Wyniki wyszukiwania dla: SHALLOW UNDERWATER CHANNEL - MOST Wiedzy

Wyszukiwarka

Wyniki wyszukiwania dla: SHALLOW UNDERWATER CHANNEL

Wyniki wyszukiwania dla: SHALLOW UNDERWATER CHANNEL

  • Reliable OFDM Data Transmission with Pilot Tones and Error-Correction Coding in Shallow Underwater Acoustic Channel

    Publikacja

    The performance of Underwater Acoustic Communication (UAC) systems are strongly related to the specific propagation conditions of the underwater channel. Horizontal, shallow-water channels are characterised by extremely disadvantageous transmission properties, due to strong multipath propagation and refraction phenomena. The paper presents the results of communication tests performed during a shallow, inland-water experiment with...

    Pełny tekst do pobrania w portalu

  • A New Direct-Sequence Spread Spectrum Signal Detection Method for Underwater Acoustic Communications in Shallow-Water Channel

    Direct-Sequence Spread Spectrum (DSSS) is one of the modulation and coding techniques used in Underwater Acoustic Communication (UAC) systems for reliable data transmision even at low signal levels. However, in a shallow water channel, there is a strong multipath propagation which causes a phase fluctuation of the received signal, affecting the performance of the spread-spectrum system. The article presents a differential method...

    Pełny tekst do pobrania w portalu

  • Transmission properties of a shallow hydroacoustic channel.

    Publikacja

    - Rok 2004

    Wielokrotne odbicia fali akustycznej od granic ośrodka są przyczyną poważnych ograniczeń możliwości transmisyjnych w płytkich kanałach hydroakustycznych. Zastosowanie modelu BNM kanału, należącego do rezultatów międzynarodowego projektu PROSIM tworzonego w ramach inicjatywy MAST-III, pozwoliło obliczyć funkcje odpowiedzi impulsowych kanału i przeprowadzić symulację transmisji sygnału cyfrowego. Artykuł prezentuje wyniki transmisji...

  • Shallow Water Experiment of OFDM Underwater Acoustic Communications

    The large variability of communication properties of underwater acoustic channels, and especially the strongly varying instantaneous conditions in shallow waters, is a challenge for the designers of underwater acoustic communication (UAC) systems. The use of phase modulated signals does not allow reliable data transmission through such a tough communication channel. However, orthogonal frequency-division multiplexing (OFDM), being...

    Pełny tekst do pobrania w portalu

  • Reliable underwater communication system for shallow coastal waters

    Publikacja

    - HYDROACOUSTICS - Rok 2014

    This paper presents a reliable and robust low data rate spread spectrum approach which is implemented in the acoustic underwater communication system for shallow coastal waters. It shows operation assumptions of spread spectrum techniques based on the wellknown Shannon equation. It describes two methods of spread spectrum: frequency hopping spread spectrum and direct sequence spread spectrum; their block diagram and their characteristics...

    Pełny tekst do pobrania w portalu

  • UNDERWATER NOISE GENERATED BY A SMALL SHIP IN THE SHALLOW SEA

    Publikacja

    Study of the sea noise has been a subject of interest for years. The first work of this scope were published at the turn of the twentieth century by Knudsen (KNUDSEN et al., 1948) and G. Wenz (WENZ, 1962). Disturbances called "shipping noise" are one of the important components of the sea noise. In this work the results of an experimental research of underwater noise produced by a small ship of a classic propulsion are...

    Pełny tekst do pobrania w portalu

  • Synchronization system for underwater acoustic communications using in shallow waters

    A reliable synchronization system of the transmitted data frame has a significant impact on the efficiency of the underwater communication system. This applies in particular to communication systems dedicated to work in shallow waters, where the phenomenon of multipath permanently occurs. To overcome these difficulties, the concept of a synchronization system consisting of two broadband signals of opposite monotonicity was presented....

    Pełny tekst do pobrania w portalu

  • Estimation of Coherence Bandwidth for Underwater Acoustic Communication Channel

    Publikacja

    A shallow underwater acoustic communication channel is characterized by strong multipath propagation. The signal reaching the receiver consists of a direct waveform and a number of its delayed and suppressed replica. A significant time dispersion of the transmitted signal and selective fading of its spectrum are observed. Coherence bandwidth defines maximal bandwidth, wherein the channel amplitude characteristic remains constant...

