Download or read book The Use of M Sequences to Optimize Underwater Acoustic Communications in Shallow Waters written by Fabio B. Louza and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The relationship between dynamic ocean acoustic fluctuations and the underwater communication in shallow waters acoustic propagation channels will be investigated, as they present a challenging environment for the transmission of information, causing inter-symbol interference (ISI) and multipath signal spreading and fading. The study and simulations will be based on data from an upwelling monitoring buoy located in the shallow waters of Arraial do Cabo -- Brazil. The focus of this thesis is to perform a systematic analysis of the role of the internal waves and upwelling on phase stability of a signal propagating through the channel, in terms of temporal coherence, using the Monterey-Miami parabolic equation (MMPE) model, and compare two approaches to optimize communication systems: prediction and/or measurement of the channel pulse responses. The first one is based on previous predicted pulse responses, given by MMPE and a matched or inverse filter to retrieve the message through multipath recombination. However, as filtering results begin to erode with time, one can estimate the refresh time of the filters necessary to keep up with real time varying sound speed profiles in these shallow waters. The second approach uses a simultaneous background experiment to directly measure and update the channel pulse response while collecting the message, based on "training pulse response measurements", classic low intensity M-sequences. Finally, the process called Hyperslice Cancellation by Coordinate Zeroing (HCCO) (Chang, 1992) will be performed to eliminate interferences between the M-sequences and the original messages.

Download or read book Digital Underwater Acoustic Communications written by Lufen Xu and published by Academic Press. This book was released on 2016-09-16 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: Digital Underwater Acoustic Communications focuses on describing the differences between underwater acoustic communication channels and radio channels, discusses loss of transmitted sound in underwater acoustic channels, describes digital underwater acoustic communication signal processing, and provides a comprehensive reference to digital underwater acoustic communication equipment. This book is designed to serve as a reference for postgraduate students and practicing engineers involved in the design and analysis of underwater acoustic communications systems as well as for engineers involved in underwater acoustic engineering. Introduces the basics of underwater acoustics, along with the advanced functionalities needed to achieve reliable communications in underwater environment Identifies challenges in underwater acoustic channels relative to radio channels, underwater acoustic propagation, and solutions Shows how multi-path structures can be thought of as time diversity signals Presents a new, robust signal processing system, and an advanced FH-SS system for multimedia underwater acoustic communications with moderate communication ranges (above 20km) and rates (above 600bps) Describes the APNFM system for underwater acoustic communication equipment (including both civil and military applications), to be employed in active sonar to improve its performance

Download or read book Design and Development of Underwater Acoustic Modem for Shallow Waters and Short Range Communication written by Vinay Divakar and published by GRIN Verlag. This book was released on 2014-09-05 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: Master's Thesis from the year 2014 in the subject Engineering - Naval Engineering, Ocean Engineering, , course: Electronics Systems Design, language: English, abstract: The existing underwater acoustic modems are designed for deep oceans and long range communication leading to immense consumption of power and high cost. These long range underwater acoustic modems are not suitable choice for deployment in underwater sensor networks, Hence the problem was chosen to design and develop a underwater acoustic modems that operates in shallow waters of depth below 100m and for a short range of below 100 m. Underwater wireless sensor network is contemporary technology that can be applied in the fields of security, surveillance, military, commercial, industrial and environmental. The major drawback is that the traditional underwater acoustic modems cannot be deployed for underwater sensor networks. This work focusses on the research and development of the underwater acoustic modem for shallow waters and short range communication. The relevant background theory required understand acoustics and for modelling the unique characteristics of the underwater channel is described in detail. Different concepts to model and implement the functionalities of the transmitter and receiver were explored, while converging to the most suitable choice of concepts. The modelled system is simulated for different channel conditions such as depth, range and induced ambient noise. The results were analysed in order to conclude the performance outcome of the system. The modelled system can efficiently operate for a depth of 30m, 50m and 70m for a range up to 50m. The hardware was developed using minimum number of components as a proof of concept for efficient data transmission and reception using acoustic signals. The hardware was tested to operate efficiently in air, however hardware tests for underwater is suggested for future work, which will provide much better performance since acoustics is more suitable for communication in water than air.

