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A low power all-digital frequency locked loop with resource-efficient frequency detector and hysteresis lock detector

Zhao Y., Mitsugi J., Min H.

IEICE Electronics Express 21 （ 20 ） 2024年

ISSN 13492543

Trillions of Internet of Things devices require rigorous design trade-offs regarding size, cost, and energy efficiency, leading to design challenges for clock modules. This paper proposes a low-power all-digital frequency locked loop (ADFLL) featuring a digital frequency detector with minimum D-type flip-flop usage and a lock detector with hysteresis lock/unlock decision zone, suitable for system-on-chip applications. The ADFLL is verified in the field-programmable gate arrays (FPGA) and is implemented as an on-chip clock generator in a radio frequency identification tag using 130 nm CMOS technology with 0.185 × 0.26 mm2 size. The generated clock has ±0.25% frequency accuracy with good temperature and process robustness.

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Wireless and continuous strain measurement of rotating helicopter blades using implanted backscatter sensors

Zhao Z., Mitsugi J.

2024 IEEE International Conference on Rfid Technology and Applications Rfid Ta 2024 153 - 156 2024年

This paper proposes a wireless strain sensing system for model helicopter rotor blades using implanted backscatter sensors. Strain measurements from two sensors were continuously collected via dedicated subcarrier frequency backscatter channels. While coherent combining of two IQ streams improved packet error rate (PER) in low-speed rotations, it negatively affected performance at high speeds setting due to Doppler shift. Numerical simulations clarified the degradation mechanism and suggested a practical solution: using a single receiving antenna. This approach was validated through laboratory experiments.

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Accurate Phase Angle Measurement of Backscatter Signal under Noisy Environment

Iwasaki T., Tokumasu O., Mitsugi J.

IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences （IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences） E106A （ 3 ） 464 - 470 2023年03月

ISSN 09168508

Backscatter communication is an emerging wireless access technology to realize ultra-low power terminals exploiting the modulated reflection of incident radio wave. This paper proposes a method to measure the phase angle of backscatter link using principal component analysis (PCA). The phase angle measurement of backscatter link at the receiver is essential to maximize the signal quality for subsequent demodulation and to measure the distance and the angle of arrival. The drawback of popular phase angle measurement with naive phase averaging and linear regression analysis is to produce erroneous phase angle, where the phase angle is close to ±π 2 radian and the signal quality is poor. The advantage of the proposal is quantified with a computer simulation, a conducted experiment and radio propagation experiments.

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Two-Stage Harmonics Rejection in FDMA Backscatter Communication System Using FFT Filterbank

Mitsugi J., Tokumasu O., Sakabe H.

IEEE Journal of Radio Frequency Identification （IEEE Journal of Radio Frequency Identification） 7 518 - 527 2023年

This paper presents a harmonics rejection method for the sensor-to-interrogator link of frequency division multiple access (FDMA) backscatter communication system exploiting an FFT filterbank. It is well known that backscatter signals produce undesired outband emissions and harmonics because of the absence of a pulse shaping filter. Harmonics, produced by introducing subcarrier coding, are particularly problematic because they interfere with particular frequency channels. The proposed method features the generation of harmonics replicas from the baseband signal in an allocated channel produced by a FFT filterbank. The generation of a harmonics replica from the baseband signal demands a delicate handling of the carrier and the subcarrier phases. This paper presents this problem and proposes a two-stage harmonics replica generation exploiting the statistical independence among the interfering and interfered baseband signals. The proposal was implemented in a software defined interrogator, and was evaluated with a wired experiment with various carrier-to-interference ratios and two real-world wireless propagation experiments using prototype battery-free backscatter sensors. These evaluations revealed that the proposed harmonic rejection method could deliver about 6 dB of processing gain.

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USCoCa: A Subcarrier Frequency Continuous Calibration Method for Backscattered Concurrent Data Mode in UHF RFID System

Zhao Y., Jiang H., Ying Z., Gao F., Li S., Shen Z., Tang K., Wang H., Mitsugi J., Min H.

2023 IEEE International Conference on RFID, RFID 2023 66 - 71 2023年

Concurrent data communication based on backscat-ter is an unnoticed research domain in the past, but recently it is considered as a promising technology for Massive IoT in the B5G/6G wireless sensor network (WSN). In this domain, it is a practical multiple access solution to use multiple subcarriers. This paper proposes a frequency continuous calibration method to improve the frequency accuracy of uplink subcarrier (USC) in the concurrent data communication mode, called USC continuous calibration (USCoCa). Tag obtains a 10kHz amplitude modulation frequency reference from reader, uses a digital frequency lock loop to calibrate the on-chip digital controlled ring oscillator, and generates USC with a wide frequency range and good frequency accuracy. The tag with USCoCa is fabricated with 0.51×1.02 mm2 area size. The test result shows that US CoCa can keep continuous calibration of USC frequency, and the USC frequency deviation is less than 0.25 % within the range of 100-620kHz frequency. At the same time, the USC frequency stability can even be maintained under the +134°C /min rate temperature environment. Therefore, USCoCa can ensure stable frequency channel assignment for the multiple sub carrier UHF RFID system and guarantee robust concurrent data stream transmission.

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Fractional Delayed Detection For Unstable Subcarrier-Coded Backscatter Link

Zhao Z., Mitsugi J.

2023 IEEE 13th International Conference on RFID Technology and Applications, RFID-TA 2023 - Proceedings 253 - 256 2023年

This paper proposes a carrier recovery method for subcarrier-coded backscatter links using a fractional, less than one-symbol, delayed detection. The fractional delayed detection extends the permissible subcarrier frequency errors but results in an unbalanced distribution of delayed symbols. This paper reveals the contribution of fractional detection in RFID sensing systems, particularly the system with an FDMA backscatter to collect streaming data. The unbalanced symbol distribution problem is resolved using a principal component analysis (PCA) of delayed symbols. The fractional delayed detection was evaluated both with a MATLAB simulation and a combination of a software-defined interrogator and a prototype wireless sensor. Both evaluations showed the effectiveness of the proposal.

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MSN: Battery-Less Multiple Subcarrier Multiple Access Sensor Node with Full-Duplex Backscatter Concurrent Data Streaming

Zhao Y., Wang H., Xu Y., Ying Z., Lu Y., Liu J., Hu T., Mitsugi J., Min H.

2023 IEEE Asian Solid-State Circuits Conference, A-SSCC 2023 2023年

To scale to trillions of Internet-of-Things (loT) nodes, devices must be battery-less by achieving energy autonomy, having a μW power floor, few off-chip components, and a small form factor. These features are beneficial for short-range high-density loT applications such as structural health monitoring (SHM) for wings and gears, human motion capture (HMC), and air conditioning system monitoring. This work focuses on the synchronous transmission of sensor data streams, called concurrent data streaming, from multiple sensor nodes for multi-points sensing. Traditional wireless communication protocols need construct wireless networks for time synchronization, increasing system complexity [1]. However, the recent development of Multiple Subcarrier Multiple Access (MSMA), enables concurrent backscatter communication by assigning multiple uplink subcarrier (USC) channels to sensor nodes [2]-[4]. To expand the deployment in the mentioned loT applications, MSMA should be compatible with existing communication protocols and achieve real-time control of starting and stopping of concurrent data streaming without wasting extra sensing system energy. To avoid channel interference among multiple nodes and catastrophic failure of concurrent data transmission, the USC frequency must always keep stable from the influence of PVT.

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Sign Language Motion Recognition by Multimodal Information Using Acceleration Data and Coordinate Data

Wakao T., Kawakita Y., Nishimura H., Tanaka H., Mitsugi J.

Journal of the Institute of Image Electronics Engineers of Japan 52 （ 2 ） 348 - 356 2023年

ISSN 02859831

This study utilized multimodal information using both acceleration data and coordinate data to recognize sign language motion. First, to confirm the effectiveness of recognizing sign language motion using individual acquisition information, the authors conducted an experiment to compare motion classification performance when each acquisition of data was treated independently. The performance comparison results showed differences in the tendency for false classifications in the classifiers constructed using only each data group. Therefore, high sign language recognition performance seemed more likely to be achieved if each classifier using multimodal information were to be integrated in a complementary manner. In this paper, three integration methods for multimodal information are proposed and compared against each other. Method 1 assumes that the classification results of classifiers trained individually on the acquired data are mixed with incorrect candidate classifiers with relatively low likelihood, and the classifiers are integrated after narrowing down the candidate classifiers using that likelihood. Method 2 considers that ranked information, even with a low likelihood, give a high probability of producing a correct classification result, and the authors carried out classification result integration by assigning a rejection condition using the rank sum of each classifier. Method 3 combines Method 1 and Method 2. It is an integration model that rejects each result with a low probability of being correct and then integrates the classifiers by value of the rank that is output as a significant classification result integration. An evaluation index γ was proposed for assessing recognition performance based on the correct rate, error rate, and rejection rate, and the above three proposed methods were evaluated based on that index.

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A Highly Integrated Passive Wireless Sensing System With Synchronized Data Streaming of Multiple Tags

Tang K., Wang M., Liu M., Zhang C., Xu S., Ji S., Lai S., Yan N., Min H., Mitsugi J.

IEEE Internet of Things Journal （IEEE Internet of Things Journal） 9 （ 17 ） 15525 - 15537 2022年09月

This article introduces a highly integrated passive wireless sensing system based on the extended electronic product code (EPC) Gen2 protocol, using sensor tags and a reader to support concurrent data streams from multiple sensors. Multiple subcarrier multiple access (MSMA) is used by assigning different subcarrier frequencies to the sensor tags for backscattering so that each tag has an independent channel for communication to achieve the simultaneous streaming of multisensor data. In order to improve the subcarrier frequency accuracy and further increase the number of communication channels, this article proposes a novel method of subcarrier frequency calibration based on the Gen2 protocol. This method enables a high-accuracy clock to be generated on-chip. At the same time, this article also proposes a method based on Gen2 protocol to start a group of tags and receive real-time data in parallel. The tag chip is fabricated in a 0.18-μm CMOS process with a die size of 850μm × 850μm, and the reader prototype is built using software-defined radio equipment. The test results show that the sensing system proposed in this article can collect and recognize concurrent data streams from multiple sensor tags synchronously. The measured sensitivity of the sensor tag is -14.9 dBm with a 3-axis accelerating sensor, and the calibration accuracy of subcarrier frequency is better than ±0.385 kHz in the range of 40-640 kHz. With this accuracy, the tags can be allocated up to 78 subcarrier communication channels theoretically.

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Fast Blind Equalizer Exploiting Statistical Features of Symbol Constellations

Takeyama N., Mitsugi J.

Journal of Information Processing （Journal of Information Processing） 30 909 - 916 2022年

This paper proposes a fast blind equalization algorithm realized by equating the higher-order statistics of transmitted and received signals’ IQ constellations over wireless channels. The idea is motivated by the fact that the transmitter and the receiver usually pre-share the modulation scheme, which determines the statistical distribution of the IQ constellation. Conventional blind equalizer algorithms are not practical because these optimize the equalizer coefficients with the gradient descent method demanding from hundreds to thousands of iterations to converge. This paper proposes a dimensionless loss function that can be extended to various modulation schemes and applies the Levenberg-Marquardt (LM) algorithm to regularize the Hessian matrix of the loss function automatically. This regu-larization compensates the singularity of the Hessian matrix which enables fast equalizing. The proposed method is evaluated in a MATLAB simulation to reveal that the algorithm can converge within dozens of iterations, achieving about a hundred times faster convergence and about a 30 times faster computation time than conventional blind equalization. The evaluation also reveals that the cause of the singularity of the Hessian matrix is the eigenvector space of equalizer coefficients which works to amplify inter-symbol-interference.

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Experimental Evaluation of Wireless Transport Package Test with Battery-free Backscatter Sensors

Mitsugi J., Tokumasu O., Ichikawa H., Ochiai T., Kawakita Y.