    Pełny tekst do pobrania w serwisie zewnętrznym

  • Considerations of Adaptive Digital Communications in Underwater Acoustic Channel

    Publikacja

    Down-link communication (DLC) and air transportable communication (ATAC) buoys as well as autonomous underwater vehicles (AUV) use acoustic links for gathering oceanographic data from underwater monitoring systems. The underwater channel propagation conditions are diverse in nature and require a special adaptive approach to the communication system design. The article presents a methodology for the communication systems design,...

    Pełny tekst do pobrania w portalu

  • Tracking of the broadband source of the underwater noise in the very shallow water conditions

    Publikacja

    The paper contains the result s, both theoretical and experimental , connected with the tracking of the underwater noise source as small ships, pontoon , diver and so on. The pro blem of security in the shallow water area is the challenge for underwater acousticians. In this paper there is take n into account the detection of the sources that move on the surface of the sea or underwater in shallow...

    Pełny tekst do pobrania w portalu

  • Wake-Up Receiver for Underwater Acoustic Communication Using in Shallow Water

    Publikacja

    A data frame transmitted over the underwater acoustic channel usually begins with a preamble. Therefore, underwater communication systems have a dedicated receiver that constantly listens to the preamble signals. A receiver that is to work effectively in shallow waters must have solutions that effectively reduce the impact of the permanently occurring multipath propagation. The article presents a solution based on complementary...

    Pełny tekst do pobrania w portalu

  • Measurement of Impulse Response of Shallow Water Communication Channel by Correlation Method

    Performances of underwater acoustic communication (UAC) systems are strongly related to specific propagation conditions of the underwater channel; conditions that can additionally change in time due to the movement of the acoustic system transmitter and receiver or to reflection by underwater objects of the transmitted signal. The time-varying impulse response is a comprehensive description of dynamically changing transmission...

    Pełny tekst do pobrania w portalu

  • Underwater communication system for shallow water using modified MFSK modulation

    Publikacja

    Opisano budowę i zasadę działania systemu komunikacji podwodnej z modulacją MMFSK. System służy do przekazywania danych i komend ze statku do obiektów podwodnych w płytkich wodach przybrzeżnych i jeziorach. Priorytetowe wymagania postawione systemowi to bardzo małe zużycie energii w części podwodnej i bardzo mała liczba błędów transmisji. Szczególną uwagę zwrócono na nietypowe źródło błędów, jakim są zniekształcenia nieliniowe...

  • Limitations of WSSUS modeling of stationary underwater acoustic communication channel

    Publikacja

    - HYDROACOUSTICS - Rok 2016

    Performances of underwater acoustic communication (UAC) systems are strongly related to specific propagation conditions of the underwater channel. Due to their large variability, there is a need for adaptive matching of the UAC systems signaling to the transmission properties of the channel. This requires a knowledge of instantaneous channel characteristics, in terms of the specific parameters of stochastic models. The wide-sense...

    Pełny tekst do pobrania w portalu

  • Probe signal processing for channel estimation in underwater acoustic communication system

    Publikacja

    Underwater acoustic communication channels are characterized by a large variety of propagation conditions. Designing a reliable communication system requires knowledge of the transmission parameters of the channel, namely multipath delay spread, Doppler spread, coherence time, and coherence bandwidth. However, the possibilities of its estimation in a realtime underwater communication system are limited, mainly due to the computational...

    Pełny tekst do pobrania w serwisie zewnętrznym

  • ADAPTIVE IDENTIFICATION OF TIME-VARYING IMPULSE RESPONSE OF UNDERWATER ACOUSTIC COMMUNICATION CHANNEL

    Publikacja

    The transmission properties of underwater acoustic communication channel can change dynamically due to the movement of acoustic system transmitter and receiver or underwater objects reflecting transmitted signal. The time-varying impulse response measurement and estimation are necessary to match the physical layer of data transmission to instantaneous channel propagation conditions. Using the correlative measurement method, impulse...

