Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1587/transcom.2023ebp3038

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Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)  

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Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)  

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

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Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)  

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Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

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Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)  

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DOI： 10.1587/transcom.2023ebp3009

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Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

DOI： 10.1587/comex.2023xbl0035

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

File： PID2023000153.pdf

DOI： 10.1109/WCNC55385.2023.10118703

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Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

File： PID2022002577.pdf

DOI： 10.1109/WCNC55385.2023.10118697

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.23919/icact56868.2023.10079677

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

File： e106-b_2_184.pdf

DOI： 10.1587/transcom.2022ebp3051

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

File： e106-b_2_193.pdf

DOI： 10.1587/transcom.2022ebp3062

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Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/ICCE-Taiwan58799.2023.10226659

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Other Link： https://dblp.uni-trier.de/db/conf/icce-tw/icce-tw2023.html#HouKKD23

Authorship：Corresponding author   Language：English  

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Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/WPMC55625.2022.10014789

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

DOI： 10.1587/transcom.2021ebp3213

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Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/APCC55198.2022.9943716

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Other Link： https://dblp.uni-trier.de/db/conf/apcc/apcc2022.html#MakabeDH22

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

DOI： 10.1587/transcom.2021ebp3187

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Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/PIMRC54779.2022.9977505

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Other Link： https://dblp.uni-trier.de/db/conf/pimrc/pimrc2022.html#DennoKH22

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/PIMRC54779.2022.9977753

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Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/vtc2022-spring54318.2022.9860405

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

DOI： 10.1587/transcom.2021ebp3075

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing  

The special electromagnetic properties of metamaterials have contributed to the development of terahertz technology, and terahertz broadband absorbers for various applications have been investigated. The design of metamaterial absorbers with tunability is in a particularly attractive position. In this work, a tunable broadband terahertz metamaterial absorber is proposed based on the phase transition material vanadium dioxide (VO₂). The simulation results show that an excellent absorption bandwidth reaches 3.78 THz with the absorptivity over 90% under normal incidence. The absorptivity of the proposed structure can be dynamically tuned from 2.7% to 98.9% by changing the conductivity of VO₂, which changes the structure from a perfect reflector to an absorber. An excellent amplitude modulation with the absorptivity is realized. The mechanism of broadband absorption is explored by analyzing the electric field distribution of the absorber based on impedance matching theory. In addition, it also has the advantage of polarization and incident angle insensitivity. The proposed absorber may have a wide range of promising applications in areas such as terahertz imaging, sensing, and detection.

DOI： 10.1063/5.0082295

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/lifetech53646.2022.9754835

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

File： Two-Dimensional_RSSI-Based_Indoor_Localization_Using_Multiple_Leaky_Coaxial_Cables_With_a_Probabilistic_Neural_Network.pdf

DOI： 10.1109/access.2022.3153083

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/icce53296.2022.9730575

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

File： 1-s2.0-S0030399221004977-main.pdf

DOI： 10.1016/j.optlastec.2021.107409

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/gcce53005.2021.9622078

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

File： e104-b_10_1336.pdf

DOI： 10.1587/transcom.2020ebp3183

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

File： A_Broadband_Switchable_Metamaterial_Absorber_Reflector_Based_On_Multi-Laps_Graphene_Sheets_in_the_Terahertz_Band.pdf

DOI： 10.1109/jphot.2021.3109045

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Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

DOI： 10.1587/transcom.2020ebp3180

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Language：English   Publishing type：Research paper (scientific journal)  

File： 20210618052654509.pdf

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

File： 09452090.pdf

DOI： 10.1109/access.2021.3088123

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/lifetech52111.2021.9391899

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

File： 09033967.pdf

DOI： 10.1109/tbc.2020.2977514

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

File： 09290415.pdf

DOI： 10.1109/tbc.2020.3039679

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.23919/icact51234.2021.9370597

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Authorship：Lead author   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, using the time-series throughput data generated from a simulated factory scenario, we study throughput prediction using convolutional neural network (CNN). Different with image or numerical recognition using CNN, in which the distribution of the prediction target during training stage usually has the similar level, the distribution of the throughput data concentrates only on several values. This centralized distribution may degrade the prediction accuracy. Therefore, we will propose a new CNN prediction method employing target vectorization which can mitigate the centralization of distribution. This method makes training process of CNN hold more possibility and improves the prediction accuracy of the throughput.

DOI： 10.23919/ICACT51234.2021.9370905

Scopus

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Other Link： https://dblp.uni-trier.de/db/conf/icact/icact2022.html#HouYSWNHDS22

Authorship：Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

File： 09328758 (1).pdf

DOI： 10.1109/access.2021.3053034

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

This letter proposes matrix factorization (MF) based interpolation of received signal strength (RSS) from a transmitter mounted on moving robot in factory environment. For realizing the reliable wireless communication, machine learning based channel prediction methods have been intensively studied in the past decade. However, some traffic models will make the observation of RSS sequence be intermittent, and the missing values must be interpolated before input to the predictor. Classical interpolation such as linear interpolation cannot appropriately estimate the missing values because the result of the interpolation depends on the observation time. In this letter, we propose to apply an MF-based interpolation technique to RSS interpolation in order to restore the true RSS variation pattern. Moreover, the basic MF-based interpolation is improved by introducing a smoothing term in an objective function to represent the smooth variation of the RSS sequence. The simulation results show that the MF-based interpolation can improve the prediction accuracy of the machine learning based channel prediction method.

File： 55 IEEEWCL.pdf

DOI： 10.1109/lwc.2021.3069979

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

DOI： 10.1587/comex.2021xbl0133

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Publishing type：Research paper (scientific journal)  

DOI： 10.1587/transcom.2020EBP3045

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Other Link： https://dblp.uni-trier.de/db/journals/ieicetb/ieicetb104.html#DennoYH21

Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, we propose a non-orthogonal multiple access with adaptive resource allocation based on factor graphs. The proposed non-orthogonal multiple access assigns multiple frequency resources for each device to send their packet. Even if the number of the devices is more than the frequency resources, the proposed non-orthogonal access allows all the devices to transmit their packets simultaneously for high capacity massive machine type communication (mMTC). Furthermore, this paper proposes adaptive resource allocation based on factor graphs that adaptively allocates the frequency resources to the devices for improvement of the transmission performances. This paper proposes two allocation criteria for the proposed adaptive allocation. This paper shows that the proposed non-orthogonal multiple access achieves superior transmission performance in 4-path Rayleigh fading channel with overloading ratio of 1.5, even without the adaptive resource allocation. The adaptive resource allocation enables the proposed non-orthogonal access to attain a gain of about 5 dB at the BER of 10(-4).

DOI： 10.1109/WPMC52694.2021.9700454

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Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.23919/ICACT51234.2021.9370597

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Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/ICSPCS53099.2021.9660311

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Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.23919/ICACT51234.2021.9370905

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Graphyonline Publications PVT, Ltd.  

File： 47 Channel_Status_Prediction_using_Auto-regressive_an_IJCSE202012.pdf

DOI： 10.15344/2456-4451/2020/159

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The emerging material of graphene has resulted in new options for the design of metamaterial devices with excellent performances, offering an attractive platform for electromagnetic absorption applications. To date, researches on patterned graphene-based metamaterial absorbers (MAs), have focused on achieving broadband absorption while maintaining many excellent properties. Here, we propose a broadband tunable MA with a perfect absorption based on a novel design of the combination of cross- and square-shaped graphene sheets. Numerical simulation results show that the bandwidth of the proposed broadband MA reaches 2.76 THz with the absorptivity greater than 90% for both the transverse electric (TE) and transverse magnetic (TM) modes, which exceeds most of broadband absorption results achieved by MAs in previous studies. A numerical analysis em ploying the equivalent circuit model for the designed structure is conducted to determine the influence of the structural parameters on the absorptivity and optimize the parameters. Results show that impedance matching is achieved between the input impedance and the free-space impedance at the absorption band. Detailed numerical simulations are conducted to calculate the surface loss density, electric field, and surface currents to obtain an understanding of the high absorption mechanism. Also, the designed MA exhibits excellent properties, such as tunability, polarization independence, incident angle insensitivity and outstanding tolerance to changes in the structural parameters, suggesting that the proposed absorber is a promising candidate for various applications in the terahertz band.

File： 4-A polarization- and angle-insensitive broadband tunable metamaterial absorber using patterned graphene resonators in the terahertz band.pdf

DOI： 10.1016/j.optlastec.2020.106513

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Cambridge University Press (CUP)  

The impulsive noise (IN) damages the performance of wireless communication in modern 5G scenarios such as manufacturing and automatic factories. The proposed receiver utilizes constant false alarm rate to obtain the threshold and combines with blanking to further improve the performance of the conventional blanking scheme with acceptable complexity. The simulated results show that the proposed receiver can achieve a lower bit error rate even if the probability of IN occurrence is very high and the power of the IN is much larger than that of the background noise.

