Radio Wave Propagation Prediction Research Articles

Efficient propagation modelling for open‐confined mixed space using a hybrid ray‐tracing/waveguide theory method

AbstractThe accurate prediction of radio wave propagation along highways plays an important role in the design of high‐speed highway communication systems. The open‐confined mixed space is a connection zone between the open space and confined tunnel along the highway. A hybrid propagation model is presented based on ray‐tracing (RT) and waveguide theory, for the efficient modelling of open‐confined mixed space. The proposed model employs RT to predict radio waves emitted by sources with arbitrary radiation patterns in open space sections, and utilises the waveguide theory approach to accelerate the prediction process in the confined tunnel sections. Both two‐ray and six‐ray RT models are included to take into account the suburban and urban environments. Numerical results are compared with simulated results generated by RT as well as experimental measurements. The validity and usefulness of the proposed model are demonstrated in an actual open‐confined mixed space environment.

Three-Dimensional Ray-Tracing-Based Propagation Prediction Model for Macrocellular Environment at Sub-6 GHz Frequencies

This paper presents a 3D ray-tracing model using geometrical optics and the uniform theory of diffraction in radio channel characterizations of macrocellular environments. On the basis of the environmental information obtained from a digitized map, the model is effectively applied. A technique considering multiple reflections and diffractions through the ray path classification is utilized in this model. Ray paths belonging to each ray category are determined using different methods. The proposed model is justified (the prediction accuracy of the model is better than 6.5 dB) with measurement data for the two scenarios and can provide reliable theory as a basis for radio wave propagation prediction and network planning in urban macrocellular environments.

The evaluation of EMI characteristics of 4G-IMT system on FAST around its RQZ

Mobile communication base stations have become ubiquitous with the popularization and development of mobile communication services. Although the Chinese government has designated a radio quiet zone (RQZ) specifically for Five-hundred-meter Aperture Spherical radio Telescope (FAST), the 4G International Mobile Telecommunications (4G-IMT) system is still heavily used to meet the communication needs around the RQZ. To assess the Electromagnetic Interference (EMI) caused by 4G-IMT base stations on the performance of FAST, this paper employs the International Telecommunication Union (ITU) deterministic radio wave propagation prediction model. The interference of 4G-IMT base stations on FAST is evaluated based on relevant parameters, such as the frequency used by both FAST and the base station, in conjunction with the FAST threshold protection requirements. The results indicate that 47.73 % of the data exceed the radio astronomy protection threshold of FAST. In addition, a field experiment was conducted to verify the accuracy of the radio wave propagation prediction method used. The root-mean-square error between the predicted value and the measured value was found to be 6.94 dB, supporting the accuracy of the predicted results. The findings of this study can help suppress interference from mobile communication services around the RQZ of FAST and optimize the electromagnetic environment around FAST.

Field strength prediction based on deep learning under small sample data

The accurate prediction of radio wave propagation is extremely important for wireless network planning and optimization. However, inexact matching between the traditional empirical model and actual propagation environments, as well as the insufficiency of the sample data required for training a deep learning model, lead to unsatisfactory prediction results. This paper proposes a field strength prediction model based on a deep neural network that is aimed at a tiny dataset composed of the geographic information and corresponding satellite images of a target area. This model connects two pretrained networks to minimize the parameters to be learned. Simultaneously, a convolutional neural network (CNN) model is constructed for comparison based on a previous advanced study in this field. Experimental results show that the proposed model can obtain the same accuracy as that of previously developed CNN models while requiring less data.