    Pełny tekst do pobrania w portalu

  • A Method for Underwater Wireless Data Transmission in a Hydroacoustic Channel under NLOS Conditions

    Publikacja

    - SENSORS - Rok 2021

    Wireless data transmission in the hydroacoustic channel under non-line-of-sight (NLOS) propagation conditions, for example, during a wreck penetration, is difficult to implement reliably. This is mostly due to the multipath propagation, which causes a reduction in the quality of data reception. Therefore, in this work an attempt has been made to develop a reliable method of wireless underwater communication test it under the NLOS...

    Pełny tekst do pobrania w portalu

  • Adaptive Identification of Underwater Acoustic Channel with a Mix of Static and Time-Varying Parameters

    Publikacja

    - Rok 2022

    We consider the problem of identification of communication channels with a mix of static and time-varying parameters. Such scenarios are typical, among others, in underwater acoustics. In this paper, we further develop adaptive algorithms built on the local basis function (LBF) principle resulting in excellent performance when identifying time-varying systems. The main drawback of an LBF algorithm is its high complexity. The subsequently...

    Pełny tekst do pobrania w serwisie zewnętrznym

  • System identification theory-based estimation of underwater acoustic channel for broadband communications.

    Publikacja

    Płytki kanał podwodny jest niestacjonarny z powodu wielokrotnych odbić fal dźwiękowych od powierzchni wody oraz ruchu nadajnika i odbiornika systemu komunikacyjnego. Dla zapewnienia szybkiej transmisji danych niezbędna jest estymacja kanału oparta na equalizacji adaptacyjnej. W systemach komunikacji podwodnej stosowane są zazwyczaj equalizery DFE z zaimplementowanymi algorytmami najmniejszych kwadratów: LMS oraz RLS.W artykule...

  • Stationary underwater channel experiment: Acoustic measurements and characteristics in the Bornholm area for model validations

    Publikacja

    - HYDROACOUSTICS - Rok 2016

    The underwater acoustical channel is time-variant, and even on small time scales there is often existing no ‘acoustical frozen ocean’. Popular is the use of WSSUS-channel transmission modeling (Wide-Sense Stationary Uncorrelated Scattering) for the stochastic description of bandpass signals in GSM mobile phones with moving participants; since this results in a halved number of model parameters. For underwater sound applications...

    Pełny tekst do pobrania w portalu

  • A method for testing the wide-sense stationary uncorrelated scattering assumption fulfillment for an underwater acoustic channel

    Wide-sense stationary and uncorrelated scattering (WSSUS) assumptions are often applied for the statistical description of wireless communication channels. However, in the case of underwater acoustic channels the WSSUS model is of limited value. The degree of similarity of in-phase and quadrature components of the channel impulse response, measured with the use of bandpass modulated signals, can be used as an indicator of WSSUS...

    Pełny tekst do pobrania w serwisie zewnętrznym

  • Study of probe signal bandwidth influence on estimation of coherence bandwidth for underwater acoustic communication channel

    A signal transmitted in a shallow Underwater Acoustic Communication (UAC) channel suffers from time dispersion due to the multipath propagation and the refraction phenomena. This causes intersymbol interference of the received signal and frequency-selective fading observed in its spectrum. Coherence bandwidth is one of the key transmission parameters used for designing the physical layer of a data transmission system to minimise...

    Pełny tekst do pobrania w portalu

  • An analytical four-layer horizontal electric current dipole model for analysing underwater electric potential in shallow seawater

    Publikacja

    - Scientific Reports - Rok 2022

    The paper presents a new analytical four‑layer (air–water–bottom–non‑conductive layer) horizontal electric dipole model which allows an accurate approximation of ship’s Underwater Electric Potential (UEP) from a sufficient depth in shallow coastal marine waters. The numerical methods, usually Finite Element Method (FEM) or Boundary Elements Method (BEM), are typically used to estimate the electric field and the distribution of...

    Pełny tekst do pobrania w portalu

  • Assessment of Wide-Sense Stationarity of an Underwater Acoustic Channel Based on a Pseudo-Random Binary Sequence Probe Signal

    Publikacja

    The performances of Underwater Acoustic Communication (UAC) systems are strongly related to the specific propagation conditions of the underwater channel. Designing the physical layer of a reliable data transmission system requires a knowledge of channel characteristics in terms of the specific parameters of the stochastic model. The Wide-Sense Stationary Uncorrelated Scattering (WSSUS) assumption simplifies the stochastic description...

