Wireless sensor networks are envisioned to be an integral part of cyber-physical systems, yet wireless networks are inherently dynamic and come with various uncertainties. One such uncertainty is wireless communicatio...Wireless sensor networks are envisioned to be an integral part of cyber-physical systems, yet wireless networks are inherently dynamic and come with various uncertainties. One such uncertainty is wireless communication itself which assumes complex spatial and temporal dynamics. For dependable and predictable performance, therefore, link estimation has become a basic element of wireless network routing. Several approaches using broadcast beacons and/or unicast MAC feedback have been proposed in the past years, but there is still no systematic characterization of the drawbacks and sources of errors in bea- con-based link estimation in low-power wireless networks, which leads to ad hoc usage of beacons in rout- ing. Using a testbed of 98 XSM motes （an enhanced version of MICA2 motes）, we characterize the negative impact that link layer retransmission and traffic-induced interference have on the accuracy of beacon-based link estimation, and we show that data-driven link estimation and routing achieve higher event reliability （e.g. by up to 18.75%） and transmission efficiency （e.g., by up to a factor of 1.96） than beacon-based approaches These findings provide solid evidence for the necessity of data-driven link estimation and demonstrate the importance of addressing the drawbacks of beacon-based link estimation when designing protocols for low-power wireless networks of cyber-physical systems.展开更多
This paper proposes a chip correlation indicator （CCI）-based link quality estimation mechanism for wireless sensor networks under non-perceived packet loss. On the basis of analyzing all related factors, it can be c...This paper proposes a chip correlation indicator （CCI）-based link quality estimation mechanism for wireless sensor networks under non-perceived packet loss. On the basis of analyzing all related factors, it can be concluded that signal-to-noise rate （SNR） is the main factor causing the non-perceived packet loss. In this paper, the relationship model between CCI and non-perceived packet loss rate （NPLR） is established from related models such as SNR versus packet success rate （PSR）, CCI versus SNR and CCI-NPLR. Due to the large fluctuating range of the raw CCI, Kalman filter is introduced to do de-noising of the raw CCI. The cubic model and the least squares method are employed to fit the relationship between CCI and SNR. In the experiments, many groups of comparison have been conducted and the results show that the proposed mechanism can achieve more accurate measurement of the non-perceived packet loss than existing approaches. Moreover, it has the advantage of decreasing extra energy consumption caused by sending large number of probe packets.展开更多
Large constellations composed of a great amount of Low Earth Orbit(LEO)satellites are widely applied in satellite communication,remote sensing,augmented satellite navigation,environment monitoring,and so on.The satell...Large constellations composed of a great amount of Low Earth Orbit(LEO)satellites are widely applied in satellite communication,remote sensing,augmented satellite navigation,environment monitoring,and so on.The satellite Orbit Determination(OD)is critical for the various function realization of the large constellation.Three different stepwise autonomous OD strategies for the large constellation of LEO satellites are proposed based on the spaceborne Global Navigation Satellite System(GNSS)observations and Inter-Satellite Link(ISL)range measurements,including the stepwise OD with both GNSS and ISL range measurements,stepwise OD with ISL range constraints,and an adaptive stepwise OD with both kinds of measurements.All of the three proposed stepwise autonomous OD approaches first estimate the initial orbit parameters for each satellite utilizing the spaceborne GNSS observations based on either a kinematic or dynamic OD strategy.The correction vector for the orbit parameters of each satellite is then individually calculated using the partial ISL range observations or ISL range constraints.The difference of the adaptive stepwise OD algorithm is that the covariance matrix of the predicted orbit parameters based on the dynamic model is modified by an adaptive factor.The LEO satellite parameters estimated with the stepwise OD strategies are equivalent to those obtained with the related integrated OD strategies.The main advantages of the proposed stepwise OD estimators are:(1)the orbit parameters of each satellite can be estimated in parallel,reducing the OD computational load for a large LEO constellation;(2)the spaceborne GNSS observations and the ILS range measurements in the three proposed approaches can be separately joined the OD procedures,making the parameter estimation flexible;(3)the adaptive stepwise OD mode with an adaptive factor acting on the covariance matrix of the predicted orbit parameters can effectively control the effects of the abnormal dynamic model information on the orbit parameter estimates.The simulation results for different OD strategies are analyzed.It is shown that the Root Mean Square Error(RMSE)of the estimated positions of the LEO satellites using the kinematic OD method is 60.527 cm,assuming the GNSS pseudorange noise of 30 cm.In contrast,the RMSE for the stepwise strategy,which considers only four adjacent ISL range measurements with an accuracy of 5 cm,is 18.287 cm.When the dynamic models for the LEO satellites are adopted,the RMSE of the estimated satellite positions using the stepwise orbit determination is further reduced to 11.340 cm.If the ISI ranging accuracy is better than 5 cm,the results remain nearly the same disregarding the ISL ranges are employed as observations or as constraints in the stepwise OD approaches.If the dynamic model information contains a few outliers,the adaptive stepwise OD can effectively control their effects on the orbit parameter estimates.展开更多
文摘Wireless sensor networks are envisioned to be an integral part of cyber-physical systems, yet wireless networks are inherently dynamic and come with various uncertainties. One such uncertainty is wireless communication itself which assumes complex spatial and temporal dynamics. For dependable and predictable performance, therefore, link estimation has become a basic element of wireless network routing. Several approaches using broadcast beacons and/or unicast MAC feedback have been proposed in the past years, but there is still no systematic characterization of the drawbacks and sources of errors in bea- con-based link estimation in low-power wireless networks, which leads to ad hoc usage of beacons in rout- ing. Using a testbed of 98 XSM motes （an enhanced version of MICA2 motes）, we characterize the negative impact that link layer retransmission and traffic-induced interference have on the accuracy of beacon-based link estimation, and we show that data-driven link estimation and routing achieve higher event reliability （e.g. by up to 18.75%） and transmission efficiency （e.g., by up to a factor of 1.96） than beacon-based approaches These findings provide solid evidence for the necessity of data-driven link estimation and demonstrate the importance of addressing the drawbacks of beacon-based link estimation when designing protocols for low-power wireless networks of cyber-physical systems.
