This paper looks into the realization of digital twin (DT) technology in unmanned aerial vehicle (UAV) networks. We propose, in particular, a framework for DT-based UAV applications in which distinct ...jobs in the digital twin interact with UAVs in the physical world via task manager scheduling. Furthermore, we investigate the use of 3D mmWave Radar imaging on UAVs and apply it to the process of radio frequency (RF) characterizing. After that, the method of 3D ray-tracing is employed to accomplish channel modelling of UAVs, which reflects RF domain digital twin match. Finally, we present numerical results to demonstrate that our developed digital twin platform can provide accurate RF presentation of UAV and therefore accomplish smart operating and administration of the actual UAV network.
To support the design of fifth-generation (5G) beamforming and beamtracking algorithms, a spatially consistent channel propagation model is needed, namely a model whose geometrical properties - ...angle-of-departure, angle-of-arrival, and delay of its multipath components - evolve smoothly while the receiver is in motion. The 3rd Generation Partnership Project (3GPP) has proposed two spatial consistency (SC) procedures - SC-A and SC-B - as part of its popular TR 38.901 model for 0.5 GHz to 100 GHz channels. In this paper, we perform a comparison of the two procedures with measurements to determine whether the procedures accurately fit our measurements. We use over 700 channel measurements collected with our high-resolution 28 GHz and 60 GHz directional channel sounders, across two indoor and three outdoor environments and for pedestrian and vehicular motion. We show that SC-A - a fully deterministic procedure - provides a much better approximation to the measured channel in all five environments than SC-B - a fully stochastic procedure. We also computed the correlation distance for both procedures - the distance over which they are valid - showing that SC-A's average correlation distance across all environments of 13.4 m is more than twice as long as SC-B's of 6.28 m, and that the channel is spatially consistent for significantly longer outdoors than indoors.
Long Range (LoRa) is a popular communication technology which has been used recently for many of the internet of things (IoT) applications. LoRa technology is being used for various smart city ...operations as well as in the field of smart agriculture. Some of the smart agricultural applications need LoRa propagation in vegetation medium. To model a wireless channel, several factors should be considered as those have significant impact on the performance of LoRa propagation through foliage medium. In this paper some of the possible factors are highlighted as those are responsible for the degradation of LoRa channel quality. Aslo an experimental study was undergone in the foliage medium (a line of five date palm trees) to investigate the LoRa physical layer performance utilizing different spread factors (SF7-SF12). The RSSI values were measured for the propagation through a line of trees and compared with the expected RSSI values. The result shows that the measured RSSI values are higher than the expected values for LoRa propagation in foliage medium. The result obtained in this paper may help LoRa propagation Channel modelling in foliage medium in future studies.
This paper presents an investigation of how to model the statistical properties of radio channels arising in industrial environments over long time horizons, e.g., hours and days. Based on extensive ...measurement campaigns, conducted at three different factory buildings, it is shown that for mobile transceivers the fading characteristics are Rayleigh or close to Rayleigh. However, for transceivers mounted at fixed locations, the use of conventional single fading distributions is not sufficient. It is shown that a suitable model structure for describing the fading properties of the radio channels, as measured by power, is a mixture of gamma and compound gamma-lognormal distributions. Furthermore, the complexity of the model generally increases with the observation interval. A model selection approach based on a connection between Kullback's mean discrimination information and the log-likelihood provides a robust choice of model structure. We show that while a (semi)-Markov chain constitute a suitable model for the channel dynamics the time dependence of the data can be neglected in the estimation of the parameters of the mixture distributions. Neglecting the time dependence in the data leads to a more efficient parametrization. Moreover, it is shown that the considered class of mixture distributions is identifiable for both continuous and quantized data under certain conditions and under those conditions a maximum likelihood under independence assumption estimator is shown to give consistent parameters also for data which are not independent. The parameter estimates are obtained by maximizing the log likelihood using a genetic and a local interior point algorithm.
6G IoV Networks Driven by RF Digital Twin Modeling Liu, Zengcan; Sun, Houjun; Marine, Gintare ...
IEEE transactions on intelligent transportation systems,
2024-March, 2024-3-00, Letnik:
25, Številka:
3
Journal Article
Recenzirano
Internet of Vehicles (IoV) is a crucial component of 6G mobile network, where energy efficiency is a major concern. To achieve green communication in IoV, this paper proposes a digital twin (DT) ...method and develops related machine learning-based energy-efficient approach. The channel model examined in this paper takes into account incident waves reflected by moving objects and the impacts of radio signals between various vehicles. 3D ray tracing is used to model the millimeter-wave channel in IoV to reflect radio frequency(RF)-domain digital twin matching. Finally, we present numerical results to justify the effectiveness of our proposed scheme.
The objective of this paper is to derive a model for the irradiance distribution of underwater optical waves propagation in the combined presence of turbulence and air bubbles. The proposed ...distribution is based on modelling the medium index of refraction as a shot noise process and using the Rytov solution to the stochastic wave equation. Since the oceanic turbulence spectrum is different than the atmospheric spectrum, recent studies show that the well-known probability density functions poorly describe optical wave propagation underwater in the combined presence of air bubbles and turbulence, and that a mixture of distributions is generally needed. This conclusion, however, does not follow from theoretical investigations. Moreover, the physical aspects of the phenomena, such as the bubble size distribution, are not included in these models, and as such may limit their applicability. The approach introduced in this paper allows for including the environment physical properties directly in to the medium index of refraction.