    Pełny tekst do pobrania w portalu

  • Performance of Coherent Modulation Scheme Used in Acoustic Underwater Communication System

    The development of an acoustic underwater communication system for shallow waters is still a big scientificand construction challenge. Currently, non-coherent modulations in combination with strong channel coding are used to achieve reliable communication with low rate in such a channel. To obtain transmission with a higher transmission rate, it is required to use coherent modulation. This paper presents the assumptions of such...

    Pełny tekst do pobrania w portalu

  • Simulation of Direct-Sequence Spread Spectrum Data Transmission System for Reliable Underwater Acoustic Communications

    Underwater acoustic communication (UAC) system designers tend to transmit as much information as possible, per unit of time, at as low as possible error rate. It is a particularly difficult task in a shallow underwater channel in which the signal suffers from strong time dispersion due to multipath propagation and refraction phenomena. The direct-sequence spread spectrum technique (DSSS) applied successfully in the latest standards...

    Pełny tekst do pobrania w portalu

  • Testing OFDM Transmission Schemes for Shallow Water Acoustic Communications

    Publikacja

    Large variability of communication properties of underwater acoustic channels, and especially strongly varying instantaneous conditions in shallow waters, is a tough challenge for the designers of underwater acoustics communication (UAC system. There is a need for developing adaptive signaling schemes that would dynamically optimize signal parameters in both physical and link layers of communication protocols. The orthogonal frequency...

  • Underwater acoustic communication system using broadband signal with hyperbolically modulated frequency

    The implementation of reliable acoustic underwater communication in shallow waters is a scientific and engineering challenge, mainly due to the permanent occurrence of the multipath phenomenon. The article presents the concept of a transmission system using a broadband signal with hyperbolically modulated frequency (HFM) to transmit data symbols and synchronize data frames. The simulation tests were carried out in channels with...

    Pełny tekst do pobrania w portalu

  • Measurements of transmission properties of Acoustic Communication Channels

    Publikacja

    Tough transmission properties of shallow water acoustic channels (SWAC) highly limit the use of underwater acoustic communication (UAC) systems. An adaptive matching of modulation and signaling schemes to instantaneous channel conditions is needed for reliabledata communications. This creates, however, unique challenges for designers when compared to radio transmission systems. When communication system elements are in move, the...

    Pełny tekst do pobrania w portalu

  • Performance of the Direct Sequence Spread Spectrum Underwater Acoustic Communication System with Differential Detection in Strong Multipath Propagation Conditions

    The underwater acoustic communication (UAC) operating in very shallow-water should ensure reliable transmission in conditions of strong multipath propagation, significantly disturbing the received signal. One of the techniques to achieve this goal is the direct sequence spread spectrum (DSSS) technique, which consists in binary phase shift keying (BPSK) according to a pseudo-random spreading sequence. This paper describes the DSSS...

    Pełny tekst do pobrania w portalu

  • Study of the Performance of DSSS UAC System Depending on the System Bandwidth and the Spreading Sequence

    A signal transmitted in an Underwater Acoustic Communication (UAC) system operating in a shallow-water channel suffers from strong time dispersion due to multipath propagation. This causes the Inter-Symbol Interference (ISI) observed in the received signal, which significantly limits the communication system’s reliability and transmission rate. In such propagation conditions, the Direct-Sequence Spread Spectrum (DSSS) method is...

    Pełny tekst do pobrania w portalu

  • Iwona Kochańska dr hab. inż.

    Iwona Kochańska jest absolwentką Wydziału Elektroniki, Telekomunikacji i Informatyki Politechniki Gdańskiej. Uzyskała tytuł zawodowy magistra inżyniera na kierunku Automatyka i Robotyka, specjalizując się w automatyce obiektów ruchomych. W 2012 roku uzyskała stopień doktora nauk technicznych w dyscyplinie telekomunikacja, w specjalności hydroakustyka. W tym samym roku rozpoczęła pracę na stanowisku adiunkta w Katedrze Systemów...

  • Transmission parameters of underwater communication channels

    Publikacja

    The underwater environment is tough and demanding as a communication channel for ultrasonic signals. The channel transmission characteristics in marine and inland waters depend much on local bathymetry and changing weather conditions. The architecture and performance of a reliable underwater acoustic communication (UAC) system should allow real-time adaptation of its transmission parameters to a large variety of possible channel...