An Accurate Maritime Radio Propagation Loss Prediction Approach Employing Neural Networks

The radio propagation loss prediction model is essential for maritime communication. The oceanic tropospheric duct is much more complicated than the atmospheric structure on land due to the rough sea surface influence, and it leads to difficulties in loss prediction. Classical radio wave propagation loss prediction models are either based on complicated electromagnetic wave theories or rely on empirical data. Consequently, they suffer from low accuracy and a limited range of application. To address this issue, a novel maritime propagation loss prediction approach is proposed, which fully exploits the data for training. In this new approach, 3D sea surface contour profiles are generated based on the Pierson–Moskowitz spectrum theory and the direction expansion formula Stereo Wave Observation Program (SWOP), by sweeping the parameters. The full-wave propagation procedure of radio signals over the sea surface is simulated by commercial EM analysis software CST Studio Suite. Based on the large quantity of simulated data, the BP neural network is employed to fit the radio propagation loss and obtain the sea surface radio wave propagation prediction model. Other classical machine learning methods are also compared to validate the proposed approach. Traditional empirical model construction relies on observation data. This approach, for the first time, proposed an automatic scheme which covers the whole procedure from the data generation to prediction model training. It avoids the requirements for on-site observation, as well as significantly decreases the cost of experiments. The application scope of the prediction model such as propagation distance range and working frequency range could be adaptive through adjustments for simulated sea size and simulated working frequency. This approach is validated to save 99% of prediction time in comparison with the full-wave simulations. The prediction model trained via our proposed method could obtain the coefficient of determination R2 which is over 0.92, demonstrating the superiority of this method.

3D RT adaptive path sensing Method: RSSI modelling validation at 4.5 GHz, 28 GHz, and 38 GHz

This paper explains a new Adaptive Path Sensing Method (APSM) for indoor radio wave propagation prediction. Measurement campaigns, which cover indoor line-of-sight (LoS), non-line-of-sight (NLoS) and different room scenarios, are conducted at the new Wireless Communication Centre (WCC) block P15a) of Universiti Teknologi Malaysia (UTM), Johor, Malaysia. The proposed APSM is evaluated through a computerized modelling tool by comparing the Received Signal Strength Indicator (RSSI) with measurement data and the conventional Shooting-Bouncing Ray Tracing (SBRT) method. Simulations of the APSM and SBRT are performed with the same layout of the new WCC block P15a by using the exact building dimensions. The results demonstrate that the proposed method achieves a better agreement with measured data, compared to the conventional SBRT outputs. The reduced computational time and resources required are also important milestones to ray tracing technology. The proposed APSM method can assist engineers and researchers to reduce the time required in modelling and optimizing reliable radio propagation in an indoor environment.

Terrain Simplification Algorithm in Radio Wave Propagation Prediction

Terrain Simplification Algorithm in Radio Wave Propagation Prediction

Prediction method of SSPE propagation based on improved terrain reconstruction

In view of the difficulty of wave propagation prediction and analysis in complex environment, a propagation prediction method of split-step parabolic equation (SSPE) based on terrain reconstruction is proposed. This method uses a two-way SSPE solution with a wide-angle propagation factor and variable step size, and uses the SSPE propagation prediction method based on improved terrain reconstruction to simulate and test the radio wave propagation characteristics of real terrain. Compared with the existing radio wave propagation prediction method, this method combines real terrain, which improves the terrain modeling effect by improving the reconstruction algorithm, and uses variable step size two-way SSPE solution to predict the propagation loss. Simulation test results show that the prediction method is within 6 dB. The accuracy meets the requirements of a high-precision radio wave propagation model, indicating that the method has practical significance and popularization value.

Accurate prediction of radio wave propagation in an environment of dielectric ground and obstacles based on the principle of domain decomposition

To study the problem of radio wave propagation in an environment of dielectric ground and obstacles, especially in low-lossy obstacles, to consider the propagation inside the obstacle, a new method is proposed to solve the two-way parabolic equation based on the principle of domain decomposition. First, a mathematical model of parabolic equations for reflection and refraction in an environment with obstacles is established. Then, the area of the obstacle is decomposed into two different subdomains; the discrete mixed Fourier transform is used to calculate the field value in the upper subdomain from the top of the obstacle to the absorption boundary, the finite difference method is used to calculate the field value of the lower subdomain inside the obstacle, and the field strengths and phases of the two subdomains coordinate with the boundary conditions. In the process of calculation, we emphatically consider the multiple reflection and transmission paths inside obstacles to make the algorithm results more accurate. In addition, we verified the stability and convergence of the method. Finally, the simulation results show that the proposed method and the method of moments have good consistency, so the algorithm has the characteristics of strong applicability and fast calculation speed, which provide a novel and reliable method to research the wave propagation problem in a modified environment of obstacles.

