T. Sakata

Osaka Gas Co., Ltd., Ōsaka, Ōsaka, Japan

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Publications (15)0 Total impact

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    ABSTRACT: A system for performance evaluation of LTE devices has been presented, with evaluation in both a live network and with a channel sounder. The results serve as reference for OTA evaluations in the anechoic room based on multi-probe setups.
    Antennas and Propagation Society International Symposium (APSURSI), 2012 IEEE; 01/2012
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    ABSTRACT: This paper presents results from an outdoor radio propagation experiment at 2.35 GHz using a channel sounder and a spherical horn antenna array. The propagation test was performed in Aalborg city in Denmark. Comparing the ray-tracing results and the results obtained with the proposed method on the measured data shows a good match in both the spatial and time domains.
    Antennas and Propagation Society International Symposium (APSURSI), 2012 IEEE; 01/2012
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    ABSTRACT: This paper presents an outdoor MIMO throughput experiment using a commercial LTE cellular network in the 2.6 GHz band. The 2-by-2 MIMO throughput was measured in a radio propagation test in an unban area of Aalborg city in Denmark. At the same time, radio channel sounding was also conducted to obtain the radio path distribution. The throughput performance was investigated using the received signal strength indicator (RSSI) and the channel sounding data.
    Antennas and Propagation (ISAP), 2012 International Symposium on; 01/2012
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    ABSTRACT: An experimental investigation of handset MIMO antennas with dual-band operation was performed using the data from a radio propagation test in an urban area of Aalborg city in Denmark and an over-the-air test using a spatial fading emulator. It is concluded from the agreement between MIMO characteristics of the both measurements that the emulator is effective in evaluating handset MIMO arrays in the case of a multipath fading environment with one spatial cluster at 776 MHz and 2.35 GHz.
    Antennas and Propagation Society International Symposium (APSURSI), 2010 IEEE; 08/2010
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    ABSTRACT: This paper presents a MIMO spatial fading emulator, used to represent a street microcell environment. The fading emulator can reproduce a multipath radio propagation environment with either a uniform or non-uniform angular power spectrum (APS) in the horizontal plane. In this paper, we used the emulator to measure the 2-by-2 MIMO characteristics of four handset arrays with two monopoles in a multipath environment with one spatial cluster of incoming waves. From our investigation, good agreement was obtained between the results from the emulator and data measured in a radio propagation test in a street microcell. This demonstrates that the emulator is effective in evaluating the MIMO performance in a multipath propagation environment.
    Antennas and Propagation (EuCAP), 2010 Proceedings of the Fourth European Conference on; 05/2010
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    ABSTRACT: Performance Evaluation of Spatial Correlation Characteristics for Handset Antennas Using Spatial Fading Emulator Based on Clarke's Model
    IEICE Transactions. 01/2010; 93-B:2514-2522.
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    ABSTRACT: This paper illustrates a large-scale MIMO propagation channel measurement in a real life environment and evaluates throughput performance of various MIMO schemes in that environment. For that purpose, 4 × 4 MIMO transceivers and a novel spatial scanner are fabricated for wideband MIMO channel measurements in the 5GHz band. A total of more than 50, 000 spatial samples in an area of 150m2, which includes a bedroom, a Japanese room, a hallway, and the living and dining areas, are taken in a real residential home environment. Statistical properties of the propagation channel and throughput performance of various MIMO schemes are evaluated by using measured data. Propagation measurement results show large dynamic channel variations occurring in a real environment in which statistical properties of the channel, such as frequency correlation and spatial correlation are not stationary any more, and become functions of the SNR. Furthermore, evaluation of throughput shows that although MIMO schemes outperform the SISO system in most areas, open loop systems perform badly in the far areas with low SNR. Paying for the cost of CSI or partial CSI at Tx, closed loop and hybrid systems have superior performance compared to other schemes, especially in reasonable SNR areas ranging from 10dB to 30dB. Spatial correlation, which is common in Japanese wooden residences, is also found to be a dominant factor causing throughput degradation of the open loop MIMO schemes.
    IEICE Transactions. 01/2010; 93-A:814-829.
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    ABSTRACT: The effects of resin-housings on the resonant frequencies of built-in antennas in handsets were investigated. A resin plate was adopted as a model for a resin-housing and was located close to a PIFA that was mounted on a rectangular metal plate (125 by 35mm<sup>2</sup>). The size of the PIFA was determined such that the resonant frequency became 2GHz. Variations in the resonant frequency were monitored when the permittivity (epsiv<sub>r</sub>), the thickness (t) of the resin plate and the distance (s) between the resin plate and the PIFA were varied. The results indicate that a reduction of 6.8% in the resonant frequency could be achieved in the case where epsiv<sub>r</sub> = 3, t = 1mm and s = 0mm. In this case, the measured results were confirmed to be in good agreement with the calculated results. Furthermore, it was found that miniaturization of 36% could be achieved by positioning a resin plate adjacent to the PIFA.