    Pełny tekst do pobrania w portalu

  • Application of OFDM technique to underwater acoustic data transmission

    Publikacja

    Performances of underwater acoustic communication (UAC) digital systems are strongly related to specific transmission properties of the underwater channel. Depending on the characteristics of the channel, an architecture and modulation techniques are usually implemented that are known as reliable solutions for data transmission in difficult radio channels. The OFDM technique seems to be the most promising nowadays. The parameters...

    Pełny tekst do pobrania w portalu

  • Propagation of Ship-Generated Noise in Shallow Sea

    Contamination of sea environment by noise and any energy radiated to water constitutes today a problem to which more and more attention is paid, in view, a.o., of consequences of an impact of these factors onto marine fauna. European Union has introduced a directive by which EU countries are made responsible to undertake efforts aimed at reaching a good envirenmental status of European seas by 2020. A main source of underwater...

    Pełny tekst do pobrania w portalu

  • Theoretical Model of Acoustic Wave Propagation in Shallow Water

    The work is devoted to the propagation of low frequency waves in a shallow sea. As a source of acoustic waves, underwater disturbances generated by ships were adopted. A specific feature of the propagation of acoustic waves in shallow water is the proximity of boundaries of the limiting media characterised by different impedance properties, which affects the acoustic field coming from a source situated in the water layer “ deformed”...

    Pełny tekst do pobrania w portalu

  • Some aspects of noise generated by a small ship in the shallow sea

    Publikacja

    - Rok 2012

    The passing and underwater moving objects produce the noises of variable intensity, which significantly increase the overall level of noise in the sea. This applies to both the sonic and ultrasonic range. The excessive levels of underwater noise adversely affects the so-called underwater acoustic climate and is the reason why this phenomenon is intensively investigated from the number of years. The results of experimental work...

    Pełny tekst do pobrania w serwisie zewnętrznym

  • Underwater Acoustic Communications in Time-Varying Dispersive Channels

    Publikacja

    Underwater acoustic communication (UAC) system designers tend to transmit as much information as possible, per unit of time, at as low as possible error rate. However, the bit rate achieved in UAC systems is much lower than for wire or radio-communication systems. This is due to disadvantageous properties of the UAC channels, namely the sea and inland waters. Estimation of UAC channel transmission properties is possible within...

    Pełny tekst do pobrania w serwisie zewnętrznym

  • Testing the Wide-Sense Stationarity of Bandpass Signals for Underwater Acoustic Communications

    Publikacja

    - Rok 2017

    The Underwater Acoustic Communication (UAC) systems work in communication channels characterized by a large variety of multipath propagation conditions that can additionally change over time. Designing a reliable communication system requires knowledge of the transmission parameters of the channel. There is a need for the development of adaptive signaling schemes that would dynamically optimize the signal parameters of the physical...

  • Multiple-Input Multiple-Output Technique for Underwater Acoustic Communication System

    Publikacja

    The performance of an underwater acoustic communication (UAC) system is limited due to tough propagation conditions in the UAC channel. Multiple-Input Multiple-Output (MIMO) technique can improve the reliability of the data transmission system, increase its speed, increase its range, and reduce the energy consumption. The paper presents an implementation method of MIMO technique in the form of coding the Space-Time Block Code and...

    Pełny tekst do pobrania w serwisie zewnętrznym

  • Shipping Low Frequency Noise and Its Propagation in Shallow Water

    One of the most significant factor influencing acoustical climate of the sea is underwater noise generated by moving ships. If the considered sea area has features of the shallow water, namely the wave frequency fulfils relation f < 10c/h, where c denotes phase speed of sound, and h is depths of the sea, then in certain distance from the wave source specific image of sound pressure distribution in the mean of wave modes appears....

    Pełny tekst do pobrania w portalu

  • The development of an underwater telephone for digital communication purposes

    Publikacja

    - HYDROACOUSTICS - Rok 2016

    The underwater telephone HTL-10 has been designed to provide voice and data communication between helicopter and submarines using acoustic waves. It works in a half-duplex mode and uses analogue power-efficient modulation in the form of a single side-band, suppressed carrier, in a wide range of frequencies. It generates the transmitted signal, and processes the received signals. It is implemented with the use of digital signal...