A GPU-Based Radio Wave Propagation Prediction With Progressive Processing on Point Cloud

Point cloud data (PCD) can record a high-resolution model of the environment much more efficiently than the conventional geometrical mesh. This feature makes PCD suitable for the radio channel prediction of a new environment, especially for the millimeter-wave (mmWave). Since the multiple propagations and visibility computation using PCD are time consuming, progressive processing on PCD is introduced to make the prediction compatible with GPU-based frameworks such as OptiX and CUDA. Compared with the surface reconstruction from PCD, progressive data from the processing reserves more domain features such as diffraction wedge and the label of planar or nonplanar points. The numerical result of an outdoor environment shows that the proposed method has a close agreement with measurement, as well as two impressive speedups, 49.8 for the ray tracing and field calculation and 18.8 for the total prediction, compared with the original method using PCD.

An efficient cylindrical coordinate subgrid parabolic equation model for predicting the power distribution and coverage of radar signals in a complex multi‐scale marine environment

An efficient cylindrical coordinate subgrid parabolic equation model is proposed to predict the power distribution and coverage of radar signals in a complex multi-scale marine environment. The model adopts different grid systems for the multi-scale marine environment including flat sea surface, islands, ships and other elements, and realizes the transformation between grids through spatial mesh refinement technology. For the prediction of radio wave propagation in a large area complex environment, the model can balance the calculation efficiency and accuracy, thus effectively reducing the memory requirement and CPU computing time. In addition, combined with digital map and radar equation, the power distribution and coverage of radar signal in complex multi-scale marine environment are calculated. Numerical results verify the correctness and efficiency of the proposed model.

Correction of Radio Wave Propagation Prediction Model Based on Improved Seagull Algorithm in Tunnel Environment

In the urban rail transit (URT) environment, the radio wave propagation prediction model and communication system planning are very important. However, due to the complexity of the tunnel propagation environment, the current prediction model can not fully cover the radio wave propagation process in the tunnel. In this paper, the propagation mechanism area is divided based on the segmentation approach. Different propagation models are used for different propagation mechanism areas to predict path loss more quickly and accurately. To improve the accuracy of the prediction model, this paper proposes an improved seagull optimization algorithm (ISOA). First, to address the shortcomings of the seagull optimization algorithm (SOA) such as easy premature convergence and slow convergence speeds, two improved methods of random search and periodic disturbance are proposed. Then, in order to verify the effectiveness and feasibility of the improved algorithm, the benchmark function is used to test the optimization performance of the ISOA and gray wolf optimization, the SOA, and particle swarm optimization. The results show that the optimization performance of ISOA is the most significant. Finally, the ISOA is used to fit and correct the continuous wave test data for a rectangular tunnel and an arch tunnel. The results show that the corrected propagation model has a higher degree of fit with the measured data than the single standard propagation model (SPM) model. The modified propagation model thus has guiding significance for the deployment of time-division long-term (TD-LTE) evolution networks in the tunnel environment.

Path Loss Prediction Model Development in a Mountainous Forest Environment

We consider a method for developing a radio-wave propagation prediction model in a mountainous forested area. A new path loss development approach uses a free-space path loss (FSPL) model and an empirical path loss model. To improve the prediction accuracy, the transmission path distance, free space area, and forest area were calculated separately. We obtained the transmission path distance for free space and forest areas from the digital surface model (DSM), which represents surface elevation information, including vegetation and object height. In this study, the results showed that by combining the empirical model with FSPL for free space area, the accuracy for all the empirical models was improved. We confirmed that the transmission distance calculation of the free space area and forest area with a combination of the empirical models showed a better performance than the model with physical distance. The predicted model results were validated using the actual radio wave propagation in the 920 MHz band measurement data. The overall path loss prediction accuracy was improved for the empirical models average of 8.05 dB on the experimental data.

