technique. Another method, the metaheuristic Simulated Annealing, was implemented for estimating the values of characteristic parameters of materials. The FDTD code was reformulated for use with CUDA with the objective of decreasing program running time.

Modeling radio signal propagation remains one of the most critical tasks in the planning of wireless communication systems, including wireless sensor networks (WSN). Despite the existence of a considerable number of propagation models, the studies aimed at characterizing the attenuation
in the wireless channel are still numerous and relevant. These studies are used in the design and planning of wireless networks deployed in various environments, including those with abundant vegetation. This paper analyzes the performance of three vegetation propagation models, ITU-R,
FITU-R, and COST-235, and compares them with path loss measurements conducted in a cassava field in Sincelejo, Colombia. Additionally, we applied four machine learning techniques: linear regression (LR), k-nearest neighbors (K-NN), support vector machine (SVM), and random forest (RF), aiming to enhance prediction accuracy levels. The results show that vegetation models based on traditional approaches are not able to adequately characterize attenuation, while models obtained by machine
learning using RF, K-NN, and SVM can predict path loss in cassava with RMSE and MAE values below 5 dB

In this paper, the computation of dual knife edge diffraction loss by Deygout multiple knife edge diffraction loss method is presented for a 6 GHz C-band microwave link. Also, the computation of equivalent single knife edge obstruction that will replace the dual obstruction by giving the same diffraction loss as the dual obstructions is presented. The results shows that for the dual obstructions M1 and M2 the total diffraction loss is 54.57746 dB as computed by the Deygout method. The individual diffraction loss from obstructions M1 and M2 are 32.85901 dB and 21.71845 dB respectively. Furthermore, a single knife edge obstruction located at the middle of the link (a distance of 1275m from the transmitter and receiver) and with line of sight clearance height of 483.5089m will be give the same diffraction loss as the dual knife edge obstructions M1 and M2. Essentially, the line of sight clearance height of the equivalent single knife edge obstruction are much more than the sum of the line of sight clearance height of the two initial obstructions.

Generally, to radio link engineers, determination of fade depth and refractivity of propagation links remains very significant, especially, during radio propagation planning. It gives a good insight into the expected performances of the communication link and serves as bedrock to improve on Quality of Service (QoS). In this paper, three years (2012 to 2014) radiosonde atmospheric parameter data from Nigerian Meteorological Agency was used to determine the point refractivity gradient along with fade depth for Calabar, in Cross River state of Nigeria. In respect of the refractivity gradient for Calabar, the results showed the highest occurrence is in January with refractivity gradient of -33.0018 N units and the lowest refractivity gradient occurred in August with value of -305.2692 N units. Furthermore, the fade depth from the three different International Telecommunication Union (ITU) models; namely, ITU-R P.530-16 model, ITU-R P.530-14 model, and ITU-R P.530-9 model also indicated ...

A MATLAB-based one-way and two-way split-step parabolic equation software tool (PETOOL) has been developed with a user-friendly graphical user interface (GUI) for the analysis and visualization of radiowave propagation over variable terrain and through homogeneous and inhomogeneous atmosphere. The tool has a unique feature over existing one-way parabolic equation (PE)-based codes, because it utilizes the two-way split-step parabolic equation (SSPE) approach with wide-angle propagator, which is a recursive forward-backward algorithm to incorporate both forward and backward waves into the solution in the presence of variable terrain. First, the formulation of the classical one-way SSPE and the relativelynovel two-way SSPE is presented, with particular emphasis on their capabilities and the limitations. Next, the structure and the GUI capabilities of the PETOOL software tool are discussed in detail. The calibration of PETOOL is performed and demonstrated via analytical comparisons and/or representative canonical tests performed against the Geometric Optic (GO) + Uniform Theory of Diffraction (UTD). The tool can be used for research and/or educational purposes to investigate the effects of a variety of user-defined terrain and range-dependent refractivity profiles in electromagnetic wave propagation.

The millimeter wave (mmWave) band will be exploited to address the growing demand for high data rates and low latency. The higher frequencies, however, are prone to limitations on the propagation of the signal in the environment. Thus, highly directional beamforming is needed to increase the antenna gain. Another crucial problem of the mmWave frequencies is their vulnerability to blockage by physical obstacles. To this aim, we studied the problem of modeling the impact of second-order effects on mmWave channels, specifically the susceptibility of the mmWave signals to physical blockers. With respect to existing works on this topic, our project focuses on scenarios where mmWaves interact with multiple, dynamic blockers. Our open source software includes diffraction-based blockage models and interfaces directly with an open source Radio Frequency (RF) ray-tracing software.

Non-stationary multipath fading channel models are necessary for the design and optimization of communications systems (the 5th generation mobile networks-5G, the (Industrial) Internet of Things, etc.). These models are considered as essential components of channel simulators which are similar to physical radio channels. This article describes a progressive novel method of adaptive non-stationary multipath fading channel models based on a real measurement of Channel Impulse Response (CIR). The designed system measures, classifies and subsequently adaptively changes the parameters of a transmission channel model. The proposed concept is based on the Software Defined Radio (SDR) and Field Programmable Gate Array (FPGA) which are implemented on the modular platform of PCI Extensions for Instrumentation (PXI). This approach enables to approximate and subsequently adaptively model any transmission environment. Thanks to the application of the adaptive parameter setting approach we can create unique dynamic models of real transmission channels which can be used for designing, testing and optimizing new trends in the field of wireless communications systems (new modulation formats, algorithm testing, channel equalization, optimization of source and channel coding, guard interval adaptation, etc.).

