The Experts below are selected from a list of 3372 Experts worldwide ranked by ideXlab platform

Shunji Yoshiyama - One of the best experts on this subject based on the ideXlab platform.

  • ring network with temporary master node for collecting data from slave nodes during failure
    1994
    Co-Authors: Shunji Yoshiyama
    Abstract:

    In a ring network where network nodes are interconnected by an optical fiber ring, one of the nodes acts as a master node and each of the other nodes acts as a slave node. The master node successively designates a different slave node in a descending order of priorities, transmits a Command Message to the designated slave node, and updates its memory with a response Message from the designated node. If the Command Message is received, each designated slave node updates its memory with data contained in the Command Message and returns a response Message to the master node. If the Command Message is not received, each slave node, acting as a temporary master node, designates a different one of the other slave nodes in descending order, transmits a Command Message to each designated node, and updates its memory with a response Message therefrom. Each temporary master node repeats the process until it receives a Command Message from another temporary master node having a priority higher than the priority of the sending node.

Santangelo Andrew - One of the best experts on this subject based on the ideXlab platform.

  • Globalstar STX3 To STX4/SpotX: An Evolution from Global Simplex to Global Duplex Communications for 1U Cubesats and Larger Vehicles
    DigitalCommons@USU, 2021
    Co-Authors: Santangelo Andrew
    Abstract:

    The STX3 module is used in devices from the LinkStar-TRK satellite radio system to SPOT locators used on the ground providing global beaconing services for a range of systems and applications such as cubesats, aircraft, ships at sea, and pipeline monitoring systems to name a few. For cubesats and small satellites the STX3 and the STX3 based LinkStar-TRK provides an invaluable low cost global data communications system. However a key drawback is the module only provides one-way “simplex” communications–there is not a mechanism to send Messages and Commands globally up to the satellite via the STX3 module. Per FCC regulations and NASA Policy Directive (NPD) 2570.5E “all spacecraft shall be equipped with mechanisms to remotely cease EM emissions unless there is a human presence with this direct capability” – thus satellite operators of STX3 based radios must provide a second radio, an uplink, to cease emissions of the STX3 module. The STX3 module becomes dependent on the functionality of another radio which defeats the global communications capability. As a result, sci_Zone in partnership with Globalstar has begun research and development of the STX4 based radio system – the LinkStar-TRK-X, an adaptation of Globalstar’s Spot-X radio providing low bandwidth global duplex communications that fits within 0.25U of a cubesat (100x100x25mm). The architecture is designed to interface with the cubesat bus, is a PC104 format board, and provides full Message downlink and Command/Message uplink services for the cubesat and small satellite. Over 90% Earth coverage is provided by the LinkStar-TRK-X radio system. The LinkStar-TRK-X design provides support for I2C and an I2C multiplexer, Space Wire, serial connections, USB, and a range of switched and unswitched power connectors to power the LinkStar-TRK-X and supported instruments. The integrated flight computer hosts the QuickSAT/VMS system providing vehicle control, communications, and instrument management functions. QuickSAT/VMS provides a web based interface for easy vehicle configuration, system testing, and management. In this presentation we will present the system design and implementation, and how LinkStar-TRK-X fits within a cubesat architecture, plus how the unit communicates with the desktop and iPhone from anywhere in orbit

Khanampompan Teerapat - One of the best experts on this subject based on the ideXlab platform.

  • Automatic Command Sequence Generation
    2007
    Co-Authors: Fisher Forest, Gladded Roy, Khanampompan Teerapat
    Abstract:

