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  • Articles  (100)
  • 2015-2019  (100)
  • 2015  (100)
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  • Articles  (100)
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  • 2015-2019  (100)
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  • 1
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    2015 Index IEEE Journal of Oceanic Engineering Vol. 40 (2015)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2015-12-25
    Description: This index covers all technical items - papers, correspondence, reviews, etc. - that appeared in this periodical during the year, and items from previous years that were commented upon or corrected in this year. Departments and other items may also be covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author's name. The primary entry includes the co-authors' names, the title of the paper or other item, and its location, specified by the publication abbreviation, year, month, and inclusive pagination. The Subject Index contains entries describing the item under all appropriate subject headings, plus the first author's name, the publication abbreviation, month, and year, and inclusive pages. Note that the item title is found only under the primary entry in the Author Index.
    Print ISSN: 0364-9059
    Electronic ISSN: 1558-1691
    Topics: Architecture, Civil Engineering, Surveying , Physics
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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  • 2
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    Editorial: Special Issues (2015)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2015-10-13
    Print ISSN: 0364-9059
    Electronic ISSN: 1558-1691
    Topics: Architecture, Civil Engineering, Surveying , Physics
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  • 3
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    IEEE Journal of Oceanic Engineering publication information (2015)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2015-10-13
    Print ISSN: 0364-9059
    Electronic ISSN: 1558-1691
    Topics: Architecture, Civil Engineering, Surveying , Physics
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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  • 4
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    Guest Editorial: Special Collection of Papers Arising From UComms14 (2015)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2015-10-13
    Print ISSN: 0364-9059
    Electronic ISSN: 1558-1691
    Topics: Architecture, Civil Engineering, Surveying , Physics
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  • 5
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    Robust Equalization of Mobile Underwater Acoustic Channels (2015)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2015-10-13
    Description: Several underwater acoustic channels exhibit impulsive ambient noise. As a consequence, communication receivers implemented on the basis of the Gaussian noise assumption may yield poor performance even at moderate signal-to-noise ratios (SNRs). This paper presents a new channel-estimate-based decision feedback equalizer (CEB–DFE) that deals with high platform mobility, exploits any sparse multipath structure, and maintains robustness under impulsive noise. The key component of this DFE is a linear-complexity sparse channel estimator, which has the ability to detect and reject impulses based on two noise models: contaminated Gaussian and symmetric alpha stable $({rm S}alpha{rm S})$ . By processing phase-shift keying (PSK) signals from three mobile shallow-water acoustic links, the gain of the proposed receiver over existing equalizers is demonstrated.
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    Topics: Architecture, Civil Engineering, Surveying , Physics
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  • 6
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    Performance Analysis and Optimal Design of Multichannel Equalizer for Underwater Acoustic Communications (2015)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2015-10-13
    Description: Adaptive equalization is a widely used method of mitigating the effects of multipath propagation and Doppler spreading in underwater acoustic communication channels. While the structure of a multichannel equalizer and least-squares-based adaptation algorithm are extensively used in practice, little is known in how to choose the number of sensors, separation between them, and lengths of the constituent filters such that the equalization performance is optimized. This paper studies the problem of optimal multichannel equalizer design in the context of time-varying underwater acoustic communication channels. In the first part, the paper presents a theoretical characterization of the equalization performance when the number of symbols that can be received in the time period over which the channel can be considered time invariant is limited. This result is then used to develop an understanding that the optimal number of equalizer coefficients is a tradeoff between the minimum mean squared error (MMSE) requirement for longer constituent filters and the insight that the limit on the number of stationary observations also limits the number of filter coefficients that can be effectively adapted. In the second part, the paper develops a theoretical model for wideband arrivals impinging upon an array of sensors of the multichannel equalizer. This model is used to develop an understanding that the optimal sensor separation is a tradeoff between the requirement for long aperture which improves resolution, and the fact that the grating lobes, caused by spatial undersampling, limit the equalizer’s ability to estimate the transmitted signal from the received signal.
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    Topics: Architecture, Civil Engineering, Surveying , Physics
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  • 7
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    On the Achievable Rate of a Class of Acoustic Channels and Practical Power Allocation Strategies for OFDM Systems (2015)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2015-10-13
    Description: In this paper, we consider a class of single-input–multiple-output (SIMO) underwater acoustic communication channels, where each propagation path can be characterized by a complex-valued Gaussian block-fading model. The capacity of such channels is computed and analyzed using three power allocation strategies: waterfilling, uniform, and on–off uniform power allocation across the signal bandwidth. Our analysis considers the effects of imperfect channel estimation, delayed feedback, and pilot overhead, which are found to contribute to about 1 (b/s)/Hz loss from 4 (b/s)/Hz at 20-dB signal-to-noise ratio (SNR) for the experimental channel. We find that given the long feedback delays associated with acoustic channels, all-on uniform power allocation, which does not require feedback and is simple to implement, emerges as a justified practical solution that outperforms the other strategies. Furthermore, when considering acoustic-specific propagation effects, such as frequency-dependent attenuation and colored noise, considerable gain can be achieved by selecting the frequency band according to the attenuation pattern and the available transmit power, e.g., at least 6-dB gain for a 10-km link when compared to transmission over a preselected frequency band of 10–15 kHz.