A Parallel FDTD/ADI-PE Method for Ultralarge-Scale Propagation Modeling of ILS Signal Analysis

In this letter, we propose a high-accuracy low-cost hybrid finite-difference time-domain (FDTD)/alternating-direction-implicit parabolic equation (ADI-PE) method for ultralarge-scale electromagnetic simulation on a distributed computing platform. The hybrid method offers fast and precise 3-D deterministic radio-wave propagation predictions in a difficult-terrain scenario with specific detailed structures in both near field and far field. Since the typical parallel ADI-PE method suffers from high-frequency data communication between different calculation cores, which greatly discount simulation efficiency in bandwidth-constrained environments, we adopt a Woodbury-formula-based parallel algorithm to find inverse matrixes of tridiagonal matrixes so that implicit and explicit steps of the PE can be finished in local computing cores. Simulation results for the instrument landing system (ILS) demonstrate the capability of the proposed method in achieving the state-of-the-art performance.

Prediction of Radio-Wave Propagation in a Shield Room: Measurement, Simulation, and Theoretical Method

In this paper, electromagnetic wave analysis was performed efficiently in a large structure using the theoretical method. While taking into consideration the important assumptions of the employed theoretical method, we created an environment for measurement and simulation. A shield room with an aperture was selected as the target structure, and a measurement system based on frequency domain was constructed and used. Using the simulation tool, Wireless Insite, electromagnetic wave analysis was performed by modeling the measurement environment. To verify the efficiency and accuracy of the theoretical method, the results of the actual measurement, the commercially available simulation tool, and the theoretical method were compared. These results showed that the theoretical method can be more efficiently interpreted than the commercially available simulation tool in an electrically large structure.

Indoor 3-D RT Radio Wave Propagation Prediction Method: PL and RSSI Modeling Validation by Measurement at 4.5 GHz

This article introduces an efficient analysis of indoor 4.5 GHz radio wave propagation by using a proposed three-dimensional (3-D) ray-tracing (RT) modeling and measurement. The attractive facilities of this frequency band have significantly increased in indoor radio wave communication systems. Radio propagation predictions by simulation method based on a site-specific model, such as RT is widely used to categorize radio wave channels. Although practical measurement provides accurate results, it still needs a considerable amount of resources. Hence, a computerized simulation tool would be a good solution to categorize the wireless channels. The simulation has been performed with an in-house developed software tool. Here, the 3-D shooting bouncing ray tracing (SBRT) and the proposed 3-D ray tracing simulation have been performed separately on a specific layout where the measurement is done. Several comparisons have been performed on the results of the measurement: the proposed method, and the existing SBRT method simulation with respect to received signal strength indication (RSSI) and path loss (PL). The comparative results demonstrate that the RSSI and the PL of proposed RT have better agreements with measurement than with those from the conventional SBRT outputs.

A New Permittivity Measurement Method for Walls in Indoor Scenes

A new double-reflection free-space method is presented in this paper for measuring the actual wall material permittivity in indoor scenes, especially for the narrow wall corners which cannot accommodate test settings used in the traditional free-space method. The method is nondestructive, accurate, and easy to implement. In addition, it does not require a priori knowledge of the thickness of the walls under test. Two experimental setups, namely, double-polarization and double-parameter free-space measurements, were conducted according to the proposed method. The presented technique acquires the accurate material permittivity on site, which is the key parameter in the modeling and simulation of the radio wave propagation (RWP) prediction. The permittivity of the walls in the buildings measured by the proposed method, which considers the influences from the aging, machining, and practical usage of the wall materials, is more accurate than that by sample test in the laboratory. The method was examined by measuring the permittivity of the designed wall corner with two perpendicular plates and validated by the waveguide measurement of the sample chosen from the tested plates. Finally, the explicit uncertainty and error analyses were derived. The proposed method is applicable for accurate modeling of RWP prediction in practice.