File： 46 an_smlbbased_ofdm_receiver_over_impulsive_noise_environment.pdf

DOI： 10.1017/atsip.2020.22

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

This paper proposes a low complexity soft input decoding in an iterative linear receiver for overloaded MIMO. The proposed soft input decoding applies two types of lattice reduction-aided linear filters to estimate log-likelihood ratio (LLR) in order to reduce the computational complexity. A lattice reduction-aided linear with whitening filter is introduced for the LLR estimation in the proposed decoding. The equivalent noise caused by the linear filter is mitigated with the decoder output stream and the LLR is re-estimated after the equivalent noise mitigation. Furthermore, LLR clipping is introduced in the proposed decoding to avoid the performance degradation due to the incorrect LLRs. The performance of the proposed decoding is evaluated by computer simulation. The proposed decoding achieves about 2 dB better BER performance than soft decoding with the exhaustive search algorithm, so called the MLD, at the BER of 10(-4), even though the complexity of the proposed decoding is 1/10 as small as that of soft decoding with the exhaustive search.

File： 42 IEICETB202005.pdf

DOI： 10.1587/transcom.2019EBP3159

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：OPTICAL SOC AMER  

Metamaterial absorbers (MAs) serve as important electromagnetic wave-absorbing devices that have captured the attention of researchers for a long term. Functioning as sensitive detectors to determine perturbations in an ambient environment is another significant subsidiary function. Here, we theoretically propose an optimized fabrication method to implement terahertz MAs with fewer steps and also evaluate both absorption and sensing performances of such MAs realized by the new method. Simulation findings demonstrate that such MAs can basically maintain the original absorption features perfectly, including near-complete absorption at resonance as well as strong robustness to wide incident angles. Specifically, the full width at half-maximum and quality factor of the absorption resonances attenuate less than 26% and 8% with this new method, remaining in the ranges of similar to 0.03-0.04 THz and similar to 20-27 for two selected example MAs. More significantly, sensing capacities of this type of MA, in terms of maximum detection range (enhancing at least 9%), observable spectral modulation (increasing at least 6.3%), and refractive index sensitivity, are improved to a large extent because of more intense coupling between resonant field and matter in the case of surface-relief MAs. This stronger coupling results from exposing more spots of the resonantly high field to direct contact with an approaching analyte, which is illustrated by field profiles of the MAs at resonance in this work. Additionally, other desirable absorber features are also explored with such MAs, like functioning as building blocks to configure multiband MAs and strong robustness against fabrication errors. Such new-style terahertz MAs shown in the paper, acting as good examples, not only prove that terahertz MAs can be fabricated by the proposed time- and cost-saving route in contrast to the traditional MA fabrication process, but also can serve as novel platforms to explore other intriguing terahertz photonic effects, such as the field enhancement effect. (C) 2020 Chinese Laser Press

File： prj-8-4-519.pdf

DOI： 10.1364/PRJ.386040

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Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/ICAIIC48513.2020.9065033

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/LifeTech48969.2020.1570619143

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Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/GCCE50665.2020.9291828

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Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/WPMC50192.2020.9309510

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Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/ICSPCS50536.2020.9310008

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

The resonances with narrow linewidths generated in metamaterials are valuable for numerous applications ranging from bio-sensing to narrow-band filter. And breaking structural symmetry of metamaterials is one of the common and efficient approaches to achieve such sharp resonances. In this paper, we present symmetry breaking introduced in vertical split ring resonators (VSRR) metamaterials to excite narrow resonance. Different from the previously reported planar asymmetric metamaterials, the three-dimensional metamaterials are dominantly excited by the magnetic field component of the terahertz illumination together with the electric component. In this case, sharp resonances with characteristic magnetic field distributions are excited. And the sharpest resonance shows up with an ultra-narrow line-width (full width at half maximum, FWHM is 5.90 GHz) and high Q of 327 at 1.93 THz. Through systematic theoretical analysis and numerical mode implementation, we reveal the sharp resonance dips are produced by resonance hybridization between a resonance mode induced by the destruction of the structural symmetry and another special resonance inherent in the symmetric VSRR metamaterials. In addition, the fabrication robustness and sensing potential of the asymmetric VSRR metamaterials are explored in this paper. The results show that the AVSRR design is insensitive to the errors in the fabrication process, like rough metal surface and smoothmetal corner, but highly sensitive to the approaching substance, which prove the excellent sensing performance.

File： 38 IEEEOSAJLT_2019_10.pdf

DOI： 10.1109/JLT.2019.2929771

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/GCCE46687.2019.9015621

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

This paper proposes an XOR physical layer network coding (XOR-PLNC) with non-linear precoding for quadrature amplitude modulations (QAMs) in bi-directional MIMO relay systems. The proposed XOR-PLNC applies power loading in order to improve the transmission performance. The proposed XOR-PLNC introduces a modulus adapted to channel gains. Moreover, the modulus is further reduced in cooperation with modulo operation which the non-linear precoding employs for improvement of transmission power efficiency. The use of the reduced modulus improves the energy efficiency of the signal transmission, which improves the transmission performance in the proposed XOR-PLNC. The performance is evaluated by computer simulations in bi-directional MIMO relay channels with 16QAM to 1024QAM.

File： 36 IEICETB201910.pdf

DOI： 10.1587/transcom.2018EBP3346

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Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

File： 37 IEEEPJ_201908.pdf

DOI： 10.1109/jphot.2019.2917539

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

This paper proposes a novel low complexity lattice reduction-aided iterative receiver for overloaded MIMO. Novel noise cancellation is proposed that increases an equivalent channel gain with a scalar gain introduced in this paper, which results in the improvement of the signal to noise power ratio (SNR). We theoretically analyze the performance of the proposed receiver that the lattice reduction raises the SNR of the detector output signals as the scalar gain increases, when the LenstraLenstra- Lova's (LLL) algorithm is applied to implement the lattice reduction. Because the SNR improvement causes the scalar gain to increase, the performance is improved by iterating the reception process. Computer simulations confirm the performance. The proposed receiver attains a gain of about 5 dB at the BER of 10(-4) in a 6 x 2 overloaded MIMO channel. Computational complexity of the proposed receiver is about 1/50 as much as that of the maximum likelihood detection (MLD).

File： 33 IEICETB201905.pdf

DOI： 10.1587/transcom.2018EBP3215

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Publishing type：Research paper (scientific journal)   Publisher：Graphyonline Publications PVT, Ltd.  

DOI： 10.15344/2456-4451/2019/142

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Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/IINTEC48298.2019.9112098

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Authorship：Last author   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/VTCFall.2019.8891589

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Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper proposes a low density signature-based packet access with phase only adaptive precoding. The proposed access allows multiple user terminals to send their packets simultaneously though only one antenna is put on terminals and on an access point, in order to increase network throughput. The proposed phase only adaptive precoding improves the transmission performance by rotating the transmission signal phase. This paper proposes a criterion that defines the optimum rotation angle, and actual two techniques to estimate the angle. When 6 packets are transmitted in 4 time slots, the proposed adaptive precoding attains about a gain of 4dB at the BER of 10(-4) in a single input single output Rician fading channel, i.e., overloading ratio is 1.5.

DOI： 10.1109/VTCSpring.2019.8746451

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Authorship：Last author   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/WPMC48795.2019.9096064

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper analyzes optical radio channel propagation characteristics by means of experimental measurement. The channel with an LED and a PD provided by the outstanding technologies co. ltd., is defined as an optical radio channel, and its delay profile is measured by NI-USRPs. As a result, small delayed paths are detected due to the LED or the PD in use. The delay profile is evaluated in a system with single carrier modulation where the frequency domain equalization is applied, in terms of the bit error rate (BER). The transmission performance is about 2dB degraded due to the small delayed paths.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/APCC47188.2019.9026476

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper will utilize a method to recover the damaged time-domain signal of the OFDM system over the WLAN channel in the industrial environment. We assume that the channel is perfectly detected. The simulated results show that the OFDM system using M-algorithm can achieve better BER performance compared to that of the conventional OFDM system in the AWGN channel when 1/2 time-domain signal is missing. On the other hand, the BER performance of the OFDM system with M-algorithm using ZF is better than that of the conventional OFDM system when 1/4 and 1/2 time-domain signal is missing in the WLAN channel. In addition, the BER performance of the OFDM system with M-algorithm using MMSE is better than that of the OFDM system with M-algorithm using ZF in the WLAN channel when 1/8, 1/4 and 1/2 time-domain signal is missing.

DOI： 10.1109/APSIPAASC47483.2019.9023219

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Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

XOR-physical layer network coding is known to achieve superior performance in terms of an end-to-end throughput and frequency utilization efficiency. This paper proposes a novel relay selection technique to further improve transmission performance. We introduce a relay selection criteria that is defined as an end-to-end BER performance in the relay network. The proposed technique select a group of relays that maximizes the criteria. This paper applies lattice reduction-aided precoding in order to improve the transmission performance and to reduce computational complexity of the relay selection. The performance of the proposed relay selection is evaluated in a 2x2 MIMO bidirectional wireless relay system. The proposed selection attains a gain of about 13dB at the BER of 10(-4).

DOI： 10.1109/VTS-APWCS.2019.8851618

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Other Link： https://dblp.uni-trier.de/db/conf/apwcs2/apwcs2019.html#YamamotoDH19

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Planar metasurfaces and metamaterial absorbers have shown great promise for label-free sensing applications at microwaves, optical and terahertz frequencies. The realization of high-qualityfactor resonance in these structures is of significant interest to enhance the sensing sensitivities to detect minute frequency shifts. We propose and demonstrate in this manuscript an ultrasensitive terahertz metamaterial absorber sensor based on a three-dimensional split ring resonator absorber with a high quality factor of 60.09. The sensing performance of the proposed absorber sensor was systematically investigated through detailed numerical calculations and a maximum refractive index sensitivity of 34.40% RIU-1 was obtained. Furthermore, the absorber sensor can maintain a high sensitivity for a wide range of incidence angles up to 60 degrees under TM polarization incidence. These findings would improve the design flexibility of the absorber sensors and further open up new avenues to achieve ultrasensitive sensing in the terahertz regime.

