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1
Content available Modeling the Geometry of an Underwater Channel for Acoustic Communication
100%
Naman H. A. , Abdelkareem A. E.
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tom nr 4
3--12
EN
The achievement of efficient data transmissions via underwater acoustic channels, while dealing with large data packets and real-time data fed by underwater sensors, requires a high data rate. However, diffraction, refraction, and reflection phenomena, as well as phase and amplitude variations, are common problems experienced in underwater acoustic (UWA) channels. These factors make it difficult to achieve high-speed and long-range underwater acoustic communications. Due to multipath interference caused by surface and ocean floor reflections, the process of modeling acoustic channels under the water’s surface is of key importance. This work proposes a simple geometry-based channel model for underwater communication. The impact that varying numbers of reflections, low water depth values, and distances between the transmitter and the receiver exert on channel impulse response and transmission loss is examined. The high degree of similarity between numerical simulations and actual results demonstrates that the proposed model is suitable for describing shallow underwater acoustic communication environments.
2
Content available Shallow Water Experiment of OFDM Underwater Acoustic Communications
100%
Kochańska I. , Schmidt J. H. , Marszal J.
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2020
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tom Vol. 45, No. 1
11--18
EN
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.
3
Content available Underwater acoustic communication system using broadband signal with hyperbolically modulated frequency
75%
Schmidt J. H. , Schmidt A. M.
Vibrations in Physical Systems
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2021
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tom Vol. 32, nr 1
art. no. 2021116
EN
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 Rician fading, reflecting the short- and medium-range shallow water channels. The simulation also took into account the presence of additive Gaussian noise in the channel on the functioning of the receiver. The obtained results prove the high reliability of the underwater communication system based on broadband HFM signals.
4
Content available Performance of coherent modulation scheme used in acoustic underwater communication system
75%
Schmidt J. H. , Schmidt A. M. , Kochańska I.
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tom Vol. 30, nr 1
art. no. 2019135
EN
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.
5
Analiza możliwości wykorzystania współczesnych metod transmisji danych w systemach łączności podwodnej
63%
Lasota H. , Kochańska I.
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tom Vol. 48, nr 9
53-56
PL
Postęp w telekomunikacji szerokopasmowej jest rezultatem rozwoju cyfrowych technik modulacji i kodowania, coraz lepiej wykorzystujących możliwości i przezwyciężających fizyczne ograniczenia przewodowych torów transmisyjnych i kanałów radiowych. Adaptacja metod transmisji danych do komunikacji podwodnej na falach akustycznych wymaga uwzględnienia specyficznych cech kanału hydroakustycznego, który łączy w sobie najtrudniejsze cechy kanałów telekomunikacyjnych. W celu pokazania możliwości wykorzystania w łączności podwodnej osiągnięć współczesnej telekomunikacji dokonano porównania istotnych własności kanałów radiowych, przewodowych i podwodnych. Wytypowano techniki modulacji stosowane w szybkich szerokopasmowych łączach telekomunikacyjnych, których aplikacja w łączności podwodnej wydaje się najbardziej uzasadniona.
EN
The progress in broadband telecommunications results from the development of digital modulation and coding techniques that are better and better matched to communication capabilities and physical limitations of cable and radio transmission channels. The adaptation of data transmission methods to underwater acoustic communications needs to consider specific features of hydroacoustic channels as they shear the most difficult features of telecommunication channels. A short comparison of radio, cable and underwater channels has been made for analysis of possibility of data transmission in underwater environment possibilities. Modulation techniques used in fast broad­band telecommunication links, that seem to be suitable for underwater communications, has been indicated.
6
Content available Erratum: A new direct-sequence spread spectrum signal detection method for underwater acoustic communications in shallow-water channel (DOI: 10.21008/j.0860-6897.2021.1.06)
63%
Kochańska I.
Vibrations in Physical Systems
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2022
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tom Vol. 33, nr 1
art. no. 2022114
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