Download or read book Encyclopedia of Ocean Engineering written by Weicheng Cui and published by Springer Nature. This book was released on 2022-06-29 with total page 2203 pages. Available in PDF, EPUB and Kindle. Book excerpt: This encyclopedia adopts a wider definition for the concept of ocean engineering. Specifically, it includes (1) offshore engineering: fixed and floating offshore oil and gas platforms; pipelines and risers; cables and moorings; buoy technology; foundation engineering; ocean mining; marine and offshore renewable energy; aquaculture engineering; and subsea engineering; (2) naval architecture: ship and special marine vehicle design; intact and damaged stability; technology for energy efficiency and green shipping; ship production technology; decommissioning and recycling; (3) polar and Arctic Engineering: ice mechanics; ice-structure interaction; polar operations; polar design; environmental protection; (4) underwater technologies: AUV/ROV design; AUV/ROV hydrodynamics; maneuvering and control; and underwater-specific communicating and sensing systems for AUV/ROVs. It summarizes the A–Z of the background and application knowledge of ocean engineering for use by ocean scientists and ocean engineers as well as nonspecialists such as engineers and scientists from all disciplines, economists, students, and politicians. Ocean engineering theories, ocean devices and equipment, ocean design and operation technologies are described by international experts, many from industry and each entry offers an introduction and references for further study, making current technology and operating practices available for future generations to learn from. The book also furthers our understanding of the current state of the art, leading to new and more efficient technologies with breakthroughs from new theory and materials. As the land resources approach the exploitation limit, ocean resources are becoming the next choice for the sustainable development. As such, ocean engineering is vital in the 21st century.

Download or read book Emerging Directions in Embedded and Ubiquitous Computing written by Mieso Denko and published by Springer. This book was released on 2007-11-27 with total page 852 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book constitutes the refereed proceedings of the EUC 2007 workshops held in conjunction with the IFIP International Conference on Embedded and Ubiquitous Computing, EUC 2007, in Taipei, Taiwan, in December 2007. The 69 revised full papers presented together with four invited papers were carefully reviewed and selected from about 200 submissions to the seven workshops. A broad range of topics are covered.