    Automatic Sequence Generator (Autogen) Version 3.0 software automatically generates Command sequences for the Mars Reconnaissance Orbiter (MRO) and several other JPL spacecraft operated by the multi-mission support team. Autogen uses standard JPL sequencing tools like APGEN, ASP, SEQGEN, and the DOM database to automate the generation of uplink Command products, Spacecraft Command Message Format (SCMF) files, and the corresponding ground Command products, DSN Keywords Files (DKF). Autogen supports all the major multi-mission mission phases including the cruise, aerobraking, mapping/science, and relay mission phases. Autogen is a Perl script, which functions within the mission operations UNIX environment. It consists of two parts: a set of model files and the autogen Perl script. Autogen encodes the behaviors of the system into a model and encodes algorithms for context sensitive customizations of the modeled behaviors. The model includes knowledge of different mission phases and how the resultant Command products must differ for these phases. The executable software portion of Autogen, automates the setup and use of APGEN for constructing a spacecraft activity sequence file (SASF). The setup includes file retrieval through the DOM (Distributed Object Manager), an object database used to store project files. This step retrieves all the needed input files for generating the Command products. Depending on the mission phase, Autogen also uses the ASP (Automated Sequence Processor) and SEQGEN to generate the Command product sent to the spacecraft. Autogen also provides the means for customizing sequences through the use of configuration files. By automating the majority of the sequencing generation process, Autogen eliminates many sequence generation errors commonly introduced by manually constructing spacecraft Command sequences. Through the layering of Commands into the sequence by a series of scheduling algorithms, users are able to rapidly and reliably construct the desired uplink Command products. With the aid of Autogen, sequences may be produced in a matter of hours instead of weeks, with a significant reduction in the number of people on the sequence team. As a result, the uplink product generation process is significantly streamlined and mission risk is significantly reduced. Autogen is used for operations of MRO, Mars Global Surveyor (MGS), Mars Exploration Rover (MER), Mars Odyssey, and will be used for operations of Phoenix. Autogen Version 3.0 is the operational version of Autogen including the MRO adaptation for the cruise mission phase, and was also used for development of the aerobraking and mapping mission phases for MRO

Rolf Sigle - One of the best experts on this subject based on the ideXlab platform.

  • improvement of lte handover performance through interference coordination
    Vehicular Technology Conference, 2009
    Co-Authors: Danish Aziz, Rolf Sigle
    Abstract:

    An Orthogonal Frequency Division Multiple Access (OFDMA) based radio-interface is specified by 3GPP for LTE system. OFDMA provides efficient spectral efficiency by reusing complete frequency band in all cells. However it projects high inter cell interference (ICI) especially on cell borders. ICI not only minimizes the cell border throughput but also effects on the handover performance in LTE. Hard handover is standardized for LTE systems using L3-filter, hysteresis, and time-to-trigger mechanisms. The UE needs to receive error free handover Command Message for successful handover. This becomes critical when high interference is present on cell borders. Inter cell interference coordination (ICIC) is a technique that has been proposed to overcome ICI problems. We have investigated the improvements of LTE handover performance through ICIC. We have shown that significant gain can be achieved by the use of ICIC while maintaining very low handover rates.

Weiming Shen - One of the best experts on this subject based on the ideXlab platform.

  • Communication model of embedded multi-protocol gateway for MRO online monitoring system
    Proceedings of the 2015 IEEE 19th International Conference on Computer Supported Cooperative Work in Design CSCWD 2015, 2015
    Co-Authors: Rong Yin, Feng Gui, Fei Li, Min Liu, Feng Zhang, Weiming Shen
    Abstract:

    Communication technologies, involving fieldbus network, Wireless Sensor Network (WSN) and industrial Ethernet, are mainly applied to complex industrial applications like continuous casting field, in order to transmit information. However, there're still some shortcomings exposed and certain higher requirements such as compatibility, expansibility, and transmission distance and speed have been put forward. Accordingly, this paper proposed a design scheme of embedded multi-protocol gateway with wire and wireless communication methods integrated. A communication model of embedded multi-protocol gateway is established, taking example by the principle of protocol conversion and the architecture of heterogeneous network integration based on Open System Interconnection Reference Model (OSI/RM). In addition, the intercommunication of such a network combining WSN, CAN bus, 3G network, WLAN, and Ethernet is realized, taking data heterogeneous and Command Message conflicting into consideration. Moreover, the use of modular and hierarchical design method made it possible for subnet communication interface to expand to different monitoring equipment and data acquisition equipment. The proposed model provides solution of heterogeneous network integration and real-time data service of high speed and wide coverage for the MRO online monitoring system.