DOI： 10.1088/2040-8986/aab66e

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-HINDAWI  

File： 7503735.pdf

DOI： 10.1155/2018/7503735

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST IMAGE INFORMATION & TELEVISION ENGINEERS  

In order to realize next generation digital terrestrial television broadcasting (DTTB) systems, the currently deployed Integrated Services Digital Broadcasting Terrestrial (ISDB-T) is still essential due to the spectrum-scarcity. This paper proposes a layered division multiplexing (LDM) scheme to simultaneously transmit ISDB-T stream and a secondary data stream over a common frequency band. The next generation DTTB system can be obtained by combining the ISDB-T and the secondary data streams. In the proposed scheme, we deploy the primary layer for transmission of ISDB-T signal and the secondary layer for transmission of secondary data stream both employed space time block coding. In addition, we only adopt partial LDM to reduce the interference between two systems, since the transmission capacity of the secondary layer exceeded the minimum requirement due to reuse of primary layer.

File： 30 ITETrans201801.pdf

DOI： 10.3169/mta.6.98

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Leaky coaxial (LCX) cable can be used as antenna for wireless communication system and wireless power transfer which can be widely applied for many application scenarios including wireless service for IoT, automated factory using a large number of wireless devices. We have designed that one LCX cable can be used as two antennas which can releases the space requirement of MIMO deployment for wireless application. In this paper, we will further evaluate the 4-by-4 LCX-MIMO channel using one composite cable with two LCX cables. In addition, we also propose a low-complexity power allocation method for the LCX-MIMO system with the user's positional information (PI). The results show that the capacity is promising when the spacing between LCX cables is small as to 2cm. In addition, our proposed low-complexity power allocation has better capacity than that of using equal power allocation when SNR value is over the low range.

DOI： 10.1109/GCCE.2018.8574729

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Other Link： https://dblp.uni-trier.de/db/conf/gcce/gcce2018.html#ZhuHDO18

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper proposes a novel low complexity lattice reduction-aided iterative receiver for overloaded MIMO. Novel noise cancellation is proposed that increases an equivalent channel gain with a scalar gain introduced in this paper, which results in the improvement of the signal to noise power ratio (SNR). The performance of the proposed receiver is theoretically analyzed that the lattice reduction guarantees the SNR of the detector to be more than a value proportional to the scalar gain, when the LenstraLenstraLovas (LLL) algorithm is applied to implement the lattice reduction. The proposed receiver attains a gain of about 5dB at the BER of 10(-4) in a 6 x 2 overloaded MIMO channel.

DOI： 10.1109/ICSPCS.2018.8631747

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Other Link： https://dblp.uni-trier.de/db/conf/icspcs/icspcs2018.html#DennoKIH18

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper proposes adaptive sideband selection for periodic interference cancellation using digital signal processing. The proposed selection enables the periodic interference cancellation to attain better performance by providing sideband signals having higher ICNR(interference to carrier and noise power ratio). An algorithm that selects such sideband signals is shown in this paper. The proposed selection achieves 18dB better SINR(output signal to interference and noise power ratio) performance than random selection in the channel with CIR(carrier to interference power ratio) of 10dB and CNR(carrier to noise power ratio) of 30dB.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper will study the busy/idle duration model and its prediction performance of autoregressive (AR) based predictor using the real environment data collected during rush-hour weekday evening at a railway station. The analysis shows that both busy and idle duration distribution largely appear as a generalized Pareto (GP) distribution with a different scale value. In addition, the scale value highly decides the prediction performance of the low-complexity linear AR based predictor. We also propose a new AR based predictor by separating busy/idle duration data into different streams to differentiate the scale value of the streams. The prediction performance of the proposed predictor can be improved for the streams with small scale value.

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：OPTICAL SOC AMER  

An ultrasensitive metamaterial sensor based on double- slot vertical split ring resonators (DVSRRs) is designed and numerically calculated in the terahertz frequency. This DVSRR design produces a fundament LC resonance with a quality factor of about 20 when the incidence magnetic field component normal to the DVSRR array. The resonant characteristics and sensing performance of the DVSRR array design are systematically analyzed employing a contrast method among three similar vertical split ring resonator (SRRs) structures. The research results show that the elimination of bianisotropy, induced by the structural symmetry of the DVSRR design, helps to achieve LC resonance of a high quality factor. Lifting the SRRs up from the substrate sharply reduces the dielectric loss introduced by the substrate. All these factors jointly result in superior sensitivity of the DVSRR to the attributes of analytes. The maximum refractive index sensitivity is 788 GHz/RIU or 1.04 x 10(5) nm/RIU. Also, the DVSRR sensor maintains its superior sensing performance for fabrication tolerance ranging from -4% to 4% and wide range incidence angles up to 50 degrees under both TE and TM illuminations. (C) 2017 Chinese Laser Press

DOI： 10.1364/PRJ.5.000571

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE INC  

Principles of single-and multi-phase-shifted chirped fiber Bragg grating (CFBG) in 2 mu m band are analyzed with transmission matrix method, and transmission characteristics, including transmissivity, wavelength and bandwidth performance, of single-and multi-phase-shifted CFBG in 2 mu m band with different grating parameters are discussed by simulation. It is found that phase-shifted position, grating length, chirped coefficient and refractive index modulation amplitude all have impacts on bandwidth of phase-shifted transmission peak. The transmission peak bandwidths of single-, dual-and tri-phase-shifted CFBG can reach to 0.0270, 0.0172 and 0.0112 nm respectively. The experiment of phase-shifted CFBG verifies the correctness of the simulation, and the bandwidths of 0.0901 and 0.0480 nm are acquired for single-and dual-phase-shifted CFBG respectively, which are narrower than previous filters based on fiber Bragg grating in 2 mu m band multi-wavelength fiber laser system. (C) 2017 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.yofte.2017.06.001

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS  

The linewidth performance of all-fiber, linear-cavity Fabry-Perot structures based on fiber Bragg gratings operating at 2-mu m band has been investigated numerically. The output linewidth performance of two symmetrical and asymmetrical cavities has been theoretically studied and comprehensively compared. The numerical analysis is based on the transmission matrix method with the simplified parameters. The simulation results show that cavity lengths, cavity lengths ratio, grating lengths, grating lengths ratio, as well as index modulation depths, affect the output linewidth performance. The tolerance ability of the asymmetrical structure is first proposed and investigated under 1 mm accuracy, and single-frequency output can be realized by properly adjusting the properties of the proposed composite linear cavity structure. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)

DOI： 10.1117/1.OE.56.5.056107

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

A hybrid mode-locked thulium-doped fiber laser incorporating a nonlinear optical loop mirror and a nonlinear polarization rotation effect is proposed in the 2 mu m band for the first time. By adjusting two polarization controllers, a stable single-polarization noise-like (SPNL) pulse operation is obtained. The SPNL pulse could work steadily for at least 400 min. At a launched pump power of 3.52 W, the hybrid mode-locked SPNL pulse centers at 2007 nm with an optical full width at half maximum of 20 nm, a polarization extinction ratio of 26.3 dB, a coherence spike width of 258 fs and a pulse energy of 42.11 nJ, respectively.

DOI： 10.1088/2040-8986/aa6267

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

A switchable single-polarization (SP) dualwavelength mode-locked thulium-doped fiber laser using the polarization maintaining fiber Bragg grating and semiconductor saturable absorber mirror is proposed in 2-mu m band. By adjusting the polarization controller, stable dual-wavelength pulse lasing operation and SP single-wavelength pulse lasing operation are obtained. The dual-wavelength pulse lasing operation is obtained at 1940.97 and 1941.73 nm. In the SP single-wavelength pulse lasing state, the polarization extinction ratios are higher than 30 dB, the SP pulse duration are 3.75 and 3.73 ps.

DOI： 10.1109/LPT.2017.2669210

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

This paper proposes a low-complexity compressed sensing (CS)-based time domain channel estimation with virtual oversampling for OFDM-based DTTB system. CS technique is first applied to sparse channel estimation in integrated services digital broadcasting-terrestrial (ISDB-T) system. Unfortunately, the CS-based time-domain channel estimation suffers from a performance degradation under the existence of fractional delay. Fractional delay is a common issue in time domain-based channel estimation due to sampling imperfection of channel delay time. Therefore, we propose virtual oversampling to deal with the fractional delay without increasing the signal bandwidth. Furthermore, exploiting the fact that the rate of change of path delay is slower than the path gain, a modified orthogonal matching pursuit is also proposed to reduce computational complexity. Numerical analyses of bit error rate and computational complexity are given to verify effectiveness of the proposed scheme.