Download or read book Underwater Sound Propagation and Acoustic Communication in a Time varying Shallow Estuarine Environment written by Zheguang Zou and published by . This book was released on 2018 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: Estuaries are water regions that connect rivers and oceans, which are very important due to heavy traffic, fishery and other coastal engineering activities. Underwater acoustic technology offers a series of effective applications and technical supports for real-time monitoring and long-term preservation of the nature environment and ecosystem in these regions. However, estuaries are shallow waters with complicated temporal and spatial environmental variability, involving a variety of physical oceanographic processes, such as tidal water mixing and ocean winds/waves, which can significantly influence the underwater sound propagation and moreover, underwater acoustic communications. In order to perform reliably and effectively in such complex time-varying shallow-water ocean environments, next-generation underwater acoustic communication systems need an all new design based on the environmental variability of the physical ocean, which takes the environmental physics and time-varying variability into account and is able to adapt and switch to the optimal mode as the environment evolves. Therefore, a deep, comprehensive and thorough understanding of the link between the time-varying ocean environment, underwater acoustic channel, and underwater acoustic communication systems is highly required. ☐ This dissertation investigated the relationship between the shallow-water, time-varying environment of estuaries, the underwater sound propagation and underwater acoustic communications, which can help the design of underwater acoustic systems so that they can adapt the time-varying environment with wiser parameter configurations. In this dissertation, field data analysis, joint numerical modeling, together with a controllable laboratory experiment were used to study acoustic channel variability of a shallow estuary and its influence on the performance of underwater acoustic communications. This dissertation included four aspects: (a) Effect of water-column variation due to the tidal dynamics in an estuary on the underwater acoustic direct path; (b) Effect of time-varying surface roughness due to the wind-driven waves on underwater acoustic surface paths; (c) Numerically modeling the effect of time-varying wind-driven shallow-water waves on coherent underwater acoustic communications using a combined model; (d) Conducting a controllable laboratory experiment to investigate the time-varying wind-driven water waves on the performance of coherent and non-coherent underwater acoustic communications. ☐ The first two aspects focused on the link between the time-varying environment of an estuary and the underwater acoustic wave propagation. With field data analysis and joint numerical modeling, the time-varying variability of acoustic direct paths and surface-bounced paths from a high-frequency acoustic experiment conducted in the Delaware Bay estuary was explored. On one hand, periodical acoustic direct path fading was found in the tidal-straining Delaware Bay estuary, with the fading period as same as the semi-diurnal tide. Based on physical oceanography and ocean acoustics, the mechanism that causes the direct path fading and its link to the water dynamics of an estuary was investigated. On the other hand, the relationship between the acoustic surface paths and the surface wind speed was investigated, and the wind-influenced shallow-water time-varying channel was studied using field data analysis and a joint model combining physical oceanography and ocean acoustics. The joint numerical model, including a wind-wave model, a surface generation algorithm and a parabolic equation acoustic model, reproduced the relationship between the wind speed and surface reflection signals. ☐ The last two aspects applied the knowledge of underwater sound propagation in shallow estuaries into analyzing the performance of underwater acoustic communication systems, i.e., investigating how the fast fluctuation of a shallow-water environment (wind-driven waves) influences different fundamental modulation schemes for underwater acoustic communications. To better analyze the effect of environmental variability of the physical ocean on underwater acoustic communications, the surface condition was set as the only variation in the numerical modeling and the controllable laboratory experiment. On one hand, a combined model including physical oceanography, ocean acoustics, and underwater acoustic communication was used to study the time-varying underwater acoustic channel under different wind speeds, and the performance of the coherent acoustic communication (QPSK) system. On the other hand, a controllable laboratory experiment was conducted to investigate bit-error-rate (BER) performance of the MFSK (representing the non-coherent acoustic communication) and the QPSK (representing the coherent acoustic communication) acoustic modulations. ☐ The main conclusions of the dissertation are as follows. For the time-varying variability of underwater acoustic channel: (a) Due to the tidal-straining water dynamics of an estuary, periodical water column exchange between the seawater and the freshwater, up-refracting sound speed profile is more likely to form by the end of ebb tide, which redirects sound signal away from the deep receivers and creates shadow zone for the sound direct path; (b) In an open estuary, the acoustic pressure of surface-bounced paths decreases with increased wind speed, as a result of increased acoustic scattering due to the wind-driven surface roughness. For underwater acoustic communications: (c) Coherent acoustic communications are sensitive to the fast time-varying variability, and performance decrease significantly with increased wind speed, as a result of increased channel variability and decreased temporal coherence; (d) Non-coherent acoustic communications are less sensitive to the channel variability, and the reduced multipath signals due to wind-wave surface may improve the system performance. ☐ The key novelties of this dissertation include: (a) Using a joint model involving physical oceanography and ocean acoustics to study the effect of time-varying estuarine environment (water-column variations and wind-driven surface waves) on underwater sound propagation and the underwater acoustic channels. (b) Using an integrated model involving physical oceanography, ocean acoustics, and underwater acoustic communications to study the effect of time-varying estuarine environment (wind-driven surface waves) on underwater acoustic communications. (c) Using field experimental data, numerical modeling and controllable laboratory experiment to study the underwater sound propagation and underwater acoustic communications in a time-varying ocean environment.

