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This paper presents an off-body channel model for polarized communications with dynamic users. The model is based on Geometrical Optics and Uniform Theory of Diffraction and accounts for free space propagation, reflections, and diffractions. It allows for arbitrary antennas’ polarizations and gain patterns and supports a number of on-body antenna placements. In order to take the influence of users’ motion into account, a mobility model for wearable antennas on dynamic users is used. Signal depolarization mechanisms are identified, and simulations are performed to analyze the influence of user dynamics on the channel. The results show that significant polarization mismatch losses occur due to wearable antenna rotations, resulting in received power variations up to 37.5 dB for the line-of-sight component and 41.4 dB for the scattered one. The importance of taking signal polarization into account is demonstrated by comparing the simulation results between polarized and nonpolarized channel models in a free space propagation scenario, where a difference up to 53 dB in between the two is observed.

Free space propagation of radio waves of all possible bands, including light, is represented by a structural time and space interrelated corpuscular-wave process, the physical basis of which is periodic transition of the energy of electromagnetic oscillation to the mass called the corpuscle, and vice versa. For this reason, the concepts of electromagnetic oscillations, the photon in the extended sense and the radio photon are introduced., Поширення в просторі радіохвиль усіх можливих діапазонів, включно зі світловими, представляється структурним взаємозалежним у часі й просторі корпускулярно-хвильовим процесом, фізичною основою якого є періодичний перехід енергії електромагнітної форми коливання в масу, названу корпускулою, і навпаки. З огляду на це введені поняття електромагнітних коливань, фотона в розширеному розумінні та радіофотона.

Mobile Ad-hoc NETwork (MANET) is a decentralized type of wireless network. The network is ad hoc because it does not rely on a pre-existing infrastructure, such as routers in wired networks or access points in managed wireless networks. One of the major issue and challenging area in MANET is the process of routing due to dynamic topologies and high mobility of mobile nodes. The efficiency and accuracy of a protocol depend on many parameters in these networks. In addition to other parameters node velocity and propagation models are among them. Calculating signal strength at the receiver is the responsibility of a propagation model while the mobility of nodes is responsible for the topology of the network. A huge amount of loss in performance is occurred due to the variation of signal strength at the receiver while increasing and decreasing the distance of nodes. In this paper, a novel approach is identified and portrayed of the said propagation models based on distance from each other. It has been analyzed to check distance based performance evaluation of Two Ray Ground and Free Space Radio Wave Propagation Models on the performance of Ad-hoc On-demand Distance Vector (AODV) Routing Protocol in MANET. The simulation has been carried out in (Network Simulator-2) NS-2 by using performance metrics that are Average Throughput (kpbs), Average Latency (milliseconds) and Average Packet Drop (packets). The results predicted that propagation models and mobility have a strong influence on the performance of AODV in considered distance based scenario.

Reverse forward scatter radar, an unusual alternative form to the traditional forward scatter radar, is investigated to demonstrate its viability and practicality. The power budget is illustrated graphically and derived by finding the maximum possible baselines for various targets, including a human. The two-ray path and the free space propagation model are considered. Reverse forward scatter radar is shown to have clear potential to be used in practice.

The main contributions of the research paper are designing and implementation of an algorithm for handoff decision in WiFi coverage zone based on Fuzzy Logic. We have designed and implemented the handoff algorithm in WiFi coverage zone considering Free Space Propagation Model. We have considered Received Signal Strength, Channel Capacity, Network Load and User Velocity as the parameters in the algorithm. We have also studied the variation in point of handoff under the various conditions of Network Load, User Velocity and location of the access points.

The use of VANET technology is to create better traffic management. Different road conditions and high mobility of vehicles cause problems in VANET such as efficient search processes, network routes that need to be maintained, and data transmission problems. DSR (Dynamic Source Routing) predefines and generates routes on demand and is designed to work on multihop ad-hoc networks without centralized control. The Friis Free Space propagation model is used to model the Line of Sight (LOS) that occurs in a free space environment. The variation of road models in Indonesia is grouped into four groups, namely express roads, intercity roads, urban roads, and residential roads. In each of these road models, simulation testing is carried out based on different vehicle number scenarios. Network Simulator v3.27 (NS-3.27) and SUMO as a mobility generator were used for the simulation. The parameters of average throughput, packet delivery ratio and MAC/PHY overhead sequentially measure the DSR performance. The results on the express roads with Friis Free Space propagation produce values of 6.52 KBps, 7.71%, 39.59 KBytes. Test results on intercity roads 5.72 KBps, 11.17%, 5.48 KBytes. Test results on urban roads 16.50 KBps, 32.22%, 0.0016 KBytes. While the test results on residential roads were 12.66 KBps, 24.72%, 0.779 KBytes. The test results show that the road model in Indonesia with the performance of the DSR routing protocol with Friis Free Space propagation on the VANET network from the best to the worst, respectively, is the urban road model, residential road model, intercity road model, and express road model.