In this paper, intensity distribution model is derived based on Rytov theory of propagation through weak turbulence. The physical processes in effect are directly included by assuming a shot noise index of refraction model.
Using the beam propagation method combined with the random phase screen method, the derived distribution is validated by simulation over a large range of turbulence levels and shows excellent agreement with the simulation data. In particular, the qualitative aspect of two peak distribution is modelled by the proposed distribution.
•A proposed approach for the intensity pdf of optical waves through random mediums.•The proposed approach incorporates the physical characteristics of the mediums.•Underwater optical waves in presence of turbulence and air bubbles is considered.•The model is verified through simulation of underwater turbulent environment .
Graph theory channel modeling is an efficient approach to simulate multipath radio propagation including the reverberation effect of electromagnetic waves. In this contribution, without modifying the ...modeling framework, we proposed a semi-deterministic channel modeling approach by associating the scatterers with realistic environment objects, and by calculating the coefficients of the propagation paths on the base of a physically sound and proven diffuse scattering theory. The diffuse multipath components are then combined with the specular components (SCs) simulated by ray-tracing (RT) to obtain a complete channel representation. The proposed method is evaluated in two reference scenarios at 3.8 and 60 GHz, respectively, by comparing the simulated channel characteristics with channel measurement data. Results show that the proposed method can accurately predict the channel characteristics in both the delay domain and the angular domain. The proposed approach is appropriate to model multipath propagation in confined indoor or dense-urban environment at millimeter (mm)-wave frequencies and above, where reverberation and rough-surface scattering can be important phenomena.
•A macroscopic mixture model is formally derived from Navier-Stokes equations using a two-step approach : RANS averaging and space homogenisation.•Theoretical connections between the local ...instantaneous description, the two-fluid model, the local drift-flux model and the spatially-averaged drift-flux model are presented.•A new path to calibrate closure laws for two-phase turbulent applications is proposed based on information provided by local two-fluid simulations.•The content of macroscopic models (spatial average of the mixture) is rigorously expressed in terms of local instantaneous fields.•Guidelines to derive closure relations either for the local drift-flux or for the macroscopic models are discussed to close the local relative velocity, the macroscopic diffusion of void fraction and the macroscopic pressure drop.
This article addresses the issue of reduced models to describe turbulent two-phase flows in industrial applications. A spatially-averaged mixture or drift-flux model is derived theoretically from the local instantaneous Navier-Stokes description. Reynolds-averaging and space-averaging are applied successively. Between these two steps, a model reduction is achieved to account for the non-equilibrium between phases via algebraic relations. Applications of this work are not limited to porous media but also include macroscopic descriptions to model high-shear regions developing near the walls for internal flows. Thermal effects, heat transfer at the wall and phase-change are also considered and briefly discussed. The final model describes the evolution of mixture variables, including effects of both sub-filter spatial variations, turbulence, and local non-equilibrium in velocity, pressure and enthalpy. This analysis provides bridges between different approaches to model two-phase flows (local instantaneous description, two-fluid model, local drift-flux model and spatially-averaged drift-flux model). It clarifies the content of each model involved by defining them in terms of local instantaneous quantities. Turbulent fluctuations and phase intermittency are crucial mechanisms. Important effects to model also include void fraction dispersion and turbulent diffusion; then, it is necessary to model the relative velocity, including the drift velocity orthogonal to gravity induced by the complex interactions between turbulent velocity fluctuations and the interfacial momentum transfer.
The final macroscopic (spatially-averaged) mixture formulation is open, in the sense that expressions to model the various terms representing the physics of the small scales are not provided; instead, the physical sense and the origin of these models are discussed. The paper is meant as a basis on which analyses on local imbalance assumptions or relative velocity closures can be assessed. CFD simulations can provide information to complement experiments in technically challenging physical conditions or on processes essential to the models yet difficult to access experimentally (such as interfacial transfers for instance). Different kinds of two-fluid models can be tested to analyse their consequences on the macroscopic spatially-averaged model. In addition, a new path to calibrate closure laws or propose new models is opened based on finer-scale descriptions. Guidelines to use fine simulations along with the open expressions to derive closure relations either for the local drift-flux or for the spatially-averaged models are presented. They concern the modelling of the local relative velocity, the spatial average of the diffusion of void fraction and of the pressure drop.
The indoor wireless optical communication channel is characterised by the multiple reflections of the light from the surrounding walls. We present a new frequency-domain simulation method for this ...channel. In contrast to the known time-domain simulation techniques, our method is not restricted to a finite order of reflections. We show that the contributions of an infinite number of reflections can be summed up analytically to a formula that can be handled by standard numerical methods. We illustrate the method by comparing it to the results of previous time domain simulations, and we apply it to the numerical evaluation of some further model scenarios with more than one transmitter.
A Review on Terahertz Communications Research Kleine-Ostmann, Thomas; Nagatsuma, Tadao
Journal of infrared, millimeter and terahertz waves,
02/2011, Letnik:
32, Številka:
2
Journal Article
Recenzirano
The increasing demand of unoccupied and unregulated bandwidth for wireless communication systems will inevitably lead to the extension of operation frequencies toward the lower THz frequency range. ...Higher carrier frequencies will allow for fast transmission of huge amounts of data as needed for new emerging applications. Despite the tremendous hurdles that have to be overcome with regard to sources and detectors, circuit and antenna technology and system architecture to realize ultrafast data transmission in a scenario with extensive transmission loss, a new area of research is beginning to form. In this article we give an overview of emerging technologies and system research that might lead to ubiquitous THz communication systems in the future.
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