scholarly journals The interference immunity of decameter circuit with spatial interference compensation

2021 ◽  
pp. 109-114
Author(s):  
И.М. Орощук ◽  
В.В. Клоков
Keyword(s):  
Data Exchange ◽  
Channel Model ◽  
World Ocean ◽  
Experimental Studies ◽  
Interference Immunity ◽  
Interference Compensation ◽  
Spatial Method ◽  
Ionospheric Channel ◽  
Spatial Interference ◽  
Correlation Properties

В статье представлена оценка помехоустойчивости декаметрового канала связи, использующего пространственный метод компенсации естественных помех. Метод компенсации базируется на результаты экспериментальных исследований пространственно-корреляционных свойств сигналов и естественных помех декаметрового диапазона. Для реализации метода используется цифровая антенная решетка с пространственно-корреляционным методом обработки сигналов. Также в канале использована гауссовая амплитудная модуляция, формирующая шумоподобный сигнал с расширенной базой. Оценка помехоустойчивости построена на модели ионосферного канала с релеевскими замираниями с учетом пространственно-корреляционных свойств сигналов и естественных помех. Анализ проведенных исследований показал возможность компенсации помех за счет роста антенных элементов в антенной решетке, которая, как следствие, позволит повысить помехоустойчивость ионосферного декаметрового канала связи при низких отношениях уровней сигнал/шум на входе приемного тракта. Возможность обеспечения высокой помехоустойчивости в ионосферных декаметровых каналах позволит использовать новые виды связи для обмена данными в судами и кораблями ВМФ в пределах акваторий Мирового океана. The interference immunity assessment of the decameter circuit using a spatial method of natural interference compensation is presented. The compensation method is based on experimental studies results of spatial and correlation properties of decameter range signals and natural interference. For the method realization the digital array with a spatially-correlation signals processing method is used. Also in the channel the Gaussian amplitude modulation forming a noise-shaped signal with extended base is used. The interference immunity assessment is based on the ionospheric channel model with the Rayleigh fadings taking into account signals and natural interference spatially-correlation properties. The simulation findings showed the interference compensation possibility due to increase in antenna array elements which, as a result, will allow to increase the interference immunity of ionospheric decameter circuit at the low levels of signal/noise ratio in the reception path entrance. The possibility of ensuring high interference immunity in ionospheric decameter circuits will allow to use new communication types for data exchange with NAVY battleships and vessels within the World Ocean water areas.

scholarly journals Channel Modeling for Underwater Acoustic Network Simulation

2020 ◽  
Author(s):  
Nils Morozs ◽  
Wael Gorma ◽  
Benjamin Henson ◽  
Lu Shen ◽  
Paul Mitchell ◽  
...  
Keyword(s):  
Channel Model ◽  
Network Simulation ◽  
World Ocean ◽  
Empirical Evaluation ◽  
Channel Modeling ◽  
Protocol Design ◽  
Simulation Code ◽  
Modeling Tool ◽  
Underwater Acoustic ◽  
Underwater Acoustic Network

This manuscript was submitted to IEEE Access on 12 Jun 2020.<div><br></div><div>Abstract:</div><div><br></div><div>Simulation forms an important part of the development and empirical evaluation of underwater acoustic network (UAN) protocols. The key feature of a credible network simulation model is a realistic channel model. A common approach to simulating realistic underwater acoustic (UWA) channels is by using specialised beam tracing software such as BELLHOP. However, BELLHOP and similar modeling software typically require knowledge of ocean acoustics and a substantial programming effort from UAN protocol designers to integrate it into their research. In this paper, we bridge the gap between low level channel modeling via beam tracing and automated channel modeling, e.g. via the World Ocean Simulation System (WOSS), by providing a distilled UWA channel modeling tutorial from the network protocol design point of view. The tutorial is accompanied by our MATLAB simulation code that interfaces with BELLHOP to produce channel data for UAN simulations. As part of the tutorial, we describe two methods of incorporating such channel data into network simulations, including a case study for each of them: 1) directly importing the data as a look-up table, 2) using the data to create a statistical channel model. The primary aim of this paper is to provide a useful learning resource and modeling tool for UAN protocol researchers. Initial insights into the UAN protocol design and performance provided by the statistical channel modeling approach presented in this paper demonstrate its potential as a powerful modeling tool for future UAN research.<br></div>

scholarly journals Visual Collaboration Leader-Follower UAV-Formation for Indoor Exploration

2022 ◽  
Vol 8 ◽  
Author(s):  
Nikolaos Evangeliou ◽  
Dimitris Chaikalis ◽  
Athanasios Tsoukalas ◽  
Anthony Tzes
Keyword(s):  
Data Exchange ◽  
Experimental Studies ◽  
Field Of View ◽  
Detection Error ◽  
Data Packets ◽  
Communication Latency ◽  
Position Detection ◽  
Rf Communication ◽  
Constant Distance ◽  
Relative Pose

UAVs operating in a leader-follower formation demand the knowledge of the relative pose between the collaborating members. This necessitates the RF-communication of this information which increases the communication latency and can easily result in lost data packets. In this work, rather than relying on this autopilot data exchange, a visual scheme using passive markers is presented. Each formation-member carries passive markers in a RhOct configuration. These markers are visually detected and the relative pose of the members is on-board determined, thus eliminating the need for RF-communication. A reference path is then evaluated for each follower that tracks the leader and maintains a constant distance between the formation-members. Experimental studies show a mean position detection error (5 × 5 × 10cm) or less than 0.0031% of the available workspace [0.5 up to 5m, 50.43° × 38.75° Field of View (FoV)]. The efficiency of the suggested scheme against varying delays are examined in these studies, where it is shown that a delay up to 1.25s can be tolerated for the follower to track the leader as long as the latter one remains within its FoV.