Download or read book Underwater Acoustic Digital Signal Processing and Communication Systems written by Robert Istepanian and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 283 pages. Available in PDF, EPUB and Kindle. Book excerpt: Underwater acoustic digital signal processing and communications is an area of applied research that has witnessed major advances over the past decade. Rapid developments in this area were made possible by the use of powerful digital signal processors (DSPs) whose speed, computational power and portability allowed efficient implementation of complex signal processing algorithms and experimental demonstration of their performance in a variety of underwater environments. The early results served as a motivation for the development of new and improved signal processing methods for underwater applications, which today range from classical of autonomous underwater vehicles and sonar signal processing, to remote control underwater wireless communications. This book presents the diverse areas of underwater acoustic signal processing and communication systems through a collection of contributions from prominent researchers in these areas. Their results, both new and those published over the past few years, have been assembled to provide what we hope is a comprehensive overview of the recent developments in the field. The book is intended for a general audience of researchers, engineers and students working in the areas of underwater acoustic signal processing. It requires the reader to have a basic understanding of the digital signal processing concepts. Each topic is treated from a theoretical perspective, followed by practical implementation details. We hope that the book can serve both as a study text and an academic reference.

Download or read book Handbook of Computer Networks and Cyber Security written by Brij B. Gupta and published by Springer Nature. This book was released on 2019-12-31 with total page 957 pages. Available in PDF, EPUB and Kindle. Book excerpt: This handbook introduces the basic principles and fundamentals of cyber security towards establishing an understanding of how to protect computers from hackers and adversaries. The highly informative subject matter of this handbook, includes various concepts, models, and terminologies along with examples and illustrations to demonstrate substantial technical details of the field. It motivates the readers to exercise better protection and defense mechanisms to deal with attackers and mitigate the situation. This handbook also outlines some of the exciting areas of future research where the existing approaches can be implemented. Exponential increase in the use of computers as a means of storing and retrieving security-intensive information, requires placement of adequate security measures to safeguard the entire computing and communication scenario. With the advent of Internet and its underlying technologies, information security aspects are becoming a prime concern towards protecting the networks and the cyber ecosystem from variety of threats, which is illustrated in this handbook. This handbook primarily targets professionals in security, privacy and trust to use and improve the reliability of businesses in a distributed manner, as well as computer scientists and software developers, who are seeking to carry out research and develop software in information and cyber security. Researchers and advanced-level students in computer science will also benefit from this reference.

Download or read book Underwater Acoustic Channel Estimation Using Multiple Sources and Receivers in Shallow Waters at Very high Frequencies written by Samar Kaddouri and published by . This book was released on 2015 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: The underwater channel poses numerous challenges for acoustic communication. Acoustic waves suffer long propagation delay, multipath, fading, and potentially high spatial and temporal variability. In addition, there is no typical underwater acoustic channel; every body of water exhibits quantiably different properties. Underwater acoustic modems are traditionally operated at low frequencies. However, the use of broadband, high frequency communication is a good alternative because of the lower background noise compared to low-frequencies, considerably larger bandwidth and better source transducer efficiency. One of the biggest problems in the underwater acoustic communications at high frequencies is time-selective fading, resulting in the Doppler spread. While many Doppler detection, estimation and compensation techniques can be found in literature, the applications are limited to systems operating at low frequencies contained within frequencies ranging from a few hundred Hertz to around 30 kHz. This dissertation proposes two robust channel estimation techniques for simultaneous transmissions using multiple sources and multiple receivers (MIMO) that closely follows the rapidly time-varying nature of the underwater channel. The first method is a trended least square (LS) estimation that combines the traditional LS method with an empirical modal decomposition (EMD) based trend extraction algorithm. This method allows separating the slow fading modes in the MIMO channels from the fast-fading ones and thus achieves a close tracking of the channel impulse response time fluctuations. This dissertation also outlines a time-varying underwater channel estimation method based on the channel sparsity characteristic. The sparsity of the underwater communication channel is exploited by using the MIMO P-iterative greedy orthogonal matching pursuit (MIMO-OMP) algorithm for the channel estimation. Both techniques are demonstrated in a fully controlled environment, using simulated and experimental data. To test the proposed channel estimation techniques, an acoustic model for a MIMO channel is developed using the method of images applied to a completely closed three-dimensional duct with a pressure release surface boundary and five rigid walls. The MIMO simulated channel provides the strength and delay of all echoes forming the channel. Both simulation and experimental results show a signicant improvement in the estimation of the channel impulse response, thus validating the two proposed algorithms.

