Updated on 2024/05/22

写真a

 
MAEHARA, Fumiaki
 
Affiliation
Faculty of Science and Engineering, School of Fundamental Science and Engineering
Job title
Professor
Degree
Doctor of Engineering ( Waseda University )

Research Experience

  • 2012
    -
    Now

    Professor, School of Science and Engineering, Waseda University, Japan

  • 2007
    -
    2012

    Associate Professor, School of Science and Engineering, Waseda University, Japan

  • 2006
    -
    2007

    Assistant Professor, School of Science and Engineering, Waseda University, Japan

  • 2005
    -
    2006

    Visiting Lecturer, The Graduate School of Information, Production and Systems, Waseda University, Japan

  • 2004
    -
    2005

    Visiting Research Fellow, University of Hanover, Germany

  • 2002
    -
    2005

    Research Fellow, The Japan Society for the Promotion of Science

  • 2000
    -
    2002

    Research Associate, School of Science and Engineering, Waseda University, Japan

  • 1995
    -
    1999

    Nippon Telegraph and Telephone Corporation (NTT), Japan

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Education Background

  • 2001.03
    -
     

    Dr. Eng. (Waseda University)  

  • 1999.04
    -
    2001.03

    Waseda University   Doctor of Engineering, Graduate School of Science and Engineering  

  • 1993.04
    -
    1995.03

    Waseda University   Graduate School, Division of Science and Engineering   Master of Engineering, Department of Electrical Engineering  

  • 1989.04
    -
    1993.03

    Waseda University   Faculty of Science and Engineering   Electronics and Communication Engineering  

Professional Memberships

  •  
     
     

    The Institute of Image Information and Television Engineers (ITE)

  •  
     
     

    Institute of Electrical and Electronics Engineers (IEEE)

  •  
     
     

    Institute of Electronics, Information and Communication Engineers (IEICE)

Research Areas

  • Communication and network engineering

Research Interests

  • Wireless signal processing

  • Wireless communication network

  • Digital Wireless Communications

Awards

  • IEICE ComEX Top Downloaded Letter Award

    2024.04  

    Winner: Yuki Inoue, Shuhei Saito, Hirofumi Suganuma, Fumiaki Maehara

  • Communications Society:Distinguished Contributions Award

    2021.09   IEICE  

  • IEEE Senior Member

    2021.08  

  • 電子情報通信学会 学生論文特集号優秀論文賞

    2020.02  

    Winner: 齊藤 彩, 小川 賀代, 前原 文明

  • Excellent Paper Award

    2020.02   2nd International Conference on AI in Information and Communication (ICAIIC 2020)  

  • IEICE Senior Member

    2013.05  

  • Communications Society:Distinguished Contributions Award

    2012.09   IEICE  

  • Best Paper Award

    2011.03   2nd International Conference on Wireless Communications, Vehicular Technology, Information Theory and Aerospace & Electronic Systems (Wireless Vitae 2011)  

    Winner: Akihiro Yamakita, Akira Kamiyama, Yuichiro Goto, Fumiaki Maehara

  • Communications Society:Distinguished Contributions Award

    2008.09   IEICE  

  • Communications Society:Distinguished Contributions Award

    2007.09   IEICE  

  • 日本電信電話株式会社 ワイヤレスシステム研究所 所長表彰

    1997.10  

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Papers

  • Effectiveness evaluation of MIMO in polarized OAM multiplexing

    Mikito Ito, Shuhei Saito, Hirofumi Suganuma, Kayo Ogawa, Fumiaki Maehara

    IEICE Communications Express   13 ( 3 ) 60 - 63  2024.03  [Refereed]

    DOI

  • Hybrid transmission scheme using FBMC and OFDM under multipath fading channels

    Yuki Inoue, Shuhei Saito, Hirofumi Suganuma, Fumiaki Maehara

    IEICE Communications Express   13 ( 1 ) 1 - 4  2024.01  [Refereed]

    DOI

  • Throughput Improvement through FTN-based MIMO Signaling in Fixed Wireless Access

    Tomohiro Matsuyama, Takumi Suzuki, Shuhei Saito, Hirofumi Suganuma, Fumiaki Maehara

    2023 11th International Japan-Africa Conference on Electronics, Communications, and Computations (JAC-ECC)    2023.12  [Refereed]

    DOI

  • Inter-mode Interference Suppression Method for OAM Multiplexing in the Presence of Ground Reflection and Beam Axis Misalignment

    Akiya Takeuchi, Shuhei Saito, Hirofumi Suganuma, Kayo Ogawa, Fumiaki Maehara

    2023 IEEE International Symposium On Antennas And Propagation (ISAP)    2023.10  [Refereed]

    DOI

  • Hybrid Multiple Access Scheme Employing NOMA and OMA Simultaneously Under Non-uniform User Distribution and Multiple Transmit Antennas

    Nozomi Sasaki, Fuga Tanaka, Shuhei Saito, Hirofumi Suganuma, Fumiaki Maehara

    2023 Joint European Conference on Networks and Communications & 6G Summit (EuCNC/6G Summit)    2023.06  [Refereed]

    DOI

  • Beam Axis Misalignment Suppression Method Employing Efficient Beamforming and IMI Cancellation for OAM Multiplexing

    Shuhei Saito, Hirofumi Suganuma, Kayo Ogawa, Fumiaki Maehara

    2023 IEEE International Conference on Communications Workshops (ICC Workshops)    2023.05  [Refereed]

    DOI

  • Improper Gaussian Signaling for Two-User MISO-NOMA Systems Considering Hardware Impairments and Imperfect SIC

    Hao Tse Chiu, Fumiaki Maehara

    IEEE Access   11   59827 - 59839  2023  [Refereed]

     View Summary

    In this paper, we study the advantages of improper Gaussian signaling (IGS) with the existence of hardware impairments (HWI) and imperfect successive interference cancellation (SIC) in the downlink two-user power-domain non-orthogonal multiple access (PD-NOMA) systems. We first provide the input-output relationships for the MIMO system with HWIs and then derive the rate expressions for each user. The improper signals are assumed to be generated by widely linear precoding (WLP) and transmitted under the PD-NOMA scheme in the context of imperfect SIC. To exhibit the supremacy of IGS, we formulate two kinds of optimization problems concerned with the max-min rate and maximizing achievable sum rate (ASR) between users under the quality of service (QoS) and the total power constraints (TPC). To deal with the non-convex log-determinant objective functions, we adopt successive concave quadratic programming (SCQP) to obtain suboptimal results by iterations. Simulation results demonstrate that IGS cases outperform ZF precoders and conventional proper Gaussian signaling (PGS) counterparts in both max-min rate and ASR, particularly in high I/Q imbalance (IQI) and less efficient SIC scenarios. Besides, the difference in the performance degradation between imperfect SIC and HWIs is compared. Finally, we briefly classify the conditions where IGS could be preferable for signal transmission.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • Performance Evaluation of MIMO-FTN Signaling under Multipath Fading Channels

    Hao-Tse Chiu, Shuhei Saito, Hirofumi Suganuma, Keita Kuriyama, Kentaro Tanaka, Hitoshi Hasegawa, Toshifumi Miyagi, Takeshi Onizawa, Fumiaki Maehara

    IEEE Access     1 - 1  2023  [Refereed]

    DOI

  • A Guard Interval Control Scheme Using Theoretical System Capacity for UAV MU-MIMO-OFDM THP Systems

    Kazuki Yao, Shuhei Saito, Hirofumi Suganuma, Fumiaki Maehara

    2022 International Symposium on Intelligent Signal Processing and Communication Systems (ISPACS)    2022.11  [Refereed]

    DOI

  • Effectiveness evaluation of OAM-MIMO with successive interference cancellation in the presence of ground reflection

    Akiya Takeuchi, Shuhei Saito, Hirofumi Suganuma, Kayo Ogawa, Fumiaki Maehara

    IEICE Communications Express   11 ( 9 ) 601 - 606  2022.09  [Refereed]

    DOI

  • Impact of multiple antennas on hybrid multiple access scheme employing NOMA and OMA simultaneously considering user request

    Fuga Tanaka, Hirofumi Suganuma, Fumiaki Maehara

    IEICE Communications Express   11 ( 6 ) 342 - 348  2022.06  [Refereed]  [International journal]

    DOI

  • Performance Analysis of Single-carrier OAM Multiplexing Considering Radiation Pattern and Polarization in the Presence of Ground Reflection

    Shuhei Saito, Hirofumi Suganuma, Kayo Ogawa, Fumiaki Maehara

    2022 IEEE International Conference on Communications Workshops (ICC Workshops)    2022.05  [Refereed]

    DOI

  • Performance improvement of faster-than-Nyquist single-carrier MIMO signaling considering the effects of colored noise

    Yuta Kumagai, Atsuya Nakamura, Shuhei Saito, Hirofumi Suganuma, Keita Kuriyama, Yu Ono, Hayato Fukuzono, Masafumi Yoshioka, Fumiaki Maehara

    IEICE Communications Express   11 ( 4 ) 176 - 182  2022.04  [Refereed]

    DOI

  • Effectiveness evaluation of FTN signaling in the presence of nonlinear distortion under multipath fading channels

    Atsuya Nakamura, Yuta Kumagai, Shuhei Saito, Hirofumi Suganuma, Keita Kuriyama, Yu Ono, Hayato Fukuzono, Masafumi Yoshioka, Fumiaki Maehara

    IEICE Communications Express   11 ( 2 ) 104 - 110  2022.02  [Refereed]

    DOI

  • System Capacity Analysis of Asynchronous FBMC and OFDM Systems in the Presence of Adjacent Channel Interference and Multipath Fading

    Hiroto Yamada, Hirofumi Suganuma, Fumiaki Maehara

    2022 IEEE Radio and Wireless Symposium (RWS)    2022.01  [Refereed]

    DOI

  • Investigation on Frequency and Radius Dependence in Vertical and Horizontal Antenna Alignments of UCA-based OAM Communication

    Mohammad Najafi, Shuhei Saito, Fumiaki Maehara

    Proceeding - 2022 International Conference on Radar, Antenna, Microwave, Electronics, and Telecommunications: Emerging Science and Industrial Innovation in Electronics and Telecommunication, ICRAMET 2022     93 - 99  2022  [Refereed]

     View Summary

    The aim of this paper is to further investigate the communication with Orbital Angular Momentum (OAM) waves between two OAM antenna arrays. The antenna arrays consist of individual dipoles, which together form a Uniform Circular Array (UCA). In this paper, two configurations that have already been discovered are assumed, in which there is no crosstalk between the individual modes. On the one hand, the vertical alignment already examined by many papers and on the other hand a horizontal alignment in which the dipoles have a certain rotation around the axis. The first investigation deals with the frequency dependency in OAM communication in the given setup. In a further investigation, the influence of the radius of the antenna arrays is conducted. The simulations will focus on the transmission of the individual OAM modes and the crosstalk between different OAM modes.

    DOI

    Scopus

  • Performance Comparisons of Faster-than-Nyquist Signaling Considering Fixed Utilized Bandwidth

    Hao Tse Chiu, Shuhei Saito, Keita Kuriyama, Kentaro Tanaka, Hitoshi Hasegawa, Toshifumi Miyagi, Takeshi Onizawa, Fumiaki Maehara

    Proceedings of the 10th International Japan-Africa Conference on Electronics, Communications, and Computations, JAC-ECC 2022     109 - 112  2022  [Refereed]

     View Summary

    In this study, we compare the system performance by considering faster-than-Nyquist (FTN) signaling employing single carrier frequency domain equalization (SC-FDE) and orthogonal frequency division multiplexing (OFDM) under the constraint of a fixed total utilized bandwidth. In this work, FDE also includes the appearance of colored noise, and the corresponding FDEs are formulated based on its effect to improve detection reliability. The advantages of FTN signaling and the preferable choices of compression and roll-off factors based on the bit error rate (BER) and system throughput are demonstrated under multipath fading channels via the simulation results.

