1
|
Zhang Y, Li H, Wang S, Chen F. A Fuzzy-PI Clock Servo with Window Filter for Compensating Queue-Induced Delay Asymmetry in IEEE 1588 Networks. Sensors (Basel) 2024; 24:2369. [PMID: 38610579 PMCID: PMC11014061 DOI: 10.3390/s24072369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2023] [Revised: 03/26/2024] [Accepted: 04/04/2024] [Indexed: 04/14/2024]
Abstract
Clock synchronization is one of the popular research topics in Distributed Measurement and Control Systems (DMCSs). In most industrial fields, such as Smart Grid and Flight Test, the highest requirement for synchronization accuracy is 1 μs. IEEE 1588 Precision Time Protocol-2008 (PTPv2) can theoretically achieve sub-microsecond accuracy, but it relies on the assumption that the forward and backward delays of PTP packets are symmetrical. In practice, PTP packets will experience random queue delays in switches, making the above assumption challenging to satisfy and causing poor synchronization accuracy. Although using switches supporting the Transparent Clock (TC) can improve synchronization accuracy, these dedicated switches are generally expensive. This paper designs a PTP clock servo for compensating Queue-Induced Delay Asymmetry (QIDA), which can be implemented based on ordinary switches. Its main algorithm comprises a minimum window filter with drift compensation and a fuzzy proportional-integral (PI) controller. We construct a low-cost hardware platform (the cost of each node is within USD 10) to test the performance of the clock servo. In a 100 Mbps network with background (BG) traffic of less than 70 Mbps, the maximum absolute time error (max |TE|) does not exceed 0.35 μs, and the convergence time is about half a minute. The accuracy is improved hundreds of times compared with other existing clock servos.
Collapse
Affiliation(s)
| | | | | | - Feifan Chen
- State Key Laboratory of Precision Measurement Technology and Instrument, Department of Precision Instrument, Tsinghua University, Beijing 100084, China; (Y.Z.); (H.L.); (S.W.)
| |
Collapse
|
2
|
Hou C, Jin X, Zhou L, Wang H, Yang X, Xu Z, Jin Z. Precision Joint RF Measurement of Inter-Satellite Range and Time Difference and Scalable Clock Synchronization for Multi-Microsatellite Formations. Sensors (Basel) 2023; 23:4109. [PMID: 37112450 PMCID: PMC10142719 DOI: 10.3390/s23084109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Revised: 04/18/2023] [Accepted: 04/18/2023] [Indexed: 06/19/2023]
Abstract
The rapid development of multi-satellite formations requires inter-satellite radio frequency (RF) measurement to be both precise and scalable. The navigation estimation of multi-satellite formations using a unified time reference demands the simultaneous RF measurement of the inter-satellite range and time difference. However, high-precision inter-satellite RF ranging and time difference measurements are investigated separately in existing studies. Different from the conventional two-way ranging (TWR) method, which is limited by its reliance on a high-performance atomic clock and navigation ephemeris, asymmetric double-sided two-way ranging (ADS-TWR)-based inter-satellite measurement schemes can eliminate such reliance while ensuring measurement precision and scalability. However, ADS-TWR was originally proposed for ranging-only applications. In this study, by fully exploiting the time-division non-coherent measurement characteristic of ADS-TWR, a joint RF measurement method is proposed to obtain the inter-satellite range and time difference simultaneously. Moreover, a multi-satellite clock synchronization scheme is proposed based on the joint measurement method. The experimental results show that when inter-satellite ranges are hundreds of kilometers, the joint measurement system has a centimeter-level accuracy for ranging and a hundred-picosecond-level accuracy for time difference measurement, and the maximum clock synchronization error was only about 1 ns.
Collapse
Affiliation(s)
- Cong Hou
- School of Aeronautics and Astronautics, Zhejiang University, Hangzhou 310027, China; (C.H.); (X.J.); (L.Z.); (H.W.); (X.Y.); (Z.J.)
- Key Laboratory of Micro-Nano Satellite Research, Hangzhou 310027, China
- Micro-Satellite Research Center, Zhejiang University, Hangzhou 310027, China
| | - Xiaojun Jin
- School of Aeronautics and Astronautics, Zhejiang University, Hangzhou 310027, China; (C.H.); (X.J.); (L.Z.); (H.W.); (X.Y.); (Z.J.)