File： 23 IEEETBCRyan20170301.pdf

DOI： 10.1109/TBC.2016.2606938

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Compressed sensing (CS) is one of the hottest research topics in the sparse signal reconstruction problem. But CS implementation has a drawback of high computational complexity due to calculation between large size of matrices. In this paper, we will propose a low-complexity CS hardware realization for channel estimation in the integrated services digital broadcasting-terrestrial (ISDB-T) system using several optimization methods to reduce the implementation complexity of CS usage. Since the ISDB-T is based on orthogonal frequency division and multiplexing system, the measurement matrix of CS computation is a truncated discrete Fourier transform (DFT) matrix. We can exploit the symmetrical property of this DFT matrix to significantly reduce its multiplication complexity and random access memory usage. To achieve fast reconstruction period, this paper also provides a hardware architecture for the proposed method and its realization in field programmable gate array. The simulation results show that the proposed methods can achieve lower complexity CS-based channel estimation with almost the identical system performance with the conventional method. Moreover, the realized hardware can achieve the fastest execution time compare to that of other existing methods.

File： 22 IEEETBCRian201701.pdf

DOI： 10.1109/TBC.2016.2617286

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

A simple linear cavity configuration for a stability wavelength-spacing-tunable single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber laser based on a nonlinear amplifying loop mirror (NALM) is proposed. The gain competition in the erbium-doped fiber (EDF) has been suppressed by the intensity dependent loss introduced by the NALM. The SLM operation is guaranteed by a section of unpumped EDF as saturable absorber. A stable dual-wavelength SLM fiber laser with a wavelength-spacing of 11.35 nm is experimentally realized. The optical signal-to-noise ratio is over 47 dB and the linewidths of two wavelengths measured by delayed self-heterodyne method are 1.1 and 1.0125 kHz, respectively. The tuning range of wavelength-spacing is 9.09-11.35 nm, correspondingly, and the THz signal is from 1.235 to 1.416 THz.

DOI： 10.1007/s11082-016-0863-9

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

We have recently proposed a multi-band wireless local area network (WLAN) system as a solution to the increasingly crowded frequency space. Efficiency can be improved by an agile transceiver that transmits on an idle channel on either or both bands concurrently, and a busy/idle (B/I) predictor will form part of the sensing unit for such a system. A probabilistic neural network (PNN) is studied here for predicting upcoming WLAN B/I status based on pattern matching and classification of previous state patterns. IEEE 802.11 wireless data frames were captured at two hot-spots on multiple channels and the B/I status estimated. The prediction performance is compared for two different locations, channels, prediction matrix dimensions, B/I vs channel occupancy ratio (COR) input types, and frequency of retraining. Results show that the PNN has good potential to estimate the number of idle slots in the upcoming 20 slots and the performance improves with regular retraining.

DOI： 10.23919/APCC.2017.8304030

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Other Link： https://dblp.uni-trier.de/db/conf/apcc/apcc2017.html#WebberMHYK17

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：OPTICAL SOC AMER  

A mode-locked thulium-doped fiber laser (TDFL) based on nonlinear polarization rotation (NPR) with different net anomalous dispersion is demonstrated. When the cavity dispersion is -1.425 ps(2), the noise-like (NL) pulse with coherence spike width of 406 fs and pulse energy of 12.342 nJ is generated at a center wavelength of 2003.2 nm with 3 dB spectral bandwidth of 23.20 nm. In the experimental period of 400 min, the 3 dB spectral bandwidth variation, the output power fluctuation, and the central wavelength shift are less than 0.06 nm, 0.04 dB, and 0.4 nm, respectively, indicating that the NPR-based TDFL operating in the NL regime holds good long-term stability. (C) 2016 Chinese Laser Press

DOI： 10.1364/PRJ.4.000318

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Multiple-input-multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) receivers with an electronically steerable passive array radiator (ESPAR) antenna can improve bit error rate (BER) performance and obtain additional diversity gain without increasing the number of radio-frequency (RF) front-end circuits. In this scheme, a minimum-mean-square-error (MMSE) channel estimator is employed for obtaining the channel state information. However, its drawbacks include insufficient estimation accuracy and high computational complexity due to the inverse matrix calculation. In this paper, we propose using a low-complexity compressed-sensing-based channel estimation for the MIMO-OFDM receiver with an ESPAR antenna. We also propose a low-complexity detection scheme to further reduce the computational cost required for the detection. The simulation results show that with using the proposed channel estimation method, the BER performance is improved, while its complexity is reduced. The simulations also show that the proposed detection scheme successfully reduces the required computational cost while minimizing the degradation in the BER.

File： 18 IEEETVT 201610 Low-ComplexityChannelEstimationandDetectionforMIMO-OFDMReceiverWithESPARAntenna.pdf

DOI： 10.1109/TVT.2015.2506782

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

Radio over Fiber (RoF) is a promising solution for providing wireless access services. Heterogeneous radio signals are transferred via an optical fiber link using an analog transmission technique. When the RoF and the radio frequency (RF) devices have a nonlinear characteristic, these will create the intermodulation products (IMPs) in the system and generate the intermodulation distortion (IMD). In this paper, the IMD interference in the uplink RF signals from the coupling effect between the downlink and the uplink antennas has been addressed. We propose a method using the dynamic channel allocation (DCA) algorithm with the predistortion (PD) technique to improve the throughput performance of the multi-channel RoF system. The carrier to distortion plus noise power ratio (CDNR) is evaluated for all channel allocation combinations; then the best channel combination is assigned as a set of active channels to minimize the effect of IMD. The results show that the DCA with PD has the lowest IMD and obtains a better throughput performance.

DOI： 10.1587/transele.E99.C.563

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE Computer Society  

DOI： 10.1109/ICPPW.2016.18

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Other Link： https://dblp.uni-trier.de/db/conf/icppw/icppw2016.html#FujimotoMASY16

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In a mobile integrated service digital broadcasting-terrestrial (ISDB-T) system, the usage of a 3-elements electrical steerable parasitic array radiator (ESPAR) antenna can be a solution to gain diversity while keeping low power consumption and compact hardware size. But, the ESPAR antenna also increases the channel estimation difficulty as the received signal from each element will interfere each others. Orthogonal matching pursuit (OMP) can become an alternative in obtaining channel information for the system with ESPAR antenna. However, the OMP technique has a drawback in huge matrix inner product in its computation. In this paper, we propose a 3-column OMP with measurement matrix strength reduction technique to reduce the complexity in the inner product computation. The propose method overall result can achieve more than 90% complexity reduction.

DOI： 10.1109/BMSB.2016.7521988

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

One-Seg service is a mobile terrestrial digital audio/video and data broadcasting service in Japan and many other countries. It transmits QPSK modulated symbols to achieve about 416 kbit/s transmission rate for mobile receivers with 428 kHz of bandwidth at UHF band. To further improve the transmission quality and spectrum efficiency, the system design must consider some major issues such as performance degradation from large Doppler shift and small size hardware for receivers which limit the system only to use low-order M-QAM modulation like BPSK or QPSK and small size of power amplifier with a low dynamic range of peak-to-average power ratio (PAPR). To reduce these impacts on the performance of One-Seg service, this paper proposes a BPSK modulated multicarrier system using parallel combinatory (PC) code. The proposed system achieves better BER performance and better PAPR characteristics with a comparable bandwidth efficiency (BWE) compared to that of the corresponding M-QAM modulated OFDM systems.

DOI： 10.1109/BMSB.2016.7521993

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper proposes a Modified Orthogonal Matching Pursuit (MOMP)-assisted MIMO-OFDM receiver for next generation DTTV with Single Frequency Network- Space Time Block Coding (SFN-STBC). The receiver uses dual polarized antennas which can receive signals from different transmitters. In this paper, we investigate the BER performance if the transmitters transmit signals with different signal power where the receiver is in near-far effect with different receive power from different transmitter. In addition, we also examine the performance of the SFN system using MOMP for channel estimation with near-far effect. The simulation shows that the BER decreases if the received signal power from different transmitters are almost equal. And also, the MOMP BER performance is about 1 dB closer compared to ideal channel information in the range of SNR Eb/No=l5dB to Eb/No=25dB region.

DOI： 10.1109/BMSB.2016.7521981

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

For some scenarios where high received power cannot be guaranteed due to user moving, the OFDM system with low order M-QAM such as BPSK/QPSK is promising. This paper will propose an orthogonal parallel combinatory ASK modulated multicarrier system to achieve flexible bandwidth efficiency (BWE) using low order ASK modulation and parallel combinatory (PC) code. PC code has been shown that it can achieve flexible BWE and better peak-to-average power ratio (PAPR) performance. Our proposal will utilize PC code for both I-phase and Q-phase of frequency-domain OFDM symbol which further improve the BWE of PC-OFDM system. The proposed system can obtain better BER performance and better PAPR performance using low order ASK modulation. Therefore, the proposed system can simplify the receiver design and provide the design freedom degree with a flexible range of BWE for system design or adaptive modulation and code control.

DOI： 10.1109/ISCIT.2016.7751581

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Language：English   Publisher：The Institute of Image Information and Television Engineers  

Integrated Service Digital Broadcasting Terrestrial (ISDB-T) transmission system is based on OFDM technique which requires cyclic prefix (CP) and pilot tones for channel estimation. Beside data sub-carriers, the usage of CP and pilot tones occupies the ISDB-T bandwidth up to 25%. However, CP is required to mitigate the inter-symbol interference (ISI) and interblock interference (IBI) and pilot tones are required to estimate the channel response information in order to equalize the multipath effect. Recently, a wireless communication scheme without CP by using chained turbo of equalization (CHATUE) technique was proposed. Furthermore, in term of channel estimation, compressed sensing (CS) has become a prominent technique that offers better performance with less pilot tones. In this paper, we proposed a channel estimation scheme for ISDB-T system without CP using CS technique. The pilot tones are inserted at several lowest value intersections location in the previous and post symbol interferences. The final result provides an ISDB-T system with more than 90% spectrum efficiency.