2022 IEEE International Conference on RFID, RFID 2022 58 - 63 2022年

Transport package test represents the integrity check of packaged commercial products exposed to an emulated transportation environment such as vibrations and shocks. This paper examines the practicality of wireless transport package test with a backscatter streaming system with battery-free backscat-ter sensors by extensive experiments. The system bases on Gen2 protocol with a set of streaming extensions. Random vibration and drop tests, defined in an ISO standard, were performed on a test subject PC. The measurement accuracy of the backscatter streaming system was compared with that of wired sensor to reveal that the accuracy of the system is sufficient for basic transport package test conditions. It was confirmed that the wireless, battery-less and lightweight natures of the backscatter sensor facilitate the test preparation and configuration changes, and is advantageous in continuous wireless streaming. In addition to the merits, the limitations of the system in transport package test are also discussed.

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Open loop demodulator for narrowband continuous backscatter wireless links

Mitsugi J., Kawakita Y.

IEEE Wireless Communications and Networking Conference, WCNC 2022-April 1425 - 1430 2022年

ISSN 15253511

Concurrent backscatter communication with multiple battery-free sensors suffers from the frequency instability of dedicated subcarrier caused by the process-power supply voltage-temperature (PVT) characteristic of the radio frequency integrated circuit (RFIC) in the battery-free sensor. This paper proposes an all-digital open-loop carrier and timing recovery circuit, which uses the most likelihood estimation of subcarrier frequency, and the delayed detection exploiting the differential zero-crossing points as the symbol timing recovery triggers. The proposal is implemented in a software defined interrogator. Conducted testing with a fading simulator and real world wireless testing with the battery-free backscatter sensors in 920 MHz band reveal the effectiveness of the proposal.

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Wireless Loose Bolt Detection with Multiple Battery-free Backscatter Sensors

Iwasaki T., Tokumasu O., Mitsugi J.

Proceedings of IEEE Sensors 2022-October 2022年

ISSN 19300395

This paper proposes a loose bolt detection system with battery-free wireless sensors based on backscatter communication. Loose bolt detection has been performed using wired or optical sensors. However, wired sensors demand temporary attachment of sensors and the routing of wires. Optical sensors demand precise alignment and the line of sight to the measurement points. The proposed backscatter system essentially eliminates those problems and can be used even when the target machine or structures are in their operation if the backscatter sensors are implanted to the target structure. On the other hand, the proposed system involves the challenges of data synchronization and the limited bandwidth. In this study, a prototype wireless loose bolt detection system based on transmittance function and damage index is developed and is comparatively evaluated with wired accelerometers by a series of experiments. The data synchronization problem was tackled by preprocessing of the collected data. It is also revealed that sufficient bandwidth in the wireless communication channels is important for accurate detection.

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A novel method to improve the subcarrier frequency accuracy for UHF RFID sensing system

Tang K., Zhang C., Wang M., Xu S., Ji S., Yan N., Min H., Mitsugi J.

2021 15th Annual IEEE International Conference on RFID, RFID 2021 （2021 15th Annual IEEE International Conference on RFID, RFID 2021） 2021年04月

ISSN 9781665440905

This paper presents a novel method to improve the subcarrier frequency accuracy of tag chip for UHF RFID sensing system based on EPC global Gen2 protocol. By changing the tag's response to the Write command, the tag returns the subcarrier before returning the response specified in the protocol. In this way, a frequency calibration loop will be established between reader and tag. This method not only enables a low-power oscillator with a precise frequency to be integrated into a tag chip, but also enables flexible configuration of the frequency. The tag chip containing this idea is fabricated in SMIC 0.18 μm CMOS process with a die size of 850 μm × 850 μm. Measurement results show that the proposed novel method can realize the calibration of the subcarrier frequency, and the subcarrier frequency deviation is less than ±0.385KHz in the range of 40KHz-640KHz. With this accuracy, the tag can be allocated up to 78 subcarrier communication channels.

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Concurrent backscatter streaming with batteryless sensors for wireless motion capture applications

Mitsugi J., Kawakita Y., Ichikawa H.

IEEE Vehicular Technology Conference （IEEE Vehicular Technology Conference） 2021-April 2021年04月

ISSN 9781728189642

This paper reports the experimental verification of concurrent backscatter streaming system comprising batteryless backscatter sensors and a software defined interrogator. The backscatter sensor is composed of a newly developed Radio Frequency Integrated Circuit (RFIC) and a commodity three axis microelectro mechanical system (MEMS) accelerometer. The concurrency is realized by allocating a dedicated subcarrier to each backscatter sensor, and using novel interference rejection signal processing in the interrogator. The communication protocol bases on ISO/IEC 18000-63 protocol with the extension of channel allocation and streaming control. The prototype system is evaluated in an experiment in where three backscatter sensors are installed on three emulated robotic mechanisms for wireless motion capture. It is confirmed that over-the-air subcarrier allocation and the concurrent capture of three robotic mechanism accelerations can be done despite the 10-4 order frequency instability of RFICs.

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Wireless Modal Testing with Multiple Battery-free Backscatter Sensors

Mitsugi J., Tokumasu O., Kawakita Y.

2021 IEEE International Conference on Wireless for Space and Extreme Environments, WiSEE 2021 （2021 IEEE International Conference on Wireless for Space and Extreme Environments, WiSEE 2021） 90 - 96 2021年

ISSN 9781665403719

This paper reports the design, implementation and the result of real-world experiment of wireless modal testing with battery-free backscatter sensors. The battery-free backscatter sensor comprises a custom radio frequency integrated circuit (RFIC), a commodity micro electro-mechanical system (MEMS) accelerometer, and an antenna. Sensor data concurrency demanded in modal analysis is realized by allocating a dedicated subcarrier to each backscatter sensor. The orchestration of wireless communications in 920 MHz based on Gen2 protocol and the wireless power supply to the backscatter sensor are performed by a software defined interrogator built on Lab-VIEW communications and USRP. We developed an over the air (OTA) subcarrier frequency allocation with a sequence of WRITE commands of Gen2 protocol, and its performance was confirmed with the experiments in an indoor radio propagation. The accuracy of the proposed wireless structural modal testing was experimentally verified by comparing with a commercial modal test system with wired accelerometers. Although the phase characteristic measurement is disturbed by the instability of the clock source of RFIC, the gain characteristics of wireless modal testing matches well with that of a commercial wired modal testing system.

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Full duplex backscatter communication with subcarrier synchronized decimation

Mitsugi J., Kawakita Y., Ichikawa H.

IEEE Wireless Communications and Networking Conference, WCNC （IEEE Wireless Communications and Networking Conference, WCNC） 2021-March 2021年

ISSN 9781728195056

Backscatter communication system, such as RFID, usually establishes bilateral communication link with time-wise half-duplex. Emerging data streaming using backscatter communication with low power or even batteryless sensors demands full duplex to stop streaming while a group of sensors backscatter. This paper introduces a full duplex method in backscatter communication using a simple decimation in backscatter sensors referred to as subcarrier synchronized decimation (SSD). Numerical simulations reveal that SSD can reconstruct the original reader-to-sensor link waveform subjected to backscatter modulation sensor-to-reader link, although the proposed method inevitably produces artificial noise because of the unequal time interval decimation. The contribution of artificial noise is investigated by using a sampling jitter model. This paper also reports a prototype implementation of SSD with USRP and LabVIEW NXG combined with a commodity DPDT switch to prove the feasibility of the proposal.

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Wireless modal analysis with backscatter sensors subjected to clock instability

Mitsugi J., Tanaka H.

WiSEE 2020 - 8th Annual IEEE International Conference on Wireless for Space and Extreme Environments, Proceedings （WiSEE 2020 - 8th Annual IEEE International Conference on Wireless for Space and Extreme Environments, Proceedings） 17 - 23 2020年10月

ISSN 9781728164519

This paper examines the practicality of concurrent sensor data streaming with backscatter communication applied to modal analysis, which demands accurate data synchronization among streams. The major synchronization error source in concurrent backscatter streaming system is the instability of backscatter sensor clock. Synchronization of the streams by resampling at receiver is necessary but careless implementation may produce artificial delay caused by the difference of anti-Alias filters tailored to the individual clock rates of backscatter sensors. In this paper, a set of signal processing to synchronize concurrent backscatter signals is designed and implemented in a prototype system. The prototype system comprises backscatter sensors, interrogators and modal analyzer, which takes care of the generation of transfer matrix. The signal processing in the modal analyzer features a recursive least square regression to recover instantaneous sampling rate of backscatter sensor and a zero-phase-filtering in overlap-And-Add approach. The proposal is evaluated by comparing the transfer matrices generated from the prototype system and a commercial modal analysis system where wired accelerometers are used. The experimental results show that the proposed signal processing can successfully synchronize concurrent backscatter streams by eliminating the artificial delay.

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Simultaneous Gen2 Inventory and Angle of Arrival Measurement of Backscatter Signals with Multiple Commodity SDRs

Mitsugi J., Kawakita Y.

2020 IEEE International Conference on RFID, RFID 2020 （2020 IEEE International Conference on RFID, RFID 2020） 5 （ 4 ） 368 - 377 2020年09月

ISSN 9781728155760

Simultaneous inventory and angle of arrival (AoA) measurement of UHF RF tags is strongly demanded for item searching in warehouses and offices. Existing high accuracy AoA measurements of RF tags mainly employ a radio comprised of multiple antennas and coherent receivers to produce synchronized multiple IQ streams. Such radio is usually realized as a dedicated hardware and software, which is not suitable for prototyping new ideas. This paper proposes a method to realize simultaneous inventory and AoA measurement with multiple commodity software defined radios (SDRs). In the proposal, the cancellation of mutual phase offsets, an well known problem of multiple commodity SDRs, is done by physically switching the combination of receiving antennas and receivers with an external RF switch and subtracting the two phase differences. This way, the calibration before AoA measurement can be done during the process of phase measurement with no human intervention. The antenna switching is integrated into a SDR Gen2 interrogator developed on a dual RF-ports USRP. The external RF switch is synchronously controlled with Gen2 inventory progress using Gen2 protocol features called action and target. The accuracy of phase offset cancellation was evaluated with wired and wireless experiments with commercial Gen2 RF tags. The experiments revealed that AoA measurement can be simultaneously performed with Gen2 inventory without any intervention achieving less than 3 degree of phase offset cancellation error.

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Channel Reservation by Even-odd Separation in Multiple Subcarrier Multiple Access

Takahashi K., Takazawa Y., Kamei H., Mitsugi J., Ichikawa H., Kawakita Y.

2019 12th International Conference on Mobile Computing and Ubiquitous Network, ICMU 2019 （2019 12th International Conference on Mobile Computing and Ubiquitous Network, ICMU 2019） 2019年11月

ISSN 9784907626419

© 2019 IPSJ. Authors propose a method for improving channel reservations in multi-subcarrier multiple-access wireless communications schemes. This scheme is designed for use with wide-area synchronous sensing zones that use functionally extended multi-subcarrier multiple-access subcarrier communication schemes for passive radio-frequency identification (RFID). When the sensing target is larger than the communication distance of the sensor, the sensing zone must be divided. Overlapping zones invariably occur in this case. Sensors in overlapping zones transmit signals to their respective receivers over the same channels and interference follows. If three or more zones are placed side by side, middle zone's communication capacity is lower than else zones. Because, middle zone can not use nearly center frequency. However, the communication capacity and its variations have not been examined for how they are affected by the zones in which overlapping sensors are used. This study investigated communications between sensors in overlapping zones by assigning channels to receivers in odd zones. The channel reservation method and the conventional method were simulated in MATLAB an compared. By allocating channels to sensors in odd zones, communication capacity can be improved and variations suppressed.

