| 1. |
- Erstorp, Elias, et al.
(author)
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Energy and Reliability Properties of the Distributed Transmission Power Control Protocol DPower
- 2024
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In: IEEE Journal of Oceanic Engineering. - : IEEE Oceanic Engineering Society. - 0364-9059 .- 1558-1691.
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Journal article (peer-reviewed)abstract
- There is an increasing demand for underwater communication, not least manifested in a need to distribute and retrieve data from networks of underwater sensors. Whilst there are exceptions, acoustic techniques are generally the only viable means of communication. However, transmitting information acoustically is energy-intensive and can limit the lifetime of battery-powered platforms. Through simulations, this paper statistically investigates a recent transmission power controller, developed for underwater networks of static, battery-powered modems. The controller is self-configuring, as the modems' locations are assumed to be unknown. Further, the controller is fully distributed for scalability and adaptability reasons. The method involves a $k$-nearest neighbor approach when selecting transmission power for packet forwarding, i.e., the transmission power is selected such that only the $k$ closest modems will receive a packet. A well-known flooding-based routing protocol suitable for ad-hoc networks is employed to assess the energy consumption with and without the power controller. The evaluation is based on simulations using 16 modems placed randomly in a square area with varying sizes and choices of $k$. The results show that in a small and dense network, up to 61-68\% energy can be saved with a minor 7\% drop in packet delivery ratio.
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| 2. |
- Erstorp, Elias Strandell, et al.
(author)
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An Adaptive Transmission Power Controller for Flooding-based Underwater Network Protocols
- 2021
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In: 2021 5th Underwater Communications and Networking Conference, UComms 2021. - : Institute of Electrical and Electronics Engineers Inc..
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Conference paper (peer-reviewed)abstract
- In this study, we present the first iteration of DPower, an energy conserving method for use in underwater acoustic networks. The method encompasses a straightforward transmission power calibration procedure and adaptive power level selection. The method was evaluated in combination with DFlood, a known and validated constrained flooding protocol developed for underwater applications. Simulations of a network with given prerequisites have shown that, with an acceptable increase in packet loss, the presented method can dramatically reduce the energy consumption and thus improve the life-time of networks.
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| 3. |
- Hutchison, Zoe L., et al.
(author)
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A modelling evaluation of electromagnetic fields emitted by buried subsea power cables and encountered by marine animals : Considerations for marine renewable energy development
- 2021
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In: Renewable energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 177, s. 72-81
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Journal article (peer-reviewed)abstract
- The expanding marine renewable energy industry will increase the prevalence of electromagnetic fields (EMFs) from power cables in coastal waters. Assessments of environmental impacts are required within licensing/permitting processes and increased prevalence of cables will increase questions concerning EMF emissions and potential cumulative impacts. It is presumed that protecting a cable by burial, may also mitigate EMF emissions and potential impacts on species. Focussing on a bundled high voltage direct current (HVDC) transmission cable, we use computational and interpretive models to explore the influence of cable properties and burial depth on the DC magnetic field (DC-MF) potentially encountered by receptive species. Greater cable pair separation increased the deviations from the geomagnetic field and while deeper burial reduced the deviations, the DC-MF was present at intensities perceivable by receptive species. An animal moving along a cable route may be exposed to variable EMFs due to varied burial depth and that combined with an animal's position in the water column determines the distance from source and EMF exposure. Modelling contextually realistic scenarios would improve assessments of potential effects. We suggest developers and cable industries make cable properties and energy transmission data available, enabling realistic modelling and environmental assessment supporting future developments.
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| 4. |
- Jalkanen, Jukka-Pekka, et al.
(author)
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Underwater noise emissions from ships during 2014-2020
- 2022
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In: Environmental Pollution. - : Elsevier BV. - 0269-7491 .- 1873-6424. ; 311
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Journal article (peer-reviewed)abstract
- This paper reports trends in the input of underwater noise source energy emission from global shipping, based on bottom-up modeling of individual ships. In terms of energy, we predict the doubling of global shipping noise emissions every 11.5 years, on average, but there are large regional differences. Shipping noise emissions increase rapidly in Arctic areas and the Norwegian Sea. The largest contributors are the containerships, dry bulk and liquid tanker vessels which emit 75% of the underwater shipping noise source energy. The COVID-19 pandemic changed vessel traffic patterns and our modeling indicates a reduction of -6% in global shipping noise source energy in the 63 Hz 1/3 octave band. This reduction was largest in the Greenland Sea, the Coastal Waters of Southeast Alaska and British Columbia as well as the Gulf of California, temporarily disrupting the increasing pre-pandemic noise emission trend. However, in some sea areas, such as the Indian Ocean, Yellow Sea and Eastern China Sea the emitted noise source energy was only slightly reduced. In global scale, COVID-19 pandemic reduced the underwater shipping noise emissions close to 2017 levels, but it is expected that the increasing trend of underwater noise emissions will continue when the global economy recovers.