DOI： 10.11485/itetr.40.4.0_29

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Language：English   Publisher：The Institute of Image Information and Television Engineers  

This system uses a low complexity channel estimation for Space Time Coding in a Single Frequency Network Digital Terrestrial Television System. The receiver employs a MIMO system with vertical and horizontal antennas. The channel estimator uses a compressed sensing in time domain which exploits the sparsity of the channel impulse response. The algorithm for estimating the delay and channel gain is Orthogonal Matching Pursuit (OMP). The BER performance shows that OMP is very close to the ideal channel estimation. In addition, the OMP performance outperforms the linear interpolation method.

DOI： 10.11485/itetr.40.4.0_21

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Language：English   Publisher：The Institute of Electronics, Information and Communication Engineers  

DOI： 10.1587/transele.E99.C.1226_e1

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Leaky coaxial cable (LCX) is widely used for wireless communication systems as an antenna for a linear-cell, which covers long and shallow areas. Since one LCX is usually utilized as one antenna, more than one LCX is required to configure a multi-input multi-output (MIMO) system. It means it is costly and space-consuming. To resolve these problems, we proposed a novel MIMO method for LCX. In this paper, we propose the method to utilize one composite cable, which consists of a pair of LCXs with different radiation characteristics, to configure a 4 x 4 MIMO channel. The measurement results confirmed that the proposed composite cable can realize a good channel condition for 4 x 4 MIMO transmission even if it is put in an anechoic chamber where no reflection path exists. On the other hand, the results also confirmed that it has good channel condition even if the spacing between a pair of LCX is as small as 2cm for the SGHz band. Therefore the proposed system can reduce the space requirement for MIMO deployment for wireless application over linear-cell environments to cope with the high rapid increase of consumer electronics devices.

DOI： 10.1109/CCNC.2015.7157953

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This paper proposed a scattered auxiliary channel subcarriers for OFDM as additional pilots. This will improve the performance of compressed sensing based channel estimation for digital terrestrial TV. The auxiliary channel is designed to convey additional information on modulating signal transmission. The simulation shows that the proposed system has less bit-error-rate compared with the system without scattered auxiliary channel subcarriers. That is because the channel estimation will detect the correct position of the channel impulses with sufficient pilots.

DOI： 10.1109/ISCIT.2015.7458345

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Leaky coaxial (LCX) cable is widely used in wireless transmission communication systems as antenna for a long and narrow area called as linear-cell. We have proposed that one single LCX cable can be used as two antennas and the method to utilize one composite cable, which consists of a pair of LCXs with different radiation characteristics, to configure a multiple input and multiple-output (MIMO) system. In this paper, we will study capacity of the proposed 4-by-4 LCX-MIMO system and compare its capacity with conventional MIMO system using omnidirectional antennas over 2.4GHz band. We also investigate the capacity difference if the spacing of two LCX cable is changed over 5GHz band. The results over 2.4GHz band show that the proposed system can reduce the space requirement for MIMO deployment for wireless application over linear-cell environments. The capacity results show that proposed LCX-MIMO channel has larger capacity than that of using monopole antennas at both sides. Over 5GHz band, the proposed LCX-MIMO channel using WF allocation scheme can have the capacity near to that of independent and identically distributed (i.i.d.) channel. It has good channel capacity even if the spacing between the pair of LCXs is as small as 2cm. On the other hand, the capacity can be largely improved using the simple EP allocation scheme if the system utilize LCX cables to configure MIMO systems for both 2.4GHz and 5GHz bands.

DOI： 10.1109/ISCIT.2015.7458355

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Compressed Sensing (CS) based channel estimation has been proven to give a better reconstruction results compared to conventional method. Despite promising a better result, CS based channel estimation still suffers from high complexity computations due to huge matrix multiplication and matrix inversion operations. This paper will propose an effective CS based channel estimation VLSI architecture for ISDB-T system. Since ISDBT system is using orthogonal frequency division multiplexing (OFDM) technique for its transmission, its CS channel estimation will utilize a measurement matrix which is formed by parts of Discrete Fourier Transform (DFT) matrix. By exploiting the fact that the measurement matrix will inherit some symmetrical properties from DFT matrix, we can achieve a low complexity CS based channel estimation for practical implementation.

DOI： 10.1109/ISCIT.2015.7458360

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

It has been conventionally assumed that a single leaky coaxial (LCX) cable only is utilized as one antenna to configure a multiple-input multiple-output (MIMO) system. In this letter, we show one single LCX cable can be used as two antennas to configure a MIMO system owing to the designed intersection angle between the different radiation directivities of both input signals. The measurement results of 2 x 2 LCX-MIMO channel quality confirm that our proposed LCX-MIMO can realize a promising channel condition over 5 GHz frequency band. It also points out that the intersection angle between radiation directivities of LCX cable needs to be considered carefully to reduce the channel degradation at the both edge portions of the LCX cable.

DOI： 10.1587/comex.4.143

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Language：English   Publisher：The Institute of Image Information and Television Engineers  

Antenna diversity is one of the solutions to multipath fading but with the cost of additional hardware for every RF chain. In mobile reception application, it is difficult to install the additional antennas and cables to the vehicle due to limitations in installation cost and features. In this paper, we propose an Integrated Services Digital Broadcasting - Terrestrial (ISDB-T) diversity receiver using a 4-element electronically steerable passive array radiator (ESPAR) antenna with periodically alternating directivity. The proposed receiver obtains diversity gain requiring only a single-RF front-end and cable, thus reducing the hardware complexity compared to conventional antenna diversity receivers. The receiver utilizes compressed sensing-based channel estimation that recovers the channel state information (CSI) with good accuracy. The simulation results show that with perfect CSI, the proposed ISDB-T receiver is capable of obtaining a diversity gain of about 15 dB for a bit error rate of 10^-3.

DOI： 10.3169/mta.3.268

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This paper proposes a method to reduce the symbol error caused by modulo operator for regularized channel inversion (RCI)-based vector perturbation (RCI-VP). The proposed method introduces dual regularization parameters of RCI precoding matrix. First regularization parameter alpha(1) is set so as to maximize the signal to interference plus noise ratio (SINR) value of each stream to find the optimal perturbation vector. The second regularization parameter alpha(2) is set so as to minimize the total MSE between the transmitted perturbation vector and received perturbation vector to reduce the symbol error caused by modulo operator. The simulated results confirm that the proposed method can improve the performance of RCI-VP over i.i.d. MIMO channel and frequency-selective fading MIMO channel.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In linear service areas such as a tunnel and along railways, leaky coaxial cable (LCX) is widely used as antenna for radio communication. Usually, one LCX is utilized as one antenna. Therefore it requires more than one LCX to configure an multi-input multi-output (MIMO) system. We have recently proposed a method that one single LCX can be utilized as two antennas by feeding different RF transmit signals to each end of the proposed cable. In this paper, we compare 2x 2 MIMO system performance using the proposed LCX and using conventional monopole antennas over 2.4GHz band for WLAN appliances. The results confirm that our proposed 2x 2 MIMO channel using a single LCX can realize a good channel condition and bit error ratio (BER) performance for MIMO transmission even within a highly correlated propagation condition. On the other hand, it also shows that the proposed LCX MIMO is promising technique for communications over linear-cell environments from the simulated results which considering the path loss and radiation pattern of LCX characteristics.

DOI： 10.1109/APSIPA.2014.7041735

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper introduces a two by two multiple-input multiple-output (MIMO) system using two closely-spaced leaky coaxial cables (LCXs). In this LCX-MIMO system, two different types of LCXs are placed in parallel with a narrow spacing, and different RF signals are fed to each of the LCXs from the same side. We show with our experimental results that the proposed LCX-MIMO set up works as well as MIMO transmission specified by the IEEE802.11n standard in the 2.4 GHz ISM band.

DOI： 10.1109/APSIPA.2014.7041676

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

We have recently proposed a novel 2 x 2 multipleinput multiple-output (MIMO) system that utilizes a single leaky coaxial cable (LCX) as two antennas. In this paper, we further propose a 4 x 4 MIMO system by combining two LCXs that have different radiation characteristics into one composite cable and evaluate characteristics of the channel with different spacing between the LCXs. Since the different radiation characteristics create different propagation paths, the proposed system with small spacing between LCXs can realize an efficient channel condition for 4 x 4 MIMO transmission. As a result of measurement at 2.4 GHz band, the smaller spacing as to 1 em between LCXs makes better 4 x 4 MIMO channel condition for transmission. This result indicates that the proposed system can reduce the space requirement for system deployment.

DOI： 10.1109/GCCE.2014.7031177

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Leaky coaxial cables (LCX) have been widely used as antennas to form linear service areas for radio communication systems. Such services of linear cells have been deployed inside tunnels, along railways, and so on. Usually, one LCX is utilized as one antenna. Therefore it requires more than one LCX to configure an multi-input multi-output (MIMO) system. In this paper, we propose a MIMO system using single LCX, which can be utilized as two antennas. When different RF transmit signals are fed to each end of the proposed cable, single LCX can work as two antennas. To confirm the feasibility of the proposed MIMO system, we conduct experiments to measure the characteristics of 2 x 2 MIMO channel using single LCX. The results confirm that our proposed 2 x 2 MIMO channel using single LCX can realize a good channel condition for MIMO transmission even within a highly correlated propagation condition. The proposed MIMO system using LCX will release the space requirement and reduce the cost of system for configuration of LCX MIMO system especially with large number of LCXs. It benefits the design and configuration of LCX-MIMO system for many scenarios of linear-cell.

