Iwona Kochańska - Publications - Bridge of Knowledge

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Year 2017
  • 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...

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

    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...

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

    - Year 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...

Year 2016
  • Limitations of WSSUS modeling of stationary underwater acoustic communication channel
    Publication

    - HYDROACOUSTICS - Year 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...

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  • Mutual Clutter Suppression Techniques for FM Sonars

    The article presents methods that help in the elimination of mutual clutter as well as the consequences of two FM sounding signal sonars operating in the same body of water and frequency band. An in-depth analysis of mutual clutter was carried out. The effects of sounding signal differentiation were determined, as was the Doppler effect on mutual clutter suppression. One of the methods analysed is of particular interest in a situation...

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

    - HYDROACOUSTICS - Year 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...

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  • Underwater Acoustic Communications in Time-Varying Dispersive Channels
    Publication

    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...

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Year 2015
  • ADAPTIVE IDENTIFICATION OF TIME-VARYING IMPULSE RESPONSE OF UNDERWATER ACOUSTIC COMMUNICATION CHANNEL
    Publication

    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...

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  • PHONEME DISTORTION IN PUBLIC ADDRESS SYSTEMS
    Publication

    - Year 2015

    The quality of voice messages in speech reinforcement and public address systems is often poor. The sound engineering projects of such systems take care of sound intensity and possible reverberation phenomena in public space without, however, considering the influence of acoustic interference related to the number and distribution of loudspeakers. This paper presents the results of measurements and numerical simulations of the...

Year 2014
  • Distortion of speech signals in the listening area: its mechanism and measurements
    Publication

    - Year 2014

    The paper deals with a problem of the influence of the number and distribution of loudspeakers in speech reinforcement systems on the quality of publicly addressed voice messages, namely on speech intelligibility in the listening area. Linear superposition of time-shifted broadband waves of a same form and slightly different magnitudes that reach a listener from numerous coherent sources, is accompanied by interference effects...

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  • Ultrawideband transmission in physical channels: a broadband interference view
    Publication

    The superposition of multipath components (MPC) of an emitted wave, formed by reflections from limiting surfaces and obstacles in the propagation area, strongly affects communication signals. In the case of modern wideband systems, the effect should be seen as a broadband counterpart of classical interference which is the cause of fading in narrowband systems. This paper shows that in wideband communications, the time- and frequency-domain...

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Year 2013
  • Considerations of Adaptive Digital Communications in Underwater Acoustic Channel
    Publication

    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,...

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  • Testing OFDM Transmission Schemes for Shallow Water Acoustic Communications
    Publication

    - Year 2013

    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...

Year 2012
  • Measurements of transmission properties of Acoustic Communication Channels
    Publication

    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...

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  • Właściwości transmisyjne podwodnego kanału akustycznego
    Publication

    - Year 2012

    Właściwości transmisyjne podwodnego kanału akustycznego są silnie uwarunkowane specyfiką jego geograficznej lokalizacji i zmieniają się w czasie. Istnieje potrzeba, by w systemie niezawodnej komunikacji dopasowywać do nich parametry warstwy fizycznej protokołu transmisji danych. Do realizacji tego celu niezbędny jest sparametryzowany opis podwodnego kanału komunikacyjnego. W artykule przedstawiono wyniki pomiarów odpowiedzi impulsowych...

Year 2011
  • Application of OFDM technique to underwater acoustic data transmission
    Publication

    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...

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  • Technika adaptacyjnej OFDM w akustycznej komunikacji podwodnej

    Postęp w bezprzewodowej komunikacji szerokopasmowej jest rezultatem rozwoju cyfrowych technik modulacji i kodowania, coraz lepiej wykorzystujących możliwości kanałów radiowych i przezwyciężających ich fizyczne ograniczenia. Adaptacja metod transmisji danych do komunikacji podwodnej na falach akustycznych wymaga uwzględnienia specyficznych cech kanału hydroakustycznego, który łączy w sobie najtrudniejsze właściwości kanałów telekomunikacyjnych....

  • Transmission parameters of underwater communication channels
    Publication

    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...

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Year 2007
Year 2006
Year 2005
Year 2004
  • Transmission of digital signals in a nonstationary hydroacoustic channel.
    Publication

    - Year 2004

    Z telekomunikacyjnego punktu widzenia właściwości transmisyjne kanału hydroakustyczny są ograniczone przez występowanie wielokrotnych odbić fali dźwiękowej od dna i powierzchni wody oraz niestacjonarność wprowadzaną głównie przez ruch powierzchni wody. Artykuł przedstawia model własności transmisyjnych kanału. Wprowadzono niestacjonarność do odpowiedzi impulsowych kanału przez założenie przypadkowej zmienności czasów przyjścia...

  • Transmission properties of a shallow hydroacoustic channel.
    Publication

    - Year 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...

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