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| 5. |
- Juretzek, Carina, et al.
(author)
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A Case Study-Based Analysis of Uncertainties on the Assessment of Impulsive Underwater Noise for the Marine Strategy Framework Directive
- 2023
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In: Journal of Marine Science and Engineering. - : MDPI AG. - 2077-1312. ; 11:4, s. 847-
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Journal article (peer-reviewed)abstract
- The Marine Strategy Framework Directive (MSFD) has been an important driver for progress in monitoring and assessment of impulsive underwater noise in the marine environment of the European Union. An important achievement of the MSFD implementation was the development of regional noise registries, providing the data basis for assessments. Recently, the EU has made tremendous efforts to propose harmonized assessment approaches and first-of-their-kind regional quantitative thresholds for impulsive underwater noise. In light of these newly developed thresholds values, we analyze the suitability of the available data in the noise registries for assessment purposes under the MSFD and review sources of uncertainties regarding quantitative results. We present three regional case studies located in the North Sea, the Baltic Sea and the Mediterranean Sea. For each of these regions, a sound-intensive activity was selected that aligned with a realistic impulsive noise event reported for the region. We made use of available data in the noise registries and applied the EU Guidance recommended for the description of impulsive noise sources, but also used alternative approaches and observations as comparison. The case study analysis includes the evaluation of data availability, data quality and data accuracy in the noise registries, and identifies corresponding consequences of the data for the uncertainty and interpretability of assessment results, especially for the quantitative evaluation of habitat areas impacted by noise. Finally, we make suggestions for the improvement of the data basis in the noise registries and the optimization of the assessment accuracy.
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| 6. |
- Lidström, Viktor, 1991-
(author)
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On the Design of Noncoherent Acoustic Underwater Communication
- 2023
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Doctoral thesis (other academic/artistic)abstract
- The underwater domain is an environment hostile to humans due to the hydrostatic pressure that rapidly increases with water depth, which has led to underwater robotics becoming an emerging technological field with many commercial-, environmental-, and security-related applications. A major challenge to untethered autonomous underwater vehicles (AUVs) is communicating robot-to-robot and robot-to-topside operator since it must, in most cases, be done acoustically. Meanwhile, the underwater acoustic (UWA) channel is widely considered one of nature's most difficult communication mediums due to the limited frequency range, complicated sound propagation physics, prolonged- and time-varying multipath, and, in some situations, non-Gaussian background noise. The wide variety of UWA channels observed in different locations, and in the same location at different times, also poses a challenge to the research methodology since sea experiments become inherently difficult to repeat. However, replay simulation of recorded channels using the public benchmark Watermark allows direct comparison between publications and is employed extensively in this thesis, complemented by sea experiments for verifying the internal validity of simulation results.No link solution is perfect for all channels, and a toolbox consisting of methods with varying information rates and robustness is necessary for an adaptive network to exploit the full capability of the channel encountered in situ. A link is called channel-agnostic if its robustness is limited by the ratio of signal power to noise (SNR), rather than the channel characteristics, thereby being robust to many channels one might encounter. The proven information rates for such link methods are relatively low; this, together with recent advancements in other areas, such as error correction codes and joint synchronisation and decoding, motivates the focus on noncoherent methods in this thesis. The second focus is link adaptation and the necessary mechanisms for its implementation in adaptive UWA networks.The thesis provides a background on various approaches to acoustic signalling, both coherent and noncoherent, and other key components of a noncoherent UWA link, such as symbol alphabets, receiver data models, error correction codes, and time-Doppler synchronisation. The topic of link adaptation in a UWA network is discussed, as is the methodology for research in UWA communication. The included papers provide a set of channel-agnostic link methods with spectral efficiencies in the range 0.02-0.22 (bit/s/Hz), with varying requirements on the SNR and the length of the communication frame, which are enabled by the presented improvements to link methods. Using a Rice-fading model for soft decoding, the robustness to parameter time variation is found to increase substantially by limiting the SNR of the likelihood parametrisation; this result applies to all methods that employ frequency shift keying (FSK). Furthermore, a novel noncoherent symbol alphabet with 1 (bit/s/Hz) maximum spectral efficiency is presented, whose dimensionality M increases the soft decoder performance, specialising to on-off keying (OOK) for M=1. A joint synchronisation and decoding framework is proposed, allowing robust time-Doppler detection with low overhead; its viability is demonstrated in an adverse shallow-water channel with relative platform velocities in the range +/- 4 (m/s). Moreover, a framework for efficient evaluation of link adaptation algorithms is presented, and a link-adaptive ad-hoc UWA network using low-latency implicit feedback is demonstrated through sea experiments.The research presented herein has been conducted as part of the Swedish Maritime Robotics Centre (SMaRC), a national cross-disciplinary research centre funded by the Swedish Foundation for Strategic Research (SSF).