DOI： 10.1109/PIMRC.2014.7136184

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper proposes a method to improve the performance of minimum-mean square error (MMSE) based vector perturbation (MMSE-VP) by introducing dual regularization parameters of MMSE precoding matrix. First regularization parameter alpha(1) is set so as to maximize the signal to interference plus noise ratio (SINR) value of each stream to find the optimal perturbation vector. The second regularization parameter alpha(2) is set as to minimize the total MSE between the transmitted perturbation vector and received perturbation vector to precancel the interference among the streams. The simulated results confirm that the proposed method can improve the performance of MMSE-VP over i.i.d. MIMO channel and indoor correlated frequency-selective fading MIMO channel.

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Language：English   Publisher：The Institute of Electronics, Information and Communication Engineers  

Because of limitation of channel state information (CSI) feedback resource, multiuser (MU) MIMO-OFDM system usually divides all usable subcarriers into several subbands and the CSI of middle subcarrier of each subband is fed back. This feedback style generates CSI error among each subband. Due to this CSI error, a MU MIMO-OFDM system based on vector perturbation (VP) yields inefficient perturbation vectors (PVs) and mismatched spatial filters, which cause severe performance degradation. In this letter, we show that the performance degradation is mainly caused from the mismatched spatial filters rather than the inefficient PVs. This result is useful to design of a computational complexity reduction for the VP based system by reducing the matrix operations for PV search.

DOI： 10.1587/comex.2.86

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

During the operation of multiuser multiple-input-multiple output (MU-MIMO) algorithms, some antennas of BS or UEs may neither transmit nor receive signals due to the long distance or unexpected damages. Therefore, the BS cannot obtain the channel state information (CSI) from/to these antennas. Without these CSI, the performance of algorithm is degraded. We call this effect as 'broken antenna effect (BAE).' To cope with this issue, this paper proposes a process to regularize the channel matrix by replacing the missing CSI with zero(s) and setting non-zero values to diagonal elements. Then, it is confirmed through computer simulation that the proposed method can adjust the number of transmitting parallel streams according to the number of 'broken' antennas, and provide MU-MIMO transmission with maximum diversity order without any change of the precoding process.

DOI： 10.1109/WCNC.2012.6213993

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

In this paper, we propose a simple but effective way of improving the performance of channel estimation (CE) for pilot cyclic prefixed single carrier (PCP-SC) system. The proposed method utilizes the property that the shifting signal of the PCP pilot signal can also be utilized to estimate the channel information. The receiver can continuously estimate the channel information by just shifting the received pilot signal. Regardless of the signal-to-noise ratio (SNR) and the pilot type, the proposed method can achieve about a 1.72 dB performance gain in terms of the mean squared error (MSE) of channel estimation with a slight increase in computational complexity. The BER performance with the proposed CE improvement are evaluated in a multipath fading channel using a zero-forcing (ZF) equalizer and an minmum mean squared error (MMSE) equalizer by computer simulation. It is shown that the proposed CE improvment method using an MMSE equalizer which has an unbiased vlaue of noise variance (NV) estimator gives a promising BER performance. The proposed method also benefits the estimation of the SNR for the single carrier system.

DOI： 10.1587/transcom.E94.B.1690

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, we propose an effective way of improving the performance of channel estimation for MIMO single-carrier block transmission (SCBT) systems. The proposed method utilizes the property that the shift of the cyclic pilot signal of each antenna branch can also be utilized to catch the channel information as a new pilot for MIMO SCBT systems. The receiver can continuously estimate the channel information by just shifting the received pilot signal. The channel estimation performance is improved by averaging all channel estimators since this averaging process can reduce the power of noise component. Regardless of the signal-to-noise ratio (SNR) and the pilot type, the proposed method can achieve about a 1.72 dB performance gain in term of the mean squared error (MSE) of channel estimation for each antenna branch with slightly computational complexity. The proposed method can be also utilized to most channel estimation methods for the MIMO SCBT system.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, we propose a simple but effective way of improving the performance of channel estimation and catching the noise variance for pilot cyclic prefixed single carrier (PCP-SC) system. The proposed method utilizes the property that the shift of the PCP pilot signal can also be utilized to catch the channel information as a new pilot. Regardless of the signal-to-noise ratio (SNR) and the pilot type, the proposed method can achieve about a 1.72 dB performance gain for the mean squared error (MSE) of channel estimation with slightly additional computational complexity. In addition, regardless of the pilot type, the receiver can generate a new random signal from the pilot signal. The new signal has an identical variance value to that of the mixed AWGN noise. The proposed estimation method for noise variance is independent of channel estimation errors. Therefore it simplifies the receiver design and improves the system performance.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, combining the parallel combinatory (PC) code and the a flexible OFDM structure [7], we report the design of a new OFDM system with PC code for various applications with a moderate transmission rate. The system can select appropriate phase sets for all modulated subcarriers for each PC code for different design requirements such as peak-to-average power ratio (PAPR) reduction or HER performance improvement. The proposed system will achieve better PAPR characteristics and promising HER performance. In addition, due to the flexible OFDM structure, the proposed PC-OFDM system will also have properties of high adaptability and compatibility.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

We have introduced a flexible OFDM structure based on a promising property of IFFT operation [7]. This structure can support uplink applications which include many transmitters using different numbers of subcarriers and one receiver with just one IFFT/FFT module with the subcarriers of the least common multiple (LCM) for the number of subcarriers of all the transmitters. In this paper, combining the Parallel combinatory (PC) code and the proposed flexible OFDM structure, we report the design of a new OFDM system with PC code for various applications with a moderate transmission rate. The system can select appropriate Phase sets for all modulated subcarriers for each PC code for different design requirements such ay peak-to-average power ratio (PAPR) reduction or BER performance improvement. The proposed system will achieve better PAPR characteristics and promising BER performance. In addition, due to the flexible OFDM structure, the proposed PC-OFDM system will also have properties of high adaptability and compatibility(1).

DOI： 10.1109/TCE.2009.5373742

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

The pilot cyclic prefixed single carrier (PCP-SC) system has the ability to achieve channel estimation in a fast-fading environment. It also enables symbol recovery even when the frequency domain of the channel has nulls. This letter proposes a simple but effective way of improving the performance of channel estimation. Regardless of the signal-to-noise ratio (SNR) and the pilot type, the receiver can achieve about a 1.72 dB performance gain for the mean squared error (MSE) of channel estimation if it implements the proposed method with slightly additional computational complexity. The proposed method can also be utilized in any type of pilot in PCP-SC and MIMO systems.

DOI： 10.1109/LSP.2009.2023953

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

This paper introduces a promising property in which the transmitter of an OFDM system can utilize an N-point IFFT operation to build the time-domain symbols of a KN-point IFFT operation. Based on this property, we propose a flexible OFDM structure. This structure will support uplink applications which include many transmitters using different numbers of subcarriers and one receiver with just one IFFT/FFT module with the subcarriers of least common multiple (LCM) for the number of subcarriers of all the transmitters. Therefore it reduces the design complexities of the receiver and increases the compatible characteristics for consumer electronics (CE). Compared with the original OFDM system, the proposed system improves the performance of the packet error ratio (PER) and the bit error ratio (BER) performance by using the appropriate K. In addition, the proposed structure can be designed to enlarge the bandwidth efficiency of the system and improve the performance of channel estimation compared with the OFDM/TDM system.(1)

DOI： 10.1109/TCE.2009.4814434

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Combined with OFDM with time division multiplexing (OFDM/TDM) system and parallel combinatory (PC) code, we propose a new OFDM system which can be utilized to the communication systems of consumer electronics. Compared with the original OFDM system, the proposed system will achieve promising BER performance and better PAPR characteristics.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper will propose a simple hut effective way to improve the performance of channel estimation of pilot cyclic prefixed single carrier (PCP-SC) system. The proposed method utilizes the property that the shift of pilot cyclic prefixed signal can also be utilized to catch the channel information as a new pilot. The receiver can continuously estimate the channel information by just shifting the received signal. Regardless or signal-to-noise ratio (SNR) and pilot type, the receiver can achieve about 1.72 dB performance gain for MSE of channel estimation if it implements the proposed method with a slight additional computational complexity. The proposed method can also be utilized in any types of pilot in PCP-SC and MIMO system.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper proposes a new OFDM system without a guard interval (GI) based on the useful characteristics of IFFT operation. The system utilizes the pilot signal to capture the channel information as well as GI does. Therefore, the bandwidth efficiency of the system can be improved. In addition, it achieves promising peak-to-average power ratio (PAPR) characteristics which also decrease the cost of handsets.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper proposes a new OFDM transmitter structure which can be realized by a smaller FFT chip based on the useful characteristics of IFFT operation. The proposed system benefits the design of handsets. In addition, it achieves promising peak-to-average power ratio (PAPR) characteristics which also decreases the cost of handsets.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper proposes a new system called the collision-captured multicarrier modulation system which can realize the capture of a packet collision. Based on the OFDM system using partial symbol transmission, the transmitter can select a specific duration to achieve promising PAPR characteristics and realize the capture of a packet collision. The simulated results show that over 90% collision occurrences and the correct position of the collided part can be captured even in severe near-far situations. The proposed system can also achieve a PAPR reduction with an acceptable BER performance degradation.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

