The Experts below are selected from a list of 152952 Experts worldwide ranked by ideXlab platform

Harald Schuh - One of the best experts on this subject based on the ideXlab platform.

  • Integrated processing of ground- and space-based GPS observations: improving GPS satellite orbits observed with sparse ground Networks
    Journal of Geodesy, 2020
    Co-Authors: Wen Huang, Benjamin Männel, Pierre Sakic, Harald Schuh
    Abstract:

    The precise orbit determination (POD) of Global Navigation Satellite System (GNSS) satellites and low Earth orbiters (LEOs) are usually performed independently. It is a potential way to improve the GNSS orbits by integrating LEOs onboard observations into the processing, especially for the developing GNSS, e.g., Galileo with a sparse sensor station Network and Beidou with a regional distributed Operating Network. In recent years, few studies combined the processing of ground- and space-based GNSS observations. The integrated POD of GPS satellites and seven LEOs, including GRACE-A/B, OSTM/Jason-2, Jason-3 and, Swarm-A/B/C, is discussed in this study. GPS code and phase observations obtained by onboard GPS receivers of LEOs and ground-based receivers of the International GNSS Service (IGS) tracking Network are used together in one least-squares adjustment. The POD solutions of the integrated processing with different subsets of LEOs and ground stations are analyzed in detail. The derived GPS satellite orbits are validated by comparing with the official IGS products and internal comparison based on the differences of overlapping orbits and satellite positions at the day-boundary epoch. The differences between the GPS satellite orbits derived based on a 26-station Network and the official IGS products decrease from 37.5 to 23.9 mm ( $$34\%$$ 34 % improvement) in 1D-mean RMS when adding seven LEOs. Both the number of the space-based observations and the LEO orbit geometry affect the GPS satellite orbits derived in the integrated processing. In this study, the latter one is proved to be more critical. By including three LEOs in three different orbital planes, the GPS satellite orbits improve more than from adding seven well-selected additional stations to the Network. Experiments with a ten-station and regional Network show an improvement of the GPS satellite orbits from about 25 cm to less than five centimeters in 1D-mean RMS after integrating the seven LEOs.

Xiangyang Li - One of the best experts on this subject based on the ideXlab platform.

  • does wireless sensor Network scale a measurement study on greenorbs
    IEEE Transactions on Parallel and Distributed Systems, 2013
    Co-Authors: Yuan He, Mo Li, Jiliang Wang, Xiangyang Li
    Abstract:

    Sensor Networks are deemed suitable for large-scale deployments in the wild for a variety of applications. In spite of the remarkable efforts the community put to build the sensor systems, an essential question still remains unclear at the system level, motivating us to explore the answer from a point of real-world deployment view. Does the wireless sensor Network really scale? We present findings from a large-scale Operating sensor Network system, GreenOrbs, with up to 330 nodes deployed in the forest. We instrument such an Operating Network throughout the protocol stack and present observations across layers in the Network. Based on our findings from the system measurement, we propose and make initial efforts to validate three conjectures that give potential guidelines for future designs of large-scale sensor Networks. 1) A small portion of nodes bottlenecks the entire Network, and most of the existing Network indicators may not accurately capture them. 2) The Network dynamics mainly come from the inherent concurrency of Network operations instead of environment changes. 3) The environment, although the dynamics are not as significant as we assumed, has an unpredictable impact on the sensor Network. We suggest that an event-based routing structure can be trained and thus better adapted to the wild environment when building a large-scale sensor Network.

Wen Huang - One of the best experts on this subject based on the ideXlab platform.

  • Integrated processing of ground- and space-based GPS observations: improving GPS satellite orbits observed with sparse ground Networks
    Journal of Geodesy, 2020
    Co-Authors: Wen Huang, Benjamin Männel, Pierre Sakic, Harald Schuh
    Abstract:

    The precise orbit determination (POD) of Global Navigation Satellite System (GNSS) satellites and low Earth orbiters (LEOs) are usually performed independently. It is a potential way to improve the GNSS orbits by integrating LEOs onboard observations into the processing, especially for the developing GNSS, e.g., Galileo with a sparse sensor station Network and Beidou with a regional distributed Operating Network. In recent years, few studies combined the processing of ground- and space-based GNSS observations. The integrated POD of GPS satellites and seven LEOs, including GRACE-A/B, OSTM/Jason-2, Jason-3 and, Swarm-A/B/C, is discussed in this study. GPS code and phase observations obtained by onboard GPS receivers of LEOs and ground-based receivers of the International GNSS Service (IGS) tracking Network are used together in one least-squares adjustment. The POD solutions of the integrated processing with different subsets of LEOs and ground stations are analyzed in detail. The derived GPS satellite orbits are validated by comparing with the official IGS products and internal comparison based on the differences of overlapping orbits and satellite positions at the day-boundary epoch. The differences between the GPS satellite orbits derived based on a 26-station Network and the official IGS products decrease from 37.5 to 23.9 mm ( $$34\%$$ 34 % improvement) in 1D-mean RMS when adding seven LEOs. Both the number of the space-based observations and the LEO orbit geometry affect the GPS satellite orbits derived in the integrated processing. In this study, the latter one is proved to be more critical. By including three LEOs in three different orbital planes, the GPS satellite orbits improve more than from adding seven well-selected additional stations to the Network. Experiments with a ten-station and regional Network show an improvement of the GPS satellite orbits from about 25 cm to less than five centimeters in 1D-mean RMS after integrating the seven LEOs.

