The Experts below are selected from a list of 3963 Experts worldwide ranked by ideXlab platform
Alf J Isaksson - One of the best experts on this subject based on the ideXlab platform.
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simulation of process control with wirelesshart networks subject to Clock Drift
Computer Software and Applications Conference, 2008Co-Authors: M De Biasi, C Snickars, Krister Landernas, Alf J IsakssonAbstract:This work describes simulation of wireless control using the WirelessHart standard. Specifically issues concerning Clock Drift between controllers and wireless network are addressed. The simulations have been done using an extension of the Simulink package TrueTime.
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COMPSAC - Simulation of Process Control with WirelessHART Networks Subject to Clock Drift
2008 32nd Annual IEEE International Computer Software and Applications Conference, 2008Co-Authors: M De Biasi, C Snickars, Krister Landernas, Alf J IsakssonAbstract:This work describes simulation of wireless control using the WirelessHart standard. Specifically issues concerning Clock Drift between controllers and wireless network are addressed. The simulations have been done using an extension of the Simulink package TrueTime.
Timothy E Levin - One of the best experts on this subject based on the ideXlab platform.
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quantifying effect of network latency and Clock Drift on time driven key sequencing
International Conference on Distributed Computing Systems, 2002Co-Authors: Geoffrey G Xie, Cynthia E Irvine, Timothy E LevinAbstract:Time-driven key sequencing (TKS) is a key management technique that synchronizes the session key used by a set of communicating principals based on time of day. This relatively low cost method of session key synchronization has been used in specialized distributed systems with low-end communicating devices where sessions are sparse and each session spans a short time period comprising a small number of messages. In this paper, we describe how TKS may be useful in several scenarios involving high speed computer networks. More importantly, we present a performance model of TKS and conduct a detailed analysis to determine the impact of Clock Drift and network latency on the required key refresh rate. We give the exact conditions for determining the range of adequate key refresh rates, and demonstrate that the derived conditions are sufficient to ensure that data are both protected and deliverable. Interestingly, these conditions may be used to obtain a key refresh rate that can tolerate a maximum amount of Clock Drift after other parameters in the system are fixed.
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ICDCS Workshops - Quantifying effect of network latency and Clock Drift on time-driven key sequencing
Proceedings 22nd International Conference on Distributed Computing Systems Workshops, 1Co-Authors: Geoffrey G Xie, Cynthia E Irvine, Timothy E LevinAbstract:Time-driven key sequencing (TKS) is a key management technique that synchronizes the session key used by a set of communicating principals based on time of day. This relatively low cost method of session key synchronization has been used in specialized distributed systems with low-end communicating devices where sessions are sparse and each session spans a short time period comprising a small number of messages. In this paper, we describe how TKS may be useful in several scenarios involving high speed computer networks. More importantly, we present a performance model of TKS and conduct a detailed analysis to determine the impact of Clock Drift and network latency on the required key refresh rate. We give the exact conditions for determining the range of adequate key refresh rates, and demonstrate that the derived conditions are sufficient to ensure that data are both protected and deliverable. Interestingly, these conditions may be used to obtain a key refresh rate that can tolerate a maximum amount of Clock Drift after other parameters in the system are fixed.
Choi Look Law - One of the best experts on this subject based on the ideXlab platform.
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A Novel E-DTDOA Based One-Way Ranging Using UWB-IR With Unsynchronized Anchors
IEEE Transactions on Industrial Informatics, 2021Co-Authors: Ankush Vashistha, Choi Look LawAbstract:In this article, a novel analytical equation is proposed to determine the equivalent time of arrival (E-TOA) for achieving sub-ns resolution, with much reduced analog-to-digital converter sampling frequency (in the order of 2–3 MHz). The timing information is extracted from high resolution channel impulse response, which is obtained using an equivalent time sampling (ETS) technique. The proposed E-TOA equation is different from the conventional real-time sampling equation due to the presence of an additional transmitter Clock Drift, and thus sensitive to both the transmitter and receiver Clock Drift variations. The validation of the E-TOA equation is carried out numerically using simulations along with experimental validation. The effect of timing uncertainties relating to the transmitter Clock start time and the receiver Clock offset is analyzed with variations in the transmitter and receiver Clock Drifts. With E-TOA measurements, an equivalent differential time difference of arrival based one-way ranging scheme for unsynchronized anchors is further proposed. It is thus demonstrated, using in house designed sensor nodes, that high ranging accuracy, in the order of few centimeters, can be achieved by utilizing the proposed analytical E-TOA technique, even with low sampling rate.
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E-DTDOA Based Localization for Wireless Sensor Networks With Clock Drift Compensation
IEEE Sensors Journal, 2020Co-Authors: Ankush Vashistha, Choi Look LawAbstract:A high time resolution localization scheme, using ultra-wide band ranging signal with bandwidth of 2GHz, is proposed for a fully asynchronous wireless sensor network (WSN). The proposed scheme is specifically useful for sensor nodes which are designed to operate at very low ADC sampling rate, in the order of 2–3 MHz, but still achieves the sampling resolution in the order of sub-nanoseconds. To achieve low sampling rate, equivalent time sampling (ETS) technique is used at the sensor nodes. Reconstructed signal obtained by ETS technique, that require periodic transmission of the same signal repetitively, is severely affected by the variation in transmitter and receiver Clock Drift as against the real time sampling where the variations are due to receiver node Clock Drift only. Thus, it requires a protocol to precisely estimate the transmitter and receiver Clock parameters. A scheme, which uses a novel mathematical equivalent time of arrival (E-TOA) model for ETS based system, for Clock Drift estimation is presented. Based on Clock Drift estimation parameters, receiver nodes are tuned to the same frequency. E-TOA measurements are further used to propose an equivalent differential time difference of arrival (E-DTDOA) based ranging algorithm, which relaxed the time synchronization requirement between the wireless nodes, and still achieving high time resolution. The E-DTDOA range measurements are subsequently used to obtain precise localization of the target node/s. The feasibility of the algorithm proposed is demonstrated experimentally using in house designed wireless sensor nodes.