    DOI

    Scopus

  • Effectiveness Evaluation of Dual-Polarized OAM Multiplexing Employing SC-FDE in Urban Street Canyon Environments

    Hirofumi Suganuma, Shuhei Saito, Kayo Ogawa, Fumiaki Maehara

    IEEE Access   10   31934 - 31941  2022  [Refereed]

    DOI

  • Performance Analysis of SC-FDE Considering Radiation Pattern in Millimeter-wave and Terahertz Broadband Communications

    Yuto Oyamada, Shuhei Saito, Hirofumi Suganuma, Keita Kuriyama, Yu Ono, Hayato Fukuzono, Masafumi Yoshioka, Fumiaki Maehara

    2021 24th International Symposium on Wireless Personal Multimedia Communications (WPMC)    2021.12  [Refereed]

    DOI

  • Hybrid Multiple Access Scheme Using NOMA and OMA Simultaneously Considering User Request

    Fuga Tanaka, Hirofumi Suganuma, Fumiaki Maehara

    2021 24th International Symposium on Wireless Personal Multimedia Communications (WPMC)    2021.12  [Refereed]

    DOI

  • Blockage Mitigation Method Employing Antenna Height and User Position in Millimeter-wave Communications

    Mitsumasa Nitta, Hirofumi Suganuma, Fumiaki Maehara

    2021 International Symposium on Intelligent Signal Processing and Communication Systems (ISPACS)    2021.11  [Refereed]

    DOI

  • Application of Least-Squares Channel Estimation to Large-scale MU-MIMO-OFDM in the Presence of Terminal Mobility

    Yutaka Itoya, Shuhei Saito, Hirofumi Suganuma, Hiromichi Tomeba, Takashi Onodera, Fumiaki Maehara

    2021 International Symposium on Intelligent Signal Processing and Communication Systems (ISPACS)    2021.11  [Refereed]

    DOI

  • Decision feedback channel estimation without prior knowledge of terminal mobility for SC-FDE

    Atsuya Nakamura, Yukiko Shimbo, Shuhei Saito, Hirofumi Suganuma, Fumiaki Maehara

    IEICE Communications Express   10 ( 10 ) 803 - 809  2021.10  [Refereed]

    DOI

  • Deep Learning Based Hybrid Multiple Access Consisting of SCMA and OFDMA Using User Position Information

    Yuta Kumagai, Naoya Gonda, Yukiko Shimbo, Hirofumi Suganuma, Fumiaki Maehara

    3rd International Conference on Artificial Intelligence in Information and Communication, ICAIIC 2021     10 - 13  2021.04  [Refereed]

     View Summary

    This paper proposes a deep-learning-based uplink hybrid multiple access scheme consisting of both sparse code multiple access (SCMA) and orthogonal frequency-division multiple access (OFDMA). SCMA improves the system throughput when the carrier-To-noise ratio (CNR) is high. However, SCMA performance is significantly degraded, compared to OFDMA, when the CNR is low. To overcome this problem, the proposed scheme introduces a combination of SCMA and OFDMA as a novel multiple access pattern. The scheme determines the appropriate pattern among SCMA-only, OFDMA-only, or their combination, by utilizing user position information through deep learning. The effectiveness of the proposed scheme is demonstrated in terms of system throughput under different user distributions via computer simulations.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • Mode group selection method for inter-mode interference suppression in OAM multiplexing

    Hirofumi Suganuma, Shuhei Saito, Kayo Ogawa, Fumiaki Maehara

    2020 International Symposium on Antennas and Propagation, ISAP 2020     355 - 356  2021.01  [Refereed]

     View Summary

    This paper proposes a mode group selection method for orbital angular momentum (OAM) multiplexing to suppress inter-mode interference (IMI) owing to the misalignment of the beam axis. We have proposed an IMI suppression method employing even-numbered OAM modes, and its effectiveness has been successfully confirmed. Odd-numbered OAM modes are robust and used in addition to even-numbered modes to improve the robustness against the IMI, and the appropriate mode group is selected based on the system capacity. The effectiveness of the proposed method is demonstrated in terms of system capacity via computer simulations.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • Transmit power control method for centrally controlled wireless LANs with MU-MIMO

    Fuga Tanaka, Soma Yamashita, Hirofumi Suganuma, Fumiaki Maehara

    2020 International Symposium on Antennas and Propagation, ISAP 2020     287 - 288  2021.01  [Refereed]

     View Summary

    This paper proposes a transmit power control method to reduce power consumption and alleviate inter-cell interference for centrally controlled wireless LANs with multi-user multiple-input multiple-output (MU-MIMO). The main feature of the proposed method is to control the transmit power of the access points (APs) according to the relationship between the number of allocated users and AP antennas. The effectiveness of the proposed method compared to the conventional fixed transmit power method is demonstrated in terms of power consumption and system throughput via computer simulations.

    DOI

    Scopus

  • An Efficient Method for Combining Multi-User MIMO Tomlinson-Harashima Precoding With User Selection Based on Spatial Orthogonality

    Hirofumi Suganuma, Yukiko Shimbo, Tomoki Maruko, Hiromichi Tomeba, Takashi Onodera, Fumiaki Maehara

    IEEE Access   9   148449 - 148458  2021  [Refereed]

    DOI

  • Effectiveness evaluation of polarization in OAM multiplexing

    Yuki Ito, Shuhei Saito, Hirofumi Suganuma, Kayo Ogawa, Fumiaki Maehara

    IEICE COMMUNICATIONS EXPRESS   10 ( 4 ) 199 - 205  2021  [Refereed]

     View Summary

    This paper investigates the system capacity of polarized orbital angular momentum (OAM) multiplexing by comparing it with OAM multiplexing without polarization for the same number of antenna elements. Since the same number of antenna elements is assumed for both approaches, their performances can be compared under the same number of simultaneous OAM streams, thereby allowing the effectiveness of polarization on UCA-based OAM multiplexing to be examined. Numerical results, obtained through computer simulations, provide the mode selectivity and system capacity with respect to link distance and carrier frequency.

    DOI

  • Impact of adjacent-channel interference on transmission performance in asynchronous FBMC/OFDM systems

    Hiroki Tabata, Hirofumi Suganuma, Fumiaki Maehara

    IEICE COMMUNICATIONS EXPRESS   10 ( 4 ) 186 - 192  2021  [Refereed]

     View Summary

    This paper investigates adjacent-channel interference (ACI) influence on asynchronous systems consisting of filter bank multicarrier (FBMC) and orthogonal frequency-division multiplexing (OFDM), under multipath fading channels. FBMC inhibits out-of-band (OOB) radiation more than OFDM, by subcarrier-wise filtering. This results in ACI reduction, while causing inter-symbol interference (ISI) and inter-carrier interference (ICI) under multipath fading channels. In this paper, we evaluate the bit error rate (BER) performance of asynchronous FBMC/OFDM systems, considering the ACI and simulations.

    DOI

  • System Capacity Evaluation of OAM Multiplexing with Multiple UCAs in the Presence of Misalignment of Beam Axis

    齋藤周平, 伊藤有希, 菅沼碩文, 小川賀代, 前原文明

    電子情報通信学会論文誌 B(Web)   J104-B ( 2 )  2021  [Refereed]

    J-GLOBAL

  • Deep Learning Based Resource Allocation Method to Control System Capacity and Fairness for MU-MIMO THP

    Yukiko Shimbo, Hirofumi Suganuma, Hiromichi Tomeba, Takashi Onodera, Fumiaki Maehara

    2021 IEEE 93RD VEHICULAR TECHNOLOGY CONFERENCE (VTC2021-SPRING)     1 - 5  2021  [Refereed]

     View Summary

    This paper proposes a deep-learning-based resource allocation method to adaptively control system capacity and fairness for multi-user multiple-input and multiple-output (MU-MIMO). In the proposed method, Tomlinson-Harashima precoding (THP) is used to enhance the transmission rate. Additionally, channel resources are appropriately allocated based on user scheduling techniques, i.e., semiorthogonal user selection (SUS) for throughput maximization and proportional fairness (PF) for fairness among users. The primary feature of the proposed method is that it appropriately allocates channel resources by utilizing the user position information and target fairness index (FI) through deep learning. This makes it possible to meet various service requirements. Numerical simulations are used to demonstrate the effectiveness of the proposed method in terms of system capacity and fairness under different MIMO configurations and user distributions.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • Efficient Inter-mode Interference Cancellation Method for OAM Multiplexing in the Presence of Beam Axis Misalignment.

    Shuhei Saito, Yuki Ito, Hirofumi Suganuma, Kayo Ogawa, Fumiaki Maehara

    2021 IEEE International Conference on Communications Workshops (ICC Workshops)     1 - 6  2021  [Refereed]

    DOI

    Scopus

    6
    Citation
    (Scopus)
  • Performance Analysis of Single-carrier Modulation with Frequency Domain Equalization in Millimeter-wave and Terahertz Broadband Communications

    Shuhei Saito, Hirofumi Suganuma, Keita Kuriyama, Yu Ono, Hayato Fukuzono, Masafumi Yoshioka, Fumiaki Maehara

    2020 International Conference on Emerging Technologies for Communications (ICETC)    2020.12  [Refereed]  [International journal]

    DOI

  • Performance Analysis of OAM Multiplexing Employing SC-FDE in the Presence of Ground Reflection

    Hirofumi Suganuma, Shuhei Saito, Kayo Ogawa, Fumiaki Maehara

    2020 IEEE Globecom Workshops, GC Wkshps 2020 - Proceedings     1 - 6  2020.12  [Refereed]

     View Summary

    This paper presents the theoretical system capacity of orbital angular momentum (OAM) multiplexing that employs single-carrier with frequency domain equalization (SC-FDE) in the presence of ground reflection. Considering that inter-symbol interference (ISI) remains even after inserting a guard interval (GI), in addition to inter-mode interference (IMI), we derive the effect of such residual IMI and ISI, and incorporate their impacts into the analysis of the system capacity. Moreover, in FDE, zeroforcing (ZF) and minimum mean square error (MMSE) are considered as the factors affecting the system capacity because the effect of noise enhancement differs among these two factors. In this study, we demonstrate theoretical results based on the tworay ground reflection model by using parameters of link distance and carrier frequency. The numerical results show that OAM multiplexing employing SC-FDE improves the system capacity compared with the case without FDE regardless of the link distance, and its effectiveness is remarkable in the cases of relatively lower carrier frequencies.

    DOI

    Scopus

    2
    Citation
    (Scopus)
  • Analysis of the Impact of Antenna Arrangement on System Capacity of MU-MIMO in the Presence of Terminal Mobility

    Hirofumi Suganuma, Yukiko Shimbo, Hiromichi Tomeba, Takashi Onodera, Fumiaki Maehara

    IEEE Vehicular Technology Conference   2020-November   1 - 5  2020.11  [Refereed]

     View Summary

    This paper investigates the impact of the antenna arrangement, such as the centralized and distributed schemes, on the theoretical system capacity of multiuser multiple-input and multiple-output (MU-MIMO) systems in the presence of terminal mobility. In our theoretical analysis, we assume that the propagation model of the centralized or distributed scheme is characterized by scattered waves that arrive at the mobile station (MS) from the same or different angles because of the antenna arrangement of the base station (BS), and theoretically analyze the multiuser interference (MUI) caused by terminal mobility. Furthermore, we compare the performances of the centralized and distributed schemes using the proposed analysis.