Yuan He - One of the best experts on this subject based on the ideXlab platform.

  • does wireless sensor Network scale a measurement study on greenorbs
    IEEE Transactions on Parallel and Distributed Systems, 2013
    Co-Authors: Yuan He, Mo Li, Jiliang Wang, Xiangyang Li
    Abstract:

    Sensor Networks are deemed suitable for large-scale deployments in the wild for a variety of applications. In spite of the remarkable efforts the community put to build the sensor systems, an essential question still remains unclear at the system level, motivating us to explore the answer from a point of real-world deployment view. Does the wireless sensor Network really scale? We present findings from a large-scale Operating sensor Network system, GreenOrbs, with up to 330 nodes deployed in the forest. We instrument such an Operating Network throughout the protocol stack and present observations across layers in the Network. Based on our findings from the system measurement, we propose and make initial efforts to validate three conjectures that give potential guidelines for future designs of large-scale sensor Networks. 1) A small portion of nodes bottlenecks the entire Network, and most of the existing Network indicators may not accurately capture them. 2) The Network dynamics mainly come from the inherent concurrency of Network operations instead of environment changes. 3) The environment, although the dynamics are not as significant as we assumed, has an unpredictable impact on the sensor Network. We suggest that an event-based routing structure can be trained and thus better adapted to the wild environment when building a large-scale sensor Network.

  • does wireless sensor Network scale a measurement study on greenorbs
    International Conference on Computer Communications, 2011
    Co-Authors: Yunhao Liu, Yuan He, Mo Li, Jiliang Wang, Kebin Liu, Lufeng Mo, Wei Dong, Zheng Yang, Min Xi, Jizhong Zhao
    Abstract:

    In spite of the remarkable efforts the community put to build the sensor systems, an essential question still remains unclear at the system level, motivating us to explore the answer from a point of real-world deployment view. Does the wireless sensor Network really scale? We present findings from a large scale Operating sensor Network system, GreenOrbs, with up to 330 nodes deployed in the forest. We instrument such an Operating Network throughout the protocol stack and present observations across layers in the Network. Based on our findings from the system measurement, we propose and make initial efforts to validate three conjectures that give potential guidelines for future designs of large scale sensor Networks. (1) A small portion of nodes bottlenecks the entire Network, and most of the existing Network indicators may not accurately capture them. (2) The Network dynamics mainly come from the inherent concurrency of Network operations instead of environment changes. (3) The environment, although the dynamics are not as significant as we assumed, has an unpredictable impact on the sensor Network. We suggest that an event-based routing structure can be trained optimal and thus better adapt to the wild environment when building a large scale sensor Network.

George S. Stavrakakis - One of the best experts on this subject based on the ideXlab platform.

  • Genetic algorithms optimized fuzzy controller for the indoor environmental management in buildings implemented using PLC and local Operating Networks
    Engineering Applications of Artificial Intelligence, 2002
    Co-Authors: Dionysia Kolokotsa, Kostas Kalaitzakis, George S. Stavrakakis, D. Agoris
    Abstract:

    Abstract In this paper, an optimized fuzzy controller is presented for the control of the environmental parameters at the building zone level. The occupants’ preferences are monitored via a smart card unit. Genetic algorithm optimization techniques are applied to shift properly the membership functions of the fuzzy controller in order to satisfy the occupants’ preferences while minimizing energy consumption. The implementation of the system integrates a smart card unit, sensors, actuators, interfaces, a programmable logic controller (PLC), local Operating Network (LON) modules and devices, and a central PC which monitors the performance of the system. The communication of the PLC with the smart card unit is performed using an RS 485 port, while the PLC-PC communication is performed via the LON Network. The integrated system is installed and tested in the building of the Laboratory of Electronics of the Technical University of Crete.

  • Interconnecting smart card system with PLC controller in a local Operating Network to form a distributed energy management and control system for buildings
    Energy Conversion and Management, 2001
    Co-Authors: D. Kolokotsa, Kostas Kalaitzakis, E Antonidakis, George S. Stavrakakis
    Abstract:

    Distributed control and energy management for buildings is a viable solution, ensuring both indoor comfort for the occupants and reduction of energy consumption. The aim of this paper is to present the architecture of a distributed building energy management system that can be installed in new as well as in existing buildings, which are more energy inefficient. The system integrates a smart card unit, acting as a user machine interface, sensors, actuators, interfaces, a PLC controller that incorporates the fuzzy control algorithm, local Operating Network (LON) modules and devices and an optional PC which monitors the performance of the system. The distributed control architecture is based on the properties of the LON. The complete system is installed and tested in the Laboratory of Electronics of the Technical University of Crete.

  • Advanced decision support techniques in combination with smart card and local Operating Network technologies for intelligent energy management in buildings
    1998
    Co-Authors: D. Kolokotsa, Kostas Kalaitzakis, George S. Stavrakakis, G. Sutherland, M. Santamouris, S. Soultanidis, P. Moumtzis, J. Brunet, P. Guillaumin, L. Pelegrini
    Abstract:

    The purpose of the present paper is to present recent developments of integrated building energy manaeement system combining intelligent decision making systems and smart card technology using Local Operating Network (LON) techniques applying mainly to existing buildings and to new buildings with minimum construction modifications. The development of the above Integrated Energy Management System (IBEMS) is focusing on 25% energy savings at existing buildings comparing to conventional control systems improving at the same time the indoor conditions and comfort. The project is funded in part by the European Commission in the framework of the Non Nuclear Energy Program JOULE III (CT97-0044)