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Statistical carrier phase recovery for narrow-band backscatter wireless link

Sato Y., Mitsugi J., Kawakita Y., Ichikawa H.

Proceedings of 2019 25th Asia-Pacific Conference on Communications, APCC 2019 （Proceedings of 2019 25th Asia-Pacific Conference on Communications, APCC 2019） 142 - 147 2019年11月

ISSN 9781728136790

© 2019 IEEE. This paper proposes a carrier recovery method tailored to narrow-band multicarrier backscatter wireless links, which employ subcarrier modulation. Because backscattered subcarrier is usually produced by low accuracy and low rate internal clock in a low power consumption or batteryless, wireless sensor, the corresponding receiver needs to compensate the subcarrier frequency drift and fluctuation dynamically for demodulation and decoding. Although a backscattered subcarrier is produced by changing the antenna reflection coefficient of wireless sensor, the backscattered signal is usually converted to a zero-crossing signal to enhance signal resolution, and edge detection based demodulator is applied at the receiver. However, in a multicarrier backscatter system, the edges at symbol boundaries of each backscattered subcarrier become indistinct because of the narrow bandwidth. Consequently, subcarrier frequency estimation with existing carrier recovery technique may results in error. This paper solves the problem by removing outliers of temporal subcarrier frequency based on the statistical distribution and applying a feedback control. The statistical carrier recovery method is examined experimentally with a prototype wireless sensor and a software defined receiver to reveal the method can automatically compensate unstable subcarrier with about 10-2 order drift and outperforms the popular frequency doubler based carrier recovery. The optimal feedback gain, 1.0, is also revealed.

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Real-time separation of collided signals in multiple zones backscatter communication system

Mitsugi J., Kamei H., Kawakita Y., Ichikawa H.

7th IEEE International Conference on Wireless for Space and Extreme Environments, WiSEE 2019 - Conference Proceedings （7th IEEE International Conference on Wireless for Space and Extreme Environments, WiSEE 2019 - Conference Proceedings） 87 - 92 2019年10月

ISSN 9781728121406

© 2019 IEEE. Backscatter communication is essential in applications where wireless and batteryless sensors are demanded. Backscatter communication system may suffer short communication range because its sensors transmit signals by means of the reflection of incident radio wave that is provided by counterpart interrogator. The use of multiple interrogators, forming multiple interrogation zones, is the usual practice to extend the range of backscatter communication system. However, if a sensor receives more than one radio waves-one from its counterpart interrogator and others from neighbor interrogators-the sensor produces modulated backscatters to all the interrogators, causing interference to neighbor interrogators. This inter-zone interference is particularly problematic when multiple sensors send stream data concurrently. This paper proposes a real-time separation of collided backscatter signals based on their statistical independence. The proposal uses a priori probability of backscatter signal to extract the independent carrier phase angles and the independent amplitudes from IQ signal observation. The measurement of channel state information with predefined symbol pattern in packet is not needed. The proposal is evaluated both in numerical simulations and a physical experiment using prototype backscatter sensors and a software-defined interrogator. The results show that collided backscatter signals can be separated in real-time without degrading the packet error rate of each signal.

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Perfectly Synchronized Streaming From Multiple Digitally Modulated Backscatter Sensor Tags

Mitsugi J., Kawakita Y., Egawa K., Ichikawa H.

IEEE Journal of Radio Frequency Identification （IEEE Journal of Radio Frequency Identification） 3 （ 3 ） 149 - 156 2019年09月

This paper proposes multiple subcarrier multiple access (MSMA), a multiple access method for perfectly synchronized concurrent data collection from a group of passive backscatter wireless sensor tags, and its experimental evaluation. By achieving less than 128~\mu \text{s} synchronization error, backscatter communications can be applied to the structural health monitoring of artifacts, such as civil structures and machinery. In MSMA, each sensor tag uses a dedicated subcarrier frequency to produce a modulated backscatter. The sensor data is superposed onto the subcarrier with either an analog or digital modulation. The inevitable harmonics among the subcarriers, stemming from the backscatter principle, can be rejected by numerically calculating the harmonic replicas and subtracting them from the observed signal using a software defined receiver. A frame-based signal processing in the receiver results in no relative synchronization error among subcarriers, even after the interference rejection. Because the interference rejection can be performed before the demodulation and decoding, the concurrency can be secured irrespective of the choice of modulation method. We developed a prototype of MSMA using LabVIEW communications software defined radio environment, and prototype sensor tags using discrete electrical parts. The performance and limitations of MSMA using digitally modulated subcarriers are evaluated both in wired and wireless environments with up to four backscatter sensors. It is confirmed that the interference rejection can achieve about 7 dB processing gain. An experiment to measure the vibration of a bridge under weekday traffic with four sensors revealed the results obtained by MSMA and wired sensor agree well.

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Frequency Efficient Concurrent Data Streaming with Passive Backscatter Wireless Sensors

Kamei H., Sato Y., Mitsugi J., Egawa K., Kawakita Y., Ichikawa H.

2018 6th IEEE International Conference on Wireless for Space and Extreme Environments, WiSEE 2018 （2018 6th IEEE International Conference on Wireless for Space and Extreme Environments, WiSEE 2018） 107 - 109 2019年02月

ISSN 9781538642443

© 2018 IEEE. This poster presentation introduces a multi-subcarrier passive backscatter wireless communication which enables frequency efficient and perfectly synchronized sensor data streaming. The inevitable mutual interferences among sub-carriers are actively rejected with a sophisticated digital signal processing in the receiver. The performance of the method, in terms of the synchronization and the interference processing gain, are experimentally evaluated with two types of prototype sensors and a software defined receiver realized with USRP 2952R and LabVIEW communications. The results show that the proposed interference rejection method works both for analog and digital modulation.

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GNU radio-based cloud development environment for software-defined radio users

Suzuki H., Ichikawa H., Mitsugi J., Kawakita Y.

Journal of Information Processing （Journal of Information Processing） 27 287 - 296 2019年

ISSN 03875806

© 2019 Information Processing Society of Japan. Software-defined radio (SDR) is used for R&D such as cognitive radio. Because sampling devices and personal computers configuring the SDR environment have fixed configurations, some reconfiguration is needed when the SDR application requires different data sources and computational resources. To enable reconfiguration, we present a cloud platform that has scalable computing resources and data sources deployed over a wide area. We use the existing SDR development environment (SDRDE) and implement it on the cloud platform. It is necessary to transfer the SDR environment to the cloud by separating the UI and data management from the existing SDRDE. In this study, we selected the GNU Radio Companion (GRC) as the base platform and implemented an SDRDE for an unspecified number of users by separating the UI. In addition, we used task parallel and distributed computing for the SDR application. In this study, we focus on compatibility with the base implementation and lifting the limits of computational resources. We confirmed the compatibility with GRC in terms of user skill sets and software assets and evaluated the system response time. Further, the relationship between CPU utilization and instructions per cycle during SDR application execution shows that in general, this approach is effective.

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Frequency efficient subcarrier spacing in multicarrier backscatter sensors system

Mitsugi J., Sato Y., Kawakita Y., Ichikawa H.

ISSN 09168508

Copyright c 2019 The Institute of Electronics, Information and Communication Engineers SUMMARY Backscatter wireless communications offer advantages such as batteryless operations, small form factor, and radio regulatory exemption sensors. The major challenge ahead of backscatter wireless communications is synchronized multicarrier data collection, which can be realized by rejecting mutual harmonics among backscatters. This paper analyzes the mutual interferences of digitally modulated multicarrier backscatter to find interferences from higher frequency subcarriers to lower frequency subcarriers, which do not take place in analog modulated multicarrier backscatters, is harmful for densely populated subcarriers. This reverse interference distorts the harmonics replica, deteriorating the performance of the existing method, which rejects mutual interference among subcarriers by 5 dB processing gain. To solve this problem, this paper analyzes the relationship between subcarrier spacing and reverse interference, and reveals that an alternate channel spacing, with channel separation twice the bandwidth of a subcarrier, can provide reasonably dense subcarrier allocation and can alleviate reverse interference. The idea is examined with prototype sensors in a wired experiment and in an indoor propagation experiment. The results reveal that with alternate channel spacing, the reverse interference practically becomes negligible, and the existing interference rejection method achieves the original processing gain of 5 dB with one hundredth packet error rate reduction.

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High Resolution Time-of-Flight Measurement with Narrow-Band COTS Ultrasonic Transducers

Saito M., Mitsugi J.

Proceedings of IEEE Sensors （Proceedings of IEEE Sensors） 2018-October 2018年12月

ISSN 9781538647073

© 2018 IEEE. Ultrasonic transducers (a pair of speaker and microphone) are extensively used in distance and wind speed measurements. The measurement of Time-of-Flight (TOF) between an ultrasonic speaker and a microphone dominates the accuracy. This paper presents a method to improve the TOF measurement accuracy using narrow-band commercial off-the-shelf (COTS) ultrasonic transducers. The method features the use of an experimentally captured waveform to correlate the transmitted and received signals and the use of a phase modulated ultrasonic signal. The method is experimentally evaluated to show that the proposal can significantly reduce the TOF measurement error, from 25.5% to 0.3%.

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Perfectly synchronized streaming from digitally modulated multiple backscatter sensor tags

Mitsugi J., Kawakita Y., Egawa K., Ichikawa H.

RFID-TA 2018 - 2018 IEEE International Conference on RFID Technology and Applications （RFID-TA 2018 - 2018 IEEE International Conference on RFID Technology and Applications） 2018年11月

ISSN 9781538650561

© 2018 IEEE. This paper proposes a multiple access method, referred to as Multiple Subcarrier Multiple Access (MSMA), for perfectly synchronized concurrent data collection from a group of passive backscatter wireless sensor tags and its experimental evaluation. By achieving less than 128 micro second synchronization error, backscatter communications can be applied to structural health monitoring of artifacts such as civil structures and machineries. In MSMA, each sensor tag uses a dedicated subcarrier frequency to produce a modulated backscatter. The sensor data is superposed onto the subcarrier either with an analog or a digital modulation. The inevitable harmonics among the subcarriers, stemming from the backscatter principle, can be rejected by numerically calculating the harmonic replicas and subtracting them from the observed signal in a software defined receiver. A frame based signal processing in the receiver results in no relative synchronization error among subcarriers even after the interference rejection. Since the interference rejection can be done before the demodulation and decoding, the concurrency can be secured irrespective to the choice of modulation method. We developed a prototype of MSMA using LabVIEW communications Software Defined Radio environment and prototype sensor tags using discrete electrical parts. The performances and limitation of MSMA using digitally modulated subcarriers are evaluated both in wired and wireless environments with up to four backscatter sensors.

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Barcode fingerprinting: Unique identification of commercial products with their JAN/EAN/UCC barcode

Ueno R., Mitsugi J.

IEEE World Forum on Internet of Things, WF-IoT 2018 - Proceedings （IEEE World Forum on Internet of Things, WF-IoT 2018 - Proceedings） 2018-January 416 - 420 2018年05月

ISSN 9781467399449

© 2018 IEEE. This paper proposes a method to uniquely identify commercial products with an item level barcode, specifically JAN/EAN/UCC, with which we usually cannot distinguish individual products. This research is motivated by the industrial and consumer needs for first-in-first-out operations of their inventories in the environment, where serial level barcodes, such as GS1-128 and SGTIN, or RFID are still not available. The proposal, referred to as Barcode Fingerprinting, utilizes the microscopic features of printed barcode stripes to discriminate each other. We zoom in a particular portion of a barcode image and apply SURF Algorithms and RANSAC Algorithms, to extract the microscopic features. The features are stored with the barcode ID and the time stamp for the future comparisons. We examined the feasibility of the proposal method by processing 100 barcodes of single brand PET bottles. The experiment reveals that we can uniquely identify each of the 100 barcodes by using Barcode Fingerprinting with a proper preprocessing of images.