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The use of symmetric multi-way two phase ranging to compensate time Drift in wireless sensor network
IEEE Transactions on Wireless Communications, 2009Co-Authors: J.x. Lee, Z.w. Lin, P.s. Chin, Choi Look LawAbstract:This paper studies the impact of crystal Clock Drift on the ranging accuracy. A novel technique in which a group of sensor devices, each having a different Clock Drift, can reduce this adverse effect by a 2-phase round robin fashion is presented. In comparison to the conventional way of point-to-point group ranging scheme, this technique has the desirable advantage of low energy consumption, which is a very important requirement in wireless sensor networks. The ability to reduce the effect of timing Drift is illustrated in the simulation results where our proposed method outperforms prior works under the effect of Clock Drift on the ranging accuracy.
M De Biasi - One of the best experts on this subject based on the ideXlab platform.
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simulation of process control with wirelesshart networks subject to Clock Drift
Computer Software and Applications Conference, 2008Co-Authors: M De Biasi, C Snickars, Krister Landernas, Alf J IsakssonAbstract:This work describes simulation of wireless control using the WirelessHart standard. Specifically issues concerning Clock Drift between controllers and wireless network are addressed. The simulations have been done using an extension of the Simulink package TrueTime.
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COMPSAC - Simulation of Process Control with WirelessHART Networks Subject to Clock Drift
2008 32nd Annual IEEE International Computer Software and Applications Conference, 2008Co-Authors: M De Biasi, C Snickars, Krister Landernas, Alf J IsakssonAbstract:This work describes simulation of wireless control using the WirelessHart standard. Specifically issues concerning Clock Drift between controllers and wireless network are addressed. The simulations have been done using an extension of the Simulink package TrueTime.
Jean-yves Royer - One of the best experts on this subject based on the ideXlab platform.
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Using Teleseismic P-Wave Arrivals to Calibrate the Clock Drift of Autonomous Underwater Hydrophones
Bulletin of the Seismological Society of America, 2020Co-Authors: Alexey Sukhovich, Julie Perrot, Jean-yves RoyerAbstract:Networks of Autonomous Underwater Hydrophones (AUHs) are successfully employed for monitoring the low-level seismicity of mid-oceanic ridges by detecting hydroacoustic phases known as T-waves. For a precise localization of a seismic event from T-wave arrival times, all AUHs must be synchronized. To this effect, at the beginning of the experiment all instrument Clocks are set to GPS time, which serves as a common reference. However, during the experiment the instrument Clock often deviates from GPS time, and since the amount of deviation differs from one instrument to another, the synchronization of the AUHs deteriorates as the experiment progresses in time. Just after the instrument recovery, the time difference (called "skew") between the instrument and the GPS Clocks is measured. Assuming that the skew varies linearly with time, the correction of a time series for the Clock Drift is a straightforward procedure. When the final skew cannot be determined, correcting for the Clock Drift is not possible and any event localization becomes problematic. In this paper, we demonstrate that the Clock Drift rate (assumed to be time-independent) can be successfully estimated from arrival times of teleseismic P-waves, commonly recorded by AUHs. Using a ray-tracing code, and accounting for the uncertainties in event hypocenter locations, origin times and the Earth seismic-velocity model, confidence intervals of the estimated Drift rates are deduced. The validity of the approach is tested on data from two AUHs with known Clock-Drifts. Our results show that a reliable estimation is possible for skews as small as 4 s per two years (corresponding to a Drift rate of about 5.5 ms • day −1). This method can also be applied to correct data of other recording instruments subject to internal-Clock Drift, such as ocean bottom seismometers, when the skew is unknown.
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Using Teleseismic P-Wave Arrivals to Calibrate the Clock Drift of Autonomous Underwater Hydrophones
Bulletin of the Seismological Society of America, 2020Co-Authors: Alexey Sukhovich, Julie Perrot, Jean-yves RoyerAbstract:ABSTRACT Networks of autonomous underwater hydrophones (AUHs) are successfully employed for monitoring the low-level seismicity of mid-oceanic ridges by detecting hydroacoustic phases known as T waves. For a precise localization of a seismic event from T-wave arrival times, all AUHs must be synchronized. To this effect, at the beginning of the experiment, all instrument Clocks are set to GPS time, which serves as a common reference. However, during the experiment, the instrument Clock often deviates from GPS time, and, because the amount of deviation differs from one instrument to another, the synchronization of the AUHs deteriorates, as the experiment progresses in time. Just after the instrument recovery, the time difference (called “skew”) between the instrument and the GPS Clocks is measured. Assuming that the skew varies linearly with time, the correction of a time series for the Clock Drift is a straightforward procedure. When the final skew cannot be determined, correcting for the Clock Drift is not possible, and any event localization becomes problematic. In this article, we demonstrate that the Clock-Drift rate (assumed to be time-independent) can be successfully estimated from arrival times of teleseismic P waves, commonly recorded by AUHs. Using a ray-tracing code, and accounting for the uncertainties in event hypocenter locations, origin times, and the Earth seismic-velocity model, confidence intervals of the estimated Drift rates are deduced. The validity of the approach is tested on data from two AUHs with known Clock Drifts. Our results show that a reliable estimation is possible for skews as small as 4 s per two years (corresponding to a Drift rate of about 5.5 ms·day−1). This method can also be applied to correct data of other recording instruments subject to internal-Clock Drift, such as ocean-bottom seismometers, when the skew is unknown.