A novel 3D ray launching technique for radio propagation prediction in indoor environments.

Radio propagation prediction simulation methods based on deterministic technique such as ray launching is extensively used to accomplish radio channel characterization. However, the superiority of the simulation depends on the number of rays launched and received. This paper presented the indoor three-dimensional (3D) Minimum Ray Launching Maximum Accuracy (MRLMA) technique, which is applicable for an efficient indoor radio wave propagation prediction. Utilizing the novel MRLMA technique in the simulation environment for ray lunching and tracing can drastically reduce the number of rays that need to be traced, and improve the efficiency of ray tracing. Implementation and justification of MRLMA presented in the paper. An indoor office 3D layouts are selected and simulations have been performed using the MRLMA and other reference techniques. Results showed that the indoor 3D MRLMA model is appropriate for wireless communications network systems design and optimization process with respect to efficiency, coverage, number of rays launching, number of rays received by the mobile station, and simulation time.

Analysis and Verification of Core Factors in Radio Wave Propagation Loss

Radio wave propagation prediction can calculate the radio frequency link parameters such as field strength coverage and reception of power, which is an important foundation of electromagnetic compatibility (EMC) analysis and frequency coordination. This paper reviews the advances in the research of radio wave propagation by the International Telecommunication Union (ITU) and the International Radio Science Consortium (USRI), analyzes the core influencing factors related to the propagation of radio waves, including the propagation environment and the propagation model used in the calculation which EMC analysis system has been verified. The related content can provide reference for electromagnetic compatibility analysis and the border coordination.

A DECOMPOSITION METHOD FOR COMPUTING RADIOWAVE PROPAGATION LOSS USING THREE-DIMENSIONAL PARABOLIC EQUATION

The parabolic equation (PE) method is widely used in radiowave propagation predictions. It has the advantages of high efficiency and stability, but it will lead to greater predicting errors in some situations, because the effects of transverse terrain gradients are not modeled. This problem can be solved by extending the 2D PE to the three-dimensional (3D) PE. However, the computing efficiency will degrade because of large scale matrix operations. In this paper, a new method is presented, in which the 3D PE is decomposed into two 2D PEs. It increases the computational efficiency and accuracy effectively. To verify the capability of the proposed method in radiowave propagation prediction, an experiment platform was set up. The computational results using this new method are compared with the experimental and Method of Moment (MoM) numerical computational results. Good agreements are achieved in the comparison. The study of radiowave propagation under complex environments is vitally important for improving the effective signal coverage in wireless communication and television broadcasting with plenty of urban buildings as well as mountainous terrains. It presents a big challenge due to the multiple wave propagation mechanisms involving the line of sight, diffraction and scattering propagation and the characteristic of large scale computation. The major issues refer to how to keep the computational accuracy and conducting the large scale computation at the same time. To meet the request for large scale computation of actual engineering problems, the modified empirical formulas are often used for analysis and computation with the drawback of poor computational accuracy, and the variance of the predicted propagation loss is generally 2 to 5 dB for the flat terrain, but for the complex terrain, the variance of the predicted propagation loss is usually about 5 to 10 dB. Many computational methods have been developed to improve the predicted accuracy. The commonly used methods are geometric diffraction methods, path integration methods and FDTD. It is hard to meet the requirement of engineering computation because these methods are computationally expensive and require high data accuracy of the terrain database at the same time (1). The Parabolic Equation (PE) method is a computational method for radiowave propagation loss besides the full wave method and ray tracing method, and has become a research focus. The PE method has high potential in radiowave propagation of mobile communication and broadcasting and television signal coverage as it can not only deal with complex terrain boundary conditions accurately, but also deal with complex atmosphere waveguide structure. Compared with the full wave method, the PE method deals with an unidirectional wave propagation, in which the equation can be solved by the step marching method in the propagation direction. The PE method can reduce the computational complexity of the full wave equation.