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Performance evaluation of variable bandwidth channel allocation scheme in multiple subcarrier multiple access

三次仁

IEICE Transactions on Communications （IEICE Transactions on Communications） E101B （ 2 ） 564 - 572 2018年02月

研究論文（学術雑誌）, ISSN 0916-8516

© 2018 The Institute of Electronics, Information and Communication Engineers. Multiple Subcarrier Multiple Access (MSMA) enables concurrent sensor data streamings from multiple wireless and batteryless sensors using the principle of subcarrier backscatter used extensively in passive RFID. Since the interference cancellation performance of MSMA depends on the Signal to Interference plus Noise Ratio of each subcarrier, the choice of channel allocation scheme is essential. Since the channel allocation is a combinatorial problem, obtaining the true optimal allocation requires a vast amount of examinations which is impracticable in a system where we have tens of sensor RF tags. It is particularly true when we have variable distance and variable bandwidth sensor RF tags. This paper proposes a channel allocation scheme in the variable distance and variable bandwidth MSMA system based on a newly introduced performance index, total contamination power, to prioritize indecision cases. The performance of the proposal is evaluated with existing methods in terms of average communication capacity and system fairness using MATLAB Monte Carlo simulation to reveal its advantage. The accuracy of the simulation is also verified with the result obtained from the brute force method.

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Monopulse Switching to Cancel Phase Offset in Aray Antenna Comprising Multiple COTS SDRs

Masato Miyazawa, Jin Mitsugi, Yusuke Kawakita, Haruhisa Ichikawa

IEEE RFID-TA 2016 2016年

研究論文（国際会議プロシーディングス）

A Multicode and Portable RFID Tag Events Emulator for RFID Information System

Iori Mizutani, Jin Mitsugi

The 6th International conference on internet of things 187 - 188 2016年

研究論文（研究会，シンポジウム資料等）

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Multi-Carrier Backscatter Communication System for Concurrent Wireless and Batteryless Sensing

Rajoria Nitish, Jin Mitsugi

6th International Conference on the Internet of Things, Doctoral Colloquium 2016年

研究論文（研究会，シンポジウム資料等）

Comparative Analysis on Channel Allocation Schemes in Multiple Subcarrier Passive Communication System

三次仁

IEICE TRANSACTIONS ON COMMUNICATIONS E98B （ 9 ） 1777 - 1784 2015年09月

研究論文（学術雑誌）, ISSN 1745-1345

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Advancement of Automatic Identification Technology

MITSUGI JIN

ICOICT （IEEE） 2014年05月

研究論文（国際会議プロシーディングス）

An integrated device and service discovery with Upnp andONS to facilitate the composition of smart home applications

Jin Mitsugi,Yuki Sato,Miyuki Ozawa, Shigeya Suzuki

World forum on internet of things （IEEE） 2014年03月

研究論文（国際会議プロシーディングス）, 査読有り

A cost effective and sustainable relief material supply visibility system for devastated areas

Shigeya Suzuki, Yuki Sato, Takehiro Yokoishi, Jin Mitsugi

World forum of internet of things （ieee） 2014年03月

研究論文（国際会議プロシーディングス）

化粧品使用のRFIDを用いた検知とパターン推測

清水真有、佐藤友樹、三次仁、中村修、村井純

電子情報通信学会ASN研究会（電子情報通信学会） 113 （ 399 ） 165 - 168 2014年01月

研究論文（研究会，シンポジウム資料等）

A Feasibility Study on Simultaneous Data Collection from Multiple Sensor RF Tags with Multiple Subcarriers

Yuki Igarashi,Yuki Sato,Yuusuke Kawakita, Haruhisa Ichikawa, Jin Mitsugi

IEEE RFID 2014 （IEEE） 2014年

研究論文（国際会議プロシーディングス）, 査読有り

ユニークIDとカテゴリIDを用いる物流可視化システム

三次仁、佐藤友紀、横石雄大

電子情報通信学会RCS研究会（電子情報通信学会） RCS2013-86 49 - 54 2013年07月

研究論文（研究会，シンポジウム資料等）, 共著

Reliable and swift device discovery in consolidated IP and ZigBee home networks

Mitsugi Jin, Yonemura Shigeru, Yokoishi Takehiro

IEICE Transactions on Communications E96-B （ 7 ） 1837 - 1844 2013年07月

ISSN 0916-8516

This paper proposes a device discovery method for consolidated IP and ZigBee home networks. The method broadcasts an IP multicasted device discovery request of UPnP, m-search, in the ZigBee network as a Constrained Application Protocol (CoAP) message. Upon receiving the m-search broadcast, ZigBee devices respond after a constant time delay with their device description Universal Resource Name (URN). We refer to this device discovery mechanism as transparent msearch. Transparent m-search enables reliable and swift device discovery in home networks which may include constrained networks such as ZigBee. It is revealed by an experiment with 41 ZigBee devices that the delayed response from ZigBee devices is essential to avoid collisions between m-search broadcast and responses from devices and, as a result, to secure the reliability of device discovery. Since the transparent m-search requires the receiving ZigBee devices to respond with their device description URNs, the execution time of device discovery is significantly improved. In our experiment with 41 ZigBee devices, a conventional m-search took 38.1 second to complete device discovery while that of transparent m-search took only 6.3 second. © 2013 The Institute of Electronics, Information and Communication Engineers.

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アダプタを用いたnonEPCシステムとEPCISの連携

横石雄大、佐藤友紀、三次仁

情報処理学会 UBI研究会 2013-UBI-38 1 - 3 2013年05月

研究論文（研究会，シンポジウム資料等）, 共著

Building a Visibility Platform:EPCIS adaptors facilitate the exchange of information

Jin MITSUGI, Keita MIYAZAKI, Yuki SATO

RFID Journal 2013年02月

研究論文（学術雑誌）, 単著

A network architecture for fast retrieval of user memory data from sensor RF tags

Igarashi Yuki, Miyazaki Keita, Sato Yuki, Mitsugi Jin

184 - 190 2013年

In this paper, a network architecture for fast retrieval of user memory data of RF tag is proposed. The architecture features a network-based resolving of user memory layout in RF tag and an optimization of reading block according to application requests and the characteristics of interrogator. We implemented the proposed network architecture and evaluated the performance with commercial interrogator and commercial RF tags both of which are conformal to the fundamental specification of ISO/IEC 18000-6 Type C. The experimental and analytical evaluation reveals that the network-based memory resolving is effective particularly for interrogators which have large inventory overhead in a reading of user memory data. In our experiment, 3.3 times read speed up is achieved with the network-based resolving. The optimization of reading block is effective regardless of the protocol implementation of interrogator. We achieve 2.5 times speed up in the experiment in three sensor data reading from RF tag which has 2K bits memory. © 2013 IEEE.

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名もない展開型宇宙アンテナの進化”

三次仁

AIAA Space Review Japan 2013年

研究論文（その他学術会議資料等）, 単著

EPC共通基盤の構築と農産物コマース/トレーサビリティシステム実証実験

三次　仁、宮崎　圭太、佐藤　友紀

流通とシステム 26 （ 7 ） 1-6 2013年

研究論文（学術雑誌）, 単著

NFC/EPCを使った地域産品災害時支援物資のトレーサビリティシステム

三次、稲葉、田代、松枝

自動認識 26 （ 7 ） 2013年

研究論文（学術雑誌）, 単著

双方向服薬支援システムの開発に向けて

鈴木詩織、小澤みゆき、三次仁

医療情報学会春季大会（医療情報学会） 2013年

研究論文（研究会，シンポジウム資料等）, 共著

Regional purchase orders dissemination and shipments aggregation of agricultural products with interworking EPC network and EDI system

Jin Mitsugi, Yuki Sato, Takehiro Yokoishi, Takashi Tashiro, Tomohiko Eda, Keiji Sato and Yasurou Kishi

IEEE RFID-TA （IEEE） 1 - 6 2013年

研究論文（国際会議プロシーディングス）, 査読有り

EPCglobalアーキテクチャに基づいた農産品直販情報システムの構築

佐藤友紀、吉田守、宮崎圭太、三次仁

電子情報通信学会和文論文誌分冊D システム開発論文特集号（電子情報通信学会） VO.J96-D （ 10 ） 276 - 283 2013年

研究論文（学術雑誌）, 共著, 査読有り

在宅療養患者の服薬状況はどのように把握されているのか

鈴木詩織、三次仁、村井純

情報処理学会デジタルプラクティス（情報処理学会） 4 （３） 276 - 283 2013年

研究論文（学術雑誌）, 共著, 査読有り

Improving medication adherence in home care using a bidirectional medication assistance system

Shiori Suzuki, Jin Mitsugi and Jun Murai

International Journal of networking science （Springer） 3 63 - 70 2013年

研究論文（学術雑誌）, 共著

物理・仮想統合センサメッセージングシステム

小澤みゆき、三次仁

電子情報通信学会NS研究会（電子情報通信学会） 113 （ 361 ） 125 - 130 2013年

研究論文（研究会，シンポジウム資料等）, 共著

Identification of missing objects with group coding of RF tags

Sato Yuki, Igarashi Yuki, Mitsugi Jin, Nakamura Osamu, Murai Jun

95 - 101 2012年

Physical objects often form a group such as objects in a shipping container. RFID enables us to identify each object and even the container itself. However, current RFID does not provide information on IDs missing from a group. This paper proposes a method to determine the unique IDs of objects missing from a group without any external database or verifier. The proposed method logically splits a group into mutually overlapped sub-groups and writes group-related information, which is generated from the unique IDs of objects in the subgroup, to RF tags' memory. When we check the integrity of a group of objects, unique IDs and group-related information of RF tags are extracted from RF tags' memory. With an iterative decoding over group-related information with the unique IDs of identified objects, missing IDs are determined. A numerical simulation reveals that the proposed method can identify 96-bit unique IDs of up to 64 objects missing from a group composed of 100 objects by writing 840-bit group-related information to each RF tag. We also examined the performance with an experiment and confirmed that we can successfully determine 16-bit IDs of up to 12 missing RF tags from a group of 20 RF tags by writing 280-bit group-related information to each RF tag. The experiment results agree well with the numerical simulation. © 2012 IEEE.

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Theory and Performance Evaluation of Group Coding of RFID tags

Yuki Sato, Jin Mitsugi, Osamu Nakamura, Jun Murai

IEEE Transactions on Automation Science and Engineering （IEEE） 10.1109/TASE.2012.2193125 (Early access) 2012年

研究論文（学術雑誌）, 共著, 査読有り

Theory and performance evaluation of group coding of RFID tags

Sato Yuki, Mitsugi Jin, Nakamura Osamu, Murai Jun

IEEE Transactions on Automation Science and Engineering 9 （ 3 ） 458 - 466 2012年

ISSN 1545-5955

Radio frequency identification (RFID) is an automatic identification technology which identifies physical objects individually according to their unique identifiers (ID) recorded in each RFID tag. Many business processes require the integrity verification of a group of objects in addition to individual object identification. This paper proposes "group coding" of RFID tags with which we can verify the integrity of groups of objects by writing parity check data to the memory of RFID tags. It was revealed by simulations and experiments that we could determine the number of missing RFID tags up to 10 with accuracy over 99% when we write 96 bits of the checksum data to 20 RFID tags. The whole duration of group decoding measured in the experiment was approximately 2 to 3 s. The time to compute group encoding and decoding was in the order of several milliseconds and thus negligible. The RFID inventory accounts for the majority of the duration. © 2004-2012 IEEE.

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Innovative financing scheme by RFID

Inaba Tatsuya, Kokuryo Jiro, Mitsugi Jin

309 - 314 2012年

This study proposes a collateral registration method of asset based lending (ABL) and evaluates parameters of supply chain management (SCM) operation that affect performance of ABL. Radio frequency identification has been deployed recently and there increases the application areas using its track and trace capability. ABL is one of them, in which company borrows money from financial service company (FSC) by using movable asset, such as inventory, as collateral. We proposed a registration method that is compatible to the current RFID standard, analyzed the SCM parameters that affect the loan condition of ABL, and summarized how companies design the SCM operation to take advantage of the financing scheme. © 2012 IEEE.