- Key Laboratory of Micro-Nano Satellite Research, Hangzhou 310027, China
- Micro-Satellite Research Center, Zhejiang University, Hangzhou 310027, China
| | - Lishan Zhou
- School of Aeronautics and Astronautics, Zhejiang University, Hangzhou 310027, China; (C.H.); (X.J.); (L.Z.); (H.W.); (X.Y.); (Z.J.)
- Key Laboratory of Micro-Nano Satellite Research, Hangzhou 310027, China
- Micro-Satellite Research Center, Zhejiang University, Hangzhou 310027, China
| | - Haoze Wang
- School of Aeronautics and Astronautics, Zhejiang University, Hangzhou 310027, China; (C.H.); (X.J.); (L.Z.); (H.W.); (X.Y.); (Z.J.)
- Key Laboratory of Micro-Nano Satellite Research, Hangzhou 310027, China
- Micro-Satellite Research Center, Zhejiang University, Hangzhou 310027, China
| | - Xiaopeng Yang
- School of Aeronautics and Astronautics, Zhejiang University, Hangzhou 310027, China; (C.H.); (X.J.); (L.Z.); (H.W.); (X.Y.); (Z.J.)
- Key Laboratory of Micro-Nano Satellite Research, Hangzhou 310027, China
- Micro-Satellite Research Center, Zhejiang University, Hangzhou 310027, China
| | - Zhaobin Xu
- School of Aeronautics and Astronautics, Zhejiang University, Hangzhou 310027, China; (C.H.); (X.J.); (L.Z.); (H.W.); (X.Y.); (Z.J.)
- Key Laboratory of Micro-Nano Satellite Research, Hangzhou 310027, China
- Micro-Satellite Research Center, Zhejiang University, Hangzhou 310027, China
| | - Zhonghe Jin
- School of Aeronautics and Astronautics, Zhejiang University, Hangzhou 310027, China; (C.H.); (X.J.); (L.Z.); (H.W.); (X.Y.); (Z.J.)
- Key Laboratory of Micro-Nano Satellite Research, Hangzhou 310027, China
- Micro-Satellite Research Center, Zhejiang University, Hangzhou 310027, China
| |
Collapse
|
3
|
Schwefel HP, Antonios I, Lipsky L. On the Calculation of Time Alignment Errors in Data Management Platforms for Distribution Grid Data. Sensors (Basel) 2021; 21:s21206903. [PMID: 34696116 PMCID: PMC8539573 DOI: 10.3390/s21206903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Revised: 10/06/2021] [Accepted: 10/12/2021] [Indexed: 11/16/2022]
Abstract
The operation and planning of distribution grids require the joint processing of measurements from different grid locations. Since measurement devices in low- and medium-voltage grids lack precise clock synchronization, it is important for data management platforms of distribution system operators to be able to account for the impact of nonideal clocks on measurement data. This paper formally introduces a metric termed Additive Alignment Error to capture the impact of misaligned averaging intervals of electrical measurements. A trace-driven approach for retrieval of this metric would be computationally costly for measurement devices, and therefore, it requires an online estimation procedure in the data collection platform. To overcome the need of transmission of high-resolution measurement data, this paper proposes and assesses an extension of a Markov-modulated process to model electrical traces, from which a closed-form matrix analytic formula for the Additive Alignment Error is derived. A trace-driven assessment confirms the accuracy of the model-based approach. In addition, the paper describes practical settings where the model can be utilized in data management platforms with significant reductions in computational demands on measurement devices.
