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    Wyświetlanie 1-6 z 6
    Tytuł:
    Shallow Water Experiment of OFDM Underwater Acoustic Communications
    Autorzy:
    Kochańska, Iwona
    Schmidt, Jan H.
    Marszal, Jacek
    Powiązania:
    https://bibliotekanauki.pl/articles/177592.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    underwater acoustic communications
    UAC
    orthogonal frequency-division multiplexing
    OFDM
    Opis:
    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 a multi-carrier amplitude and phase modulation technique applied successfully in the latest standards of wireless communications, gives the chance of reliable communication with an acceptable error rate. This paper describes communication tests conducted with the use of a laboratory model of an OFDM data transmission system in a shallow water environment in Wdzydze Lake.
    Źródło:
    Archives of Acoustics; 2020, 45, 1; 11-18
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Performance of coherent modulation scheme used in acoustic underwater communication system
    Autorzy:
    Schmidt, Jan H.
    Schmidt, Aleksander M.
    Kochańska, Iwona
    Powiązania:
    https://bibliotekanauki.pl/articles/127757.pdf
    Data publikacji:
    2019
    Wydawca:
    Politechnika Poznańska. Instytut Mechaniki Stosowanej
    Tematy:
    underwater acoustic communications
    shallow underwater channel
    coherent modulation
    akustyczna komunikacja podwodna
    płytki kanał podwodny
    modulacja koherentna
    Opis:
    The development of an acoustic underwater communication system for shallow waters is still a big scientific and 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 a transmission system and the results of data transmission carried out by this system in the channel with the Rician fading, which reflects the short range shallow water channel. A digital version of the carrier phase modulation known as Phase-Shift Keying was selected for simulation.
    Źródło:
    Vibrations in Physical Systems; 2019, 30, 1; 1-8
    0860-6897
    Pojawia się w:
    Vibrations in Physical Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Synchronization system for underwater acoustic communications using in shallow waters
    Autorzy:
    Schmidt, Jan H.
    Schmidt, Aleksander M.
    Powiązania:
    https://bibliotekanauki.pl/articles/24201990.pdf
    Data publikacji:
    2023
    Wydawca:
    Politechnika Poznańska. Instytut Mechaniki Stosowanej
    Tematy:
    synchronization system
    underwater acoustic communications
    shallow water
    układy synchronizacji
    akustyczna komunikacja podwodna
    wody płytkie
    Opis:
    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. The method of receiving these signals has been described in detail. The stochastic channel model with Rician fading and the Watermark simulator was used to test the efficiency of the synchronization system in the underwater multipath channel.
    Źródło:
    Vibrations in Physical Systems; 2023, 34, 1; art. no. 2023102
    0860-6897
    Pojawia się w:
    Vibrations in Physical Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A new direct-sequence spread spectrum signal detection method for underwater acoustic communications in shallow-water channel
    Autorzy:
    Kochańska, Iwona
    Powiązania:
    https://bibliotekanauki.pl/articles/2146643.pdf
    Data publikacji:
    2021
    Wydawca:
    Politechnika Poznańska. Instytut Mechaniki Stosowanej
    Tematy:
    underwater acoustic communications
    UAC
    direct sequence spread spectrum
    DSSS
    akustyczna komunikacja podwodna
    bezpośrednie modulowanie nośnej sekwencją kodową
    Opis:
    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 for DSSS signal detection. It is based on the calculation of the correlation coefficient of adjacent segments of signal at the output of filter matched to the spreading sequence used in the transmitter. A positive value of the correlation coefficient means that a given modulation symbol carries the same information bit as the previous one; a negative value means that the opposite bit has been transmitted. The reliability of the proposed method has been compared to classical method of DSSS signal detection, which consists in detecting the information directly from the signal at the output of the matched filter. Simulation and measurement tests of underwater acoustic communications in strong multipath propagation conditions have shown that the proposed method allows obtaining lower values of the DSSS transmission Bit Error Rate (BER) than the classical detection technique while maintaining the same data transmission rate.
    Źródło:
    Vibrations in Physical Systems; 2021, 32, 1; art. no. 2021106
    0860-6897
    Pojawia się w:
    Vibrations in Physical Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Performance of the Direct Sequence Spread Spectrum Underwater Acoustic Communication System with Differential Detection in Strong Multipath Propagation Conditions
    Autorzy:
    Schmidt, Jan H.
    Kochańska, Iwona
    Schmidt, Aleksander M.
    Powiązania:
    https://bibliotekanauki.pl/articles/31339747.pdf
    Data publikacji:
    2024
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    direct sequence spread spectrum
    DSSS
    m-sequences
    Kasami codes
    shallow-water channel
    multipath propagation
    underwater acoustic communications
    UAC
    Opis:
    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 data transmission tests in the simulation and experimental environment, using different types of pseudo-noise sequences: m-sequences and Kasami codes of the order 6 and 8. The transmitted signals are of different bandwidth and the detection at the receiver side was performed using two detection methods: non-differential and differential. The performed experiments allowed to draw important conclusions for the designing of a physical layer of the shallow-water UAC system. Both, m-sequences and Kasami codes allow to achieve a similar bit error rate, which at best was less than 10−3. At the same time, the 6th order sequences are not long enough to achieve an acceptable BER under strong multipath conditions. In the case of transmission of wideband signals the differential detection algorithm allows to achieve a significantly better BER (less than 10−2) than nondifferential one (BER not less than 10−1). In the case of narrowband signals the simulation tests have shown that the non-differential algorithm gives a better BER, but experimental tests under conditions of strong multipath propagation did not confirm it. The differential algorithm allowed to achieve a BER less than 10−2 in experimental tests, while the second algorithm allowed to obtain, at best, a BER less than 10−1. In addition, two indicators have been proposed for a rough assessment which of the detection algorithms under current propagation conditions in the channel will allow to obtain a better BER.
    Źródło:
    Archives of Acoustics; 2024, 49, 1; 129-140
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Simulation of direct-sequence spread spectrum data transmission system for reliable underwater acoustic communications
    Autorzy:
    Kochańska, Iwona
    Schmidt, Jan H.
    Powiązania:
    https://bibliotekanauki.pl/articles/128008.pdf
    Data publikacji:
    2019
    Wydawca:
    Politechnika Poznańska. Instytut Mechaniki Stosowanej
    Tematy:
    underwater acoustic communications
    UAC
    direct sequence spread spectrum
    DSSS
    PRBS
    akustyczna komunikacja podwodna
    bezpośrednie modulowanie nośnej sekwencją kodową
    pseudolosowa sekwencja bitów
    Opis:
    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 of wireless communications, gives the chance of reliable data transmission with an acceptable error rate in a shallow underwater channel. It utilizes pseudo-random sequences to modulate data signals, and thus increases the transmitted signal resilience against the inter symbol interference (ISI) caused by multipath propagation. This paper presents the results of simulation tests of DSSS data transmission with the use of different UAC channel models using binary spreading sequences.
    Źródło:
    Vibrations in Physical Systems; 2019, 30, 1; 1-8
    0860-6897
    Pojawia się w:
    Vibrations in Physical Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-6 z 6

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