A novel MIMO (multiple input multiple output) satellite channel model that allows the generation of associated channel impulse response (CIR) time series depending on the movement profile of a land mobile terminal is presented in this paper. Based on high precise wideband measurements in L-band the model reproduces the correlated shadowing and multipath conditions in rich detail. The model includes time and space variant echo signals appearing and disappearing in dependence on the receive antenna position and movement, and the actual azimuths and elevations to the various signal sources. Attenuation and path delays relative to the hypothetical line of sight (LOS) ensure usability for ranging purposes. Parameters for car and pedestrian applications in urban and suburban environments are provided. The channel characteristics are determined independently of the transmitted signal. Therefore the usability, for example, for GPS and GALILEO, as well as wideband communication services from...

In this paper, mathematical model and algorithm for determination of minimum antenna mast height for terrestrial line of sight microwave link with zero path inclination is presented. The mathematical expressions developed are used for computing relevant link parameters while the algorithm gives the procedure for using the mathematical expressions for computing the minimum antenna mast heights. Sample 40km 10GHz Ku-band microwave link is used to demonstrate the application of the model and algorithm; in this case, the transmitter is located at longitude 7.711747 and latitude 5.178536 and the receiver is located at longitude 8.039903and latitude 5.055223. The link is required to make a minimum of 100% clearance with respect to the Fresnel zone 1. The results show that the transmitter and receiver antenna are at the same line of sight height of 158.7 m whereas the transmitter antenna mast height is 68.8 m while the receiver antenna mast height is 109.7m. Also, the maximum obstruction height of 128.58m occurred at a distance of 14306.98m from the transmitter with percentage clearance of 100% in respect of Fresnel zone 1. The result shows that the model can be used to ensure that the specified percentage clearance is achieved through the application of the models presented in this paper.

The ICE (Instrument Champ Électrique) experiment on board the DEMETER (Detection of ElectroMagnetic Emissions Transmitted from Earthquake Regions) satellite recorded frequency-banded wave emissions below the electron cyclotron frequency, with band spacing frequency low-hybrid resonance, in the vicinity of the magnetic equatorial plane. Those radiations were observed in the beginning of the year 2010 on the night side of Earth and rarely on the day side. We distinguish two components: one appears as frequency bands continuous in time between a few kilohertz and up to 50 kHz, and the other one is from 50 to 800 kHz. The first component exhibits positive and negative frequency drift rates in the Southern Hemisphere and Northern Hemisphere, at latitudes between 40 and 20 •. The second one displays multiple spaced frequency bands. Such bands mainly occur near the magnetic equatorial plane with a particular enhancement of the power level when the satellite latitude is close to the magnetic equatorial plane. We show in this study the similarities and the discrepancies between the non-free-space DEMETER frequency-banded emissions and the well-known free-space terrestrial kilometric radiation. The hollow cones of the DEMETER frequency-banded wave emissions are oriented towards Earth's ionosphere. We suggest that the source region is localized in regions poleward of the plasmapause where the ratio of the plasma frequency to gyro-frequency is smaller than one.

The ICE (Instrument Champ Électrique) experiment on board the DEMETER (Detection of ElectroMagnetic Emissions Transmitted from Earthquake Regions) satellite recorded frequency-banded wave emissions below the electron cyclotron frequency, with band spacing frequency low-hybrid resonance, in the vicinity of the magnetic equatorial plane. Those radiations were observed in the beginning of the year 2010 on the night side of Earth and rarely on the day side. We distinguish two components: one appears as frequency bands continuous in time between a few kilohertz and up to 50 kHz, and the other one is from 50 to 800 kHz. The first component exhibits positive and negative frequency drift rates in the Southern Hemisphere and Northern Hemisphere, at latitudes between 40 and 20 •. The second one displays multiple spaced frequency bands. Such bands mainly occur near the magnetic equatorial plane with a particular enhancement of the power level when the satellite latitude is close to the magnetic equatorial plane. We show in this study the similarities and the discrepancies between the non-free-space DEMETER frequency-banded emissions and the well-known free-space terrestrial kilometric radiation. The hollow cones of the DEMETER frequency-banded wave emissions are oriented towards Earth's ionosphere. We suggest that the source region is localized in regions poleward of the plasmapause where the ratio of the plasma frequency to gyro-frequency is smaller than one.

We introduce a new methodology that allows the construction of wave frequency distributions due to growing incoherent whistler-mode waves in the magnetosphere. The technique combines the equations of geometric optics (i.e., raytracing) with the equation of transfer of radiation in an anisotropic lossy medium to obtain spectral energy density as a function of frequency and wavenormal angle. We describe the method in detail and then demonstrate how it could be used in an idealized magnetosphere during quiet geomagnetic conditions. For a specific set of plasma conditions, we predict that the wave power peaks off the equator at 15 ı magnetic latitude. The new calculations predict that wave power as a function of frequency can be adequately described using a Gaussian function, but as a function of wavenormal angle, it more closely resembles a skew normal distribution. The technique described in this paper is the first known estimate of the parallel and oblique incoherent wave spectrum as a result of growing whistler-mode waves and provides a means to incorporate self-consistent wave-particle interactions in a kinetic model of the magnetosphere over a large volume.