Collapse
Affiliation(s)
- Hans-Peter Schwefel
- Department of Electronic Systems, Aalborg University, 9220 Aalborg, Denmark;
- GridData GmbH, 83278 Traunstein, Germany
| | - Imad Antonios
- Department of Computer Science, Southern Connecticut State University, New Haven, CT 06515, USA
- Correspondence:
| | - Lester Lipsky
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT 06269, USA;
| |
Collapse
|
4
|
Cochran RD, Gauthier DJ. Qubit-Based Clock Synchronization for QKD Systems Using a Bayesian Approach. Entropy (Basel) 2021; 23:e23080988. [PMID: 34441128 PMCID: PMC8391395 DOI: 10.3390/e23080988] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 07/27/2021] [Accepted: 07/27/2021] [Indexed: 11/16/2022]
Abstract
Quantum key distribution (QKD) systems provide a method for two users to exchange a provably secure key. Synchronizing the users' clocks is an essential step before a secure key can be distilled. Qubit-based synchronization protocols directly use the transmitted quantum states to achieve synchronization and thus avoid the need for additional classical synchronization hardware. Previous qubit-based synchronization protocols sacrifice secure key either directly or indirectly, and all known qubit-based synchronization protocols do not efficiently use all publicly available information published by the users. Here, we introduce a Bayesian probabilistic algorithm that incorporates all published information to efficiently find the clock offset without sacrificing any secure key. Additionally, the output of the algorithm is a probability, which allows us to quantify our confidence in the synchronization. For demonstration purposes, we present a model system with accompanying simulations of an efficient three-state BB84 prepare-and-measure protocol with decoy states. We use our algorithm to exploit the correlations between Alice's published basis and mean photon number choices and Bob's measurement outcomes to probabilistically determine the most likely clock offset. We find that we can achieve a 95 percent synchronization confidence in only 4140 communication bin widths, meaning we can tolerate clock drift approaching 1 part in 4140 in this example when simulating this system with a dark count probability per communication bin width of 8×10-4 and a received mean photon number of 0.01.
Collapse
|
5
|
Gorawski M, Grochla K, Marjasz R, Frankiewicz A. Energy Minimization Algorithm for Estimation of Clock Skew and Reception Window Selection in Wireless Networks. Sensors (Basel) 2021; 21:s21051768. [PMID: 33806434 PMCID: PMC7961599 DOI: 10.3390/s21051768] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 02/23/2021] [Accepted: 02/26/2021] [Indexed: 11/21/2022]
Abstract
The synchronization of time between devices is one of the more important and challenging problems in wireless networks. We discuss the problem of maximization of the probability of receiving a message from a device using a limited listening time window to minimize energy utilization. We propose a solution to two important problems in wireless networks of battery-powered devices: a method of establishing a connection with a device that has been disconnected from the system for a long time and developed unknown skew and also two approaches to follow-up clock synchronization using the confidence interval method. We start with the analysis of measurements of clock skew. The algorithms are evaluated using extensive simulations and we discuss the selection of parameters balancing between minimizing the energy utilization and maximizing the probability of reception of the message. We show that the selection of a time window of growing size requires less energy to receive a packet than using the same size of time window repeated multiple times. The shifting of reception windows can further decrease the energy cost if lower packet reception probability is acceptable. We also propose and evaluate an algorithm scaling the reception window size to the interval between the packet transmission.
Collapse
Affiliation(s)
- Michał Gorawski
- Institute of Theoretical and Applied Informatics, Polish Academy of Sciences, ul. Bałtycka 5, 44-100 Gliwice, Poland; (M.G.); (R.M.)
| | - Krzysztof Grochla
- Institute of Theoretical and Applied Informatics, Polish Academy of Sciences, ul. Bałtycka 5, 44-100 Gliwice, Poland; (M.G.); (R.M.)
- Correspondence: ; Tel.: +48-322-317-319
| | - Rafał Marjasz
- Institute of Theoretical and Applied Informatics, Polish Academy of Sciences, ul. Bałtycka 5, 44-100 Gliwice, Poland; (M.G.); (R.M.)
| | | |
Collapse
|
6
|
Faizullin M, Kornilova A, Akhmetyanov A, Ferrer G. Twist-n-Sync: Software Clock Synchronization with Microseconds Accuracy Using MEMS-Gyroscopes. Sensors (Basel) 2020; 21:s21010068. [PMID: 33374447 PMCID: PMC7795013 DOI: 10.3390/s21010068] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 12/18/2020] [Accepted: 12/20/2020] [Indexed: 11/23/2022]
Abstract
Sensor networks require a high degree of synchronization in order to produce a stream of data useful for further purposes. Examples of time misalignment manifest as undesired artifacts when doing multi-camera bundle-adjustment or global positioning system (GPS) geo-localization for mapping. Network Time Protocol (NTP) variants of clock synchronization can provide accurate results, though present high variance conditioned by the environment and the channel load. We propose a new precise technique for software clock synchronization over a network of rigidly attached devices using gyroscope data. Gyroscope sensors, or IMU, provide a high-rate measurements that can be processed efficiently. We use optimization tools over the correlation signal of IMU data from a network of gyroscope sensors. Our method provides stable microseconds accuracy, regardless of the number of sensors and the conditions of the network. In this paper, we show the performance of the gyroscope software synchronization in a controlled environment, and we evaluate the performance in a sensor network of smartphones by our open-source Android App, Twist-n-Sync, that is publicly available.