Download or read book Combined Spatial Diversity and Time Equalization for Broadband Multiple Channel Underwater Acoustic Communications written by Violeta Skoro Kaskarovska and published by . This book was released on 2015 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: High data rate acoustic communications become feasible with the use of communication systems that operate at high frequency. The high frequency acoustic transmission in shallow water endures severe distortion as a result of the extensive intersymbol interference and Doppler shift, caused by the time variable multipath nature of the channel. In this research a Single Input Multiple Output (SIMO) acoustic communication system is developed to improve the reliability of the high data rate communications at short range in the shallow water acoustic channel. The proposed SIMO communication system operates at very high frequency and combines spatial diversity and decision feedback equalizer in a multilevel adaptive configuration. The first configuration performs selective combining on the equalized signals from multiple receivers and generates quality feedback parameter for the next level of combining. The second configuration implements a form of turbo equalization to evaluate the individual receivers using the feedback parameters as decision symbols. The improved signals from individual receivers are used in the next iteration of selective combining. Multiple iterations are used to achieve optimal estimate of the received signal. The multilevel adaptive configuration is evaluated on experimental and simulated data using SIMO system with three, four and five receivers. The simulation channel model developed for this research is based on experimental channel and Rician fading channel model. The performance of the channel is evaluated in terms of Bit Error Rate (BER) and Signal-to-Noise-and-Interference Ratio (SNIR). Using experimental data with non-zero BER, multilevel adaptive spatial diversity can achieve BER of 0 % and SNIR gain of 3 dB. The simulation results show that the average BER and SNIR after multilevel combining improve dramatically compared to the single receiver, even in case of extremely high BER of individual received signals. The results demonstrate the ability of the proposed multilevel adaptive combining approach to significantly improve the performance of the shallow water acoustic channel, while preserving the same transmission power and channel bandwidth.

Download or read book High rate Digital Acoustic Communications in a Shallow Water Channel written by Young-hoon Yoon and published by . This book was released on 1999 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The subject of this dissertation is coherent digital acoustic communication in the underwater environment. The objective of the research is to develop algorithms for reliable communication in the shallow underwater channel. Investigation is focused on channel depth less than 100 m and distances between transmitter and receiver from 5 km to 50 km. Based on the characteristics of the underwater acoustic channel and using a conventional approach, the achievable transmission range and the required acoustic power is determined for given channel conditions and system parameters. A channel model suitable for the investigation of shallow water communication is developed which takes into account transmitter-receiver geometry, environmental conditions and system parameters. The model is based on multiple reflections in the channel with weightings according to signal attenuation due to spreading, reflection losses and absorption. Time-variability is introduced by incorporating Doppler frequency shifts due to transmitter/receiver motion. A new method of evaluating performance of a system operating in such multipath conditions is proposed by introduction of a signal-to-multipath ratio (SMR), which is a measure of intersymbol interference (ISI) caused by the multipath. The SMR allows assessment of system performance for various receiver/transmitter positions and channel parameters. It can be used, for instance, to find the transmitter/receiver depth for optimum transmission. A suitable equalizer can improve a SMR. For example, a decision feedback equalizer (DFE) using a least mean square (LMS) and fast optimized LMS criterion is effective in coping with ISI as demonstrated by computer simulations. Hardware complexities of several equalizer algorithms are investigated for a selected channel. The performance degradation due to the presence of Gaussian noise in addition to multipath is analyzed by simulation. A novel structure of an equalizer suitable for the time-variant underwater acoustic channel is proposed. By adaptively adjusting the number of equalizer taps depending on the channel condition, the proposed structure offers reduced hardware complexity. Computer simulations demonstrate the effectiveness of this approach. It is anticipated that the results of this work will find application in the design of high data rate transmission systems for ocean bottom instrumentation, the design of telemetry for autonomous underwater vehicles, and others.