    Pełny tekst do pobrania w portalu

  • Using Fast Frequency Hopping Technique to Improve Reliability of Underwater Communication System

    Publikacja

    Acoustic underwater communication systems designed to work reliably in shallow coastal waters must overcome major limitations such as multipath propagation and the Doppler effect. These restrictions are the reason for the complexity of receivers being built, whose task is to decode a symbol on the basis of the received signal. Additional complications are caused by the low propagation speed of the acoustic wave in the water and...

    Pełny tekst do pobrania w portalu

  • Balance errors in numerical solutions of shallow water equations

    Publikacja

    The analysis of the conservative properties of the shallow water equations is presented in the paper. The work focuses on the consistency of numerical solution of these equations with the conservation laws of mass and momentum. The investigations involve two different conservative forms which are solved by an implicit box scheme. The theoretical analysis supported by numerical experiments is carried out for rectangular channel...

    Pełny tekst do pobrania w portalu

  • ECHOES REDUCTION DURING DIGITAL DATA TRANSMISSION IN HYDROACOUSTIC CHANNEL – LABORATORY EXPERIMENT

    Publikacja

    - Rok 2019

    The possibility of using a hydroacoustic channel for digital data transmission is very limited. This is due to the effect of multipath propagation of the emitted acoustic wave and the damping of the mechanical wave in this medium, which increase with frequency. The first of these phenomena results in inter-symbol interference disturbances in data transmission systems, including even hundreds of symbols. Due to the number of reflections...

    Pełny tekst do pobrania w portalu

  • MSIS sonar image segmentation method based on underwater viewshed analysis and high-density seabed model

    Publikacja

    - Rok 2017

    High resolution images of Mechanically Scanned Imaging Sonars can bring detailed representation of underwater area if favorable conditions for acoustic signal to propagate are provided. However to properly asses underwater situation based solely on such data can be challenging for less than proficient interpreter. In this paper we propose a method to enhance interpretative potential of MSIS image by dividing it in to subareas depending...

    Pełny tekst do pobrania w serwisie zewnętrznym

  • An Integrated Approach to an Assessment of Bottlenecks for Navigation on Riverine Waterways

    Publikacja
    • M. Schoeneich
    • M. Habel
    • D. Szatten
    • D. Absalon
    • J. Montewka

    - Water - Rok 2023

    Water transport, both sea and inland, is the cheapest, least invasive, and safest option for non-standard loads; hence, it is important to increase the percentage share of inland waterway transport on the rivers of Central and Eastern Europe. Transporting cargo is particularly difficult on shallow waterways because rivers overloaded with sediment determine the vertical parameters on inland waterways. A ship’s safe manoeuvrability...

    Pełny tekst do pobrania w portalu

  • Analysis of Impulse Responses Measured in Motion in a Towing Tank

    Publikacja

    - Electronics - Rok 2022

    The growing interest in developing autonomous underwater vehicles (AUVs) and creating underwater sensor networks (USNs) has led to a need for communication tools in underwater environments. For obvious reasons, wireless means of communication are the most desirable. However, conducting research in real conditions is troublesome and costly. Moreover, as hydroacoustic propagation conditions change very significantly, even during...

    Pełny tekst do pobrania w portalu

  • Analysis of Impulse Responses Measured in Motion in a Towing Tank

    Publikacja

    - Rok 2023

    The growing interest in developing autonomous underwater vehicles (AUVs) and creating underwater sensor networks (USNs) has led to a need for communication tools in underwater environments. For obvious reasons, wireless means of communication are the most desirable. However, conducting research in real conditions is troublesome and costly. Moreover, as hydroacoustic propagation conditions change very significantly, even during...

    Pełny tekst do pobrania w serwisie zewnętrznym

  • Sensing Direction of Human Motion Using Single-Input-Single-Output (SISO) Channel Model and Neural Networks

    Publikacja

    - IEEE Access - Rok 2022

    Object detection Through-the-Walls enables localization and identification of hidden objects behind the walls. While numerous studies have exploited Channel State Information of Multiple Input Multiple Output (MIMO) WiFi and radar devices in association with Artificial Intelligence based algorithms (AI) to detect and localize objects behind walls, this study proposes a novel non-invasive Through-the-Walls human motion direction...

    Pełny tekst do pobrania w portalu