基金supported by the National Natural Science Foundation of China (61262020)Aeronautical Science Foundation of China (2010ZC56008)Nanchang Hangkong University Postgraduate Innovation Foundation (YC2011030)
文摘This paper proposes a chip correlation indicator （CCI）-based link quality estimation mechanism for wireless sensor networks under non-perceived packet loss. On the basis of analyzing all related factors, it can be concluded that signal-to-noise rate （SNR） is the main factor causing the non-perceived packet loss. In this paper, the relationship model between CCI and non-perceived packet loss rate （NPLR） is established from related models such as SNR versus packet success rate （PSR）, CCI versus SNR and CCI-NPLR. Due to the large fluctuating range of the raw CCI, Kalman filter is introduced to do de-noising of the raw CCI. The cubic model and the least squares method are employed to fit the relationship between CCI and SNR. In the experiments, many groups of comparison have been conducted and the results show that the proposed mechanism can achieve more accurate measurement of the non-perceived packet loss than existing approaches. Moreover, it has the advantage of decreasing extra energy consumption caused by sending large number of probe packets.
基金funded by the National Natural Science Foundation of China(Grant No.42388102,No.41931076).
文摘Large constellations composed of a great amount of Low Earth Orbit(LEO)satellites are widely applied in satellite communication,remote sensing,augmented satellite navigation,environment monitoring,and so on.The satellite Orbit Determination(OD)is critical for the various function realization of the large constellation.Three different stepwise autonomous OD strategies for the large constellation of LEO satellites are proposed based on the spaceborne Global Navigation Satellite System(GNSS)observations and Inter-Satellite Link(ISL)range measurements,including the stepwise OD with both GNSS and ISL range measurements,stepwise OD with ISL range constraints,and an adaptive stepwise OD with both kinds of measurements.All of the three proposed stepwise autonomous OD approaches first estimate the initial orbit parameters for each satellite utilizing the spaceborne GNSS observations based on either a kinematic or dynamic OD strategy.The correction vector for the orbit parameters of each satellite is then individually calculated using the partial ISL range observations or ISL range constraints.The difference of the adaptive stepwise OD algorithm is that the covariance matrix of the predicted orbit parameters based on the dynamic model is modified by an adaptive factor.The LEO satellite parameters estimated with the stepwise OD strategies are equivalent to those obtained with the related integrated OD strategies.The main advantages of the proposed stepwise OD estimators are:(1)the orbit parameters of each satellite can be estimated in parallel,reducing the OD computational load for a large LEO constellation;(2)the spaceborne GNSS observations and the ILS range measurements in the three proposed approaches can be separately joined the OD procedures,making the parameter estimation flexible;(3)the adaptive stepwise OD mode with an adaptive factor acting on the covariance matrix of the predicted orbit parameters can effectively control the effects of the abnormal dynamic model information on the orbit parameter estimates.The simulation results for different OD strategies are analyzed.It is shown that the Root Mean Square Error(RMSE)of the estimated positions of the LEO satellites using the kinematic OD method is 60.527 cm,assuming the GNSS pseudorange noise of 30 cm.In contrast,the RMSE for the stepwise strategy,which considers only four adjacent ISL range measurements with an accuracy of 5 cm,is 18.287 cm.When the dynamic models for the LEO satellites are adopted,the RMSE of the estimated satellite positions using the stepwise orbit determination is further reduced to 11.340 cm.If the ISI ranging accuracy is better than 5 cm,the results remain nearly the same disregarding the ISL ranges are employed as observations or as constraints in the stepwise OD approaches.If the dynamic model information contains a few outliers,the adaptive stepwise OD can effectively control their effects on the orbit parameter estimates.