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Room occupancy determination with particle filtering of networked pyroelectric infrared (PIR) sensor data

Yokoishi Takehiro, Mitsugi Jin, Nakamura Osamu, Murai Jun

2012年

Occupancy determination of a large room, such as university campus room, using pyroelectric infrared (PIR) sensors is difficult because PIR sensors are inherently insensitive to humans that are motionless and it is difficult to achieve 100% coverage even with multiple sensors. To overcome these problems, the authors propose using particle filtering of networked multiple PIR sensor data to improve the accuracy of the occupancy state determination. The particle filtering can eliminate incorrect occupancy state transition without incurring large delays. Our method is robust to the incompleteness of the coverage and accuracy. The authors performed an experiment in a campus room (15.3m×6.4m) with 4 PIR sensors to prove the validity of the proposal. The experiment shows that the proposal can improve the occupancy determination accuracy from 29.6% to 98.3%. The system has been continuously used in the university power saving project. © 2012 IEEE.

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UHF 帯 RFID における効率的な複数 RF タグエミュレーション.

神谷尚保, 三次仁, 中村修, 村井純.

電子情報通信学会論文誌 B B Vol.J94-B （ 3 ） 468–479 2011年04月

研究論文（学術雑誌）, 単著

Bridging UPnP and ZigBee with CoAP

Mitsugi Jin, Yonemura Shigeru, Hada Hisakazu, Inaba Tatsuya

2011年

Incorporation of heterogeneous wireless sensor and actuator networks (WS&AN) is an essential challenge of web based Internet of Things (IoT) architectures. We propose to use UPnP and end-to-end HTTP communication using CoAP to bridge WS&AN and IoT system. UPnP enables automatic discovery of sensor devices which directly connect to a WS&AN via a gateway. Instead of translating WS&AN and UPnP protocols at the gateway, we propose to use CoAP in WS&AN. This provides flexible communications between sensor devices and applications. Drawback of this end-to-end Web based IoT information system is vulnerability to excessive traffics from sensor devices or from the applications because there is no authority to monitor and control traffics in the architecture. We examined the performance of our implementations to find that the transmit performance of a single sensor device could be limited by the serial communications of embedded transceiver. Excessive data requests from applications might also result in the packet loss and wasteful WS&AN congestion. If the traffic is confined within the performance limits, the implemented UPnP and ZigBee bridging using CoAP shows satisfactory performance. We can subscribe up to 16 sensor devices data with 500 msec using simple HTTP POST requests. © 2011 ACM.

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Enabling globally unique sensor ID with dual-interface RF tag

Mitsugi Jin, Hada Hisakazu, Inaba Tatsuya, Ihara Katsumasa, Kojima Goushi, Kondo Tomonori

1628 - 1631 2011年

In any sensor information system, unique identification (ID) of each sensor is indispensable. Usual practices to secure uniqueness of sensor ID is to use MAC or network address or to use a proprietary ID in application layer. In pervasive computing era, it is desirable to uniquely identify a sensor with a URN regardless of types of network to which the sensor is connected. This paper proposes to embed a dual interface RF tag, which records a globally unique ID, EPC (Electronic Product Code), used in business transactions, to sensor microcontroller(MCU). The dual interface RF tag allows us to access its tag data either via RF interface and a baseband interface. This enables a sensor MCU to use EPC to uniquely identify the sensor for its whole product lifecycle. Since EPC have been only accessed through the RF interface, we developed a modified UPnP to automatically discover EPC enabled sensors through the baseband interface for various access networks. Taking advantage of the existing network RFID architecture, we can search services related to an EPC in a form of URL and also can publish and subscribe sensor data service with a standardized web service interface. This paper reports a hardware implementation of dual interface RF tag with a ZigBee transceiver. Timing requirement of RFID protocol to access RF tag's memory can be met by a software control of off-the-shelf MCU GPIO. A 96 bits EPC stored in an dual interface RF tag can be retrieved in 12.3 msec. For the automatic device discovery of an EPC enabled sensor attached to a ZigBee network, a modified UPnP is also developed. The proposal is implemented in a working prototype with 49 sensors which geographically dispersed in 3 locations which can continuously collect 181 sensor data for various applications. We also evaluated the minimum time interval to publish sensor data to find 300 msec is the shortest interval in our implementation. This interval is dominated by the communications capacity between sensor MCU and on-board transceiver chip. © 2011 IEEE.

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Bidirectional medication support system for medical staff and home care patients

Suzuki Shiori, Yokoishi Takehiro, Hada Hisakazu, Mitsugi Jin, Nakamura Osamu, Murai Jun

147 - 151 2011年

We have developed a system using a combination of a multi-hop sensor network and 3G networks to support patients daily medication in home care. Each medication of a patient is represented by a sequence of close-open-close events of an off-the-shelf pill box, which are detected by a small Hall sensor. The system enables home visiting nurses to remotely monitor their patients' medication and to give feedback on the medication status to patients. This bidirectional communication between medical staff and patients is essential to motivate patients' medication and to make their experience of being taken care for at homes more comfortable. A semi-automatic message generation system helps medical staff to send feedback without spending excessive time and effort. We have been examining this system for more than three months with three subjects and found that a simple open/close sensing of an off-the-shelf pill box can provide a valuable medication history. It has also shown that the feedback system improves the rate of failure medication from 5.3% to 0.0% in the best case. © 2011 IEEE.

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EPC based internet of things architecture

Hada Hisakazu, Mitsugi Jin

527 - 532 2011年

The Internet of Things is a concept of connecting small real space physical objects to the Internet using sensor network, RFID, and other forms of wireless network technologies. In this paper, we present an EPC (Electronic Product Code) based Internet of Things (IoT) architecture. The key concept of the architecture is EPC network over heterogeneous access network. We particularly focused on a ZigBee network as it can collect the latest information about 'Things'. The EPC Network provides certain static information about 'Things' such as name and manufacturer. To support end-to-end communication between sensor nodes and applications, Constrained Application Protocol (CoAP) instead of Hyper Text Transfer Protocol (HTTP) over ZigBee is developed. A gateway on a local area network converts HTTP and CoAP. A pseudo Universal Plug and Play (UPnP) protocol supports JOIN/LEAVE management of sensor nodes. We also prove a prototype home appliances management system that adopt our architecture over a ZigBee network. Our prototype provides energy-saving application using home appliances information collected through the system. © 2011 IEEE.

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Group coding of RF tags to verify the integrity of group of objects

Sato Yuki, Mitsugi Jin, Nakamura Osamu, Murai Jun

200 - 206 2011年

RFID is an essential technology to uniquely identify physical objects. In many practical business processes using RFID, we check not only individual objects but also check if there is no missing objects and no extra objects in a group of objects. While individual objects identifications are done by using RFID, group verifications are usually done by looking up a shipping list or corresponding EDI data which require a network connection. In this paper, we propose "group coding of RF tags" by which we can verify the integrity of a group of objects just by writing additional data in RF tags' memory. The additional data is computed from unique IDs of objects that belong to the group. We propose fundamental and general group codings. With the fundamental group coding, we can check if the integrity of a group of objects is preserved or not. It is a parity check of hashes of unique IDs in a group. We also propose general group coding by extending the fundamental group coding. With the general group coding, we can estimate the number of missing objects if the integrity of a group is not verified. The strength of the missing number estimation can be controlled by the size of data written to RF tags. It can be considered as a Low Density Parity Check (LDPC) in physical objects. The theory of group coding is confirmed by a numerical simulation and an experiment. It is shown by the simulation and experiment that we can detect 10 missing RF tags out of 20 RF tags with 99.5% reliability by writing 96-bit data into each RF tags besides its 96-bit unique ID. © 2011 IEEE.

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THE INTERNET OF THINGS

三次仁

IEEE WIRELESS COMMUNICATIONS 17 （ 6 ） 8 - 9 2010年12月

研究論文（学術雑誌）, ISSN 1536-1284

The Internet of things

Iera Antonio, Floerkemeier Christian, Mitsugi Jin, Morabito Giacomo

IEEE Wireless Communications 17 （ 6 ） 8 - 9 2010年12月

ISSN 1536-1284

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Low power and agile sensor data retrieval using dual interface passive RF tag

Sugimoto Kenichi, Mitsugi Jin, Nakamura Osamu, Murai Jun

100 - 105 2010年

Consider a situation where one desires to retrieve sensor data from an arbitrary environment via a moving interrogator. Maintenance of street lights and electric apparatus in conduits for example. The fundamental problems with this system have been 1)the trade-off relation between power consumption by sensor and the data retrieval rate for the interrogator, and 2)the data retrieval agility for the moving interrogator. A higher duty ratio incurs more power consumption in sensors whereas a lower duty ratio leads to a less reliable retrieval rate. Even though there have been such efforts as"adaptive sleep period control" which was derived form the packet arrival rate,they didn't systemically solve the problem, particularly for moving-interrogator environment. This paper presents a solution of separating the timing of sensor-sampling and the timing of sensor-data retrieval. The asynchronous data retrieval mechanism is facilitated by a dual interfaced UHF passive RF tag known as a " record tag "which the authors have been developing. This paper examines the power consumption composition of a prototype recorder tag. The power consumption efficiency of the proposed data-retrieval method is discussed in comparison with that of the existing method in term of " Sensor Sampling Interval vs.Battery Life Expectancy"The author also evaluated the viability of retrieving sensor data through a moving-interrogator. We specifically inspected the relationship of " Interrogator's moving Speed vs Successful Data Retrieval Rate "The tests showed that with a commercial 1.2V rechargeable battery, the recorder tag lasts for 21 days forluminance and temperature sensing using a 30 minute samplinginterval, extending the traditional battery lifespan ten times longer, yet still preserving 100% time availability for sensor data retrieval. The power consumption is expected to be eight times as efficient when using optimized circuitry. Experiments in an emulated fading environment reveal that the data retrieval rate is observed to be the highest when the maximum relative speed between the moving-interrogator and the recorder tag is less than 3km/h, with an optimized distance of separation being 10cm for a 27dBm EIRP interrogator. The moving speed, 3km/h, can be improved by optimizing the anti-collision procedure and by enhancing the sensitivity of the recorder tag. © 2010 IEEE.

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1000-RF-tag emulation with an 8bit micro processor

Kamiya Naoyasu, Mitsugi Jin, Sugimoto Kenichi, Nakamura Osamu, Murai Jun

350 - 355 2010年

UHF band passive RFID is an essential identification technology in pervasive computing world. One of the industrial demands to UHF band passive RFID is fast reading of many RF tags. This is particularly relevant for item-level-tagging of CDs, DVDs, books and consumer electronics. Many high-speed MAC protocols have been proposed thus far. Quantitative evaluation of reading speed, however, is not easy because we need to lay out many RF tags and measure the reading durations usually through interrogator APIs, which differ from interrogator to interrogator. In this paper, the authors propose two efficient multiple RF tag emulation algorithms which leverage the probabilistic nature of MAC protocol. We have implemented the algorithms onto a programmable battery assisted passive tag (BAP), equipped with an 8bit micro processor and evaluated the reading speed of commercial interrogators. It was revealed that the BAP can efficiently emulate the behavior of more than 1000 Gen2 RF tags for the reading speed evaluation with a trivial penalty on accuracy. ©2010 IEEE.