Collapse
Affiliation(s)
- Marsel Faizullin
- Skolkovo Institute of Science and Technology, 121205 Moscow, Russia; (M.F.); (A.K.); (A.A.)
| | - Anastasiia Kornilova
- Skolkovo Institute of Science and Technology, 121205 Moscow, Russia; (M.F.); (A.K.); (A.A.)
| | - Azat Akhmetyanov
- Skolkovo Institute of Science and Technology, 121205 Moscow, Russia; (M.F.); (A.K.); (A.A.)
- Software Engineering Department, Saint Petersburg State University, 199034 St. Petersburg, Russia
| | - Gonzalo Ferrer
- Skolkovo Institute of Science and Technology, 121205 Moscow, Russia; (M.F.); (A.K.); (A.A.)
- Correspondence:
| |
Collapse
|
7
|
Yi Ği Tler HN, Badihi B, Jäntti R. Overview of Time Synchronization for IoT Deployments: Clock Discipline Algorithms and Protocols. Sensors (Basel) 2020; 20:E5928. [PMID: 33092256 DOI: 10.3390/s20205928] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 10/09/2020] [Accepted: 10/10/2020] [Indexed: 11/17/2022]
Abstract
Internet of Things (IoT) is expected to change the everyday life of its users by enabling data exchanges among pervasive things through the Internet. Such a broad aim, however, puts prohibitive constraints on applications demanding time-synchronized operation for the chronological ordering of information or synchronous execution of some tasks, since in general the networks are formed by entities of widely varying resources. On one hand, the existing contemporary solutions for time synchronization, such as Network Time Protocol, do not easily tailor to resource-constrained devices, and on the other, the available solutions for constrained systems do not extend well to heterogeneous deployments. In this article, the time synchronization problems for IoT deployments for applications requiring a coherent notion of time are studied. Detailed derivations of the clock model and various clock relation models are provided. The clock synchronization methods are also presented for different models, and their expected performance are derived and illustrated. A survey of time synchronization protocols is provided to aid the IoT practitioners to select appropriate components for a deployment. The clock discipline algorithms are presented in a tutorial format, while the time synchronization methods are summarized as a survey. Therefore, this paper is a holistic overview of the available time synchronization methods for IoT deployments.
Collapse
|
8
|
Fernández-Madrigal JA, Navarro A, Asenjo R, Cruz-Martín A. Characterization, Statistical Analysis and Method Selection in the Two-Clocks Synchronization Problem for Pairwise Interconnected Sensors. Sensors (Basel) 2020; 20:s20174808. [PMID: 32858927 PMCID: PMC7507003 DOI: 10.3390/s20174808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 08/07/2020] [Accepted: 08/14/2020] [Indexed: 11/22/2022]
Abstract
Time synchronization among sensor devices connected through non-deterministic media is a fundamental requirement for sensor fusion and other distributed tasks that need a common time reference. In many of the time synchronization methods existing in literature, the estimation of the relation between pairs of clocks is a core concept; moreover, in applications that do not have general connectivity among its devices but a simple pairwise topology, such as embedded systems, mobile robots or home automation, two-clock synchronization is actually the basic form of the time estimation problem. In these kinds of applications, especially for critical ones, not only the quality of the estimation of the relation between two clocks is important, but also the bounds the methods provide for the estimated values, and their computational effort (since many are small systems). In this paper, we characterize, with a thorough parameterization, the possible scenarios where two-clock synchronization is to be solved, and then conduct a rigorous statistical study of both scenarios and methods. The study is based on exhaustive simulations run in a super-computer. Our aim is to provide a sound basis to select the best clock synchronization algorithm depending on the application requirements and characteristics, and also to deduce which ones of these characteristics are most relevant, in general, when solving the problem. For our comparisons we have considered several representative methods for clock synchronization according to a novel taxonomy that we also propose in the paper, and in particular, a few geometrical ones that have special desirable characteristics for the two-clock problem. We illustrate the method selection procedure with practical use-cases of sensory systems where two-clock synchronization is essential.