We present an effective method of collision recovery for orthogonal frequency division multiplexing (OFDM)-based communications. For the OFDM system, the modulated message data can be demodulated using the partial time-domain OFDM symbol. Therefore, the partial time-domain symbol can be adopted to reconstruct the whole OFDM time-domain symbol with estimated channel information. This property can be utilized to recover packets from the collisions. Since most collisions are cases in which a long packet collides with short packets, the collided part is assumed to be short. The simulated results show that the method can recover all packets with different specific probabilities and can be developed to solve the problem of hidden terminals.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper proposes a new system called the collision-captured OFDM system which can realize the capture of a packet collision based on the OFDM system using partial symbol transmission. The simulated results show that over 90% of collision occurrences and the correct position of the collided part can be captured even in severe near-far situations.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper proposes a new peak-to-average power ratio (PAPR) reduction technique for OFDM systems. The proposed system selects the specific duration of each time-domain OFDM symbol which can achieve a promising PAPR, to transmit equal bits of data. Compared with the OFDM system using amplitude clipping, PST can obtain comparable PAPR performance and achieve a 0.5 - 3 dB BER performance gain by choosing the appropriate parameters. In addition, PST does not need any complex modules to fix the original phases of the clipped samples, so it decreases the cost of transmitters.

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

In this paper, we propose a new modulation named parallel combinatory/high compaction multi-carrier modulation (PC/HC-MCM) using the techniques of parallel combinatory orthogonal frequency division multiplexing (PC-OFDM) and high compaction multi-carrier modulation (HC-MCM). Two types of PC/HC-MCM systems, which are named as modulated PC/HC-MCM system and (unmodulated) PC/HC-MCM system, can be designed. The modulated PC/HC-MCM system achieves better bit-error rate (BER) performance than that of HC-MCM system with equal bandwidth efficiency (BWE). The PC/HC-MCM system can obtain the better peak-to-average power ratio (PAPR) characteristics by selecting appropriate constellation for each subcarrier. On the other hand, since PC/HC-MCM can divide the PC-OFDM symbol duration into multiple time-slots, the advantages of frequency hopping (FH) can be applied in the PC/HC-MCM system. Therefore, we also combine the PC/HC-MCM and frequency hopping multiple access (FHMA) to propose a novel multiple access (MA) system. It can simultaneously transmit multiple users' data within one symbol duration of PC-OFDM.

DOI： 10.1093/ietfec/e90-a.11.2556

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

We present an effective method of collision recovery for orthogonal frequency division multiplexing (OFDM)-based communications. For the OFDM system, the modulated message data can be demodulated using the partial time-domain OFDM signal. Therefore, the partial time-domain signal can be adopted to reconstruct the whole OFDM time-domain signal with estimated channel information. This property can be utilized to recover packets from the collisions. Since most collisions are cases in which a long packet collides with a short packet, the collided part is assumed to be short. The simulated results show that the method can recover the two collided packets with a certain probability and can be developed to solve the problem of hidden terminals. This method will dramatically benefit the protocol design of wireless networks, including ad hoc and sensor networks.

DOI： 10.1093/ietfec/e90-a.7.1312

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DOI： 10.1016/s1004-4132(06)60070-4

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Publisher：IEEE  

DOI： 10.1109/LifeTech53646.2022.9754939

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Other Link： https://dblp.uni-trier.de/db/conf/lifetech/lifetech2022.html#NagayamaZHHD22

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DOI： 10.1587/bplus.10.86

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This article proposes a positioning method for radio terminals by using Leaky Coaxial Cable(LCX) antenna. A Longitudinal position detection method in 2 by 2 LCX-MIMO system using signal TDoA has already proposed. This article expands this system in 4 by 4 LCX-MIMO system and explains how to detect a radial position in 4 by 4 system. In addition, MUSIC algorithm is introduced in the proposal method to estimate position accurately. As a result of performance evaluation by the computer, it is found that the proposed method has high accuracy compared with the conventional method.

DOI： 10.11485/itetr.39.4.0_45

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This article proposes an accuracy improving method by using signal Time Difference Of Arrival (TDOA) in LCX positioning system for radio terminals. The MUSIC algorithm is introduced in the proposal method to estimate position accurately without increasing frequency bandwidth. As a result of computer simulation, it is found that the proposed method has high accuracy compared with the estimation method which using IFFT.

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We studied multi-input multi-output(MIMO) techniques for a linear cell with leaky coaxial cables (LCXs) to reduce hand over frequency in a small cell and to keep spacial multiplicity high in the line-of-sight conditions. In this paper, an advantage of linear cell with an LCX is described, and then a structure of the LCX and a principle of electromagnetic radiation from the LCX are explained. After we introduce the proposed methods that are 2 by 2 MIMO with a single LCX and with closely separation LCXs, feasibility of the proposed methods are shown by results of a condition number calucuration and experiments using equipments of wireless local area networks on the market.

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Data offloading by distributed many femto-cell base stations is one of solutions to provide large wireless communication capacity. Radio over Fiber (RoF) technique can integrate the base stations and reduce the cost of maintenance. In this paper, a simultaneous transmission scheme for both optical On-Off Keying (OOK) signal and radio frequency (RF) signal is proposed. The quality of the RF signal transmitted with 10G Ethernet is experimentally evaluated. An interference suppression scheme and an optimum threshold for detecting OOK signal are proposed.

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Data offloading by distributed many femto-cell base stations is one of solutions to provide large wireless communication capacity. Radio over Fiber (RoF) technique can integrate the base stations and reduce the cost of maintenance. In this paper, a simultaneous transmission scheme for both optical On-Off Keying (OOK) signal and radio frequency (RF) signal is proposed. The quality of the RF signal transmitted with 10G Ethernet is experimentally evaluated. An interference suppression scheme and an optimum threshold for detecting OOK signal are proposed.

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Data offloading by distributed many femto-cell base stations is one of solutions to provide large wireless communication capacity. Radio over Fiber (RoF) technique can integrate the base stations and reduce the cost of maintenance. In this paper, a simultaneous transmission scheme for both optical On-Off Keying (OOK) signal and radio frequency (RF) signal is proposed. The quality of the RF signal transmitted with 10G Ethernet is experimentally evaluated. An interference suppression scheme and an optimum threshold for detecting OOK signal are proposed.

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Data offloading by distributed many femto-cell base stations is one of solutions to provide large wireless communication capacity. Radio over Fiber (RoF) technique can integrate the base stations and reduce the cost of maintenance. In this paper, a simultaneous transmission scheme for both optical On-Off Keying (OOK) signal and radio frequency (RF) signal is proposed. The quality of the RF signal transmitted with 10G Ethernet is experimentally evaluated. An interference suppression scheme and an optimum threshold for detecting OOK signal are proposed.

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Data offloading by distributed many femto-cell base stations is one of solutions to provide large wireless communication capacity. Radio over Fiber (RoF) technique can integrate the base stations and reduce the cost of maintenance. In this paper, a simultaneous transmission scheme for both optical On-Off Keying (OOK) signal and radio frequency (RF) signal is proposed. The quality of the RF signal transmitted with 10G Ethernet is experimentally evaluated. An interference suppression scheme and an optimum threshold for detecting OOK signal are proposed.

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筆者らは,見通し伝搬路のような伝搬路相関の高い環境における伝送特性を改善するため,ベクトル摂動(Vector Perturbation)に基づく8×8アンテナ構成の非線形マルチユーザMIMO-OFDM伝送システムを開発した.本稿ではその概要を述べ,屋外見通し伝搬路における伝送実験を通じ,空間フィルタリングに基づく線形マルチユーザMIMO伝送と比較して本伝送方式が約1.9倍の周波数利用効率を達成可能であることを示す.更に,本伝送実験を通じて明らかになった非線形マルチユーザMIMOの実用化に向けた課題についても述べる.

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In recent years, mobile communication terminals such as smartphone are necessities of life, a number of terminals are present at high density in such train. Public wireless LAN service also increased with increasing the mobile communication terminal. It is expected that traffic becomes 10 times in 2020, insufficient capacity of the entrance circuit is concerned. Public wireless LAN service is provided in high-speed mobile such as the Shinkansen. It is the performance degradation cannot be controlled to fast channel fluctuation in the ordinary equalization, new measures are needed. We proposed that switching the receiving antenna in reverse order direction of travel of the train. It is the technology to fix the reception point at a fixed position, to slow down the channel change. The antenna switching technology has problems (1)setting of appropriate antenna element spacing, (2)timing and switching cycle of the antenna, (3)reduction of the influence of the circuit and switch,(4) responding to MIMO. In this draft, it is simulated the characteristics of the received signal for antenna switching technology as a basic study. Result of simulation, it obtained the reception characteristics as much as quiescent even when moving at high speed by the antenna switching technology has been found. However, as an error of antenna switching, the problem of discontinuity occurs in reception characteristics was found.

