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Algorithm of Creating Propagation Attenuation Maps Based on Parabolic Equation Method
Modern wireless communication systems use various technological solutions to increase the efficiency of created radio networks. This efficiency also applies to radio resources. Currently, the utilization of a radio environment map (REM) is one of the directions allowing to improve radio resource management. The REM is increasingly used in emerging mobile ad-hoc networks (MANETs), in particular military tactical networks. In this case, the use of new technologies such as software-defined radio and network, cognitive radio, radio sensing, and building electromagnetic situational awareness made it possible to implement REM in tactical MANETs. Propagation attenuation maps (PAMs) are crucial REM elements that allow for determining the ranges of radio network nodes. In this paper, we present a novel algorithm for PAM based on a parabolic equation method (PEM). The PEM allows determining the signal attenuation along the assumed propagation direction. In this case, we consider terrain topography to obtain a more realistic analysis. Then, we average the adjacent attenuation profiles defined for the selected directions in places where attenuation has not been calculated. To this aim, linear regression is applied. Finally, we define several metrics that allow for the accuracy assessment of determining the PAM as a function of its dimensions.
Radio environment maps (REMs) are beginning to be an integral part of modern mobile radiocommunication systems and networks, especially for ad-hoc, cognitive, and dynamic spectrum access networks. The REMs will use emerging military systems of tactical communications. The REM is a kind of database used at the stage of planning and management of the radio resources and networks, which considers the geographical features of an area, environmental propagation properties, as well as the parameters of radio network elements and available services. At the REM, for spatial management of network nodes, various methods of propagation modeling for determining the attenuation and capacity of wireless links and radio ranges are used. One method of propagation prediction is based on a numerical solution of the wave equation in a parabolic form, which allows considering, i.a., atmospheric refraction, terrain shape, and soil electrical parameters. However, the determination of a current altitudinal profile of atmospheric refraction may be a problem. If the propagation-prediction model uses a fixed refraction profile, then the calibration of this model based on empirical measurements is required. We propose a methodology for calibrating the analyzed model based on an example empirical research scenario. The paper presents descriptions of the propagation model, test-bed and scenario used in measurements, and obtained signal attenuation results, which are used for the initial calibration of the model.
In this paper, we present the dependency between density of a sensor network and map quality in the radio environment map (REM) concept. The architecture of REM supporting military communications systems is described. The map construction techniques based on spatial statistics and transmitter location determination are presented. The problem of REM quality and relevant metrics are discussed. The results of field tests for UHF range with a different number of sensors are shown. Exemplary REM maps with different interpolation algorithms are presented. Finally, the problem of density of a sensor network versus REM map quality is analyzed.
Cognitive Radio (CR) usually performs an analysis of the existing environment, enabling collection of all information on current spectrum use and available resources, to decide on its own transmission parameters to optimize communication performance. From practical point of view, the principal task of spectrum sensing is an efficient detection of different types of signals. This paper presents behavior of Sensing Client (SC) as a logical block of Supervisor (SP) in CR node, to obtain information about backup channels' ranking list. Methodology of creation, refreshing the ranking list of backup channels and change of used channel by SP are the main goals of this research. The ranking list of backup channels is based on spectrum sensing results collected by all nodes according to predefined sensing policy, enabling different sensing schemes like detector type, number of slots for sensing, sensing period etc. Channels with the highest positions on the ranking list are potential backup channels, used in case of jamming, interferences from legacy systems, decreasing link quality caused by nodes positions changes etc. To analyze behavior of SC, several simulation scenarios were developed. All tests were performed for CR network topology with presence of jammers and interferences from other users. Presented results are based on CORASMA simulator.
Radio environment maps (REMs) and geolocation database represent an important source of information for the operation of cognitive radio networks, replacing or complementing spectrum sensing information. This paper provides a survey of methods for constructing the radio frequency layer of radio environment map (RF-REM) using distributed measurements of the signal levels at a given frequency in space and time. The signal level measurements can be obtained from fixed or mobile devices capable of sensing radio environment and sending this information to the REM. The signal measurements are complemented with information already stored in different REM content layers. The combined information is applied for estimation of the RF-REM layer. The RF-REM construction methods are compared, and their advantages and disadvantages with respect to the spatial distribution of signal measurements and computational complexity is given. This survey also indicates possible directions of further research in indirect RF-REM construction methods. It emphasizes that accurate RF-REM construction methods should in the best case support operation with random and clustered signal measurements, their operation should not be affected by measurements outliers, and it must estimate signal levels comparably on all RF-REM locations with moderate computational effort.
http://www.itiis.org/download.jsp?filename=TIIS%20Vol%208,%20No%2011-8.pdf
An important contribution to the literature that introduces powerful new methods for modeling and simulating radio wave propagation
A thorough understanding of electromagnetic wave propagation is fundamental to the development of sophisticated communication and detection technologies. The powerful numerical methods described in this book represent a major step forward in our ability to accurately model electromagnetic wave propagation in order to establish and maintain reliable communication links, to detect targets in radar systems, and to maintain robust mobile phone and broadcasting networks.