Collapse
Affiliation(s)
| | - Angeles Navarro
- Department of Computer Architecture, University of Málaga, 29016 Málaga, Spain; (A.N.); (R.A.)
| | - Rafael Asenjo
- Department of Computer Architecture, University of Málaga, 29016 Málaga, Spain; (A.N.); (R.A.)
| | - Ana Cruz-Martín
- Department of System Engineering and Automation, University of Málaga, 29016 Málaga, Spain;
| |
Collapse
|
9
|
Abbas G, Abbas ZH, Haider S, Baker T, Boudjit S, Muhammad F. PDMAC: A Priority-Based Enhanced TDMA Protocol for Warning Message Dissemination in VANETs. Sensors (Basel) 2019; 20:E45. [PMID: 31861746 DOI: 10.3390/s20010045] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/09/2019] [Revised: 12/11/2019] [Accepted: 12/17/2019] [Indexed: 11/17/2022]
Abstract
Vehicular ad hoc networks (VANETs) are the key enabling technology for intelligent transportation systems. Carrier-sense multiple access with collision avoidance (CSMA/CA) is the de facto media access standard for inter-vehicular communications, but its performance degrades in high-density networks. Time-division multiple access (TDMA)-based protocols fill this gap to a certain extent, but encounter inefficient clock synchronization and lack of prioritized message delivery. Therefore, we propose a priority-based direction-aware media access control (PDMAC) as a novel protocol for intra-cluster and inter-cluster clock synchronization. Furthermore, PDMAC pioneers a three-tier priority assignment technique to enhance warning messages delivery by taking into account the direction component, message type, and severity level on each tier. Analytical and simulation results validate the improved performance of PDMAC in terms of clock synchronization, channel utilization, message loss rate, end-to-end delays, and network throughput, as compared with eminent VANET MAC protocols.
Collapse
|
10
|
Nohales MA, Liu W, Duffy T, Nozue K, Sawa M, Pruneda-Paz JL, Maloof JN, Jacobsen SE, Kay SA. Multi-level Modulation of Light Signaling by GIGANTEA Regulates Both the Output and Pace of the Circadian Clock. Dev Cell 2019; 49:840-851.e8. [PMID: 31105011 PMCID: PMC6597437 DOI: 10.1016/j.devcel.2019.04.030] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2018] [Revised: 02/16/2019] [Accepted: 04/17/2019] [Indexed: 01/29/2023]
Abstract
Integration of environmental signals with endogenous biological processes is essential for organisms to thrive in their natural environment. Being entrained by periodic environmental changes, the circadian clock incorporates external information to coordinate physiological processes, phasing them to the optimal time of the day and year. Here, we present a pivotal role for the clock component GIGANTEA (GI) as a genome-wide regulator of transcriptional networks mediating growth and adaptive processes in plants. We provide mechanistic details on how GI integrates endogenous timing with light signaling pathways through the global modulation of PHYTOCHROME-INTERACTING FACTORs (PIFs). Gating of the activity of these transcriptional regulators by GI directly affects a wide array of output rhythms, including photoperiodic growth. Furthermore, we uncover a role for PIFs in mediating light input to the circadian oscillator and show how their regulation by GI is required to set the pace of the clock in response to light-dark cycles.