Taking the Gaussian-Schell model vortex beam as an example, the free-space propagation of magnetic spectral Stokes singularities of stochastic electromagnetic beams in the paraxial approximation is studied and compared with the corresponding electric spectral Stokes singularities. It is shown that there exist magnetic spectral Stokes singularities of stochastic electromagnetic beams. By varying the spatial correlation length or propagation distance, the motion, creation, and annihilation of magnetic spectral Stokes singularities, the V point and handedness reversal of C point will take place. In comparison with the electric spectral Stokes singularities of stochastic electromagnetic beams, their positions are not the same, and the left- and right-handedness spaces do not coincide.

In this study, based on the extended Huygens–Fresnel principle, the propagation expressions of circular edge dislocation beams and circular–linear edge dislocation beams were obtained. The propagation properties of the two types of beam were compared in free space and atmospheric turbulence. The results show that, when circular–linear edge dislocation beams propagate in free space or atmospheric turbulence, because the linear edge dislocation is located in different beam locations, circular edge dislocation vanishes or evolves into a pair of optical vortices. However, when circular edge dislocation beams propagate in space, circular edge dislocation exists stably in free space propagation, while it evolves into a pair of optical vortices in atmospheric turbulence propagation. Therefore, the propagation properties of circular edge dislocation can be adjusted by adding linear edge dislocation when circular edge dislocation beams propagate through free space and atmospheric turbulence. This research can be useful for applications in optical communications.

In this paper, we propose a numerical approach to simulate the degree of coherence (DOC) of a partially coherent beam (PCB) with a Schell-model correlator in any transverse plane during propagation. The approach is applicable for PCBs whose initial intensity distribution and DOC distribution are non-Gaussian functions, even for beams for which it is impossible to obtain an analytical expression for the cross-spectral density (CSD) function. Based on our approach, numerical examples for the distribution of the DOC of two types of PCBs are presented. One type is the partially coherent Hermite&ndash, Gaussian beam. The simulation results of the DOC agree well with those calculated from the analytical formula. The other type of PCB is the one for which it is impossible to obtain an analytical expression of CSD. The evolution of the DOC with the propagation distance and in the far field is studied in detail. Our numerical approach may find potential applications in optical encryption and information transfer.

Free space propagation loss of aeronautical radio navigation station is calculated according to transmitting antenna height, receiving antenna height, frequency, distance between transmitting antenna and receiving antenna, comparing with traditional free space propagation loss algorithm. The data calculated from the algorithm is checked by flight check data combined with site data around navigation station.

This paper investigates the possibility of real-life using the brand new type of digital modulation, which implies the transmission of white Gaussian noise whose variance changes in time. That modulation has been entitled as variance shift keying. The signals obtained on its basis have a high level of transmission security, and they even cannot be detected by standard means of matched filtering. However, the paper suggests the decision on how to process these signals at the receiver site. It is proposed to use a specially developed optimal receiver, whose restoration quality appears to be better in comparison with the conventional cumulative receiver. The digital simulation of propagation in frequency selective media has shown the signal with variance shift keying is possible to be used in real conditions since its distribution of instantaneous amplitudes remains Gaussian. © 2018 Academic Mind. The work was supported by Act 211 Government of the Russian Federation, contract № 02.A03.21.0006. The research was executed by the grant of the Ministry of education and science of the Russian Federation (project № 8.2538.2017/4.6).

Recently, much attention has been paid to unmanned aircraft systems (UAS), especially for civilian purposes such as disaster prevention and transportation. This paper considers big long-flight-type UASs remotely piloted from ground station by radio communication link, since these types of UASs require higher reliability. The purpose of this paper is to consider a communication system which transmits real-time video of the surroundings of aircraft from unmanned aircraft to the ground pilot. In this paper, the aeronautical mobile airport communications system (AeroMACS) is considered as a command and non-payload communications (CNPC) link between unmanned aircraft and ground pilot. Flight tests using the experimental aircraft and AeroMACS prototype system are conducted to obtain the air-to-ground propagation profile. In addition, the placements of airborne antennas are considered, because the positional relationship between airborne antenna and ground fixed antenna is not constant during the flight. The results of flight tests show the effectiveness of our system, and the received signal strength indicator (RSSI) obtained by flight tests has the same tendency as the free space propagation model. Finally, the results of flight tests show that a vertical placement on top and bottom of aircraft body is effective for the multiple inputs and multiple outputs (MIMO) antenna configuration of UAS.

Safety assessment of exposure caused by cellular base stations based on calculation methods is often performed using free space propagation in order to include the worst case. For prospective technologies (e.g. small cells in the vicinity of people), this approach might lead to a high exploitation of exposure limits. This paper investigates the overestimation of downlink exposure being predicted with a free space propagation model in comparison to a deterministic 2D knife edge diffraction model in an exemplary urban environment for a rooftop mounted base station. The results show that overestimation is quite low in the vicinity of the base station, particularly in LOS regions. In a distance between 100 and 200 m the overestimation is constantly rising, whereas for distances larger than 200 m it stays nearly constant.