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2010 Internet of Things, IoT 2010

Michahelles Florian, Mitsugi Jin, Murai Jun

Unknown Journal 2010年

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Avoidance method of interference between RFID systems including interference-zone change according to the distance between channels

Uryu Akira, Umeda Yohtaro, Takyu Osamu, Mitsugi Jin

204 - 207 2010年

In a long-range RFID system, the communication range is far longer than that in a conventional short-range RFID system. However, the long-range RFID system tends to suffer interfering problem between systems. In this report, we evaluate the interference avoidance method of assigning the frequency channels and time slots to reader with using the information of the reader position. From the computer simulation, we show that the number of required time slots for avoiding the interference can be reduced and the frequency utilization efficiency can be increased when the dependence between the interference geometrical distance between readers and the frequency distance between channels is taken into account. © 2010 IEEE.

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Efficient Frequency Sharing of Baseband and Subcarrier Coding UHF RFID Systems

三次仁

IEICE TRANSACTIONS ON COMMUNICATIONS E92B （ 12 ） 3794 - 3802 2009年12月

研究論文（学術雑誌）, ISSN 0916-8516

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Efficient frequency sharing of baseband and subcarrier coding UHF RFID systems

Mitsugi Jin, Kawakita Yuusuke

IEICE Transactions on Communications E92-B （ 12 ） 3794 - 3802 2009年

ISSN 0916-8516

UHF band passive RFID systems are being steadily adopted by industries because of their capability of long range automatic identification with passive tags. For an application which demands a large number of readers located in a limited geographical area, referred to as dense reader mode, interference rejection among readers is important. The coding method, baseband or subcarrier coding, in the tag-to-reader communication link results in a significant influence on the interference rejection performance. This paper examines the frequency sharing of baseband and subcarrier coding UHF RFID systems from the perspective of their transmission delay using a media access control (MAC) simulator. The validity of the numerical simulation was verified by an experiment. It is revealed that, in a mixed operation of baseband and subcarrier systems, assigning as many channels as possible to baseband system unless they do not exploit the subcarrier channels is the general principle for efficient frequency sharing. This frequency sharing principle is effective both to baseband and subcarrier coding systems. Otherwise, mixed operation fundamentally increases the transmission delay in subcarrier coding systems. Copyright © 2009 The Institute of Electronics, Information and Communication Engineers.

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A practical method for UHF RFID interrogation area measurement using battery assisted passive tag

三次仁

IEICE TRANSACTIONS ON COMMUNICATIONS E91B （ 4 ） 1047 - 1054 2008年04月

研究論文（学術雑誌）, ISSN 0916-8516

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A tamper detection method for RFID tag data

Yamamoto Akira, Suzuki Shigeya, Hada Hisakazu, Mitsugi Jin, Teraoka Fumio, Nakamura Osamu

51 - 57 2008年

Recently, system designers, especially in the field of product life-cycle management system start considering use of user memory bank of UHF RFID tags. By storing most useful life-cycle data onto a tag, user can access to the data even without access to back-end databases. One of the major issues to make use of the user memory bank is detection of memory tampering. Although technology vendors start introducing new functionalities such as fine grained locking along with high capacity user memory, these tags with new functionalities require new non-standardized air protocol to operate - require modified version of reader/writers. Also, these tags are usually more expensive. In this paper, we introduce a novel approach to this problem: tag side write journaling mechanism and "Tag Memory Cloaking," which protect the journal by using. Tag Private Memory region, which is only readable and not writable from external devices such as a reader/writer, but writable by tag itself. Also, any write to the user memory automatically add journal entry - offset and length of the write - into the Tag Private Memory region. Later, a user can check existence of overlapped writes to user memory by checking the journal records. Since we have not modified any of air protocol, standard compliant read/writer can fully capable of all of our proposed operations: write to the tag, read, then detect unusual modification to user memory area. We have implemented the functionality to Programmable Battery Assisted Passive tag (BAP), then validated the method with several standard compliant reader/writers. © 2008 IEEE.

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Generalized handling of user-specific data in networked RFID

Osaka Kosuke, Mitsugi Jin, Nakamura Osamu, Murai Jun

173 - 183 2008年

As RFID technology has been widely adopted, it has been acknowledged that user-specific data carrying RFID tags can be conveniently used. Since the typical user-specific data is sensor data, some existing studies have proposed new RFID architectures for sensor data handling. However, there are industrial demands to include non-sensor data, such as sales records, repair history, etc., as well as sensor data in the purview of our study. To realize handling of such general user-specific data, we need to satisfy requirements such as the minimum set of data semantics required to access the user-specific data, flexible user-specific data memory schema determination and partial collection of user-specific data. For this purpose, we designed the role of "session manager", which communicates with associate applications and notifies an interrogator what to do upon retrieval of a unique identification number. The session manager with the structured user-specific data can provide flexible collection and processing of user-specific data in the networked RFID. Since the fundamental drawback of the session manager might be the lookup overhead, we examined the overhead with a simulation based on experimental data. It was revealed that the overhead is equivalent to and in some cases even better than that of the existing method, which relies on structural tag memory. © 2008 Springer-Verlag Berlin Heidelberg.

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A practical method for UHF RFID interrogation area measurement using battery assisted passive tag

Mitsugi Jin, Tokumasu Osamu

IEICE Transactions on Communications E91-B （ 4 ） 1047 - 1054 2008年

ISSN 0916-8516

For the success of a large deployment of UHF RFID, easyto-use and low-cost engineering tools to facilitate the performance evaluation are demanded particularly in installations and for trouble shooting. The measurement of interrogation area is one of the most typical industrial demands to establish the stable readability of UHF RFID. Exhaustive repetition of tag position change with a read operation and a usage of expensive measurement equipment or special interrogators are common practices to measure the interrogation area. In this paper, a practical method to measure the interrogation area of a UHF RFID by using a battery assisted passive tag (BAP) is presented. After introducing the fundamental design and performances of the BAP that we have developed, we introduce the measurement method. In the method, the target tag in the target installation is continuously traversed either manually or automatically while it is subjected to a repetitive read of a commercial interrogator. During the target tag traversal, the interrogator's commands are continuously monitored by a BAP. With an extensive analysis on interrogator commands, the BAP can differentiate between its own read timings and those of the target tag. The read timings of the target tag collected by the BAP are recorded synchronously with the target tag position, yielding a map of the interrogation area. The present method does not entail a measurement burden. It is also independent of the choice of interrogator and tag. The method is demonstrated in a practical UHF RFID installation to show that the method can measure a 40 mm resolution interrogation area measurement just by traversing the target tag at a slow walking speed, 300 mm/sec. Copyright © 2008 The Institute of Electronics, Information and Communication Engineers.

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RFID in Japan

Inaba Tatsuya, Mitsugi Jin, Murai Jun, Konomi Shin'ichi

405 - 413 2007年04月

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Next-generation broadband mobile satellite communication system in the ubiquitous network era

Ueba Masazumi, Ohata Kohei, Mitsugi Jin

NTT Technical Review 5 （ 1 ） 34 - 44 2007年01月

ISSN 1348-3447

After investigating the potential market for satellite communications in around 2010 that will have advantages over future terrestrial communication networks, we concluded that there will be a large demand for broadband communications services for passengers in vehicles such as long-haul trains, seagoing vessels, and airplanes. In this article, we describe a next-generation broadband scalable mobile satellite communication system for Japan that can offer economical broadband Internet service for passengers in such vehicles. We describe possible services, estimate the potential market, and discuss the requirements for such services to flourish. Finally, we discuss enabling technologies required for the system.

Activity weather

Tanaka Hiroya, Kamiyama Yusuke, Tamamura Koga, Kinase Ryo, Mitsugi Jin, Hada Hidekazu

1 - 14 2007年

Radio frequency identification (RFID) technology is now widely used for tracking a great variety of objects in spatio-temporal dimensions. In the field of urban management and analysis, personal RFID is a powerful tool for tracing both individual pedestrians and crowd dynamics. In this research, we have focused our attention on how public services can use RFID technology, especially from the viewpoint of attractive and real-time visualization. In a trial demonstration, we installed nine RFID-reader gates in an urban district and provided hundreds of passive RFID-tags to pedestrians. Using this basic RFID-infrastructure, we developed a public display service which visualized and reported urban activities in the style of a real-time weather map. A large display shows the density of people at each location by using geometric contour lines and virtual clouds. Accumulated data is automatically updated and the 'weather' map quickly changes as time passes. The weather-like visualization helps the user understand the dynamics, flows, and trends of crowds, and promotes intuitive forecasting of urban activity.

Multipath identification using steepest gradient method for dynamic inventory in UHF RFID

Mitsugi Jin, Shibao Yu

2007年

UHF passive RFID has been already in practice. Industrial applications sometimes suffer insufficient tag readability. Engineering may be needed to enhance the readability, accordingly. One of the factor to deteriorate the readability is the multipath fading. Identification of principal reflecting paths is essential to improve the readability deterioration by, for example, using antenna diversity and usage of microwave absorbance materials to suppress reflections. In this paper, a path identification method for UHF RFID using the measured power profile is presented. The method only requires a series of the received power measurement at the position of the target tag. By applying the steepest gradient method, we can optimize the parameters that defines the reflecting plane and eventually identifies the path direction. Together with theoretical development of the method, numerical example shows the validity of the method. © 2007 IEEE.

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Layer 3 diversity reception technology for Ku-Band mobile satellite communication systems

Nagase Fumiaki, Mitsugi Jin, Nakayama Masayoshi, Ueba Masazumi

IEICE Transactions on Communications E89-B （ 6 ） 1856 - 1861 2006年06月

ISSN 0916-8516

We describe a layer 3 diversity reception scheme that enhances the transmission characteristics of Ku-band mobile satellite communication systems. This scheme can realize high-speed communication for vehicles that experience shadowing caused by terrestrial obstacles such as tunnels, buildings and bridges, especially for trains that frequently experience shadowing from the trolley wire structures. Layer 3 diversity was chosen for long distance diversity to prevent signal shadowing caused by terrestrial obstacles while minimizing the alterations of existing receivers. The technology enables high-speed communication under shadowing conditions in a running train environment. Copyright © 2006 The Institute of Electronics, Information and Communication Engineers.

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Anti-collision performance of Gen2 Air Protocol in random error communication link

Kawakita Yuusuke, Mitsugi Jin

68 - 71 2006年

When a multitude of RFID tags are in the interrogating field, an anti-collision technology must be used. In literatures, the reading performance was mainly investigated on the error-free communication links between reader and tags. In the practical situations, particularly where a number of readers and other wireless devices share the same frequency band, the performance on the erroneous links would be significant interest. In this paper, we evaluated Gen2 Air Protocol paying attention to the anti-collision performance in random error communication link. As a result of simulation, two findings were obtained. Firstly, there is an appropriate number of slots depending on the number of tags. This number hardly changes even if a random error is incurred on the link. Secondly, the singulation speed might be significantly degraded particularly in erroneous links, if the optimal number of slots is not chosen. The findings can be interpreted such that the necessary link quality can be derived if the number of tags and permissible time are known a priori to the implementation. For instance, if 64 tags are required to be read in one second, it is necessary to ensure the link quality to be better than BER=10^-4 in random error environment. © 2005 IEEE.

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Experimental study on UHF passive RFID readability degradation

Mitsugi Jin, Hada Hisakazu

52 - 55 2006年

Readability of passive RFID fundamentally depends on the tag empowering. The minimum required power, usually referred to as sensitivity, depends on the chip and antenna manufacturing. The sensitivity affects the readability but it is not the sole determinant of readability. The readability of RFID comprises a number of factors, particularly in the UHF band. This paper proposes a classification of tag readability degradation factors and measurement methods to quantify the factors. It is shown that tag performance change at the attachment may affect the readability. A tag probe, a power measurement antenna at the position of tag attachment, can monitor essential data to comprehend the situation and establish a countermeasure to improve the tag readability. The operating environment, involving reader antenna positions and standing waves result from the multipath fading, is another important factor for the readability. The characteristics of the environment could be also grasped by using the tag probe. © 2005 IEEE.