Collapse
Affiliation(s)
- Maria A Nohales
- Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Wanlu Liu
- Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, Los Angeles, CA 90095, USA; Zhejiang University, University of Edinburgh Institute, Zhejiang University School of Medicine, Hangzhou 310058, P.R. China
| | - Tomas Duffy
- Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Kazunari Nozue
- Department of Plant Biology, University of California, Davis, Davis, CA 95616, USA
| | - Mariko Sawa
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San Diego, San Diego, La Jolla, CA 92093, USA
| | - Jose L Pruneda-Paz
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San Diego, San Diego, La Jolla, CA 92093, USA
| | - Julin N Maloof
- Department of Plant Biology, University of California, Davis, Davis, CA 95616, USA
| | - Steven E Jacobsen
- Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, Los Angeles, CA 90095, USA; Howard Hughes Medical Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Steve A Kay
- Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA.
| |
Collapse
|
11
|
He C, Wang Y, Yu W, Song L. Underwater Target Localization and Synchronization for a Distributed SIMO Sonar with an Isogradient SSP and Uncertainties in Receiver Locations. Sensors (Basel) 2019; 19:E1976. [PMID: 31035606 DOI: 10.3390/s19091976] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Revised: 04/16/2019] [Accepted: 04/24/2019] [Indexed: 12/02/2022]
Abstract
A distributed single-input multiple-output (SIMO) sonar system is composed of a sound source and multiple underwater receivers. It provides an important framework for underwater target localization. However, underwater hostile environments bring more challenges for underwater target localization than terrestrial target localization, such as the difficulties of synchronizing all the underwater receiver clocks, the varying underwater sound speed and the uncertainties of the locations of the underwater receivers. In this paper, we take the sound speed variation, the time synchronization and the uncertainties of the receiver locations into account, and propose the underwater target localization and synchronization (UTLS) algorithm for the distributed SIMO sonar system. In the distributed SIMO sonar system, the receivers are organized in a star topology, where the information fusion is carried out in the central receiver (CR). All the receivers are not synchronized and their positions are known with uncertainties. Moreover, the underwater sound speed is approximately modeled by a depth-dependent sound speed profile (SSP). We evaluate our proposed UTLS algorithm by comparing it with several benchmark algorithms via numerical simulations. The simulation results reveal the superiority of our proposed UTLS algorithm.
Collapse
|
12
|
Saint-Charles A, Michard-Vanhée C, Alejevski F, Chélot E, Boivin A, Rouyer F. Four of the six Drosophila rhodopsin-expressing photoreceptors can mediate circadian entrainment in low light. J Comp Neurol 2016; 524:2828-44. [PMID: 26972685 DOI: 10.1002/cne.23994] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2015] [Revised: 02/23/2016] [Accepted: 02/25/2016] [Indexed: 12/30/2022]
Abstract
Light is the major stimulus for the synchronization of circadian clocks with day-night cycles. The light-driven entrainment of the clock that controls rest-activity rhythms in Drosophila relies on different photoreceptive molecules. Cryptochrome (CRY) is expressed in most brain clock neurons, whereas six different rhodopsins (RH) are present in the light-sensing organs. The compound eye includes outer photoreceptors that express RH1 and inner photoreceptors that each express one of the four rhodopsins RH3-RH6. RH6 is also expressed in the extraretinal Hofbauer-Buchner eyelet, whereas RH2 is only found in the ocelli. In low light, the synchronization of behavioral rhythms relies on either CRY or the canonical rhodopsin phototransduction pathway, which requires the phospholipase C-β encoded by norpA (no receptor potential A). We used norpA(P24) cry(02) double mutants that are circadianly blind in low light and restored NORPA function in each of the six types of photoreceptors, defined as expressing a particular rhodopsin. We first show that the NORPA pathway is less efficient than CRY for synchronizing rest-activity rhythms with delayed light-dark cycles but is important for proper phasing, whereas the two light-sensing pathways can mediate efficient adjustments to phase advances. Four of the six rhodopsin-expressing photoreceptors can mediate circadian entrainment, and all are more efficient for advancing than for delaying the behavioral clock. In contrast, neither RH5-expressing retinal photoreceptors nor RH2-expressing ocellar photoreceptors are sufficient to mediate synchronization through the NORPA pathway. Our results thus reveal different contributions of rhodopsin-expressing photoreceptors and suggest the existence of several circuits for rhodopsin-dependent circadian entrainment. J. Comp. Neurol. 524:2828-2844, 2016. © 2016 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Alexandra Saint-Charles