    DOI

    Scopus

  • Performance analysis of polarized oam multiplexing considering the effect of polarization interference

    Shuhei Saito, Yuki Ito, Hirofumi Suganuma, Kayo Ogawa, Fumiaki Maehara

    2020 IEEE International Conference on Communications Workshops, ICC Workshops 2020 - Proceedings     1 - 6  2020.06  [Refereed]

     View Summary

    This paper investigates the system capacity of polarized orbital angular momentum (OAM) multiplexing considering the impact of polarization interference. Dipole antenna is considered as the practical radiation pattern and the composition of the received mode signal is clarified by analyzing the effect of cross-polarization interference from other modes, as well as both cross-polarization interference in a certain mode and co-polarization interference from different modes. Based on the interference analysis, system capacity is precisely evaluated by comparison with the isotropic antenna case, employing a link distance and carrier frequency parameter. The numerical results show that cross-polarization interference from other modes rises at the regular mode interval, presenting a significant impact on system capacity, particularly for relatively short link distances or low carrier frequencies.

    DOI

    Scopus

    3
    Citation
    (Scopus)
  • Adaptive Repetition Control Using Terminal Mobility for Uplink Grant-Free URLLC

    Shinichi Ozaku, Yukiko Shimbo, Hirofumi Suganuma, Fumiaki Maehara

    IEEE Vehicular Technology Conference   2020-May   1 - 5  2020.05  [Refereed]

     View Summary

    This paper proposes an adaptive repetition control using terminal mobility to alleviate the packet collision for uplink grant-free (GF) ultra-reliable and low-latency communications (URLLC). In GF, the packet collision among mobile stations (MSs) becomes a serious problem because the grant-issuing procedure conducted in grant-based (GB) transmission is eliminated. Especially in the K-repetitions method, intra-cell interference is increased due to excessive repetitions, resulting in decreased reliability. In the proposed approach, the number of necessary repetitions is determined using fading correlation easily obtained from the terminal speed. This is because the time diversity benefit within repetitions is dependent on the fading correlation. Using the proposed repetition control, the number of repetitions can be reduced especially in the low fading correlation, alleviating the packet collision. The effectiveness of our proposed method is demonstrated in an actual multi-user URLLC scenario by computer simulations.

    DOI

    Scopus

    7
    Citation
    (Scopus)
  • Deep Learning Based CoMP Transmission Method Using Vehicle Position Information for Taxi Radio Systems

    Kazuki Kojima, Yukiko Shimbo, Hirofumi Suganuma, Fumiaki Maehara

    2020 International Conference on Artificial Intelligence in Information and Communication, ICAIIC 2020     253 - 256  2020.02  [Refereed]

     View Summary

    This paper proposes a coordinated multi-point (CoMP) transmission method based on deep learning for taxi radio systems to prevent inter-cell interference (ICI). In CoMP, it is essential to select whether to use simultaneous transmission or time division multiplexing (TDM) considering the effect of the ICI. The feature of the proposed method is to determine such a transmission mode by using vehicle position information as taxi radio systems have such position information. Moreover, the proposed method makes it possible to avoid the online system capacity calculation also required for CoMP thanks to the use of deep learning. The effectiveness of the proposed method is demonstrated in comparison with a traditional online calculation method under the practical scenario based on the taxi radio system in Japan.

    DOI

    Scopus

    4
    Citation
    (Scopus)
  • Theoretical system capacity of multi-user MIMO-OFDM THP in the presence of terminal mobility

    Mizutani Ryota, Shimbo Yukiko, Suganuma Hirofumi, Tomeba Hiromichi, Onodera Takashi, Maehara Fumiaki

    IEICE Communications Express (Web)   9 ( 4 )  2020  [Refereed]

    J-GLOBAL

  • Efficient Combination of MU-MIMO THP and User Scheduling for Achieving Both High System Capacity and Fairness

    新保薫子, 菅沼碩文, 留場宏道, 小野寺毅, 前原文明

    電子情報通信学会論文誌 B(Web)   J103-B ( 9 )  2020  [Refereed]

    J-GLOBAL

  • Hybrid Multiple Access Using Simultaneously NOMA and OMA

    Hirofumi Suganuma, Hiroaki Suenaga, Fumiaki Maehara

    Proceedings - 2019 International Symposium on Intelligent Signal Processing and Communication Systems, ISPACS 2019     1 - 2  2019.12  [Refereed]

     View Summary

    This paper proposes a hybrid multiple access scheme using both non-orthogonal multiple access (NOMA) and orthogonal multiple access (OMA) to overcome the inherent problems of NOMA. In NOMA, as multiple access is performed within the power domain, a small difference in the channel gain between users or an increase in the number of simultaneous users reduces the effectiveness. To cope with these problems, the proposed scheme applies a novel combination of NOMA and OMA as well as NOMA for multiple access patterns, and then determines the best pattern based on the system capacity. The effectiveness of the proposed scheme is demonstrated in comparison with conventional hybrid multiple access using NOMA and OMA through computer simulations.

    DOI

    Scopus

    14
    Citation
    (Scopus)
  • Repetition Control Method Using Terminal Mobility for Uplink Grant-Free URLLC

    Shinichi Ozaku, Yukiko Shimbo, Hirofumi Suganuma, Fumiaki Maehara

    Proceedings - 2019 International Symposium on Intelligent Signal Processing and Communication Systems, ISPACS 2019     1 - 2  2019.12  [Refereed]

     View Summary

    This paper proposes a repetition control method using terminal mobility to alleviate the packet collision for uplink grant-free (GF) ultra-reliable and low-latency communications (URLLC). Because the time diversity benefit within repetitions is basically dependent on a fading correlation, the proposed approach determines the number of necessary repetitions using a fading correlation easily obtained from the terminal speed. Using the proposed repetition control, the number of repetitions can be reduced especially in low fading correlations, alleviating packet collision. The effectiveness of our proposed method is demonstrated in terms of latency by computer simulations.

    DOI

    Scopus

    2
    Citation
    (Scopus)
  • Inter-mode interference suppression employing even-numbered modes for UCA-Based OAM multiplexing

    Hirofumi Suganuma, Shuhei Saito, Kayo Ogawa, Fumiaki Maehara

    2019 IEEE Globecom Workshops, GC Wkshps 2019 - Proceedings     1 - 6  2019.12  [Refereed]

     View Summary

    This paper proposes an inter-mode interference suppression method that employs only even-numbered modes for uniform circular array (UCA)-based orbital angular momentum (OAM) multiplexing. Given that interference from adjacent OAM modes becomes severe when the beam axis is misaligned, the proposed method uses only the even-numbered modes while leaving the odd-numbered modes unused, which effectively prevents the inter-mode interference. Moreover, we verify the effectiveness of the proposed method by applying it to multiple-input and multiple-output (MIMO) with zero-forcing (ZF) alone or ZF with successive interference cancellation because severe inter-mode interference is caused by transmitting multiple streams from multiple UCAs in each mode. The effectiveness of the proposed method compared with the traditional method, which uses all OAM modes, is demonstrated in terms of the system capacity through computer simulations.

    DOI

    Scopus

    7
    Citation
    (Scopus)
  • Centralized Resource Allocation Method for Multiuser MIMO Capable Wireless LANs

    Soma Yamashita, Hirofumi Suganuma, Tomoki Murakami, Yasushi Takatori, Fumiaki Maehara

    International Symposium on Wireless Personal Multimedia Communications, WPMC   2019-November   1 - 5  2019.11  [Refereed]

     View Summary

    This paper proposes a centralized resource allocation method to alleviate the problem of intercell interference for multiuser multiple-input multiple-output (MU-MIMO) capable wireless LANs. In this method, the control engine connected to all access points (APs) predicts the system throughput considering intercell interference by using the number of detectable APs and users, which allocates users for APs to achieve the highest throughput. After conducting AP selection, each AP adopts semi-orthogonal user selection (SUS) as user scheduling to improve MU-MIMO performance. The effectiveness of the proposed method is demonstrated using computer simulations in comparison with the traditional maximum received-signalstrength-indicator-based (RSSI-based) AP selection using random user scheduling.

    DOI

    Scopus

    2
    Citation
    (Scopus)
  • Guard Interval Control Scheme Using Theoretical System Capacity for MU-MIMO-OFDM Systems

    SUGANUMA Hirofumi, SAITO Shuhei, MARUKO Tomoki, MAEHARA Fumiaki

      J102-B ( 8 ) 659 - 668  2019.08  [Refereed]

     View Summary

    MU-MIMO-OFDM can be seen as a promising technique for achieving high speed and large capacity thanks to both spatial multiplexing and robustness against multipath fading. However, in MU-MIMO-OFDM, the guard interval (GI) length should be determined in accordance with the longest delay time among all MSs, which results in the significant degradation in transmission efficiency. In this paper, we propose the GI control scheme using theoretical system capacity for MU-MIMO-OFDM systems. In the proposed scheme, the GI length is determined to maximize the theoretical system capacity while allowing some amount of inter-symbol interference (ISI), which reduces the transmission overhead. Moreover, the proposed scheme theoretically analyzes the system capacity from the channel state information (CSI) using correlation calculation. The effectiveness of the proposed scheme is demonstrated in comparison with the traditional GI length scheme adjusted to the largest multipath delay by means of computer simulations.

    DOI

  • Performance analysis of OAM-MIMO using SIC in the presence of misalignment of beam axis

    Shuhei Saito, Hirofumi Suganuma, Kayo Ogawa, Fumiaki Maehara

    2019 IEEE International Conference on Communications Workshops, ICC Workshops 2019 - Proceedings     1 - 6  2019.05  [Refereed]

     View Summary

    This paper proposes a method that employs successive interference cancellation (SIC) to further enhance the capacity of uniform circular array (UCA)-based orbital angular momentum (OAM)-MIMO systems. The main feature of the proposed method is to stabilize the performance of UCA-based OAM-MIMO systems by conducting SIC based on the results of parallel interference cancellation (PIC), which exploits the additional full space diversity benefit. The development of the proposed approach is motivated by the feature that large differences in the received power of different UCAs are advantageous to SIC. Moreover, the impact of the misalignment of the beam axis on the effectiveness of the proposed method is also investigated by considering a more realistic scenario. Our numerical results show that the effectiveness of the proposed method increases with increasing number of UCAs, and its advantage is retained within a certain amount of the misalignment of the beam axis.

    DOI

    Scopus

    10
    Citation
    (Scopus)
  • Efficient proportional fairness scheduling method using user distribution in MU-MIMO THP

    Yukiko Shimbo, Hirofumi Suganuma, Hiromichi Tomeba, Takashi Onodera, Fumiaki Maehara

    IEEE Vehicular Technology Conference   2019-April   1 - 5  2019.04  [Refereed]

     View Summary

    This paper proposes an efficient proportional fairness (PF) scheduling method using user distribution in MU-MIMO Tomlinson-Harashima precoding (THP). Although PF realizes fairness among users, heavy computational loads are experienced due to user selection, which must calculate the system capacity for all possible user combinations. To overcome this problem, the proposed approach partially allocates channel resources for semiorthogonal user selection (SUS), which causes unfairness while maintaining throughput maximization with low computational loads. This is inspired by the fact that user scheduling for throughput maximization such as SUS increases the degree of fairness under non- uniform user distributions. Hence, in the proposed method, the user distribution is measured by the spread of channel state information (CSI) power obtained from multiple antennas, and the resource allocation to PF and SUS is adaptively controlled based on this spread. Computer simulations are used to demonstrate the effectiveness of the proposed method in comparison with the traditional MU-MIMO THP with PF in terms of fairness among users and calculation costs.