Download or read book 6GN for Future Wireless Networks written by Ao Li and published by Springer Nature. This book was released on 2023-07-07 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt: This 2-volume set constitutes the proceedings of the 5th International Conference on 6G for Future Wireless Networks, 6GN 2022, held in Harbin, China, in December 2022. The 60 full papers were selected from 194 submissions and present the state of the art and practical applications of 6G technologies. The papers are arranged thematically in tracks as follows: Resource Allocation for 6G Networks; Security and Privacy for 6G Networks; Big data mining and pattern analysis techniques for 6G Networks; Artificial intelligent techniques for 6G Networks; Mobile Edge Computing for 6G Networks; Unmanned Aerial Vehicle Communication for 6G Networks.

Download or read book Analysis and Optimization of OFDM Underwater Acoustic Communications written by Xiaopeng Huang and published by . This book was released on 2011 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Channel Equalization for Wireless Communications written by Gregory E. Bottomley and published by John Wiley & Sons. This book was released on 2012-01-03 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: The most thorough, up-to-date reference on channel equalization—from basic concepts to complex modeling techniques In today's instant-access society, a high premium is placed on information that can be stored and communicated effectively. As a result, storage densities and communications rates are being pushed to capacity, causing information symbols to interfere with one another. To help unclog pathways for the clearer conveyance of information, this book offers in-depth discussion of the significant contributions and future adaptability of channel equalization and a set of approaches for solving the problem of intersymbol interference (ISI). Chapter explorations in Channel Equalization include: Channel equalization topics presented with incremental learning methodology—from the very fundamental concept to more advanced mathematical knowledge Coverage of technology used in second-, third- and fourth-generation cellular communication systems A set of homework problems that reinforce concepts discussed in the book Tutorial explanations of recent developments currently captured in IEEE technical journals Unlike existing digital communications books that devote cursory attention to channel equalization, this invaluable guide addresses a crucial need by focusing solely on the background, current state, and future direction of this increasingly important technology. A unique mix of basic concepts and complex frameworks for delivering digitized data make Channel Equalization a valuable reference for all practicing wireless communication engineers and students dealing with the pressing demands of the information age.

Download or read book Wiley Encyclopedia of Telecommunications Volume 4 written by John G. Proakis and published by Wiley-Interscience. This book was released on 2003 with total page 576 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Contains 275 tutorial articles focused on modern telecommunications topics. The contents include articles on communication networks, source coding and decoding, channel coding and decoding, modulation and demodulation, optical communications, satellite communications, underwater acoustic communications, radio propagation, antennas, multiuser communications, magnetic storage systems, and a variety of standards"--V.1, p. v.

Download or read book Springer Handbook of Acoustics written by Thomas Rossing and published by Springer Science & Business Media. This book was released on 2007-06-21 with total page 1179 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is an unparalleled modern handbook reflecting the richly interdisciplinary nature of acoustics edited by an acknowledged master in the field. The handbook reviews the most important areas of the subject, with emphasis on current research. The authors of the various chapters are all experts in their fields. Each chapter is richly illustrated with figures and tables. The latest research and applications are incorporated throughout, including computer recognition and synthesis of speech, physiological acoustics, diagnostic imaging and therapeutic applications and acoustical oceanography. An accompanying CD-ROM contains audio and video files.

Download or read book Underwater Acoustic Sensor Networks written by Yang Xiao and published by CRC Press. This book was released on 2010-05-19 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt: A detailed review of underwater channel characteristics, Underwater Acoustic Sensor Networks investigates the fundamental aspects of underwater communication. Prominent researchers from around the world consider contemporary challenges in the development of underwater acoustic sensor networks (UW-ASNs) and introduce a cross-layer approach for effec