Doppler Compensation Algorithms for DSP-based Implementation of OFDM Underwater Acoustic Communication Systems PDF Download

Author: Ammar Ebdelmelik Abdelkareem
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Author: Lei Wan
Publisher:
ISBN:
Category :
Languages : en
Pages : 147

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Author: Sheng Zhou
Publisher: John Wiley & Sons
ISBN: 1118693817
Category : Science
Languages : en
Pages : 498

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Book Description
A blend of introductory material and advanced signal processing and communication techniques, of critical importance to underwater system and network development This book, which is the first to describe the processing techniques central to underwater OFDM, is arranged into four distinct sections: First, it describes the characteristics of underwater acoustic channels, and stresses the difference from wireless radio channels. Then it goes over the basics of OFDM and channel coding. The second part starts with an overview of the OFDM receiver, and develops various modules for the receiver design in systems with single or multiple transmitters. This is the main body of the book. Extensive experimental data sets are used to verify the receiver performance. In the third part, the authors discuss applications of the OFDM receiver in i) deep water channels, which may contain very long separated multipath clusters, ii) interference-rich environments, where an unintentional interference such as Sonar will be present, and iii) a network with multiple users where both non-cooperative and cooperative underwater communications are developed. Lastly, it describes the development of a positioning system with OFDM waveforms, and the progress on the OFDM modem development. Closely related industries include the development and manufacturing of autonomous underwater vehicles (AUVs) and scientific sensory equipment. AUVs and sensors in the future could integrate modems, based on the OFDM technology described in this book. Contents includes: Underwater acoustic channel characteristics/OFDM basics/Peak-to-average-ratio control/Detection and Doppler estimation (Doppler scale and CFO)/Channel estimation and noise estimation/A block-by-block progressive receiver and performance results/Extensions to multi-input multi-output OFDM/Receiver designs for multiple users/Cooperative underwater OFDM (Physical layer network coding and dynamic coded cooperation)/Localization with OFDM waveforms/Modem developments A valuable resource for Graduate and postgraduate students on electrical engineering or physics courses; electrical engineers, underwater acousticians, communications engineers

Author: Robert Istepanian
Publisher: Springer Science & Business Media
ISBN: 1475736177
Category : Technology & Engineering
Languages : en
Pages : 283

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Book Description
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.

Author: Xilin Cheng
Publisher: Springer
ISBN: 3319332074
Category : Technology & Engineering
Languages : en
Pages : 116

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Following underwater acoustic channel modeling, this book investigates the relationship between coherence time and transmission distances. It considers the power allocation issues of two typical transmission scenarios, namely short-range transmission and medium-long range transmission. For the former scenario, an adaptive system is developed based on instantaneous channel state information. The primary focus is on cooperative dual-hop orthogonal frequency division multiplexing (OFDM).This book includes the decomposed fountain codes designed to enable reliable communications with higher energy efficiency. It covers the Doppler Effect, which improves packet transmission reliability for effective low-complexity mirror-mapping-based intercarrier interference cancellation schemes capable of suppressing the intercarrier interference power level. Designed for professionals and researchers in the field of underwater acoustic communications, this book is also suitable for advanced-level students in electrical engineering or computer science.

Author: Seyedhabib Mirhedayati Roudsari
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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This thesis focuses on time-varying Doppler compensation for underwater acoustic communications using an orthogonal frequency division multiplexing (OFDM) system. An underwater acoustic channel simulator is developed based on the geometry of the system deployment and by considering the statistics of the random variation of the channel. This channel simulator is capable of modelling any relative motion between the transmitter and receiver. The effect of the underwater acoustic (UWA) channel on OFDM system is studied by incorporating a model in system level simulation of the communication link. The time-varying Doppler compensation method is then introduced as an innovative method which is able to compensate for Doppler shift due to time-varying relative velocity between the transmitter and receiver. Finally, the proposed Doppler compensation method is integrated to an ultrasonic OFDM system and the communication reliability is evaluated through simulations and measurements in realistic deployment conditions. Specifically, for a distance of 150 m a net throughput after synchronization, channel estimation and decoding 760 bit/s was demonstrated with a bit error rate of 0.035 for a low SNR of 5.5 dB. More importantly, it will be shown that the assessment of the communication performance realized using simulations is very close to that of the measured performance.

Author: Milica Stojanovic
Publisher:
ISBN:
Category : Orthogonal frequency division multiplexing
Languages : en
Pages :

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Book Description
An adaptive algorithm is proposed for OFDM signal detection on Doppler-distorted, time-varying multipath channels. The focus of the approach is on low complexity post-FFT signal processing. The receiver performs MMSE combining of signals received across an array, using adaptive channel estimation. Non-uniform Doppler compensation across subbands is performed using a single adaptively estimated parameter representing the Doppler rate. Algoirthm performance is demonstrated on experimental data, transmitted through a shallow water channel over the distance of 2.5 km. QPSK modulation with a varying number of carriers is used in a 24 kHz acoustic bandwidth. Excellent performance is achieved with up to 1024 carriers, yielding an overall bit rate of 30 kbps.