    DOI

    Scopus

  • Performance enhancement of OAM-MIMO using successive interference cancellation

    Shuhei Saito, Hirofumi Suganuma, Kayo Ogawa, Fumiaki Maehara

    IEEE Vehicular Technology Conference   2019-April   1 - 5  2019.04  [Refereed]

     View Summary

    This paper proposes a method that employs successive interference cancellation (SIC) to further enhance the capacity of uniform circular array (UCA)-based orbital angular momentum (OAM)- MIMO systems. The central feature of the proposed approach is to exploit the additional space diversity benefit in the remaining streams by means of SIC owing to the large difference in the received power among different UCAs in each OAM mode. Therefore, it is expected that the proposed method can further stabilize the performance of UCA-based OAM-MIMO along with the communication distance. Our numerical results show that the proposed method outperforms the traditional method without SIC in terms of the system capacity owing to the large received power difference among different UCAs.

    DOI

    Scopus

    6
    Citation
    (Scopus)
  • Low complexity fair user scheduling employing spatial orthogonality for mu-MIMO systems

    Ei Nandar Maung, Yukiko Shimbo, Hirofumi Suganuma, Fumiaki Maehara

    2019 26th International Conference on Telecommunications, ICT 2019     437 - 441  2019.04  [Refereed]

     View Summary

    This paper proposes a low complexity fair user scheduling method employing semi-orthogonal user selection (SUS) for multi-user multiple-input multi-output (MU-MIMO) systems. The intent of the proposed approach is to consider the spatial orthogonality of users into fair user scheduling of the MU-MIMO system, which enhances the system capacity when compared to the traditional round robin (RR) based user scheduling. In the proposed method, the spatial orthogonality is calculated based on SUS which only requires the calculation of inner products among the channel state information (CSI). Therefore, both the improvement of the system capacity and fairness can be achieved with a reduced computational load. Moreover, in contrast to proportional fairness (PF), the proposed user scheduling does not require the heavy calculation of all possible user combinations as is required in MU-MIMO precoding, which is an effective and practical approach. The effectiveness of the proposed method is demonstrated and compared with RR and PF in terms of fairness and computational load.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • Impact of Power Normalization on System-Level Performance in MU-MIMO with User Scheduling

    Ryota Mizutani, Yukiko Shimbo, Hirofumi Suganuma, Fumiaki Maehara

    ISAP 2018 - 2018 International Symposium on Antennas and Propagation    2019.01  [Refereed]

     View Summary

    This paper investigates the system-level performance of multi-user MIMO (MU-MIMO) with different power normalization in consideration of user scheduling. In this paper, matrix normalization (MN) and vector normalization (VN) are taken as the power normalization methods. As for user scheduling, semiorthogonal user selection (SUS) or proportional fairness (PΓ) is adopted, because they are opposed to each other in terms of the quality indexes, such as system capacity and fairness. Specifically, we evaluate the impact of these power normalization methods on the quality indexes and clarify the favorable matching between the power normalization and user scheduling to achieve certain quality indexes.

  • Theoretical performance evaluation of MU-MIMO THP with user scheduling

    Karen Taguchi, Ryota Mizutani, Yukiko Shimbo, Hirofumi Suganuma, Fumiaki Maehara

    IEICE COMMUNICATIONS EXPRESS   8 ( 11 ) 439 - 444  2019  [Refereed]

     View Summary

    This paper presents the theoretical system-level performance of multi-user multiple-input and multiple-output (MU-MIMO) Tomlinson-Harashima precoding (THP) with user scheduling. In our performance evaluation, proportional fairness (PF), which makes a reasonable compromise between fairness among users and the benefit of multi-user diversity, is implemented as a user scheduling technique, and the effect of modulo loss resulting from TRIP modulo operation at the receiver is taken into account using mod-Lambda channel-based analysis, which provides accurate theoretical performance. Moreover, considering the application to the PF metric, the performance of the mod-Lambda channel-based PF metric is compared with that of the traditional Shannon-Hartley theorem-based metric.

    DOI

  • MU-MIMO-OFDMにおける理論システム容量を用いたガードインターバル長制御法

    菅沼碩文, 齋藤周平, 丸小倫己, 前原文明

    電子情報通信学会論文誌 B(Web)   J102-B ( 8 )  2019  [Refereed]

    J-GLOBAL

  • Clipping and filtering employing deterministic transmit power control in MU-MIMO-OFDM systems

    Tomoki Maruko, Gen Osada, Shoya Takebuchi, Fumiaki Maehara

    18th International OFDM Workshop 2014, InOWo 2014     106 - 111  2019  [Refereed]

     View Summary

    MU-MIMO-OFDM can be seen as an attractive approach to realize high system capacity under the limitation on hardware cost and frequency selective fading. However, MU-MIMO-OFDM has an inherent problem of nonlinear distortion which is more severe than SISO-OFDM case. In this paper, we propose the OFDM clipping and filtering scheme employing deterministic transmit power control to overcome the BER degradation due to the severe nonlinear distortion. In the proposed approach, the transmit power level can be determined by the closed form formula thanks to the fact that the transmit signals at each antenna follows Rayleigh distribution. The effectiveness of the proposed approach is verified in terms of the BER and throughput by means of computer simulations.

  • Combination Strategy Based on Theoretical Aspects for Effective and Efficient Wireless Communications

    Fumiaki Maehara, Hiromichi Tomeba, Takashi Onodera

    ISPACS 2018 - 2018 International Symposium on Intelligent Signal Processing and Communication Systems     313 - 318  2018.11  [Refereed]

     View Summary

    In recent years, wireless communications systems, such as 5th generation (5G) mobile systems, have been developed as a complex combination of various elementary technologies. Therefore, it is important to consider how to effectively and efficiently combine these technologies from the viewpoint of network operation and system configuration. In this context, theoretical analysis is essential as a means of bridging the gap between different technologies. Moreover, finding common objectives among different technologies is expected to reduce computational cost. In this paper, the combination of multiuser MIMO (MU-MIMO) and user scheduling, such as resource allocation or user selection, are taken up as examples based on an awareness of the above issues. As for network operation, MU-MIMO resource allocation based on theoretical channel capacity considering the effect of time selective fading is introduced. Moreover, the efficient combination of MU-MIMO employing Tomlinson Harashima precoding (THP) and user selection using space orthogonality as a common measure is presented.

    DOI

    Scopus

  • A receiving antenna allocation scheme for downlink MU-MIMO-OFDM transmission

    Tomoki Murakami, Yasushi Takatori, Fumiaki Maehara

    Electronics (Switzerland)   7 ( 8 )  2018.08  [Refereed]

     View Summary

    This paper proposes a novel receiving antenna allocation scheme for downlink multiuser multiple input multiple output orthogonal frequency division multiplexing (MU-MIMO-OFDM) transmission; an access point (AP) simultaneously transmits data frames to a combination of allocated receiving antennas on a subcarrier basis at each station (STA). The proposed scheme combines a limited channel state information (CSI) feedback sequence with a receiving antenna decision method. In the proposed scheme, each STA estimates the channel responses of all receiving antennas by using the training preamble transmitted from an AP, and then feeds the channel response of the antenna with maximum norm back to the AP when the spatial correlation value between receiving antennas is higher than a threshold. Otherwise, each STA feeds full channel responses back to the AP. This scheme decreases the amount of CSI fed back while exploiting the spatial diversity gain, and the AP’s computational complexity is also decreased regarding the antenna allocation. Moreover, the receiving antenna decision method eliminates the overhead to notify the allocated antenna information from the AP to each STA by simply comparing its own receiving antenna powers. We clarify the effectiveness of the proposed scheme in our computer simulations using channel responses measured in an indoor environment. The results show that the proposed scheme maintains the channel capacity of the downlink MU-MIMO-OFDM transmission while greatly reducing the overhead and computational complexity.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • Control overhead reduction method employing frequency correlation for MU-MIMO-OFDM THP with user scheduling

    Yukiko Shimbo, Nobuhiro Hiruma, Hirofumi Suganuma, Fumiaki Maehara

    IEEE Vehicular Technology Conference   2018-June   1 - 5  2018.07  [Refereed]

     View Summary

    This paper proposes a method for control overhead reduction by employing frequency correlation for MU-MIMO-OFDM THP with semi-orthogonal user selection (SUS). The feature of the proposed approach is to reduce the control overhead generated by subcarrier-based user selection results by limiting the sub-carriers according to the frequency correlation. The motivation behind this approach comes from the fact that the same user selection results could be applicable to neighboring subcarriers by increasing the frequency correlation. A simple theoretical formula containing a parameter for a power delay profile is adopted to facilitate the derivation of the frequency correlation. Frequency correlation is achieved by generating the power delay profile by averaging the channel state information (CSI) over multiple transmit antennas with the aid of MU-MIMO. Moreover, our efficient method, which ensures the benefit of ordering by reusing the SUS results for the ordering calculation, is adopted to coordinate SUS and THP ordering. The effectiveness of the proposed method is demonstrated in terms of both system capacity and control overhead reduction by comparing it with the subcarrier-based approach.

    DOI

    Scopus

    3
    Citation
    (Scopus)
  • Influence of the Number of Uniform Circular Arrays on System Capacity in OAM Multiplexing

    Shuhei Saito, Hirofumi Suganuma, Kayo Ogawa, Fumiaki Maehara

    International Symposium on Wireless Personal Multimedia Communications, WPMC   2018-November   268 - 272  2018.07  [Refereed]

     View Summary

    This paper investigates the influence of the number of uniform circular arrays (UCAs) on the system capacity in orbital angular momentum (OAM) multiplexing. In UCA-based OAM, although multiple UCAs can alleviate the difference in the received signal power among OAM modes, the maximum number of OAM modes is limited. The primary contribution of our work is to evaluate the waterfilling-based system capacity of UCA-based OAM with the number of UCAs at constant transmit power and number of antenna elements, to demonstrate the benefit of multiple UCAs according to the communication distance. Our numerical results show that the multiple UCAs stabilize the system capacity irrespective of the communication distance, whereas the single UCA is effective particularly in short-range communications.

    DOI

    Scopus

    6
    Citation
    (Scopus)
  • Theoretical System Capacity of Multi-User MIMO THP in the Presence of Terminal Mobility

    Hirofumi Suganuma, Yukiko Shimbo, Nobuhiro Hiruma, Hiromichi Tomeba, Takashi Onodera, Fumiaki Maehara

    IEEE Vehicular Technology Conference   2018-August   1 - 5  2018.07  [Refereed]

     View Summary

    This paper investigates the theoretical system capacity of multi-user multiple-input and multiple-output (MU-MIMO) Tomlinson-Harashima precoding (THP) in the presence of terminal mobility. Considering that MU-MIMO generally suffers from transmission performance degradation over time selective fading channels owing to terminal mobility, we incorporate the impact of mobility as well as the modulo loss peculiar to THP into the system capacity analysis. In particular, the multiuser interference (MUI) due to terminal mobility is theoretically derived and included as the undesired component in the mod-Lambda channel required for analyzing the effect of the modulo loss. The proposed analysis enables a fair comparison in terms of the system capacity between THP and linear precoding (LP), and demonstrates the superiority of THP over LP in the presence of terminal mobility.

