T. Sakata

Panasonic Corporation, Ōsaka, Ōsaka, Japan

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Publications (17)0.91 Total impact

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    ABSTRACT: This paper presents a spatial fading emulator for evaluating handset MIMO antennas in a cluster environment. The proposed emulator is based on Clarke's model and has the ability to control RF signals directly in spatial domain to generate an accurate radio propagation channel model, which includes both uniform and non-uniform angular power spectra (APS) in the horizontal plane. Characteristics of a propagation channel such as fading correlations, eigenvalues and MIMO channel capacities of handset antennas located in the vicinity of the emulator's ring can be evaluated. The measured results show that the fading emulator with 31 antenna probes is sufficient to evaluate fading correlation and MIMO channel capacity of handset antenna in the case of a narrow APS with the standard deviation of more than 20 degrees.
    No preview · Article · Oct 2014 · IEICE Transactions on Communications
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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.
    No preview · Conference Paper · Jul 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.
    No preview · Conference Paper · Jan 2012
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    ABSTRACT: Recently, Long Term Evolution (LTE) cellular mobile communication has been started in a number of countries. The LTE system employs a Multi Input Multi Output (MIMO) antenna array for achieving high-data-rate wireless communication. The radio propagation characteristics and antenna array configuration have a great impact on the MIMO performance [1]. Thus, MIMO propagation tests have been carried out to evaluate the MIMO characteristics in realistic environments [2]. So far, the MIMO channel capacity has been used in almost all investigations. However, the MIMO capacity is not sufficient for estimating MIMO data transmission characteristics in an actual wireless communication system.
    No preview · Conference Paper · Jan 2012
  • Hiroshi Iwai · Kei Sakaguchi · Tsutomu Sakata · Atsushi Yamamoto
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    ABSTRACT: This paper describes a spatial fading emulator based on Clarke's model that can evaluate spatial correlation characteristics between signals received by handset antennas including human-body effect under emulated multipath propagation environments. The proposed model is composed of scatterers, phase-shifters and attenuators. The scatterers are located at equal intervals on the circumference of a circle. Phase-shifters and attenuators in a control circuit are used to control the phase and amplitude of each wave radiated from the scatterers in order to emulate multipath propagation environments, such as Rayleigh or Nakagami-Rice distribution, to be generated at their center. In this paper, the maximum distance between receiving antennas that could be used to evaluate spatial correlation characteristics between antennas was investigated experimentally. The measurement results show that 15 scatterers with a radius of 1.5 m are sufficient to evaluate spatial correlation characteristics within the branch separation of 1.7 lambda when parallel dipole antennas are used as receiving antennas.
    No preview · Article · Oct 2010 · IEICE Transactions on Communications
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    ABSTRACT: There have been a significant number of investigations into handset MIMO antennas applicable for cellular mobile radios [1], [2]. Some measurement apparatuses have been proposed for evaluating MIMOs or diversity arrays for a handset terminal [3], [4]. A spatial fading emulator consists of a number of transmitting antennas in order to reproduce a multipath fading channel in the spatial domain [4]. However, there has been little study of the effectiveness of the emulator in an actual cellular environment. This paper presents the experimental investigation of a dual-band handset MIMO antenna using a spatial fading emulator in a street microcell environment to compare with experimental data of a radio propagation test. Four handset arrays, which included two monopole antennas with dual-band operation, were used for the test, thus permitting the evaluation of 2-by-2 MIMO characteristics. The propagation test was conducted in a central downtown area of Aalborg city in Denmark. Comparison between the measured results obtained by the emulator and the propagation confirmed the effectiveness of the emulator.
    No preview · Conference Paper · Aug 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.
    No preview · Conference Paper · May 2010
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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.
    Full-text · Article · Apr 2010 · IEICE Transactions on Fundamentals of Electronics Communications and Computer Sciences
  • Tsutomu Sakata · Atsushi Yamamoto · Koichi Ogawa · J.-i. Takada
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    ABSTRACT: This paper presents a radio frequency (RF) controlled spatial fading emulator for the evaluation of a handset MIMO antenna. The RF-controlled fading emulator can control RF signals directly in the spatial domain to produce an accurate radio propagation channel model, which includes the uniform and non-uniform angular power spectra (APS) in the horizontal plane. Fading correlation and MIMO channel capacities of a quasi-dipole array, in the case of up to three spatial clusters, are measured by using the emulator. From agreement between the measured data and theoretical values, the effectiveness of the emulator was confirmed.
    No preview · Conference Paper · Oct 2009
  • Hiroshi Iwai · Tsutomu Sakata · Atsushi Yamamoto · Kei Sakaguchi
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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.
    No preview · Article · Sep 2007 · IEICE Transactions on Communications
  • H. Iwai · T. Sakata · A. Yamamoto · K. Ogawa
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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.
    No preview · Conference Paper · Jul 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
    Full-text · Conference Paper · Aug 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
    Full-text · Conference Paper · Jun 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
    No preview · Conference Paper · Oct 2005
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    H. Iwai · A. Yamamoto · T. Sakata · K. Ogawa · K. Sakaguchi · K. Araki
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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.
    Full-text · Conference Paper · Aug 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.
    Full-text · Conference Paper · Aug 2005

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