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    Topics: Architecture, Civil Engineering, Surveying , Physics
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  • 8
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    Underwater Acoustic Network Simulation With Lookup Tables From Physical-Layer Replay (2015)
    Institute of Electrical and Electronics Engineers (IEEE)
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    Publication Date: 2015-10-13
    Description: An underwater acoustic network simulation methodology is presented that is based on lookup tables (LUTs) with physical-layer error ratios. These LUTs are prepared with a validated replay channel simulator, which is here driven by channel measurements from the Kauai Acomms MURI 2011 (KAM11) experiment. Three physical-layer candidates are considered: a coherent single-carrier scheme, a coherent multicarrier scheme, and an incoherent scheme. The three modulation schemes are operated at a fixed message size and at four different data rates. Low rates are more robust to noise, interference, and channel dispersion, but also more prone to collisions in a network with busy traffic, because the packets are longer. Error statistics for colliding packets have been measured and are incorporated in the network simulator as collision LUTs. Example simulations are presented for a reduced flooding protocol with or without retransmissions. The results demonstrate how retransmissions pose a tradeoff between performance at high and low traffic load. The best network performance is obtained if the highest data rate is selected that yields a reasonably well-connected network. Collision avoidance is more important than the extended connectivity offered by low-rate signaling. On the other hand, at a given bit rate, a physical-layer scheme with extended connectivity but relatively weak links is shown to outperform a scheme with stronger links over fewer connections.
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    Topics: Architecture, Civil Engineering, Surveying , Physics
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  • 9
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    Measurements and Modeling of Effects of Out-of-Plane Reverberation on the Power Delay Profile for Underwater Acoustic Channels (2015)
    Institute of Electrical and Electronics Engineers (IEEE)
    Details
    Publication Date: 2015-10-13
    Description: Long reverberation tails are often observed in shallow-water acoustic channel impulse responses (CIRs). Examples from three significantly different environments along the Norwegian coast are presented. It is shown that 2-D propagation modeling fails to reproduce the long tails. Nevertheless, inclusion of the impulse response tails is necessary in connection with model-based simulators of communication performance, to avoid too optimistic estimates of bit error rates, etc. This is demonstrated by simulation examples for one of the environments, comparing results for truncated and complete impulse responses. High wind speeds and Doppler spread signals indicate that surface reverberation must be taken into account for modeling the tail energy. In bistatic scenarios such as the ones considered here, backscattering computations in a single vertical 2-D plane are not sufficient. A 3-D ray-based model, Rev3D, is utilized to include effects of out-of-plane scattering from the sea bottom as well as the sea surface. The scattering-strength functions include azimuthal variation, with significantly enhanced scattering close to the forward direction. Rev3D modeling supports the hypothesis that out-of-plane scattering and reverberation are main mechanisms behind the observed continuous, exponentially decaying impulse responses. Modeling incorporates available environmental information concerning sound-speed profiles, bottom topography and type, surface wave spectra, etc. Good agreement of measured and modeled time series is obtained for two of the locations. For the remaining location, modeling correctly recovers a significantly lower decay rate of the reverberation tail in comparison to the other locations, but the modeled decay rate is somewhat too large.
    Print ISSN: 0364-9059
    Electronic ISSN: 1558-1691
    Topics: Architecture, Civil Engineering, Surveying , Physics
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  • 10
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    Parametric Replay-Based Simulation of Underwater Acoustic Communication Channels (2015)
    Institute of Electrical and Electronics Engineers (IEEE)
    Details
    Publication Date: 2015-10-13
    Description: This paper presents an underwater acoustic channel simulation methodology that combines parametric modeling with stochastic replay of at-sea measured channel impulse responses. The motivation behind this approach is to extend the scope of use of replay-based methods by allowing some parameterization of the channel properties while complying with some level of realism. Such an approach is beneficial for extensive testing of communication links. The key idea is to deliberately distort the statistics of the experimental channel in order to meet some user-specified constraints. Our approach is based on a relative entropy minimization between the original time-varying channel impulse response and the simulated one. A particular attention is given to constraints on the channel Doppler spread and on the level of covariance between channel taps. The testing capabilities provided by parametric replay-based simulations are illustrated with real data collected in the bay of Brest, France.
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    Electronic ISSN: 1558-1691
    Topics: Architecture, Civil Engineering, Surveying , Physics
    Published by Institute of Electrical and Electronics Engineers (IEEE)
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