The first new book on guided wave propagation modeling and simulation to appear in nearly two decades, Radio Wave Propagation and Parabolic Equation Modeling addresses the fundamentals of electromagnetic wave propagation generally, with a specific focus on radio wave propagation through various media. The authors explore an array of new applications, and detail various virtual electromagnetic tools for solving several frequent electromagnetic propagation problems. All of the methods described are presented within the context of real-world scenarios typifying the differing effects of various environments on radio-wave propagation. This valuable text:
Addresses groundwave and surface wave propagation
Explains radar applications in terms of parabolic equation modeling and simulation approaches
Introduces several simple and sophisticated MATLAB scripts
Teaches applications that work with a wide range of electromagnetic, acoustic and optical wave propagation modeling
Presents the material in a quick-reference format ideal for busy researchers and engineers
Radio Wave Propagation and Parabolic Equation Modeling is a critical resource for electrical, electronics, communication, and computer engineers working on industrial and military applications that rely on the directed propagation of radio waves. It is also a useful reference for advanced engineering students and academic researchers.
Wireless sensor networks are an increasingly popular tool for monitoring various environmental parameters. They can also be used for monitoring the electromagnetic spectrum. Wireless sensors, due to their small size, typically have simplified radio receivers with reduced sensitivity and use small antennas. As a result, their effective performance area is similarly limited. This is especially important in urban areas where there are various kinds of adverse propagation phenomena related to area coverage. The aim of this paper is to present the phenomena in the wireless sensor networks and propose criteria and methods to optimize their deployment to ensure maximizing the probability of detection of emissions, minimization of unmonitored areas, and to provide the necessary hardware redundancy in the priority areas. Influence of detection parameters, number of sensors and range constraints between sensors on received outcomes are also presented.
Any new design of a reasonably sophisticated radio should incorporate certain SDR features. The additional up-front time and costs incurred to add flexibility and programmability will be recouped by reducing the number of design changes later and a potentially larger market.
The parabolic equation (PE) method is proposed to model millimeter-wave propagation in rain medium. The rain medium is treated as an anisotropy mixture comprising of spherical and ellipsoidal raindrops with different sizes in atmosphere. Taking into account the effects of size, distribution, temperature, and shape of the raindrops on the dielectric property, we introduce an analytical formula for the effective permittivity of the rain medium. The PE model for estimating rain attenuation is developed via revising the refractive index by the effective permittivity. The values of specific rain attenuation predicted by the model agree well with those obtained by the ITU-R model, which verifies the accuracy of our method. Finally, the PE model is applied to simulate the propagation characteristics of millimeter wave in rain over irregular terrain.
Latest regulations on TV white space communications and trend toward spectrum access through geolocation databases relax the regulatory constraints on cognitive radios. Radio environment map (REM) is a kind of improved geolocation database and an emerging topic with the latest regulations on TV white space communications. It constructs a comprehen- sive temperature map of the cognitive radio network operation area by utilizing multi-domain information from geolocation databases, characteristics of spectrum use, geographical terrain models, propagation environment, and regulations. REMs act as cognition engines by building long-term knowledge via processing spectrum measurements collected from sensors to estimate the state of locations without any measurement data. Active transmitter LocatIon Estimation based REM con- struction technique is proposed and compared with the well-known REM construction techniques such as Kriging and inverse distance weighted interpolation in shadow and multipath fading channels. The simulation results suggest that the LocatIon Estimation based REM construction outperforms the compared methods in terms of RMSE and correct detection zone ratio by utilizing additional information about channel parameters that can be estimated by classical least squares method easily.
* Chapter 1: Introduction * Chapter 2: Parabolic equation framework * Chapter 3: Parabolic equation algorithms * Chapter 4: Tropospheric radiowave propagation * Chapter 5: Rays and modes * Chapter 6: Oversea propagation * Chapter 7: Irregular terrain modelling * Chapter 8: Domain truncation * Chapter 9: Impedance boundary modelling * Chapter 10: Propagation over the rough sea surface * Chapter 11: Hybrid methods * Chapter 12: Two-dimensional scattering * Chapter 13: Three-dimensional scattering for the scalar wave equation * Chapter 14: Vector PE * Appendices
This paper addresses the use of parabolic equation in radiowave propagation problems involving impedance-boundary modeling. The Fourier split-step technique for solving the parabolic equation provides numerical efficiency but lacks the ability to represent complex boundary conditions. A method that makes use of the domain decomposition technique to solve two-dimensional problems of impedance-boundary modeling using the Fourier split-step technique is introduced. A test case, using an urban scenario represented by buildings with various electrical parameters, was used to validate the results given by the method with results obtained by geometrical optics
For mobile ad hoc networks used in network-centric operations, there is a growing need for a systematic methodology for analyzing/predicting the performance of the network over the mission duration. With the advance in cognitive networking as a possible means of exploiting unused spectrum, there is now a growing need to study how to design a cognitive network using an automated methodology. In this article we study the concepts and challenges for automatic design/ reconfiguration of cognitive MANETs. We describe the design objectives, imposed constraints, and involved parameters in MANETs. We describe how cognitive techniques can be employed to exploit the unused spectrum in military architectures. We then discuss the challenges facing the design/reconfiguration of a cognitive network and their implications at different network layers. We also describe possible implementation options for designing MANETs that employ cognitive features at all layers.
Creating radio environment maps (REMs) based on various path loss models
- M Kryk
Electromagnetic situation awareness building in ad-hoc networks with cognitive nodes
- P Skokowski