- Paris-Saclay Institute of Neuroscience, Université Paris Sud, Centre National de la Recherche Scientifque, Université Paris-Saclay, 91190, Gif-sur-Yvette, France
| | - Christine Michard-Vanhée
- Paris-Saclay Institute of Neuroscience, Université Paris Sud, Centre National de la Recherche Scientifque, Université Paris-Saclay, 91190, Gif-sur-Yvette, France
| | - Faredin Alejevski
- Paris-Saclay Institute of Neuroscience, Université Paris Sud, Centre National de la Recherche Scientifque, Université Paris-Saclay, 91190, Gif-sur-Yvette, France
| | - Elisabeth Chélot
- Paris-Saclay Institute of Neuroscience, Université Paris Sud, Centre National de la Recherche Scientifque, Université Paris-Saclay, 91190, Gif-sur-Yvette, France
| | - Antoine Boivin
- Paris-Saclay Institute of Neuroscience, Université Paris Sud, Centre National de la Recherche Scientifque, Université Paris-Saclay, 91190, Gif-sur-Yvette, France
| | - François Rouyer
- Paris-Saclay Institute of Neuroscience, Université Paris Sud, Centre National de la Recherche Scientifque, Université Paris-Saclay, 91190, Gif-sur-Yvette, France
| |
Collapse
|
13
|
Lin L, Yang C, Ma M. Maximum-Likelihood Estimator of Clock Offset between Nanomachines in Bionanosensor Networks. Sensors (Basel) 2015; 15:30827-38. [PMID: 26690173 DOI: 10.3390/s151229830] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 11/28/2015] [Accepted: 12/01/2015] [Indexed: 11/16/2022]
Abstract
Recent advances in nanotechnology, electronic technology and biology have enabled the development of bio-inspired nanoscale sensors. The cooperation among the bionanosensors in a network is envisioned to perform complex tasks. Clock synchronization is essential to establish diffusion-based distributed cooperation in the bionanosensor networks. This paper proposes a maximum-likelihood estimator of the clock offset for the clock synchronization among molecular bionanosensors. The unique properties of diffusion-based molecular communication are described. Based on the inverse Gaussian distribution of the molecular propagation delay, a two-way message exchange mechanism for clock synchronization is proposed. The maximum-likelihood estimator of the clock offset is derived. The convergence and the bias of the estimator are analyzed. The simulation results show that the proposed estimator is effective for the offset compensation required for clock synchronization. This work paves the way for the cooperation of nanomachines in diffusion-based bionanosensor networks.
Collapse
|
14
|
Russcher M, Chaves I, Lech K, Koch BCP, Nagtegaal JE, Dorsman KF, Jong A', Kayser M, van Faassen HMJR, Kema IP, van der Horst GTJ, Gaillard CAJM. An observational study on disturbed peripheral circadian rhythms in hemodialysis patients. Chronobiol Int 2015; 32:848-57. [PMID: 26101944 DOI: 10.3109/07420528.2015.1048868] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The quality of life of hemodialysis (HD) patients is hampered by reduced nocturnal sleep quality and excessive daytime sleepiness. In addition to the sleep/wake cycle, levels of circadian biomarkers (e.g. melatonin) are disturbed in end-stage renal disease (ESRD). This suggests impaired circadian clock performance in HD patients, but the underlying mechanism is unknown. In this observational study, diurnal rhythms of sleep, serum melatonin and cortisol concentrations and clock gene mRNA expression are compared between HD patients (n = 9) and healthy control subjects (n = 9). In addition, the presence of circulating factors that might affect circadian rhythmicity is tested in vitro with cell culture experiments. Reduced sleep quality (median sleep onset latency [interquartile range] of 23.9 [17.3] min for patients versus 5.0 [10] minutes for controls, p < 0.01; mean (± SD) sleep efficiency 70.2 ± 8.1% versus 82.9 ± 10.9%, p = 0.02 and mean awake minutes after sleep onset 104.8 ± 27.9 versus 54.6 ± 41.6 minutes, p = 0.01) and increased daytime sleepiness (mean Epworth Sleepiness Score of 10.0 ± 4.8 versus 3.9 ± 2.0, p < 0.01) were confirmed in HD patients. Reduced nocturnal melatonin concentrations (1 AM: 98.1 [122.9] pmol/L versus 12.5 [44.2] pmol/L, p = 0.019; 5 AM: 114.0 [131.6] pmol/L versus 11.8 [86.8] pmol/L, p = 0.031) and affected circadian control of cortisol rhythm and circadian expression of the clock gene REV-ERBα were found. HD patient serum had a higher capacity to synchronize cells in vitro, suggesting an accumulated level of clock resetting compounds in HD patients. These compounds were not cleared by hemodialysis treatment or related to frequently used medications. In conclusion, the abovementioned results strongly suggest a disturbance in circadian timekeeping in peripheral tissues of HD patients. Accumulation of clock resetting compounds possibly contributes to this. Future studies are needed for a better mechanistic understanding of the interaction between renal failure and perturbation of the circadian clock.