    DOI

    Scopus

    5
    Citation
    (Scopus)
  • On the feasibility of an adaptive movable access point system in a static indoor WLAN environment

    Tomoki Murakami, Shingo Oka, Yasushi Takatori, Masato Mizoguchi, Fumiaki Maehara

    IEICE Transactions on Communications   E101B ( 7 ) 1693 - 1700  2018.07  [Refereed]

     View Summary

    This paper investigates an adaptive movable access point (AMAP) system and explores its feasibility in a static indoor classroom environment with an applied wireless local area network (WLAN) system. In the AMAP system, the positions of multiple access points (APs) are adaptively moved in accordance with clustered user groups, which ensures effective coverage for non-uniform user distributions over the target area. This enhances the signal to interference and noise power ratio (SINR) performance. In order to derive the appropriate AP positions, we utilize the k-means method in the AMAP system. To accurately estimate the position of each user within the target area for user clustering, we use the general methods of received signal strength indicator (RSSI) or time of arrival (ToA), measured by the WLAN systems. To clarify the basic effectiveness of the AMAP system, we first evaluate the SINR performance of the AMAP system and a conventional fixed-position AP system with equal intervals using computer simulations. Moreover, we demonstrate the quantitative improvement of the SINR performance by analyzing the ToA and RSSI data measured in an indoor classroom environment in order to clarify the feasibility of the AMAP system.

    DOI

    Scopus

    2
    Citation
    (Scopus)
  • Theoretical performance evaluation of system capacity in multi-user MIMO THP with ordering

    Hirofumi Suganuma, Nobuhiro Hiruma, Fumiaki Maehara

    Wireless Telecommunications Symposium   2018-April   1 - 6  2018.05  [Refereed]

     View Summary

    This paper investigates the theoretical system capacity of MU-MIMO Tomlinson-Harashima precoding (THP) with the ordering process. In this paper, the impact of the modulo loss peculiar to THP on the system capacity is taken into account, which makes us recognize the significance of its impact comparing with the Shannon-Hartley-based results. Moreover, the ordering process generally performed before THP to enhance the system capacity is also considered in our performance analysis. In detail, the impact of the modulo loss is analyzed by using the mod-A channel, where the result of the V-BLAST-like suboptimum ordering is reflected as the power normalization factor. The proposed performance analysis considers these two actual effects, which provides a fair comparison between THP with ordering and linear precoding (LP) as well as the impact of the modulo loss, which has great potential to improve user scheduling techniques that require accurate measurements of the instantaneous system capacity.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • Efficient combination of MU-MIMO THP and user scheduling to achieve both high system capacity and fairness

    Yukiko Shimbo, Nobuhiro Hiruma, Fumiaki Maehara

    IEICE COMMUNICATIONS EXPRESS   7 ( 1 ) 7 - 12  2018  [Refereed]

     View Summary

    This letter proposes an efficient method for combining MU-MIMO Tomlinson Harashima precoding (THP) with user scheduling techniques to realize fairness among users as well as high system capacity. The concept of the proposed approach is to first adopt semiorthogonal user selection (SUS) for throughput maximization and then apply proportional fairness (PF) to the remaining users, which regains fairness lowered by using SUS for throughput maximization. Moreover, considering that THP adopted as a precoder for PF requires the calculation of ordering and precoding for each user combination, the proposed method adopts linear precoding (LP) instead of THP to relax the computational effort during operation of PF. This approach is inspired by the fact that LP achieves almost the same system capacity as THP with ordering when conducting PF. The effectiveness of the proposed method is demonstrated by comparing it to MU-MIMO THP with SUS or PF in terms of system capacity and fairness among users, by means of computer simulations.

    DOI

  • Propagation characteristics of Laguerre-Gaussian beams through atmospheric turbulence in optical wireless communication

    Aya Saito, Fumiaki Maehara, Kayo Ogawa

    2017 International Symposium on Antennas and Propagation, ISAP 2017   2017-January   1 - 2  2017.12  [Refereed]

     View Summary

    The scintillation and bit error rate performance of optical wireless communication systems employing Laguerre-Gaussian (LG) beams were evaluated considering the size of the transmitted beam and receiving aperture. As a result, it was found that the system employing LG beams with a high radial number can reduce the effect of scintillation and improve communication quality.

    DOI

    Scopus

    2
    Citation
    (Scopus)
  • Performance evaluation of MU-MIMO THP with user scheduling in terms of system capacity and fairness

    Yukiko Shimbo, Nobuhiro Hiruma, Fumiaki Maehara

    2017 International Symposium on Antennas and Propagation, ISAP 2017   2017-January   1 - 2  2017.12  [Refereed]

     View Summary

    This paper presents the performance evaluation of multi-user MIMO (MU-MIMO) employing Tomlinson Harashima precoding (THP) in consideration of user scheduling techniques from the viewpoint of system capacity and fairness. In this paper, the ordering process is adopted for THP, and both semiorthogonal user selection (SUS) and proportional fairness (PF) are considered as user scheduling techniques. Their opposite characteristics make it possible to establish the degree of matching between precoding and user scheduling techniques. The system-level performance with unequal CNR users is evaluated through computer simulations, and it is compared with the performance of linear precoding (LP).

    DOI

    Scopus

    5
    Citation
    (Scopus)
  • Efficient Ordering Calculation Method Using Frequency Correlation for MU-MIMO-OFDM THP

    Nobuhiro Hiruma, Tomoki Maruko, Hiromichi Tomeba, Takashi Onodera, Fumiaki Maehara

    IEEE Vehicular Technology Conference   2017-June   1 - 5  2017.11  [Refereed]

     View Summary

    This paper proposes an efficient ordering calculation method employing frequency correlation in multiuser multiple-input multiple-output orthogonal frequency division multiplexing (MU-MIMO-OFDM) Tomlinson Harashima Precoding (THP). Although the ordering process is effective to improve the transmission performance of THP, it requires a large amount of computational effort due to sub-carrier-based operation. To cope with this problem, the proposed method thins out the sub-carriers conducting the ordering process based on the frequency correlation. The basic idea behind this proposal is that the ordering results are considered to be the same among the neighboring sub-carriers in a relatively small delay spread. Moreover, the frequency correlation is derived from a delay profile which can be determined by multiple transmit antennas. The effectiveness of the proposed method is demonstrated in terms of calculation cost and the bit error rate (BER) by comparing with the traditional MU-MIMO-OFDM THP without thinning.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • Performance of adaptive movable access point system in the presence of positioning error

    Shingo Oka, Tomoki Murakami, Yasushi Takatori, Masato Mizoguchi, Fumiaki Maehara

    IEEE Radio and Wireless Symposium, RWS     150 - 152  2017.03  [Refereed]

     View Summary

    This paper proposes an adaptive movable access point (AMAP) system to enhance the system capacity in dense wireless-device environments. In the proposed approach, the positions of access points (APs) are adaptively moved in accordance with clustered user distribution, which is sure to be effective in ununiform user distribution due to dense device environments. In order to derive the appropriate positions of APs, we utilize k-means method and estimate the user's position which is essential for k-means method by means of receive signal strength indicator (RSSI) or time of arrival (ToA). The effectiveness of the proposed systems is evaluated in the presence of the positioning error obtained from the experimental results concerning RSSI and ToA and is demonstrated in comparison with the fixed position of AP with equal intervals.

    DOI

    Scopus

    2
    Citation
    (Scopus)
  • Inter-symbol interference suppression scheme employing periodic signals in coded network MIMO-OFDM systems

    Hirofumi Suganuma, Shuhei Saito, Tomoki Maruko, Fumiaki Maehara

    IEEE Radio and Wireless Symposium, RWS     42 - 44  2017.03  [Refereed]

     View Summary

    This paper proposes an inter-symbol interference (ISI) suppression scheme employing periodic signals for network MIMO-OFDM systems. Network MIMO-OFDM suffers from the ISI due to long time difference of arrival ( TDOA) especially in large cells. In the proposed scheme, the periodic signals generated by only the even-numbered sub-carriers are adopted for ISI-affected users while the traditional non-periodic signals are used for ISI-free users. Moreover, to realize the transmission mode selection between the periodic and non-periodic signals, the theoretical derivation method of the BER is newly derived considering the impact of channel coding. The effectiveness of the proposed method is demonstrated in comparison with the traditional non-periodic transmission by means of computer simulations.

    DOI

    Scopus

    10
    Citation
    (Scopus)
  • A simple CoMP transmission method employing vehicle position information for taxi radio systems

    Naoki Kurihara, Keisuke Ujihara, Fumiaki Maehara

    Proceedings - 2017 IEEE Topical Conference on Wireless Sensors and Sensor Networks, WiSNet 2017     73 - 75  2017.03  [Refereed]

     View Summary

    This paper proposes a simple coordinated multipoint (CoMP) transmission method for taxi radio systems in order to prevent inter-cell interference (ICI) without a significant renewal of facilities. The proposed method takes advantage of the interesting property that the ICI which is essential for CoMP can be represented by the communication distance easily obtained from vehicle position information in a 2-cells scenario. Moreover, the proposed approach can be adopted for more than 3 cells by combining the ICI between 2 cells. The proposed method exploits diversity reception in the case of time division multiplexing (TDM), which makes it possible to improve the channel capacity in overlapped area. The effectiveness of the proposed method is demonstrated in comparison with the case of no coordination (w/o CoMP) under the practical scenario based on the taxi radio system in Japan.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • An enhanced MMSE subchannel decision feedback equalizer with ICI suppression for FBMC/OQAM systems

    Chih Wei Chen, Fumiaki Maehara

    2017 International Conference on Computing, Networking and Communications, ICNC 2017     1041 - 1045  2017.03  [Refereed]

     View Summary

    This paper proposes an enhanced decision feedback equalizer (DFE) for filter bank multicarrier (FBMC) systems over offset quadrature amplitude modulation (OQAM) based on a minimal mean square error (MMSE) criterion. For each subcarrier, besides one feedforward (FF) filter and one feedback (FB) filter, we add two intercarrier interference (ICI)-suppressing filters, which feed back detected precursors extracted from neighboring subchannels to enhance ICI suppression in the presence of multipath channels. Our simulation results indicate our proposal makes a considerable improvement comparing with MMSE-DFE under a severe ICI and ISI scenario despite few extra costs in computational complexity.

    DOI

    Scopus

    12
    Citation
    (Scopus)
  • Downlink multiuser MIMO-OFDM transmission using simple receive antenna selection

    Tomoki Murakami, Keisuke Ujihara, Yasushi Takatori, Masato Mizoguchi, Fumiaki Maehara

    ISAP 2016 - International Symposium on Antennas and Propagation     604 - 605  2017.01  [Refereed]

     View Summary

    This paper proposes a downlink MU-MIMOOFDM transmission using simple receive antenna selection. In the proposal, base station transmits to users with selected receive antenna per subcarrier to obtain diversity gain. The proposal also decreases computational complexity by narrowing down the number of antenna combination in accordance with correlation value between receive antennas at each user. From experimental evaluations, it is indicated that the proposal offers high channel capacity with greatly reduced antenna combination.