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Since the traffic by mobile phones and wireless LAN terminals is increasing day by day, we are faced with deficiency of radio resource in a densely populated place, such as a conference centre and a train terminal in a big city. Although to introduce small cell and MIMO technique is effective for the problem, the frequency of handover will increase and MIMO capacity will deteriorate due to an increase of line-of -sight situation. Since linear-cell can reduce the frequency of handover, we are focused on leaky coaxial cable (LCX) which can work on the microwave band. This paper introduce a novel 2×2 multiple-input multiple-output (MIMO) system using only a single LCX, which can double the capacity. We evaluate MIMO capacity as an index of condition number. They are shown that cumulative frequency of MIMO-achievable positions and data throughput at few positions as an initial result of the evaluation. Results of study on location detection for triggering a handover are also discussed.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

To reduce the modulo boundary setting error of vector perturbation using MMSE spatial filtering, this paper proposes a new setting method which considers both the desired signal component and the inter-stream interference component in the received signal after precoding. The effectiveness of the proposed method is confirmed through computer simulation of a downlink multiuser MIMO-OFDM transmission which assumes WINNER II A1 LOS channel.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

The authors have evaluated the performance of MIMO-OFDM transmission based on vector perturbation (VP)precoding in small-cell environment, and studied several techniques to overcome some issues for developing practical systems. This paper shows some results of performance evaluation of the VP-based nonlinear multiuser MIMO-OFDM transmission obtained from computer simulations and indoor experiments using radio equipment developed by the authors. In addition, some issues developing practical systems are explained.

CiNii Article

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

The authors have evaluated the performance of MIMO-OFDM transmission based on vector perturbation (VP) precoding in small-cell environment, and studied several techniques to overcome some issues for developing practical systems. This paper shows some results of performance evaluation of the VP-based nonlinear multiuser MIMO-OFDM transmission obtained from computer simulations and indoor experiments using radio equipment developed by the authors. In addition, some issues developing practical systems are explained.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper proposes a symmetric extended symbol mapping, which assigns signal points symmetrically about the modulo boundaries on the IQ plane of vector perturbation (VP). Although VP improves the throughput of multiuser multiple-input multiple-output (MU-MIMO)transmission over highly correlated channels, the error of modulo boundary setting of a demodulator leads significant performance degradation. The proposed method alleviates the impact of the boundary setting errors by assigning same signal points around the modulo boundaries. Simulation results confirm that the proposed method effectively improves the BER performance.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper evaluates the performance of 8×8 downlink multiuser MIMO-OFDM transmission based on vector perturbation (VP) precoding which employs zero-forcing (ZF) or MMSE spatial filtering. Through computer simulations assuming a frame format similar to 3GPP Release 10 downlink and WINNER II A1 LOS channel, it is shown that MMSE-based VP can reduce the norm of the transmission signal vector compared with ZF-based VP, and thus it can achieve higher average sum-rate if the modulo boundary size for demodulation is set properly. It is also confirmed that the modulo boundary size must be set by taking account for the amount of inter-stream interference.

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Language：English   Publisher：The Institute of Electronics, Information and Communication Engineers  

Vector perturbation (VP) algorithm requires perfect channel state information (CSI) for optimal perturbation vector search and generating a spatial filter to pre-equalize the MIMO channel function. Due to the limited CSI feedback and realistic computational complexity (CC) due to hardware implementation, MU-MIMO OFDM system will yield the inefficient perturbated vector and mismatched spatial filter which causes large spectrum efficiency (SE) loss. In this paper, by simulation, it shows that most of performance loss of VP algorithm is derived from the mismatched spatial filter. Therefore, we propose a low-complexity linear interpolation for spatial filter to reduce the SE loss. The proposed interpolation scheme firstly rebuilds the CSI of partial subcarriers from limited feedback CSI by time and frequency domain transformation (TFT). After that, the spatial filter matrices of these partial subcarriers are calculated. Finally the spatial filter matrices of all subcarriers are interpolated by a linear interpolation. The complexity analysis and simulated results show that the proposed interpolation scheme can reduce the SE loss of VP based MU-MIMO OFDM system with low computational complexity.

CiNii Article

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Language：English   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

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Language：English   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

CiNii Books

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Language：English   Publisher：The Institute of Electronics, Information and Communication Engineers  

CiNii Article

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

In this paper, on downlink multiuser MIMO-OFDM system, we evalute the impact of reducing the number of subaband on the performance of linear and non-linear algorithms for the purpose of channel feedback load reduction. We also evalute the impact of an analog feedback method, which sends back a channel value estimated at reciever side and can reduce the channel feedback load further. The simulation result shows that reducing the number of subband to 50, the spectral efficiency of linear and non-linear algorithms degrades. Especially the saturated spectral efficiency of linear algorithm degrades largely. In addition, it is shown that using analog feedback, the performance of VP and BD-VP improves largely with reducing the channel feedback load to about 1/3 to 1/4 against the digital feedback. Especially the performance of BD-VP improves in case of high SNR and high Rician factor.

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Language：English   Publisher：The Institute of Electronics, Information and Communication Engineers  

In this paper, we evaluate the spectral efficiency of the block diagonalized vector perturbation (BD-VP), vector perturbation (VP) and Tomlinson-Harashima precoding (THP) algorithms over correlated MIMO channels with channel state information (CSI) error. The simulated results show that the VP algorithm has high spectral efficiency than the BD-VP algorithm, but it needs a large computational complexity (CC). Although the BD-VP algorithm is more sensitive to high channel correlation than the THP algorithm for a small signal to noise power ratio (SNR) area, we show that it can utilize the interpolation method with noise component cancellation (NCC) to outperform the THP algorithm and achieve to the system capacity of the VP algorithm over correlation channels. Based on the simulated results, the BD-VP algorithm appears a possible way to realize the large spectral efficiency with a relatively small computational complexity over correlated MIMO channels for the picocell or femtocell systems with CSI error.

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Applicant：株式会社フジクラ, 株式会社国際電気通信基礎技術研究所

Application no：特願2015-005292  Date applied：2015.1.14

Announcement no：特開2016-059025  Date announced：2016.4.21

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Applicant：株式会社フジクラ, 株式会社国際電気通信基礎技術研究所

Application no：特願2015-005292  Date applied：2015.1.14

Patent/Registration no：特許第5903699号  Date registered：2016.3.25  Date issued：2016.3.25

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Applicant：株式会社国際電気通信基礎技術研究所

Application no：特願2014-049770  Date applied：2014.3.13

Announcement no：特開2015-177211  Date announced：2015.10.5

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Applicant：株式会社国際電気通信基礎技術研究所

Application no：特願2014-023958  Date applied：2014.2.12

Announcement no：特開2015-154122  Date announced：2015.8.24

Patent/Registration no：特許第6330173号  Date registered：2018.5.11  Date issued：2018.5.11

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Applicant：株式会社国際電気通信基礎技術研究所

Application no：特願2014-023958  Date applied：2014.2.12

Announcement no：特開2015-154122  Date announced：2015.8.24

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Applicant：株式会社国際電気通信基礎技術研究所

Application no：特願2014-021876  Date applied：2014.2.7

Announcement no：特開2015-149639  Date announced：2015.8.20

Patent/Registration no：特許第6330172号  Date registered：2018.5.11  Date issued：2018.5.11

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Applicant：株式会社国際電気通信基礎技術研究所

Application no：特願2014-021876  Date applied：2014.2.7

Announcement no：特開2015-149639  Date announced：2015.8.20

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Applicant：住友電気工業株式会社, 株式会社国際電気通信基礎技術研究所

Application no：特願2013-244164  Date applied：2013.11.26

Announcement no：特開2015-104008  Date announced：2015.6.4

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Applicant：住友電気工業株式会社, 株式会社国際電気通信基礎技術研究所

Application no：特願2013-244165  Date applied：2013.11.26

Announcement no：特開2015-104009  Date announced：2015.6.4

Patent/Registration no：特許第6478367号  Date registered：2019.2.15 

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Applicant：株式会社国際電気通信基礎技術研究所

Application no：特願2013-012273  Date applied：2013.1.25

Announcement no：特開2014-160885  Date announced：2014.9.4

Patent/Registration no：特許第6047744号  Date registered：2017.2.3  Date issued：2016.12.2

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Applicant：株式会社国際電気通信基礎技術研究所

Application no：特願2012-221726  Date applied：2012.10.3

Announcement no：特開2014-075679  Date announced：2014.4.24

Patent/Registration no：特許第6019298号  Date registered：2016.10.14 

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Applicant：株式会社国際電気通信基礎技術研究所

Application no：特願2012-070049  Date applied：2012.3.26

Announcement no：特開2013-201706  Date announced：2013.10.3

Patent/Registration no：特許第5845549号  Date registered：2015.12.4 

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Applicant：株式会社国際電気通信基礎技術研究所

Application no：特願2012-069134  Date applied：2012.3.26

Announcement no：特開2013-201633  Date announced：2013.10.3

Patent/Registration no：特許第5830757号  Date registered：2015.11.6 

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Applicant：株式会社国際電気通信基礎技術研究所

Application no：特願2011-036536  Date applied：2011.2.23

Announcement no：特開2012-175476  Date announced：2012.9.10

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Applicant：株式会社国際電気通信基礎技術研究所

Application no：特願2011-035526  Date applied：2011.2.22

Announcement no：特開2012-175407  Date announced：2012.9.10

Patent/Registration no：特許第5681901号  Date registered：2015.1.23 

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