Collapse
Affiliation(s)
- Marije Russcher
- Department of Hospital Pharmacy, Meander Medical Center , Amersfoort , The Netherlands
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Mànuel A, Roset X, Del Rio J, Toma DM, Carreras N, Panahi SS, Garcia-Benadí A, Owen T, Cadena J. Ocean bottom seismometer: design and test of a measurement system for marine seismology. Sensors (Basel) 2012; 12:3693-719. [PMID: 22737032 DOI: 10.3390/s120303693] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Accepted: 03/12/2012] [Indexed: 11/22/2022]
Abstract
The Ocean Bottom Seismometer (OBS) is a key instrument for the geophysical study of sea sub-bottom layers. At present, more reliable autonomous instruments capable of recording underwater for long periods of time and therefore handling large data storage are needed. This paper presents a new Ocean Bottom Seismometer designed to be used in long duration seismic surveys. Power consumption and noise level of the acquisition system are the key points to optimize the autonomy and the data quality. To achieve our goals, a new low power data logger with high resolution and Signal–to-Noise Ratio (SNR) based on Compact Flash memory card is designed to enable continuous data acquisition. The equipment represents the achievement of joint work from different scientific and technological disciplines as electronics, mechanics, acoustics, communications, information technology, marine geophysics, etc. This easy to handle and sophisticated equipment allows the recording of useful controlled source and passive seismic data, as well as other time varying data, with multiple applications in marine environment research. We have been working on a series of prototypes for ten years to improve many of the aspects that make the equipment easy to handle and useful to work in deep-water areas. Ocean Bottom Seismometers (OBS) have received growing attention from the geoscience community during the last forty years. OBS sensors recording motion of the ocean floor hold key information in order to study offshore seismicity and to explore the Earth’s crust. In a seismic survey, a series of OBSs are placed on the seabed of the area under study, where they record either natural seismic activity or acoustic signals generated by compressed air-guns on the ocean surface. The resulting data sets are subsequently used to model both the earthquake locations and the crustal structure.
Collapse
|
16
|
Robinson P, Schmid U. The Asynchronous Bounded-Cycle model. Theor Comput Sci 2011; 412:5580-5601. [PMID: 22031790 PMCID: PMC3191501 DOI: 10.1016/j.tcs.2010.08.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
This paper shows how synchrony conditions can be added to the purely asynchronous model in a way that avoids any reference to message delays and computing step times, as well as system-wide constraints on execution patterns and network topology. Our Asynchronous Bounded-Cycle (ABC) model just bounds the ratio of the number of forward- and backward-oriented messages in certain ("relevant") cycles in the space-time diagram of an asynchronous execution. We show that clock synchronization and lock-step rounds can be implemented and proved correct in the ABC model, even in the presence of Byzantine failures. Furthermore, we prove that any algorithm working correctly in the partially synchronous Θ-Model also works correctly in the ABC model. In our proof, we first apply a novel method for assigning certain message delays to asynchronous executions, which is based on a variant of Farkas' theorem of linear inequalities and a non-standard cycle space of graphs. Using methods from point-set topology, we then prove that the existence of this delay assignment implies model indistinguishability for time-free safety and liveness properties. We also introduce several weaker variants of the ABC model, and relate our model to the existing partially synchronous system models, in particular, the classic models of Dwork, Lynch and Stockmayer and the query-response model by Mostefaoui, Mourgaya, and Raynal. Finally, we discuss some aspects of the ABC model's applicability in real systems, in particular, in the context of VLSI Systems-on-Chip.
Collapse
Affiliation(s)
- Peter Robinson
- Corresponding author. Tel.: +43 158801 18253; fax: +43 158801 18297.
| | | |
Collapse
|