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Spatial beam analysis with large displacement for deployable truss structures

Ozawa Satoru, Harada Satoshi, Mitsugi Jin

Nihon Kikai Gakkai Ronbunshu, C Hen/Transactions of the Japan Society of Mechanical Engineers, Part C 70 （ 11 ） 3108 - 3115 2004年11月

ISSN 0387-5024

A formula of multibody finite element analysis based on the corotational formulated finite element method and the direct coordinate partitioning for deployable truss structures is proposed. A beam element used in linear finite element analyses is a basic element in the formula. A corotational frame is defined by node coordinate systems attached to a beam element. A tangent stiffness matrix contains a virtual rotation displacement of the corotational frame. By the appropriate transformation of this virtual displacement, a simple geometric stiffness for the formula is obtained. The formula makes it possible to analyze the deploying motions of large deformed deployable truss structures, to be applicable to general finite elements, and to increase convergence speed of the Newton method in a solution algorithm. This improvement is achieved by neglecting virtual work done by rigid body motion in the process of employing the geometric stiffness to the conventional formula. A validity of this formula is confirmed through results of a numerical deployment analysis of a deployable beam structure.

Enhanced multi-correlator AFC for fast and wide range frequency acquisition

Yamashita Fumihiro, Kobayashi Kiyoshi, Nakasuga Yoshinori, Mitsugi Jin, Ueba Masazumi

IEICE Transactions on Communications E87-B （ 8 ） 2072 - 2081 2004年08月

ISSN 0916-8516

This paper presents a new automatic-frequency control (AFC) configuration capable of removing wide range frequency offsets (up to about ±0.625 fs, where is is signal symbol rate). The new configuration consists of an AFC that removes frequency offsets between ±0.125 fs and another AFC that detects the frequency offset range coarsely between ±0.625 fs. This paper describes the principle of the new AFC configuration. The proposed AFC configuration employs four correlators to enhance the acquisition range. It also adopts the reverse modulation scheme to decrease the acquisition time. The performance of the new AFC configuration is confirmed via computer simulations. It is shown that the proposed configuration can accommodate wide range frequency offsets as well as reduce the. acquisition time.

Shadowing countermeasure technology with layer 3 diversity reception for Ku band mobile satellite communication systems

Nagase Fumiaki, Mitsugi Jin, Nakayama Masayoshi, Ueba Masazumi

349 - 354 2004年

A layer 3 diversity reception scheme that enhances the transmission characteristics of Ku band mobile satellite communication systems is presented. The initial thrust for developing this scheme is to realize high-speed communication for trains that experience shadowing caused by terrestrial obstacles such as tunnels, buildings, bridges and structures that support trolley wires. Layer 3 diversity was chosen for long distance diversity to prevent signal shadowing caused by terrestrial obstacles and to yield packets in the same order as in the original packet stream while minimizing the alterations of existing receivers. The technology enables high-speed communication under simulated shadowing conditions in a running train environment while assuring correct packet order. Copyright © 2004 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Broadband and scalable mobile satellite communication system for future access networks

Ueba Masazumi, Ohata Kohei, Mitsugi Jin, Umehira Masahiro

395 - 404 2004年

The future prospects of satellite communications by the year 2010 in Japan, is discussed. The prospects of providing services of broadband Internet services to passengers in airplane, long-haul trains, or sea-going vessel is under process. After estimating the demand, a next-generation of broadband and scalable mobile satellite communication systems is proposed that could offer these services at affordable price. It is stated that to realize such a system key technologies must be developed to meet the technical challenges posed by the communication system and the problem related to the payload of the satellite.

Communication capacity enhancement with adaptive resource assignment for multi-beam mobile satellite communication systems

Nakasuga Yoshinori, Mitsugi Jin, Ohata Kohei, Ueba Masazumi

336 - 348 2004年

Mobile satellite communication systems are attracting much attention as an effective way to provide broadband communications in planes, ships, and long-haul trains in which economical services are not effectively provided by terrestrial systems. Such a system usually requires a wide frequency bandwidth and a satellite with high electrical output power, but these resources are severely restricted. A multi-beam system with frequency reuse is able to spread the usable bandwidth virtually. Applying an adaptive modulation method to the system achieves efficient use of resources. In this system, optimally assigning resources to beams is indispensable in enhancing the system capacity. However, this optimization method becomes complex since it is necessary to consider the influence of inter-beam interference which may depend on the variation in the communication traffic distribution. We propose a new adaptive resource assignment method in order to overcome this complexity and to enhance the system capacity. In the proposed method, a bandwidth vector and an approximate curve of the spectrum efficiency are introduced. Based on case studies assuming 19 beams, we show that the proposed method achieves 4.2 times higher system capacity than that of a system in which resources of each beam are fixed. Copyright © 2004 by NTT Corporation.

Phased array fed reflector antennas with interpolation network for next generation mobile satellite communication systems

Suzuki Yoshinori, Imaizumi Yutaka, Mitsugi Jin, Ueba Masazumi

3043 - 3046 2004年

The phased array fed reflector antennas with interpolation network for next generation mobile satellite communication systems are discussed. A small satellite, such as 2kW-payload power, was used to reduce system cost. The improvement in onboard antenna performance is achieved by increasing reflector diameter. A modification of the directional constrained minimum power (DCMP) method is proposed to handle interpolation networks. The validity of the method is confirmed by calculating antenna patterns of a designed phased-array-fed reflector antenna.

AFC configuration applicable to a wide range of frequency offset

Yamashita Fumihiro, Kobayashi Kiyoshi, Nakasuga Yoshinori, Mitsugi Jin, Ueba Masazumi

2003年

This paper presents a new automatic-frequency control (AFC) configuration capable of removing a large amount of frequency offset (up to about +/- 0.625 fs, where fs means symbol rate of signals). The new AFC consists of the AFC that removes frequency offsets between +/- 0.125 fs and another AFC that detects the frequency offset range coarsely between +/- 0.625 fs. First, the principle of the new AFC configuration is described. Then, the performance of the new AFC is confirmed via computer simulation. It is shown that the proposed AFC configuration can accommodate wide range frequency offsets as well as reduce the acquisition time. © 2003 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Ku band mobile multimedia satellite communications system for trains

Nagase Fumiaki, Mitsugi Jin, Nakayama Masayoshi, Ueba Masazumi

2003年

This paper presents the results of train experiments and their analysis of Ku band mobile multimedia satellite communication system. First, the requirements for the satellite-tracking antenna are described. And then, the satellite signal availability as well as the network performance, which were measured on trains, are described. Based on these data, it is confirmed that the satellite visibility from a train, which varies in accordance with the train's route, can be related to network throughput and the network throughput can be conceived as a high-speed Internet access. It is verified that major cause of network throughput degradation was identified by our laboratory tests. © 2003 by the American Institute of Aeronautics and Astronautics.

A novel technique for suppressing heat in onboard High-Power amplifiers

Kaho Takana, Nakasuga Yoshinori, Mitsugi Jin, Ueba Masazumi

2003年

Satellite communication systems have entered the mobile multimedia communication era. To support small earth terminals, the satellites must have high levels of effective isotropic radiated power. Onboard high-power amplifier not only need to generate high RF output power, but also to generate as little heat as possible. To address this issue, we present a new technique that reduces the amount of heat generated in high power amplifiers on a satellite. The technique makes use of heat suppression signals so as to maintain the amplifier's power efficiency. The potential impact on satellite systems is presented. To minimize the interference of the heat suppression signals on the carrier, some techniques are proposed using a multi-port amplifier and an antenna array and a reflector. © 2003 by the American Institute of Aeronautics and Astronautics, Inc.

An excitation weight determination method for onboard phased array antennas with weight interpolation network

Suzuki Yoshinori, Imaizumi Yutaka, Mitsugi Jin, Ueba Masazumi

517 - 522 2003年

In order to realize lightweight onboard satellite antennas, we proposed a technique that uses linear interpolation to reduce the number of control circuits. Compared to the conventional approach, the reduction is about 70%. To apply the technique to practical multi-beam systems with frequency reuse, it is necessary to meet the requirement in term of beam isolation. This paper presents a method for determining the excitation weights so as to meet the requirement of multi-beam systems with frequency reuse. We confirm the validity of the method by calculating the antenna patterns generated by the excitation weights output.

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IP network performance of a Ku band mobile multimedia satellte system

Nagase Fumiaki, Tanaka Hiroshi, Mitsugi Jin, Ueba Masazumi

2002年

We have proposed a mobile multimedia satellite communication system designed to realize high-speed multimedia communications. This system uses a mobile network for the return link and a newly developed tracking antenna that receives high-speed satellite signals for the forward link. This paper describes the system configuration, the tracking antenna performance and the IP network's performance in mobile environments. The tracking antenna was accurate to within 0.80 degree rms and 0.25 degree rms in azimuth and elevation, respectively. These accuracies meet the pointing loss requirement, 1 dB, in the link analysis. The network performance of the system was evaluated both in stationary and mobile environments by measuring the round trip time and the throughput. These characteristics were measured for several return link implementations, e.g., PDC (Japanese Cellular Standard), PDC-Packet (Packet communication service of PDC) and Satellite phone. Even in mobile environments, 1 Mbit/s of throughput, which is limited by the system round trip time, can be achieved for file downloading with TCP as transport protocol. This throughput can be increased to almost the network limit when XTP is applied as the transport protocol. © 2002 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Mobile multimedia satellite communication system

Nagase Fumiaki, Tanaka Hiroshi, Nakayama Masayoshi, Mitsugi Jin, Ueba Masazumi, Mizuno Hideki

NTT R and D 51 （ 4 ） 317 - 324 2002年

ISSN 0915-2326

We have proposed the mobile multimedia satellite communication system designed to realize high-speed multimedia communications. This system uses a mobile network for the return link and the newly developed satellite-tracking antenna that receives high-speed satellite signals for the forward link. This paper describes the system configuration featuring the satellite-tracking antenna performance and network performances measured by network throughput. The satellite-tracking antenna achieves 0.42 degree rms and 0.13 degree rms accuracy in the azimuth and the elevation, respectively. These accuracies meet the pointing loss requirements, 1 dB, in the link analysis. Even in mobile environments, 1 Mbit/s of throughput, which is limited by the system round trip time, can be achieved for file downloading when TCP is used as the transport protocol. This throughput can be improved when XTP is applied as the transport protocol.

Single-hop connection between user terminals for geo-satellite mobile communication systems

Ebina Kazuhito, Nakasuga Yoshinori, Yamashita Fumihiro, Kataoka Nobuyuki, Mitsugi Jin, Ueba Masazumi

NTT R and D 51 （ 4 ） 325 - 332 2002年

ISSN 0915-2326

Single-hop connection methods, which establish direct mobile to mobile communication links in the existing domestic mobile satellite communications system, are investigated. The difficulty for the single-hop connection stems from the PDC frame format, in which traffic and control channels reside in one frame. Two single-hop connection methods, based on a non-regenerative transponder satellite and a regenerative transponder satellite, are derived and evaluated in accordance with the required functionality on mobile terminal, base station and satellite. In each of the two methods, the satellite transponder has to involve such circuit as narrow-band filter bank, channel switch and beam switch. A regenerative transponder satellite has to have MODEM and frame decompose/compose circuits, additionally. Those circuits can be build by applying digital signal processing technology with relatively small circuit under a given satellite life time and space environment.

Deployment analysis of large space antenna using flexible multibody dynamics simulation

Mitsugi Jin, Ando Kazuhide, Senbokuya Yumi, Meguro Akira

Acta Astronautica 47 （ 1 ） 19 - 26 2000年07月

ISSN 0094-5765

Flexible multibody dynamics is applied to the deployment analysis of a large space antenna composed of a reflective mesh, a cable network and a deployable truss structure. It is clarified that the tension of some of the cables increase when the reflector is stowed. The largest deployment force is observed slightly before the completion of the deployment. A proper allocation of both translational and rotational springs can provide an efficient deployment force. A deployment experiment on a 4.8 m aperture reflector model verifies the computational results. It is concluded that a flexible multibody dynamics simulation is an indispensable design tool for reducing the weight and ensuring the secure deployment of low-cost mesh reflectors.