  • Inter-symbol interference suppression scheme employing periodic signals in network MIMO-OFDM systems

    Hirofumi Suganuma, Tomoki Maruko, Fumiaki Maehara

    ISAP 2016 - International Symposium on Antennas and Propagation     276 - 277  2017.01  [Refereed]

     View Summary

    This paper proposes an inter-symbol interference (ISI) suppression scheme employing periodic signals for network MIMO-OFDM systems. Network MIMO-OFDM suffers from the ISI due to long time difference of arrival (TDOA) among the users especially in large cells. In the proposed scheme, the periodic signals generated by only the even-numbered sub-carriers is adopted for suppressing the ISI and the appropriate transmission mode is chosen between the traditional non-periodic and periodic signals based on the theoretical BER obtained by means of correlation operation. The proposed approach makes the most of the useful properties that a certain ISI-affected user does not interfere at all with the other users, which enables us to make the countermeasure individually. The effectiveness of the proposed method is demonstrated in comparison with the traditional non-periodic transmission by means of computer simulations.

  • Theoretical derivation method of bit error rate for coded SC-FDE transmission

    Shuhei Saito, Hirofumi Suganuma, Fumiaki Maehara

    IEICE COMMUNICATIONS EXPRESS   6 ( 5 ) 182 - 187  2017  [Refereed]

     View Summary

    This letter derives the theoretical BER of coded SC-FDE transmission taking advantage of the traditional theoretical results of the instantaneous SINR. The proposed approach is inspired by the fact that the theoretical channel coding gain under AWGN is directly applicable to the traditional FDE performance due to the flat SINR characteristic within an FDE block. The proposed derivation method can provides the theoretical coded BER without any effort of actual signal processing such as modulation, demodulation, and channel coding. The validity of the proposed approach is confirmed by the agreement with the computer simulation results under frequency selective fading channels.

    DOI

  • MU-MIMO-OFDM THPにおける周波数相関を用いたオーダリング処理コスト削減法

    蛭間信博, 丸小倫己, 留場宏道, 小野寺毅, 前原文明

    電子情報通信学会論文誌 B(Web)   J100-B ( 8 )  2017  [Refereed]

    J-GLOBAL

  • A coordinated multipoint transmission method employing vehicle position information for taxi radio systems

    Keisuke Ujihara, Naoki Kurihara, Yoshinori Sakata, Fumiaki Maehara

    Proceedings - Asia-Pacific Conference on Communications, APCC 2016     440 - 444  2016.10  [Refereed]

     View Summary

    This paper proposes a simple coordinated multipoint (CoMP) transmission method for taxi radio systems. The feature of the proposed method is to realize CoMP only by using the vehicle position information, which enables us to free from a significant renewal of facilities. The proposed approach is inspired by the idea that the channel capacity based on the inter-cell interference (ICI) can be represented by the communication distance which is easily obtained from the vehicle position information. In addition, the proposed method is applicable to more than 3 cells by using the same approach applied to 2 cells. The effectiveness of the proposed method is demonstrated in comparison with the case of no coordination (w/o CoMP) under the practical scenario based on the taxi radio system.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • Efficient combination of multi-user MIMO THP and user selection based on spatial orthogonality

    Tomoki Maruko, Takahiro Yamaguchi, Tomoki Yoshimura, Hiromichi Tomeba, Takashi Onodera, Fumiaki Maehara

    IEEE Wireless Communications and Networking Conference, WCNC   2016-September   1 - 5  2016.09  [Refereed]

     View Summary

    This paper proposes an efficient method for combing multi-user MIMO (MU-MIMO) employing Tomlinson Harashima precoding (THP) with semiorthogonal user selection (SUS). Although the ordering of MU-MIMO THP and SUS create space diversity benefit and multi-user diversity benefit, respectively, a significant computational effort is required, which is expected to be relaxed while retaining the system level performance. The proposed method is inspired by the fact that the ordering calculations of MU-MIMO THP and SUS are commonly based on the spatial orthogonality. If that is the case, the result of the ordering of SUS is fully reused for the ordering of MU-MIMO THP, which can eliminate the calculation process of the ordering of MU-MIMO THP. The effectiveness of the proposed method is demonstrated in comparison with the traditional method with the ordering of MU-MIMO THP by means of computer simulations.

    DOI

    Scopus

    11
    Citation
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  • Theoretical Shannon capacity performance of nonlinearly amplified uplink OFDMA signals in the presence of terminal mobility

    Takahiro Yamaguchi, Kei Nishimura, Fumiaki Maehara

    IEEE Vehicular Technology Conference     1 - 5  2016.07  [Refereed]

     View Summary

    This paper proposes the theoretical derivation method of the Shannon capacity for nonlinearly amplified uplink Orthogonal Frequency Division Multiple Access (OFDMA) in the presence of terminal mobility. In our theoretical derivation, the impact of the intercarrier interference (ICI) arising from terminal mobility as well as the multiuser interference (MUI) caused by nonlinear amplification of the mobile stations (MSs) on OFDMA signals is taken into account. Considering the fact that these interferences differ with the sub-carrier allocation methods such as localized FDMA (LFDMA) and interleaved FDMA (IFDMA), we derive the probability density function (PDF) of the instantaneous signal-to-noise-plus-distortion-plus-interference ratio (SNDIR) for each sub-carrier allocation method. Since the SNDIR is successfully expressed in the closed form, the proposed formula enables us to evaluate the Shannon capacity without conducting time consuming computer simulations.

    DOI

    Scopus

    2
    Citation
    (Scopus)
  • A novel modulo loss suppression scheme employing theoretical BER formula for MU-MIMO THP systems

    Kei Nishimura, Tomoki Maruko, Hiromichi Tomeba, Takashi Onodera, Minoru Kubota, Fumiaki Maehara, Fumio Takahata

    2015 IEEE 82nd Vehicular Technology Conference, VTC Fall 2015 - Proceedings     1 - 5  2016.01  [Refereed]

     View Summary

    This paper proposes a novel modulo loss suppression scheme employing a theoretical BER formula for multi-user multiple-input multiple-output (MU-MIMO) Tomlinson-Harashima Precoding (THP) systems. The main feature of the proposed approach is to control the constellation distance by using the simple theoretical bit error rate (BER) formula in order to overcome the modulo loss. Behind this proposal, there is an interesting fact that the BER performance is dependent on the influence of both the thermal noise and the modulo loss and that its influence is determined by the constellation distance. In the proposed approach, we newly derive a theoretical simple BER formula for MU-MIMO THP and then find out the optimal constellation distance to suppress the modulo loss. The effectiveness of the proposed scheme is demonstrated in comparison to the traditional MU-MIMO THP with fixed distance by means of computer simulations.

    DOI

    Scopus

    3
    Citation
    (Scopus)
  • MU-MIMO-OFDMにおける送信電力制御を用いた非線形ひずみ抑圧法

    丸小倫己, 長田弦, 長田弦, 竹渕翔矢, 竹渕翔矢, 前原文明

    電子情報通信学会論文誌 B(Web)   J99-B ( 11 )  2016  [Refereed]

    J-GLOBAL

  • Inter-symbol interference suppression scheme using periodic signals for coded MIMO-OFDM systems

    Kaito Udagawa, Takahiro Yamaguchi, Fumiaki Maehara

    19th International Conference on OFDM and Frequency Domain Techniques, ICOF 2016     23 - 27  2016  [Refereed]

     View Summary

    This paper proposes the inter-symbol interference (ISI) suppression scheme employing periodic signals for coded MIMO-OFDM systems. The feature of the proposed approach is to choose the appropriate transmission mode composed of traditional non-periodic signals or periodic signals with only even-numbered sub-carriers according to the delay spread. To provide the selection criterion for choosing between these transmission modes, we develop the theoretical bit error rate (BER) estimation method using the correlation calculation for coded MIMO-OFDM. The effectiveness of the proposed scheme is demonstrated in comparison with the traditional non-periodic symbol transmission.

  • Antenna decision method for downlink multiuser MIMO systems with receive antenna allocation

    Tomoki Murakami, Yasushi Takatori, Masato Mizoguchi, Fumiaki Maehara

    IEEE Antennas and Propagation Society, AP-S International Symposium (Digest)   2015-October   304 - 305  2015.10  [Refereed]

     View Summary

    This paper proposes an antenna decision method for downlink multiuser MIMO (MU-MIMO) with receive antenna allocation per subcarrier. When receive antenna allocation is used, each receiver requires the information of the antenna allocation before receiving the data; for this an overhead signal is used. The proposed method decreases the overhead by deciding an antenna with comparison of received power at each antenna of the receiver. Computer simulations show that the proposed method offers highly accurate antenna decision and high channel capacity with one OFDM symbol.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • Decision feedback channel estimation scheme using terminal speed for single-carrier frequency-domain equalization

    Hirotaka Mihara, Fumiaki Maehara

    IEEE Vehicular Technology Conference   2015   1 - 5  2015.07  [Refereed]

     View Summary

    This paper proposes an adaptive decision feedback channel estimation (DFCE) scheme using the knowledge of terminal speed in single-carrier frequency-domain equalization (SC-FDE). Since SC signals generally have the large envelope variation in frequency spectrum, the subcarrier signals with the small magnitude cause the noise enhancement. The proposed scheme adopts DFCE only for the subcarriers with the relatively large magnitude. Moreover, the proposed scheme adaptively controls the forgetting factor according to the channel condition such as noise dominant channel and time selectivity dominant channel. The feature of the proposed approach is to theoretically derive the effect of time selective fading by using the terminal speed and to detect the actual channel condition. The effectiveness of the proposed scheme is demonstrated in comparison with the traditional DFCE with the fixed forgetting factor by means of computer simulations.

    DOI

    Scopus

    2
    Citation
    (Scopus)
  • Simple resource allocation scheme for heterogeneous traffic in MU-MIMO-OFDMA systems

    Yoshinori Sakata, Tomoki Murakami, Yasushi Takatori, Masato Mizoguchi, Fumiaki Maehara

    Proceedings of the 20th Asia-Pacific Conference on Communication, APCC 2014     189 - 193  2015.04  [Refereed]

     View Summary

    This paper proposes an adaptive resource allocation scheme to cope with heterogeneous traffic for multiuser multiple-input multiple-output orthogonal frequency division multiple access (MU-MIMO-OFDMA). The feature of the proposed approach is to maximize the frame efficiency by simultaneously allocating frequency and space resources under different user's packet size and channel condition. However, since frequency and space resources generate numerous number of allocation patterns, we reduce the number of patterns thanks to the fact that broadband frequency channels in OFDMA provide almost the same performance. Computer simulation shows the effectiveness of the proposed scheme by comparing with the conventional scheme without resource allocation.

    DOI

    Scopus

    2
    Citation
    (Scopus)
  • MU-MIMO THPにおいてmodulo誤りの影響を低減するHybrid ARQ方式

    竹渕翔矢, 丸小倫己, 留場宏道, 小野寺毅, 窪田稔, 前原文明, 高畑文雄

    電子情報通信学会論文誌 B(Web)   J98-B ( 1 )  2015  [Refereed]

    J-GLOBAL

  • MU-MIMO-OFDMA伝送における不均一なトラヒック及び受信電力を考慮したリソース割り当て法

    坂田佳謙, 村上友規, 鷹取泰司, 溝口匡人, 前原文明

    電子情報通信学会論文誌 B(Web)   J98-B ( 7 )  2015  [Refereed]

    J-GLOBAL

  • Vector perturbation using signal space conversion assisted vector ranking algorithm

    Hiromichi Tomeba, Takashi Onodera, Minoru Kubota, Fumiaki Maehara, Fumio Takahata

    IEEE Wireless Communications and Networking Conference, WCNC     1218 - 1223  2014.11  [Refereed]

     View Summary

    Nonlinear precoding multi-user multiple-input multiple-output using vector perturbation (VP MU-MIMO) can provide good frequency efficiency at the cost of computational complexity, which exponentially increases as the number of spatial multiplexed users increases. This is because the original VP precoding requires to exhaustively search the optimum transmit signal vector among all the combinations of each user's transmit signal candidates. To reduce the computational complexity, in this paper, we propose signal space conversion assisted vector ranking algorithm, which exploits the equivalency between the search of optimum transmit signal vector in the VP precoding and the signal detection from received signal in the general signal transmission. And, its transmission performance and computational complexity are evaluated by computer simulation.