The generation and propagation of interfering coherent composite vortex beams are simulated and experimentally verified. Dynamic control of the resulting intensity profile is manipulated through interferometric phase modulation.

The concept of vectorial nonparaxial cosh-squared-Gaussian (ChsG) beams is introduced and their free space propagation equations are derived analytically by using the vectorial Rayleigh-Sommerfeld diffraction integrals, and far-field expressions as well as paraxial propagation formula are obtained in free space. Numerical calculations and analysis show that, the f-parameter and decentered parameter plays an important role in determining the far-field properties of the vectorial nonparaxial ChsG beams.

Except for the Lissajous singularities, the singular Lissajous line is shown to be in existence, which is emergent from the incoherent addition of two uncorrelated vector electric fields at arbitrarily different frequencies. The free-space propagation of the emergent Lissajous singularities and singular Lissajous line and their interaction are studied theoretically and illustrated numerically.

The dynamic evolution of Lissajous singularities in free-space propagation is studied. It is shown that the pair creation and annihilation, handedness reversal and change in the degree of polarization of Lissajous singularities, as well as the rotation and change in the shape of Lissajous figures may appear upon propagation.

The finiteness of diffractive orders of the phase grating and the relations between the diffractive orders and the incident angle are discussed in this article. The distribution of each diffractive order is illustrated at different incident angles, and the diffractive direction of each diffraction wave is given. It is pointed out that while only the zero-order reflection wave and the zero-order transmit exist in the free-space layer, the diffraction waves of higher diffractive orders may exist in the substrate layer.

The scintillation properties of a rectangular dark hollow beam (DHB) in a weak turbulent atmosphere are investigated. Explicit expression for the on-axis scintillation index of a rectangular DHB is derived. It is found that the scintillation index value of a rectangular DHB can be smaller than that of Gaussian, elliptical Gaussian and rectangular flat-topped beams in a weak turbulent atmosphere under certain conditions. Our results will be useful in long-distance free-space optical communications. The scintillation properties of a rectangular DHB are closely controlled by its initial beam parameters.

We present analysis of the technical challenges facing deployment of long-distance free-space links employing orbital angular momentum multiplexing. Our analysis indicates atmospheric mitigation techniques, and modal purity are important consideration for system design.

The propagation of concentric vortex beams for communication through turbid water is studied and temporally modulated. Experiments show the spatial profile is maintained over 11.2 attenuation lengths using commercial antacids as a scattering agent.

To investigate a supposed relationship between exposure by mobile phone base stations and wellbeing, an epidemiological cross sectional study is carried out within the German Mobile Telecommunication Research Program. In a parallel project, a method for the classification of electromagnetic exposure due to mobile phone base stations has been developed. This is based on the results of measurements of high frequency immissions in the interior of more than 1100 rooms and at outdoor locations, the calculation of the emissions of mobile phone antennas under free space propagation conditions and empirically determined transmission factors for the propagation of electromagnetic waves in different types of residential areas for passage of walls and windows. Standard tests (correlation-test, kappa-test, Bland-Altman-Plot, analysis of sensitivity and specificity) show that the method for computational exposure assessment developed in this project is applicable for a first classification of exposures due to mobile phone base stations in epidemiological studies.

In this paper, it is investigated that how the atmosphere effects on the synchronization accuracy in free-space quantum key distribution (QKD). We measured the synchronization error of a free-space QKD in our near-ground platform. According to experimental results and theoretical calculations, we deduce that the intensity fluctuation of synchronization light due to atmosphere disturbance contributes far more to the synchronization accuracy than others. By using the constant fraction discrimination method, the synchronization error of the free-space QKD, passing through the aerosphere, can be limited within 300 ps which meets the synchronization requirement of a satellite-to-ground QKD system.

A model of isodiffracting hollow Gaussian pulsed beams (HGPBs) is presented. Based on the Fourier transform method, an analytical formula for the HGPBs propagating in free space is derived, which enables us to study the spatiotemporal behaviour of the ultrashort pulsed beams. Some interesting phenomena of ultrashort pulsed beams, such as the symmetrical temporal profiles, the dark rings, etc, are discussed in detail and illustrated numerically.

A new kind of partially coherent beam named partially coherent off-axis flat-topped beam is proposed. The cross-spectral density of this beam can be expressed as a finite series of off-axis Gaussian–Schell-model beams with different parameters. Analytical propagation formulae for the partially coherent off-axis flat-topped beam through aligned and misaligned optical systems are derived. As a numerical example, the propagation properties of the partially coherent off-axis flat-topped beam in free space are discussed.