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Analyses of cable-membrane structure combined with deployable truss

Ando Kazuhide, Mitsugi Jin, Senbokuya Yumi

Computers and Structures 74 （ 1 ） 21 - 39 2000年01月

ISSN 0045-7949

The authors have been developing a large deployable mesh reflector for advanced satellite communication. This large reflector consists of a mesh membrane surface and a deployable truss structure. In this paper, analysis methods for a large deployable mesh reflector structure are introduced, and the theoretical basis for the analysis is explained. By using those analysis methods, we manufactured prototype reflector modules and carried out an experiment on them. The validity of the analysis methods were verified from the results of the analyses and experiments. The design procedure of mesh reflector surface and the effect of the mesh surface tension on the truss deployment are discussed.

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Comparative analysis of deployable truss structures for mesh antenna reflectors

Mitsugi Jin

AIAA Journal 36 （ 8 ） 1546 - 1548 1998年08月

ISSN 0001-1452

Direct strain measure for large displacement analyses on hinge connected beam structures

Mitsugi J.

Computers and Structures 64 （ 1-4 ） 509 - 517 1997年07月

ISSN 0045-7949

A multibody dynamics formulation based on a nonlinear finite element method is presented, particularly targeting beams connected with hinges. A nonlinear kinematics, called direct strain measure, is employed to extract the strains of beams subjected to large displacement, including finite rotations but small strain. Hinges are mathematically expressed in terms of the relation between connecting nodes, rather than Lagrange multipliers. The resultant dynamic equation is a differential equation of minimum set of degree of freedom, while the sparsity of mass and stiffness matrices are preserved. Computational examples prove the validity of the proposed method. © 1997 Civil-Comp Ltd and Elsevier Science Ltd.

Thermal distortion of over 10 Meter diameter reflectors formed by truss structure

Miyasaka Akihiro, Mitsugi Jin

1997年

This paper describes how an on-board satellite large reflector structure was designed based on the thermal distortion predicted by structural analysis in coordination with thermal estimation. As the reflector consists of many small similar modules, it is possible to simplify the analytical model and the fabrication process. Module size and number are decided by estimating the surface accuracy for a 13 m aperture reflector. The maximum thermal distortion is found to be occurred during eclipses. As the module number increases, the thermal distortion increases. When the antenna system is used in 2.5. G Hz (S frequency bands), total surface accuracy needs to be 2.4 mm RMS (specified value). This requirement is satisfied by a reflector composed of 14 modules; maximum error is 1.6 mm RMS by slight repositioning the reflector.

Module composition and deployment method on deployable modular-mesh antenna structures

Watanabe Mitsunobu, Meguro Akira, Mitsugi Jin, Tsunoda Hiroaki

Acta Astronautica 39 （ 7 ） 497 - 505 1996年10月

ISSN 0094-5765

A deployable modular-mesh antenna is the concept behind a large space antenna. To ensure reliable deployment, a synchronously deployable truss structure forming a curved reflector surface has been developed. The proposed antenna's main reflector formed by two types of modules using mesh and cable network maintains a sufficient level of rigidity at deployment and deploys with high reliability. Importance has also been placed on the numerical analyses of cables, the mesh, and the truss structures. The truss structure analysis is based on a non-linear finite element method, rather than on multi-body dynamics, so that elastic motions of all truss members during the deployment can easily be handled. © 1997 Elsevier Science Ltd.

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Dynamic analysis of cable-driven flexible multibody systems and its experimental verification

Mitsugi Jin, Senbokuya Yumi

1530 - 1535 1996年

This paper presents a method to handle a cable element in the flexible multibody dynamics simulation. The formulation for the cable element successfully separates the material and geometric stiffness matrices irrespective to the choice of rotational parameter. The proposed formulation has been implemented in the previously developed flexible multibody dynamics computer program. An experiment on a simple deployable truss structure whose deployment is controlled by a cable reveals that the proposed method can yield results that are accurate enough for industrial applications.

Direct strain measure for large-deformation analyses of beam structures

Mitsugi Jin

AIAA Journal 33 （ 10 ） 1934 - 1939 1995年10月

ISSN 0001-1452

A nonlinear kinematics called the direct strain measure is proposed for large deformation and finite rotation analyses of a two-node Timoshenko beam. The kinematics extracts pure elastic deformations without deriving any virtual frame to describe rigid body motion. Internal force and stiffness matrices are derived to constitute a Newton's method for finding the solution. Computational results show that the present method is valid for Timoshenko beams whose relative angular displacement in an element is less than 0.5 rad.

Finite-element method approach for multibody dynamics

Mitsugi Jin

Nippon Kikai Gakkai Ronbunshu, C Hen/Transactions of the Japan Society of Mechanical Engineers, Part C 61 （ 587 ） 2909 - 2915 1995年07月

ISSN 0387-5024

A finite-element-method-based formulation for flexible multibody dynamics, particularly targeting flexible link mechanisms, is proposed. The formulation is composed of two techniques: kinematics of largely displaced Euler beam element and direct coordinate partitioning. The kinematics is basically a corotational method. Direct coordinate partitioning, which is effective only in finite-element-based multibody dynamics, partitions the independent and dependent degrees of freedom hinge by hinge. A computational example on a slider crank with an assembly error shows the validity of the formulation and the developed program, SPADE.

Direct coordinate partitioning for multibody dynamics based on finite element method

Mitsugi Jin

2481 - 2487 1995年

An unconventional coordinate partitioning method for flexible multibody dynamics based on the corotational finite element method is proposed. The method establishes the relationship between the nodal degrees of freedom and independent degrees of freedom hinge by hinge, and results in a set of differential equations as the governing equation. Computational examples show that the proposed method can give a physically valid solution for flexible motion during mechanical motion.

Modular cable-mesh deployable structure for large-scale satellite communication antennas

Meguro Akira, Mitsugi Jin, Ando Kazuhide

Electronics and Communications in Japan, Part I: Communications (English translation of Denshi Tsushin Gakkai Ronbunshi) 77 （ 8 ） 90 - 100 1994年08月

ISSN 8756-6621

This paper describes a concept and key technologies for a modular mesh deployable antenna. A modular concept is suggested. The advantage of the modular concept and the influence of alignment errors on the surface accuracy are estimated quantitatively. The antenna reflector consists of a mesh surface, a cable network, and deployable truss modules. The cable network comprises three kinds of cables - surface, tie, and back cables. Adjustment of tie cable lengths improves the surface accuracy. Synchronous deployment truss structures are considered as a supporting structure. Their design method, bread board models, and deployment analysis are explained.

Static analysis of cable networks and their supporting structures

Mitsugi J.

Computers and Structures 51 （ 1 ） 47 - 56 1994年04月

ISSN 0045-7949

A nonlinear static analysis method for cable structures, particularly emphasizing cable networks, is presented. Cable strains are measured from the current geometry and compressed cables are analytically disassembled with the construction of the equilibrium equation and the stiffness matrix. Finite rotations of cable intersections, referred to as nodes, and cable elements passing through more than two nodes are included in the formulation. An integrated analysis with a linear finite element method is also presented to account for the elastic deformations of supporting structures for the cable networks. The formulation is programmed for a CRAY2 supercomputer using parallel processing to solve the linear equations. Applications of the method used for mesh antenna development are also presented. © 1994.

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Traversing singularities in nonlinear analyses on cable network structures

Mitsugi Jin

Nippon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A 60 （ 571 ） 867 - 874 1994年03月

ISSN 0387-5008

Nonlinear analyses of cable network structures using Newton's iteration often encounter difficulties in solving for a singular stiffness matrix stemming from the tension-stabilizing nature and slackening of cables. This paper presents a solution method, called null space projection, to traverse such a singular linear system in Newton's iteration. In the method, the current unbalance of internal and external forces is projected on the null space of the stiffness matrix and the contributions of null space basis for the variable updating are derived such that the total potential energy is reduced. Numerical example shows that the method successfully traverses singular systems in Newton's iteration process and consequently gives the equilibrium state of the structure.

Pillow distortion analysis for modular mesh antenna

Shimizu Masashi, Ando Kazuhide, Mitsugi Jin

780 - 783 1993年

Deployable modular mesh antenna and its surface adjustment

Mitsugi J., Yasaka T.

International Journal of Space Structures 8 （ 1-2 ） 53 - 61 1993年

ISSN 0266-3511

The deployable modular mesh antenna is composed of independently fabricated and tested antenna modules to reduce difficulties in ground testing. Each module comprises a metallic mesh shaped by a cable network and a deployable truss structure. This paper states the basic constitution of each module, especially of the cable network, and results of surface shape adjustment simulations and experiments. Employing the present method, reflector distortions after the fabrication can be adjusted by changing cable lengths without any sensitivity analysis. Numerical simulations and experiments clarify that the attainable surface accuracy of a module is determined mainly by the accuracy of the truss structure.

Ground verification of deployment dynamics of large deployable space structures

Meguro Akira, Mitsugi Jin

Journal of Spacecraft and Rockets 29 （ 6 ） 835 - 841 1992年11月

ISSN 0022-4650

This paper describes a precise verification procedure for antenna-deployment mechanisms using ground-deployment test data. Ground-deployment tests are carried out for a communication antenna reflector for the Engineering Test Satellite VI (ETS-VI). The antenna-deployment mechanism studied consisted of a bearing, a helical spring, a chassis, and a latch mechanism. The characteristics of individual parts were measured under space and ground conditions. Then the initial characteristic of a deployment mechanism is statistically predicted. Ground verification of a deployment mechanism is usually difficult because of atmospheric and gravitational effects especially at the system level. Therefore, a new verification procedure is employed. Two kinds of suspending system are developed to compensate for gravity effects. The characteristics of a deployment mechanism can be estimated by identifying system parameters for the equation of deployment motion. This estimation procedure covers all development stages, so that a characteristic history of a deployment mechanism can be easily obtained. Atmospheric and gravitational effects on deployment motion are taken into account as system parameters. It is clarified that all mechanical parts retain their initial characteristics during assembly and environmental testing.

Nonlinear static and dynamic analysis method of cable structures

Mitsugi Jin, Yasaka Tetsuo

AIAA Journal 29 （ 1 ） 150 - 152 1991年01月

ISSN 0001-1452

Cables are very promising structural elements for space applications since they can be packaged easily in a small volume and function as truss members when in a stretched state. However, an exact analysis of cable structures is difficult because of cable slackening and large deformations. In this paper, a nonlinear cable structure analysis method is derived based on Hamilton's principle and a general purpose cable structure analysis code (CASA) is developed. Higher-order strains are included in the method by taking positions, not displacements, as variables, and cable slackenings are given by a nonlinear, axial stiffness of cable. Nonlinear static and linear dynamic analyses of structures composed of cables and/or trusses can be treated by the present method.

Shape control of the tension truss antenna

Mitsugi Jin, Yasaka Tetsuo, Miura Koryo

AIAA Journal 28 （ 2 ） 316 - 322 1990年02月

ISSN 0001-1452

The tension truss antenna is a deployable mesh surface antenna featuring a cable network, called a tension truss, that gives a parabolic shape to the reflective mesh. Cables in the tension truss are rigid enough to prevent their elongation due to the tension, and the number of nodes and cables satisfies the statistically determinant condition. In this paper, surface sensitivity to magnitude and direction errors of the applied force, which gives the tensile force to the tension truss, is evaluated by Monte Carlo simulation. Results show that the surface deformation of a tension truss antenna is smaller than that of an antenna whose cable network is made of flexible cables. It is concluded that the tension truss antenna is a promising candidate for a large space antenna.

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