    DOI

    Scopus

  • OFDM Clipping and Filtering Method Employing Theoretical SNDR-Based Transmit Power Control

    TAKEBUCHI Shoya, OSADA Gen, ARAI Takuto, KAMIYA Naokuni, MAEHARA Fumiaki

    The transactions of the Institute of Electronics, Information and Communication Engineers. B   97 ( 2 ) 216 - 228  2014.02  [Refereed]

    CiNii

  • 複数アンテナを有する端末に適したAP連携マルチユーザMIMO伝送法

    村上友規, 工藤理一, 鷹取泰司, 溝口匡人, 前原文明

    電子情報通信学会論文誌 B(Web)   J97-B ( 7 )  2014  [Refereed]

    J-GLOBAL

  • Theoretical derivation of bit error rate for uplink OFDMA employing space diversity reception over nonlinear fading channels

    Kei Nishimura, Shoya Takebuchi, Fumiaki Maehara

    20th European Wireless Conference, EW 2014     366 - 371  2014  [Refereed]

     View Summary

    This paper proposes the theoretical derivation method of the bit error rate (BER) performance for uplink Orthogonal Frequency Division Multiple Access (OFDMA) employing space diversity reception under nonlinear fading channels. The proposed method provides the simple series form formula which takes into account the space diversity benefit as well as two different subcarrier allocation methods such as localized FDMA (LFDMA) and interleaved FDMA (IFDMA). Hence, the proposed formula makes it possible to easily confirm the performance difference between LFDMA and IFDMA while computer simulations require high computational complexity. The validity of the proposed formula is confirmed by the agreement with the computer simulation results under various kinds of system parameters such as the subcarrier allocation methods, the number of MSs, the number of antennas, and the input back-off(IBO).

  • A cross-layer switching of OFDMA and MU-MIMO for future WLAN systems

    Murakami Tomoki, Takatori Yasushi, Mizoguchi Masato, Maehara Fumiaki

    IEICE ComEX   3 ( 9 ) 263 - 268  2014  [Refereed]

     View Summary

    We propose a cross-layer switching method of orthogonal frequency division multiple access (OFDMA) and multiuser multiple input multiple output (MU-MIMO) for the future wireless local area network systems. The proposed method, employed on the medium access control layer, switches between OFDMA and MU-MIMO as the transmission method after processing by using physical layer information such as an overhead of channel state information feedback, station number, and data length in order to improve the transmission efficiency. Simulation results show that the proposed method achieves higher total throughput than conventional OFDMA or MU-MIMO where switching is not performed.

    DOI CiNii

  • Multi-User MIMO Transmission Scheme Employing Redundant Degrees of Freedom

    SHIRAI Toru, TAKEBUCHI Shoya, MAEHARA Fumiaki

    The transactions of the Institute of Electronics, Information and Communication Engineers. B   J96-B ( 5 ) 551 - 554  2013.05  [Refereed]

    CiNii J-GLOBAL

  • Theoretical Derivation Method of Bit Error Rate in MB-OFDM UWB

    TAKEBUCHI Shoya, KANEKO Ryouhei, MAEHARA Fumiaki

    The Transactions of the Institute of Electronics, Information and Communication Engineers. A   J96-A ( 5 ) 273 - 277  2013.05  [Refereed]

    CiNii J-GLOBAL

  • A deterministic transmit power control for OFDM clipping and filtering

    Shoya Takebuchi, Gen Osada, Fumiaki Maehara

    IEEE Vehicular Technology Conference     1 - 5  2013  [Refereed]

     View Summary

    This paper proposes a deterministic approach employing transmit power control to overcome the BER degradation of OFDM clipping and filtering. The feature of the proposed method is to perform the transmit power control before clipping and filtering to prevent the nonlinear distortion due to clipping process and furthermore, the optimal transmit power is automatically controlled based in the signal-to-noise-plus-distortion ratio (SNDR) derived by the simple mathematical formula. Therefore, the proposed method is expected to straightforwardly improve the BER without any iterative process which is required in the conventional clipping and filtering method. The effectiveness of the proposed method is demonstrated in comparison with the traditional clipping and filtering method by means of computer simulations. Copyright © 2013 by the Institute of Electrical and Electronic Engineers, Inc.

    DOI

    Scopus

    3
    Citation
    (Scopus)
  • Theoretical derivation of bit error rate for uplink OFDMA over nonlinear fading channels

    Kei Nishimura, Shoya Takebuchi, Fumiaki Maehara

    IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC     761 - 765  2013  [Refereed]

     View Summary

    This paper proposes the theoretical derivation method of both the frequency spectrum and the bit error rate (BER) performance for uplink Orthogonal Frequency Division Multiple Access (OFDMA) in the presence of the nonlinear distortion. Since OFDMA has two different subcarrier allocation methods such as localized FDMA (LFDMA) and interleaved FDMA (IFDMA), there is the difference, in terms of the influence of the nonlinear distortion at each mobile station (MS) on the out-band radiation and the BER degradation, between LFDMA and IFDMA. Therefore, it is meaningful to clarify this difference by means of the theoretical approach. The feature of the proposed approach is to represent both the frequency spectrum and the BER performance by the simple series form formula, which enables us to overview these performances without any time-consuming computer simulations. The validity of the proposed formula is confirmed by the agreement with the computer simulation results with the parameters of the number of MSs and the input back-off (IBO). © 2013 IEEE.

    DOI

    Scopus

    2
    Citation
    (Scopus)
  • Hybrid ARQ for modulo loss reduction in multi-user MIMO THP systems

    Shoya Takebuchi, Hiromichi Tomeba, Takashi Onodera, Minoru Kubota, Fumiaki Maehara, Fumio Takahata

    ISPACS 2013 - 2013 International Symposium on Intelligent Signal Processing and Communication Systems     375 - 380  2013  [Refereed]

     View Summary

    Multi-user MIMO (MV-MIMO) using Tomlinson-Harashima precoding (THP) has great potential to achieve high system capacity in wireless systems. On the other hand, hybrid ARQ (HARQ) is essential to realize the reliable wireless packet transmission and therefore, the combination of THP with HARQ can be seen as a promising approach to achieve reliable high-capacity wireless transmissions. However, this combination has a problem of severe performance degradation due to the accumulation of modulo loss which is the inherent drawback of THP. In this paper, we propose the HARQ scheme to cancel the accumulation of modulo loss in Multi-user MIMO THP systems. The main feature of the proposed approach is to add the same perturbation vector as the initial transmit packet to the retransmit packets in order to prevent the accumulation of modulo loss. The effectiveness of the proposed scheme is demonstrated in comparison with the conventional packet combining scheme by means of computer simulations.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • Performance evaluation of OFDM clipping and filtering method using transmit power control

    S. Takebuchi, T. Arai, F. Maehara

    Proc. World Telecommunications Congress 2012 (WTC2012)   ( PS-25 )  2012.03  [Refereed]

  • Multi-User MIMO transmission scheme aiming to exploit transmit diversity benefit

    T. Shirai, M. Shimizu, F. Maehara

    Proc. World Telecommunications Congress 2012 (WTC2012)   ( PS-22 )  2012.03  [Refereed]

  • Theoretical BER Controlled Transmission Mode Selection Method for OFDM ISI Suppression Scheme Using Periodic Signals

    FUKUI Tatsuya, YAMAKITA Akihiro, MAEHARA Fumiaki

    The transactions of the Institute of Electronics, Information and Communication Engineers. B   J95-B ( 1 ) 48 - 60  2012.01  [Refereed]

    CiNii J-GLOBAL

  • Coverage performance of UWB in-car wireless communication in the presence of multiple terminals

    Takuto Arai, Toru Shirai, Yuki Watanabe, Fumiaki Maehara

    RWW 2012 - Proceedings: IEEE Radio and Wireless Symposium, RWS 2012     111 - 114  2012  [Refereed]

     View Summary

    Recent years, the increase in complicated wire harness increases the weight and consequently harms the environment friendliness especially in a luxury car. Therefore, it is expected that in-car network is effectively built by using wireless connection as well as wired connection. In this paper, we investigate the coverage area performance of MB-OFDM UWB in-car communication in the presence of plural mobile terminals. In our approach, simultaneous multi-user wireless transmission is realized by multi-user MIMO (MU-MIMO) employing linear precoding with restriction of the total transmit power which satisfies the UWB power density limitation. Numerical results show the influence of the number of terminals on the coverage area under in-car propagation and verify the applicability of MU-MIMO to MB-OFDM UWB in-car wireless communication. © 2012 IEEE.

    DOI

    Scopus

    2
    Citation
    (Scopus)
  • A novel clipping and filtering method employing transmit power control for OFDM systems

    Shoya Takebuchi, Takuto Arai, Fumiaki Maehara

    IEEE Wireless Communications and Networking Conference, WCNC   ( PHY08 ) 221 - 225  2012  [Refereed]

     View Summary

    This paper proposes a novel clipping and filtering method employing transmit power control to improve the bit error rate (BER) performance in MIMO-OFDM transmission. The feature of the proposed approach is to perform the transmit power control before clipping and filtering to alleviate the BER degradation caused by clipping and filtering. Since the transmit power control to satisfy maximum signal-to-noise-plusdistortion ratio (SNDR) tends to lower the transmit power level especially in a relatively large CNR, the combination of its transmit power control with clipping and filtering surely improves the BER performance while suppressing the out-of-band radiation. Considering that MIMO systems suffer from the nonlinear distortion much more than SISO systems, the performance evaluation is to be conducted on MIMO systems, and the effectiveness of the proposed approach is demonstrated in comparison with the traditional clipping and filtering method with the constant transmit power level.

