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Iwata T.,Japan National Institute of Advanced Industrial Science and Technology | Matsuzawa T.,Japan National Institute of Advanced Industrial Science and Technology | Kawauchi T.,Mitsubishi Group | Fukushima S.,Space Engineering Development Co. | And 5 more authors.
Institute of Navigation - International Technical Meeting 2011, ITM 2011 | Year: 2011

The First Japanese positioning satellite, MICHIBIKI, Quasi-Zenith Satellite-1, was launched successfully on September 11, 2010 from the Tanegashima Space Center of Japan Aerospace Exploration Agency (JAXA). The first three months after the launch were devoted to initial functional verification tests. The National Institute of Advanced Industrial Science and Technology (AIST) has been developing the remote synchronization system of an onboard crystal oscillator (RESSOX) for the Quasi-Zenith Satellite System (QZSS), and planned initial functional verification tests to be conducted at the Time Management Station (TMS) in Koganei (Tokyo) in November and at the TMS in Onna (Okinawa) in December of 2010. Those TMSs are facilities of the National Institute of Information and Communication Technology (NICT). RESSOX reduces overall cost, satellite power consumption, and onboard weight and volume. Moreover, RESSOX has a longer lifetime than a system with onboard atomic clocks. However, MICHIBIKI carries rubidium atomic clocks and RESSOX will be used in the experiments to examine its potential use in future QZSS. Six basic functional capability tests were planned: (1) measurement of time difference between RESSOX control signal and a space vehicle clock, (2) feed-forward capability of RESSOX Experiment One, (3) feedback capability of RESSOX Experiment One, (4) control performance during communication interruption (CI) of RESSOX Experiment One, (5) capability of RESSOX Experiment Two, and (6) control performance during CI of RESSOX Experiment Two, and (1), (2), (4), (5), and (6) were verified. In Experiment One, the RESSOX control signal that includes information on the standard time is sent from ground stations, and the onboard crystal oscillator of MICHIBIKI is controlled to synchronize the arrival of the RESSOX control signal. This is similar to such time calibration signals as WWV or JJY, but compensates the delay. In Experiment Two, on the basis of the results of a time comparison between the onboard crystal oscillator and the standard time conducted by NICT, the voltage applied to the onboard crystal oscillator is calculated at the ground station and is transmitted to MICHIBlKI to control the crystal oscillator. In the actual operation, 35-minute CI occurs twice a day because of the need to avoid interference with other GEO satellites. Therefore, the control performance during CI should be considered. In this paper, first, Experiments One and Two will be described. Second, the results of actual initial functional verification tests are demonstrated. Finally, issues for real experiments are discussed.


Wijayanto Y.N.,National Institute of Information and Communication Technology NICT | Wijayanto Y.N.,Indonesian Institute of Sciences | Kanno A.,National Institute of Information and Communication Technology NICT | Nakajima S.,National Institute of Information and Communication Technology NICT | And 4 more authors.
Progress in Electromagnetics Research Symposium | Year: 2015

We propose an electrical-optical converter using electric-field-coupled metamaterial antennas on an electro-optic (EO) modulator for wireless millimeter-wave/terra-hertz applications. By wireless signal irradiation to the proposed device, strong millimeter-wave/terra-hertz electric field can be induced on the electric-field-coupled metamaterial antennas. The induced electric field can be used for optical modulation through EO effects when a lightwave propagates into an optical waveguide located under regions of the induced millimeter-wave/terra-hertz electric field. Analysis in millimeter-wave and optical modulation of the proposed device are discussed in detail for operational frequency of 100 GHz. Device experiment in fabrication and preliminary measurement are also reported.


An X.,Technical University of Delft | Sum C.-S.,National Institute of Information and Communication Technology NICT | Prasad R.V.,Technical University of Delft | Harada H.,National Institute of Information and Communication Technology NICT | Niemegeers I.,Technical University of Delft
IEEE Communications Letters | Year: 2010

60GHz radio is a promising technology since it can offer multi-Gbps data rate. However, 60 GHz radio based transmission is easily disturbed by co-channel interference (CCI). In this letter, a novel analytical model is provided to investigate the performance of using synchronization (sync) frames to mitigate CCI. The performance improvement while using sync frames is demonstrated in terms of throughput and the guaranteed transmission distance. © 2010 IEEE.


Nakanishi T.,National Institute of Information and Communication Technology NICT | Homma H.,National Institute of Information and Communication Technology NICT | Kim K.-S.,National Institute of Information and Communication Technology NICT | Zettsu K.,National Institute of Information and Communication Technology NICT | And 3 more authors.
Frontiers in Artificial Intelligence and Applications | Year: 2011

Various knowledge resources are spread to a world-wide scope. Unfortunately, most of them are community-based and never thought to be used among different communities. That makes it difficult to gain "connection merits" in a web-scale information space. This paper presents a three-layered system architecture for computing dynamic associations of events to related knowledge resources. The important feature of our system is to realize dynamic interconnection among heterogeneous knowledge resources by event-driven and event-centric computing with resolvers for uncertainties existing among those resources. This system navigates various associated data including heterogeneous data-types and fields depending on user's purpose and standpoint. It also leads to effective use for the sensor data because the sensor data can be interconnected with those knowledge resources. This paper also represents application to the space weather sensor data. © 2011 The authors and IOS Press. All rights reserved.


Zhang X.,National Institute of Information and Communication Technology NICT | Ser W.,Nanyang Technological University | Harada H.,National Institute of Information and Communication Technology NICT
European Signal Processing Conference | Year: 2010

In this paper, a broadband beamspace adaptive microphone array that constructs a multibeam network is proposed. A beampattern synthesis method that has its frequency invariant property focusing on the desired direction only was used to form the beams. The main idea is to replace the blocking matrix and the quiescent vector in the conventional General Sidelobe Canceler (GSC) with the frequency invariant beam- pattern synthesis method. Simulation results show that this proposed method has faster convergence rate than an existing algorithm. © EURASIP, 2010.


Dien Hoang V.,National Institute of Information and Communication Technology NICT | Zhang X.,National Institute of Information and Communication Technology NICT | Filin S.,National Institute of Information and Communication Technology NICT | Harada H.,National Institute of Information and Communication Technology NICT
IEEE International Conference on Networks, ICON | Year: 2012

Radio frequencies have become a scarce resource in many countries and white space communication promised to alleviate this problem. Standardization for devices operating in white space frequencies became indispensable and 1900.7 working group was formed from the white space ad hoc group in DySPAN for that task. This paper aims to provide an overall understanding of the 1900.7 standard. The network architecture, design, requirement, use cases, reference models and progress of 1900.7 are discussed in details in this paper. © 2012 IEEE.

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