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| 7. |
- Linne, Markus, et al.
(author)
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Development of calibration technique for underwater transducers in free field conditions below 1000 Hz with results on an acoustical recorder
- 2022
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In: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 0001-4966 .- 1520-8524. ; 152:6, s. 3606-3615
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Journal article (peer-reviewed)abstract
- A calibration technique with potential for low frequencies and sizeable systems of underwater transducers is being developed at the Swedish Defence Research Agency. The technique is based on the three-transducer spherical wave reciprocity method for use in an ice-covered lake with a depth of 220 m in the Swedish arctic zone. The calibration is performed at a depth of approximately 100 m with inter-transducer separations of 50 m, 86.6 m, and 100 m, allowing for frequencies down to 59 Hz using time-gated tone burst signals. In this paper, the calibration location, system, and technique are introduced, and the calibration results of an acoustical recorder in the range of 59 Hz-1 kHz are presented. The sensitivity is varying with frequency around -148 dB re 1 V/mu Pa, and the uncertainty budget is discussed.
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| 8. |
- Sigray, Peter, et al.
(author)
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Particle motion observed during offshore wind turbine piling operation
- 2022
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In: Marine Pollution Bulletin. - : Elsevier BV. - 0025-326X .- 1879-3363. ; 180
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Journal article (peer-reviewed)abstract
- Measurement of particle motion from an offshore piling event in the North was conducted to determine noise levels. For this purpose, a bespoken sensor was developed that was both autonomous and sensitive up to 2 kHz. The measurement was undertaken both for unmitigated and mitigated piling. Three different types of mitigation techniques were employed. The acceleration zero-to-peak values and the acceleration exposure levels were determined. The results show that inferred mitigation techniques reduce the levels significantly as well as de-creases the power content of higher frequencies. These results suggest that mitigation has an effect and will reduce the effect ranges of impact on marine species.
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| 9. |
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SMaRC Swedish Maritime Robotics Centre : Mid-Term Evaluation Report 2020
- 2020
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Reports (other academic/artistic)abstract
- This is the midterm report of the project SMaRC (Swedish Maritime Robotics Centre), which is one of four industrial research centres (IRC) funded by the Swedish Foundation for Strategic Research (SSF). SMaRC is a unique collaborative research environment consisting of key industry, academia, and governmental partners in Sweden. The focus of the centre is to enable a transformational/disruptive shift towards the next generation of marine robots.The aim of this report is to describe how SMaRC will provide industrial outcomes that deliver into societal benefit areas, by linking user-defined scenarios with capabilities. This will strengthen the research focus as well as create a transparent mapping from scientific activities to end-user needs. The SMaRC project has now reached its midpoint and is running according to plan. The initial start-up process is now passed and key milestones of the project have been reached and demonstrated at the joint workshop and demonstration periods. SMaRC has already participated in very challenging Antarctic expeditions, developed and tested its own underwater robots, and demonstrated new capabilities for perception, navigation, endurance and autonomy in both simulator environments and in field experiments. For the upcoming second half of the project period, the focus will be on integration and demonstration to move closer to the industrial and end-user needs. The future research plan is connected to six targeted scenarios highlighting key capabilities to reach within the research projects. The demonstration of these scenarios also supports enhanced cooperation with both national and international partners.
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