    Antennas and Propagation Society International Symposium, 2007 IEEE; 07/2007
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    ABSTRACT: This paper presents an investigation of radio-wave propagation characteristics in the 5 GHz band in a residential two-story house. We investigated the 3-D angular spectra of incident waves when a transmitter and a receiver were situated on the first and second floors, respectively. First of all, correlation in the measured “home environment” containing furniture such as beds, a sofa and tables was determined to confirm a quasi-static environment. Then, 3-D angular spectra measurements were performed by using an eight-element Yagi-Uda antenna as a receiving antenna. Furthermore, the 4-by-4 MIMO channel capacity at each elevation angle was estimated by using elevation angular spectra and the propagation characteristics between the first and second floors were evaluated. The results indicated that the channel capacity in the elevation direction was strongly influenced by the direction of the transmitting antenna.
    01/2007;
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    ABSTRACT: This paper presents an empirical study of the bit-error-rate (BER) performance of a handset adaptive antenna array in a Rayleigh-fading channel with a cross-polarized signal generated using a variable cross-polarization power ratio (XPR) spatial fading emulator. We have investigated the BER characteristics of a handset adaptive antenna consisting of a 1/4-wavelength monopole antenna and a planar inversed-F antenna (PIFA) as a function of XPR. It can be concluded that the measured average BER of an adaptive antenna array with both theta and phi components has an excellent BER performance in a multipath propagation environment with a cross-polarized component
    Antennas and Propagation Society International Symposium 2006, IEEE; 08/2006
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    ABSTRACT: In this paper, throughput performance of MIMO-OFDM system in real residential home environment was evaluated by using wideband MIMO channel measurement data. Computer simulations were carried out to compare the performance of MIMO-OFDM systems with various detection methods, i.e. MMSE, VBLAST, QRM-MLD and SVD-MIMO, in addition to that of the SISO-OFDM system. The results showed that the SVD-MIMO transmission can provide the highest average and outage throughput under the assumption of perfect CSI feedback. On the other hand, QRM-MLD yielded the best performance among the systems without CSI available at the transmitter. It was also found that the outage throughput performance of MMSE and VBLAST degrades severely due to the existence of spatial correlation in the real home environment
    Vehicular Technology Conference, 2006. VTC 2006-Spring. IEEE 63rd; 06/2006
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    ABSTRACT: An area coverage of 4times4 MIMO-OFDM system was measured in residential home environment at 5 GHz band. A novel spatial scanner was fabricated to suit the needs of measurements in environments with household furniture such as beds, sofa and tables. The coverage was calculated based on a total of 55,000 spatial samples in an area of 150 m<sup>2</sup> which includes two rooms, a hallway and living and dining areas. The results shown that the 4times4 MIMO system can greatly increase the area coverage compared to SISO system, especially at high data rate, it was also found that the introduction of optimum power allocation in the MIMO system is effective to increase area boundary with lower data rate
    Personal, Indoor and Mobile Radio Communications, 2005. PIMRC 2005. IEEE 16th International Symposium on; 10/2005
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    ABSTRACT: This paper presents a spatial fading emulator dedicated to the evaluation of signals at antennas in land-based mobile communication systems under multipath fading environments. Rayleigh and Nakagami-Rice distributions are achieved by controlling the phase and amplitude of waves radiated from the scatterers that are used to form the fading emulator. Evaluation of the performance of handset antennas in realistic situations (e.g. talking) under multipath propagation environments can now be expected.
    Antennas and Propagation Society International Symposium, 2005 IEEE; 08/2005
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    ABSTRACT: Little work has been done on the measurement of the BER characteristics of an adaptive antenna in a multipath-fading channel. The paper presents an empirical study of the BER performance of a mobile communications handset adaptive antenna array in a Rayleigh-fading channel generated using a spatial fading emulator. The spatial fading emulator (Iwai, H. et al., IEEE-APS Conf., 2005), which is based on Clarke's model (Vaughan, R and Andersen, J.B., The IEE, 2003), produces Rayleigh-fading channels for both the desired and interference signals. The effectiveness of an adaptive antenna array composed of 2 half-wavelength dipoles subjected to signals generated by the spatial fading emulator was confirmed by measurements of the BER performance.
    Antennas and Propagation Society International Symposium, 2005 IEEE; 08/2005

Publication Stats

21 Citations

Top Journals

Institutions

  • 2006
    • Osaka Gas Co., Ltd.
      Ōsaka, Ōsaka, Japan
  • 2005–2006
    • Tokyo Institute of Technology
      • • Electrical and Electronic Engineering Department
      • • Graduate School of Science and Engineering
      Tokyo, Tokyo-to, Japan