Quantitative Study on Equivalent Roughness Conversion Coefficient and Roughness Effect of Centrifugal Compressor

2019 ◽  
Vol 142 (2) ◽  
Author(s):  
Yonghong Tang ◽  
Guang Xi ◽  
Zhiheng Wang ◽  
Yubao Tian
Keyword(s):  
Centrifugal Compressor ◽  
Conversion Coefficient ◽  
Channel Model ◽  
Experimental Studies ◽  
Weighted Average ◽  
Peak Efficiency ◽  
Centrifugal Compressors ◽  
Roughness Effect ◽  
Average Roughness ◽  
Roughness Model

Abstract Applying an appropriate roughness model is one of the most effective ways to improve the accuracy of the numerical simulation for centrifugal compressors, and it is also the key to the study of surface deterioration such as compressor fouling and corrosion. The basis for using the roughness model is to determine the conversion relation between physical roughness and equivalent roughness. In this paper, numerical and experimental studies on the roughness conversion relation for the centrifugal compressors were performed by means of a unique self-developed “pseudo front stage (PFS)” device. An equivalent roughness conversion coefficient of 8.5 was determined on the basis of fitting performance of the U-bend and return channel model. The validity of the conversion coefficient in improving the performance prediction accuracy of the centrifugal compressors was verified by three centrifugal compressor models. The concept of weighted average roughness was proposed to quantify the roughness sensitivity and roughness level of the centrifugal compressor. Quantitative research on the roughness effect of centrifugal compressors indicated that the peak efficiency degradation due to the roughness effect in the compressors was linearly associated with the logarithm of the relative roughness when the impeller of the centrifugal compressor was in the hydraulically rough regime. Doubling or halving the roughness value of all components of a centrifugal compressor in the hydraulically rough flow regime will result in a change in the peak efficiency of the compressor by about 1.72%.

scholarly journals Bioenergetics and growth in marine fish of the Arctic

2020 ◽  
Author(s):  
L. I. Karamushko ◽  
Keyword(s):  
Marine Fish ◽  
Marine Biology ◽  
World Ocean ◽  
Experimental Studies ◽  
The Arctic ◽  
Extensive Literature ◽  
Polar Regions ◽  
Functional Relationships ◽  
Adaptive Capabilities ◽  
High Level

The basis of the monograph is the long-term experimental research with the use of extensive literature material, which allowed to study the adaptive mechanisms of various forms of metabolic processes in Arctic marine fish species. The functional relationships between somatic and energy metabolism were revealed and it was shown that fish living in the polar regions of the World Ocean have low growth rates, basic metabolism and reproductive contribution, but a high level of adaptive capabilities aimed at the survival of the species. The results of experimental studies on the exposure to sub-lethal levels of waterborne petroleum on the metabolism in the Arctic cod Boreogadus saidaare presented.The book is supposed for the specialists in ecology, ichthyology, physiology and marine biology.

scholarly journals On the Cross Correlation Properties of MIMO Wideband Channels under Nonisotropic Propagation Conditions

2015 ◽  
Vol 2015 ◽  
pp. 1-13
Author(s):  
Ana Maria Pistea ◽  
Hamidreza Saligheh Rad
Keyword(s):  
Cross Correlation ◽  
Channel Model ◽  
Multiple Input Multiple Output ◽  
Evaluation Process ◽  
Frequency Selectivity ◽  
Power Spectral ◽  
Channel Bandwidth ◽  
Input Multiple Output ◽  
Propagation Pattern ◽  
Correlation Properties

Wideband (WB) and ultrawideband (UWB) systems combined with multiple-input multiple-output (MIMO) technology increase both the systems performances and the complexity of the channel models required to evaluate their capabilities. Because in real scenarios waves propagate nonisotropically, the accuracy of the channel model is increased if nonisotropic propagation is considered. The channel bandwidth is the key term in the evaluation process of these systems because large bandwidths introduce frequency selectivity, a unique phenomenon of WB and UWB systems with more complexity in the latter case. This is due to the fact that, unlike WB technology in which the propagating signal is the only affected parameter by the frequency selectivity, in the UWB case, this phenomenon also affects the antenna propagation pattern (APP). In this paper, we developed a novel channel model based on the statistical analysis of two-dimensional cross correlation functions (CCFs) of WB/UWB MIMO nonisotropic channels. A mathematical solution to assess the frequency selective behavior of the UWB APP is also presented. The CCF reveals how the power spectral density (PSD) of the channel is influenced by bandwidth, nonisotropic propagation, and APP.

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