Author: Gell Tiger Lee Pittman
Publisher:
ISBN:
Category : Algorithms
Languages : en
Pages : 187

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Book Description
The primary thrust of this thesis is the development of a computer-based simulation of an Orthogonal Frequency Division Multipexing (OFDM) based underwater acoustic communication system. The product will support the testing and evaluation of various digital signal processing algorithms applicable to underwater acoustic communication system using OFDM as well as the study of the effects of acoustic channel and communication system factors of the key parameters of the system such as bit error rate, received signal to noise ratio, frequency band of employment and overall system bit rate. The underwater acoustic sound channel is modeled using a physics based parabolic equation approximation. The simulation models the key components in the transmitter and receiver that contribute to the overall performance of the system. The results of the thesis provide expected values for system performance in terms of bit rate, bit error rate and received SNR for given frequency bands and are validated through comparison to theoretically derived expectations and to ocean testing of OFDM underwater communication systems.

Author: Saed Daoud
Publisher:
ISBN:
Category :
Languages : en
Pages : 115

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Book Description
In this thesis we consider Orthogonal Frequency Division Multiplexing (OFDM) technique by taking into account in the receiver design the fundamental and unique characteristics of Underwater Acoustic (UWA) channels in the context of Relay-Assisted (RA) systems. In particular, OFDM technique is used to combat the problem of Intersymbol Interference (ISI), while to handle the Intercarrier Interference (ICI), a pre-processing unit is used prior to the Minimum Mean Squared Error (MMSE) frequency-domain equalization called Multiple Resampling (MR), which minimizes the effect of time variation. This pre-processor consists of multiple branches, each corresponds to a Doppler scaling factor of a path/user/cluster, and performs of frequency shifting, resampling, and Fast Fourier Transform (FFT) operation. As a suboptimal alternative to MR pre-processing, Single Resampling (SR) pre-processing is also used to reduce the effect of ICI in the system, and it consists of only one branch that performs frequency shifting, resampling, and FFT operation, which corresponds to one approximated resampling factor, that is a function of one or more of the actual Doppler scaling factors. The problem of bandwidth scarcity is considered in the context of Two Way Relaying (TWR) systems in an attempt to increase the bandwidth efficiency of the system, while the problem of fading is considered in the context of Distributed Space-Time Block Coding (D-STBC) to boost the system reliability. Also, joint TWR-D-STBC system is proposed to extract the advantages of both schemes simultaneously. Second, motivated by the fact that OFDM is extremely sensitive to time variation, which destroys the orthogonality between the subcarriers, we consider another candidate to UWA channels and competitor to OFDM scheme, namely, block-based Single Carrier (SC) modulation with Frequency Domain Equalization (FDE). We start by the Point-to-Point (P2P) systems with path-specific Doppler model and Multiple Access Channel (MAC) system with user-specific Doppler model. The Maximum Likelihood (ML) receiver in each case is derived, and it is shown that a MR pre-processing stage is necessary to handle the effect of time variation, as it is the case in OFDM. Different from OFDM, however, the structure of this pre-processing stage. Specifically, it consists of multiple branches and each branch corresponds to a Doppler scaling factor per path or per user, and performs frequency shifting, resampling, and followed by and integration. FFT operation is not a part of the pre-processor. The goal of this pre-processing stage is to minimize the level of time variation in the time domain. So, the output of the pre-processor will still be time-varying contaminated by ISI, and hence an equalization stage is required. To avoid the complexity of the optimum Maximum Likelihood Sequence Detector (MLSD), we propose the use of MMSE FDE, where the samples are transformed to the frequency domain by means of FFT operation, and after the FDE transformed back to the time domain, where symbol-by-symbol detection becomes feasible. Also, the channels are approximated such that all paths or all users have the same Doppler scaling factor, and the pre-processing stage in this case consists of only one branch and it is called SR. Having the basic structure of SC-FDE scheme, we then consider the corresponding schemes that are considered for OFDM systems, namely: TWR, D-STBC, and TWR-D-STBC schemes. A complete complexity analysis, bandwidth efficiency, and extensive Average Bit Error Rate (ABER) simulation results are given. It is shown that MR schemes outperforms its SR counterparts within a given signaling scheme (i.e., OFDM or SC-FDE). However, this superiority in performance comes at the expense of more hardware complexity. Also, for uncoded systems, MR-SC-FDE outperforms its OFDM counterpart with less hardware complexity, because in SC-FDE systems, FFT operation is not part of the MR pre-processor, but rather a part of the equalizer. Finally, under total power constraint, it is shown that TWR-D-STBC scheme serves as a good compromise between bandwidth efficiency and reliability, where it has better bandwidth efficiency with some performance loss compared to D-STBC, while it has better performance and the same bandwidth efficiency compared to TWR.

Author: Baosheng Li
Publisher:
ISBN:
Category : Orthogonal frequency division multiplexing
Languages : en
Pages :

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Book Description
Underwater acoustic channels are wideband in nature due to the fact that the signal bandwidth is not neglibible with respect to the center frequency. OFDM transmissions over UWA channels encounter frequency-dependent Doppler drifts that destroy the orthogonality among OFDM subcarriers. In this paper, we propose a two-step approach to mitigating the frequency-dependent Doppler drifts in zero-padded OFDM transmissions over fast-varying channels: (1) non-uniform Doppler compensation via resampling that converts a "wideband" problem into a "narrowband" problems; and (2) high-resolution uniform compensation on the residual Doppler. Based on block-by-block processing, our receiver does not rely on channel dependence across OFDM blocks, and is thus desirable for fast-varying UWA channels. We test our receiver with data from a shallow water experiment at Buzzards Bay, Massachusetts. Our receiver achieves excellent performance even when the transmitter and the receivers have a relative speed up to 10 knots, where the Doppler drifts are several times larger than the OFDM subcarrier spacing.