| 1. |
- Bossér, Daniel, et al.
(författare)
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A Statistically Motivated Likelihood for Track-Before-Detect
- 2022
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Ingår i: 2022 IEEE INTERNATIONAL CONFERENCE ON MULTISENSOR FUSION AND INTEGRATION FOR INTELLIGENT SYSTEMS (MFI). - : IEEE. - 9781665460262 - 9781665460279
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Konferensbidrag (refereegranskat)abstract
- A theoretically sound likelihood function for passive sonar surveillance using a hydrophone array is presented. The likelihood is derived from first order principles along with the assumption that the source signal can be approximated as white Gaussian noise within the considered frequency band. The resulting likelihood is a nonlinear function of the delay-and-sum beamformer response and signal-to-noise ratio (SNR). Evaluation of the proposed likelihood function is done by using it in a Bernoulli filter based track-before-detect (TkBD) framework. As a reference, the same TkBD framework, but with another beamforming response based likelihood, is used. Results from Monte-Carlo simulations of two bearings-only tracking scenarios are presented. The results show that the TkBD framework with the proposed likelihood yields an approx. 10 seconds faster target detection for a target at an SNR of -27 dB, and a lower bearing tracking error. Compared to a classical detect-and-track target tracker, the TkBD framework with the proposed likelihood yields 4 dB to 5 dB detection gain.
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| 2. |
- Bossér, Daniel, et al.
(författare)
-
A Statistically Motivated Likelihood for Track-Before-Detect
- 2022
-
Ingår i: 2022 IEEE International Conference on Multisensor Fusion and Integration for Intelligent Systems (MFI). - : IEEE. - 9781665460279 - 9781665460262
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Konferensbidrag (refereegranskat)abstract
- A theoretically sound likelihood function for passive sonar surveillance using a hydrophone array is presented. The likelihood is derived from first order principles along with the assumption that the source signal can be approximated as white Gaussian noise within the considered frequency band. The resulting likelihood is a nonlinear function of the delay-and-sum beamformer response and signal-to-noise ratio (SNR).Evaluation of the proposed likelihood function is done by using it in a Bernoulli filter based track-before-detect (TkBD) framework. As a reference, the same TkBD framework, but with another beamforming response based likelihood, is used. Results from Monte-Carlo simulations of two bearings-only tracking scenarios are presented. The results show that the TkBD framework with the proposed likelihood yields an approx. 10 seconds faster target detection for a target at an SNR of -27 dB, and a lower bearing tracking error. Compared to a classical detect-and-track target tracker, the TkBD framework with the proposed likelihood yields 4 dB to 5 dB detection gain.
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| 3. |
- Bossér, Daniel, et al.
(författare)
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Underwater Environment Modeling for Passive Sonar Track-Before-Detect
- 2023
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Ingår i: OCEANS 2023 - LIMERICK. - : Institute of Electrical and Electronics Engineers (IEEE). - 9798350332278 - 9798350332261
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Konferensbidrag (refereegranskat)abstract
- Underwater surveillance using passive sonar and track-before-detect technology requires accurate models of the tracked signal and the background noise. However, in an underwater environment, the signal channel is time-varying and prior knowledge about the spatial distribution of the background noise is unavailable. In this paper, an autoregressive model that captures a time-varying signal level caused by multi-path propagation is presented. In addition, a multi-source model is proposed to describe spatially distributed background noise. The models are used in a Bernoulli filter track-before-detect framework and evaluated using both simulated and sea trial data. The simulations demonstrate clear improvements in terms of target loss and improved ability to discern the target from the noisy background. An evaluation of the track-before-detect algorithm on the sea trial data indicates a performance gain when incorporating the proposed models in underwater surveillance and tracking problems.
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| 4. |
- Lidström, Viktor, et al.
(författare)
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A Framework For Testing Data Driven Underwater Link Adaptation
- 2022
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Ingår i: 2022 Sixth Underwater Communications And Networking Conference (UCOMMS). - : Institute of Electrical and Electronics Engineers (IEEE).
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Konferensbidrag (refereegranskat)abstract
- To make full use of the underwater acoustic channel, a high degree of adaptivity is typically required. A novel framework for efficient evaluation of link adaptation employing channel replay simulation with Watermark and a lookup table is proposed. The approach is used to compare link adaptation based on SNR and CRC feedback using measured sea data. The best performance is obtained with a CRC criterion since it detects if a communication link has poor behaviour. The method is further improved by introducing a memory mechanism that disables a link with repeated low reliability.
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| 5. |
- Lidström, Viktor, 1991-
(författare)
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On the Design of Noncoherent Acoustic Underwater Communication
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)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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| 6. |
- Ma, Xiaoliang, Docent, et al.
(författare)
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DigiWays: A Digitalisation Testbed for Sustainable Traffic Management on Swedish Motorways
- 2023
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Ingår i: 2023 IEEE World Forum on Internet of Things: The Blue Planet: A Marriage of Sea and Space, WF-IoT 2023. - : Institute of Electrical and Electronics Engineers Inc..
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Konferensbidrag (refereegranskat)abstract
- Motorway traffic management system plays important roles for modern Intelligent Transport Systems (ITS). The Swedish motorways near large cities such as Stockholm are equipped with a large number of sensors for traffic monitoring and advanced traffic management purposes. This paper introduces our recent experiments of digitalising motorway traffic system using vehicle-to-everything (V2X) communication and other sensors deployed for measuring road traffic and road-side air pollutants. In addition to the deployment of V2X testbed, a Cyber-Physical system (CPS) framework is presented to integrate the deployed sensors with the computational models for estimation and prediction of traffic and road-side environmental conditions. A digital twin of motorway traffic flow is established using traffic flow models of different levels. The computation in experiment of the cyber space shows that traffic states can be estimated using V2X sensing data by applying the model-based estimation approach.
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| 7. |
- Skog, Isaac, et al.
(författare)
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Signals-of-Opportunity-Based Hydrophone Array Shape and Orientation Estimation
- 2024
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Ingår i: IEEE Journal of Oceanic Engineering. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0364-9059 .- 1558-1691.
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Tidskriftsartikel (refereegranskat)abstract
- A signal-of-opportunity-based method to automatically calibrate the orientations and shapes of a set of hydrophone arrays using the sound emitted from nearby ships is presented. The calibration problem is formulated as a simultaneous localization and mapping problem, where the locations, orientations, and shapes of the arrays are viewed as the unknown map states, and the position, velocity, etc., of the source as the unknown dynamic states. A sequential likelihood ratio test, together with a maximum a posteriori source location estimator, is used to automatically detect suitable sources and initialize the calibration procedure. The performance of the proposed method is evaluated using data from two 56-element hydrophone arrays. Results from two sea trials indicate that: 1) signal sources suitable for the calibration can be automatically detected; 2) the shapes and orientations of the arrays can be consistently estimated from the different data sets with shape variations of a few decimeters and orientation variations of less than 2(degrees) and 3) the uncertainty bounds calculated by the calibration method are in agreement with the true calibration uncertainties. Furthermore, the bearing time record from a sea trial with an autonomous mobile underwater signal source also shows the efficacy of the proposed calibration method. In the studied scenario, the root-mean-square bearing tracking error was reduced from 4(degrees) to 1(degrees) when using the calibrated array shapes compared to assuming the arrays' to be straight lines. Also, the beamforming gain increased by approximately 1 dB.
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