    DOI

    Scopus

    5
    Citation
    (Scopus)
  • Theoretical Derivation Method of BER Performance for OFDM Systems in the Presence of Nonlinear Distortion

    YAMAKITA Akihiro, KAMIYAMA Akira, GOTO Yuichiro, MAEHARA Fumiaki

    The Transactions of the Institute of Electronics, Information and Communication Engineers. A   J94-A ( 9 ) 723 - 733  2011.09  [Refereed]

    CiNii J-GLOBAL

  • Bit Metric Derivation Method Using Residual CCI Signals for Adaptive Antenna Array Coupled with Channel Coding

    WANG Yunhan, MAEHARA Fumiaki, TAKAHATA Fumio, ONODERA Takashi, URABE Shuuji

    The transactions of the Institute of Electronics, Information and Communication Engineers. B   J94-B ( 8 ) 959 - 969  2011.08  [Refereed]

    CiNii J-GLOBAL

  • An application of time division multiplexing on multi-user MIMO THP systems in the presence of high mobility terminals

    Yunhan Wang, Manato Shimizu, Fumiaki Maehara, Fumio Takahata

    IEEE Vehicular Technology Conference    2011  [Refereed]

     View Summary

    Multi-user MIMO (MU-MIMO) employing Tomlinson Harashima Precoding (THP) is a powerful technique to enhance the system capacity in multi-user mobile communications systems. However, MU-MIMO has an inherent drawback in the degradation of the transmission performance due to the time variant fading channels which are caused by the mobility of the mobile station (MS). Considering that MU-MIMO is mainly applied to mobile communications systems, the performance degradation due to this terminal mobility has to be solved. This paper proposes a novel MU-MIMO THP transmission scheme for the sake of alleviating the performance degradation due to the terminal mobility. The feature of the proposed approach is to incorporate the concept of time division multiplexing (TDM) into MU-MIMO THP system, which enables the transmission of high mobility user to take precedence over that of the lower mobility user. Thanks to the use of TDM, the proposed scheme exploits the space diversity benefit because TDM decreases the number of MSs within a time slot. The effectiveness of the proposed scheme is demonstrated in comparison with the traditional MU-MIMO THP scheme by means of computer simulations. © 2011 IEEE.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • Nonlinear suppression scheme employing transmit power control for MIMO-OFDM systems

    Takuto Arai, Yunhan Wang, Naokuni Kamiya, Fumiaki Maehara

    2011 2nd International Conference on Wireless Communication, Vehicular Technology, Information Theory and Aerospace and Electronic Systems Technology, Wireless VITAE 2011     46 - 48  2011  [Refereed]

     View Summary

    MU-MIMO-OFDM is an effective technique to achieve high capacity and reliable wireless communications systems because both the robustness against multi path fading and the high spectrum efficiency can be effectively achieved by the combination of OFDM with MU-MIMO. However, MU-MIMO-OFDM significantly suffers from the nonlinear distortion which is a main drawback of OFDM. In this paper, we propose nonlinear distortion suppression scheme employing transmit power control for MU-MIMO-OFDM. The main feature of the proposed scheme is to apply the deterministic transmit power control to MU-MIMO-OFDM without any destruction of the space orthogonality. The effectiveness of the proposed scheme is demonstrated in comparison with the traditional MU-MIMO-OFDM over the nonlinear fading channels.

    DOI

    Scopus

  • Simple series from formula of BER performance for M-ary QAM/OFDM signals with MRC diversity reception over nonlinear fading channels

    Akihiro Yamakita, Akira Kamiyama, Yuichiro Goto, Fumiaki Maehara

    2011 2nd International Conference on Wireless Communication, Vehicular Technology, Information Theory and Aerospace and Electronic Systems Technology, Wireless VITAE 2011    2011  [Refereed]

     View Summary

    This paper proposes the theoretical derivation method of the bit error rate (BER) for M-ary QAM/OFDM signals using maximal ratio combining (MRC) reception under nonlinear fading channels. Since the BER performance especially in the presence of nonlinear fading channels is mostly obtained by time-consuming computer simulations, we provide the simple analytical tool in order to prevent its computational cost. The feature of the proposed formula is to be represented by the simple series form formula without any integral calculation and to be applicable to arbitrary modulation schemes. The validity of the proposed approach is confirmed by the agreement with the computer simulation results under various kinds of system parameters such as the input back-off (IBO) and the number of branches. © 2011 IEEE.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • An Application of Time Division Multiplexing on Multi-User MIMO THP Systems in the Presence of High Mobility Terminals

    Yunhan Wang, Manato Shimizu, Fumiaki Maehara, Fumio Takahata

    2011 IEEE VEHICULAR TECHNOLOGY CONFERENCE (VTC FALL)    2011  [Refereed]

     View Summary

    Multi-user MIMO (MU-MIMO) employing Tomlinson Harashima Precoding (THP) is a powerful technique to enhance the system capacity in multi-user mobile communications systems. However, MU-MIMO has an inherent drawback in the degradation of the transmission performance due to the time variant fading channels which are caused by the mobility of the mobile station (MS). Considering that MU-MIMO is mainly applied to mobile communications systems, the performance degradation due to this terminal mobility has to be solved. This paper proposes a novel MU-MIMO THP transmission scheme for the sake of alleviating the performance degradation due to the terminal mobility. The feature of the proposed approach is to incorporate the concept of time division multiplexing (TDM) into MU-MIMO THP system, which enables the transmission of high mobility user to take precedence over that of the lower mobility user. Thanks to the use of TDM, the proposed scheme exploits the space diversity benefit because TDM decreases the number of MSs within a time slot. The effectiveness of the proposed scheme is demonstrated in comparison with the traditional MU-MIMO THP scheme by means of computer simulations.

  • Generic permutation network for QC-LDPC decoder

    Xiao Peng, Xiongxin Zhao, Zhixiang Chen, Fumiaki Maehara, Satoshi Goto

    IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences   E93-A ( 12 ) 2551 - 2559  2010.12  [Refereed]

     View Summary

    Permutation network plays an important role in the reconfigurable QC LDPC decoder for most modem wireless communication systems with multiple code rates and various code lengths This paper presents the generic permutation network (GPN) for the reconfigurable QC LDPC decoder Compared with conventional permutation networks this proposal could break through the input number restriction such as power of 2 and other limited number and optimize the network for any application in demand Moreover the proposed scheme could greatly reduce the latency because of less stages and efficient control signal generating algorithm In addition the proposed network processes the nature of high parallelism which could enable several groups of data to be cyclically shifted simultaneously The synthesis results using the 90 nm technology demonstrate that this architecture can be implemented with the gate count of 18 3k for WiMAX standard at the frequency of 600 MHz and 10 9k for WiFi standard at the frequency of 800 MHz

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • A Coverage area prediction method using theoretical BER formula for in-car MB-OFDM UWB communication

    Y. Watanabe, R. Kaneko, A. Yamakita, F. Maehara

    Proc. The 10th International Conference on ITS Telecommunications (ITST 2010)   TH1-3  2010.11  [Refereed]

  • The effectiveness of bit metric derivation method using residual CCI power in post-FFT type OFDM adaptive array

    Y. Wang, F. Maehara, F. Takahata

    Proc. 15th International OFDM Workshop 2010 (InOWo'10)     120 - 124  2010.09  [Refereed]

  • Coverage performance of 480Mbps MB-OFDM UWB in-car communication

    Y. Arai, R. Kaneko, F. Maehara

    Proc. 2010 Asia-Pacific Radio Science Conference (AP-RASC'10)   CBDEFK2-6  2010.09  [Refereed]

  • OFDM nonlinear distortion suppression scheme for MIMO system

    T. Arai, N. Kamiya, F. Maehara

    Proc. 2010 Asia-Pacific Radio Science Conference (AP-RASC'10)   CP-9  2010.09  [Refereed]

  • Coverage performance of MB-OFDM UWB in-car wireless communication

    Fumiaki Maehara, Ryouhei Kaneko, Akihiro Yamakita, Satoshi Goto

    2010 7th International Symposium on Communication Systems, Networks and Digital Signal Processing, CSNDSP 2010     417 - 421  2010.07  [Refereed]

     View Summary

    Recent years, increasing weight and deployment cost of complicated wire harness are revealing especially in a luxury car. Therefore, it is expected that in-car network is built by wireless communication having an excellent environment-compatibility, as well as wired network. In this paper, we investigate the applicability of multiband orthogonal frequency division multiplexing ultra-wideband (MB-OFDM UWB) to in-car wireless communication from the viewpoint of the coverage area and then describe the practical problems to be solved for in-car UWB wireless communication. © 2010 IEEE.

    DOI

    Scopus

    5
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  • Coverage area prediction method of extremely reliable in-car MB-OFDM UWB communication

    Ryouhei Kaneko, Akihiro Yamakita, Fumiaki Maehara

    IEEE Vehicular Technology Conference    2010.05  [Refereed]

     View Summary

    This paper proposes a coverage area prediction method for extremely reliable in-car MB-OFDM UWB communication. Since sensor and control networks inside a car require extremely high quality of service (QoS), it is almost impossible for computer simulations to provide very low bit error rate (BER). In the proposed approach, very low BER performance is obtained by approximating the simulated BER with simple exponential functions thanks to the fact that coded MB-OFDM UWB system does not theoretically introduce any error floor. In other words, once the simulated BER can be transformed into a simple mathematical formula such as exponential function, the coverage area can be predicted irrespective of the target QoS. By using this approach, we demonstrate the coverage area to satisfy the BER of 1 × 10-12.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • Permutation network for reconfigurable LDPC decoder based on banyan network

    Xiao Peng, Zhixiang Chen, Xiongxin Zhao, Fumiaki Maehara, Satoshi Goto

    IEICE Transactions on Electronics   E93-C ( 3 ) 270 - 278  2010.03  [Refereed]

     View Summary

    Since the structured quasi-cyclic low-density parity-check (QC-LDPC) codes tor most modern wireless communication systems include multiple code rates, various block lengths. and the corresponding different sizes of submatrices in parity check matrix (PCM), the reconfigurable LDPC decoder is desirable and the permutation network is needed to accommodate any Input number (IN) and shift number (SN) for cyclic shift In this paper we propose a novel permutation network architecture for the reconfigurable QC-LDPC decoders based on Banyan network We prove that Banyan network ha, the nonblocking property or cyclic shift when the IN is power of 2, and give the control signal generating algorithm Through introducing the bypass network, we put forward the nonblocking scheme for any IN and SN In addition, we present the hardware design of the control signal generator. which can greatly reduce the hardware complexity and latency The synthesis results using the TSMC 0 mu m pin library demonstrate that the proposed permutation network can be implemented with the area of 0 546 mm(2) and the frequency of 292 MHz

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • 伝搬路の相関性を考慮したMIMO-OFDM-SDMシステムにおける受信機構成

    吉原龍彦, 吉田真之, 前原文明, 高畑文雄, 小野寺毅, 卜部周二

    電子情報通信学会論文誌 B   J93-B ( 3 )  2010  [Refereed]

    J-GLOBAL

  • High parallel variation banyan network based permutation network for reconfigurable LDPC decoder

    Xiao Peng, Zhixiang Chen, Xiongxin Zhao, Fumiaki Maehara, Satoshi Goto

    Proceedings of the International Conference on Application-Specific Systems, Architectures and Processors     233 - 238  2010  [Refereed]

     View Summary

    Permutation network plays an important role in the reconfigurable QC-LDPC decoder for most modern wireless communication systems with multiple code rates and various code lengths. In this paper, we propose the variation Banyan network (VBN) based permutation network architecture for the reconfigurable QC-LDPC decoders and give the control signal generating algorithm for cyclic shift. Through introducing the bypass network, we put forward the nonblocking scheme for any input number and shift number. In addition, the optimized VBN is proposed for WiMAX and WiFi standard, which can shift at most 4 groups of input data, and greatly reduce the hardware complexity. The synthesis results using the 90nm technology demonstrate that the proposed permutation network can be implemented with the gate count of 18.3k and the frequency of 600 MHz. © 2010 IEEE.

    DOI

    Scopus

    12
    Citation
    (Scopus)
  • An adaptive SC-FDE transmission enhancing frequency diversity benefit

    Ryouhei Kaneko, Yunhan Wang, Fumiaki Maehara

    IEEE International Symposium on Spread Spectrum Techniques and Applications     45 - 49  2010  [Refereed]

     View Summary

    This paper proposes an adaptive single-carrier modulation with frequency domain equalization (SC-FDE) scheme further enhancing frequency diversity benefit. We have so far proposed the periodic spectrum transmission realized by the even-numbered time domain samples, which further improves the bit error rate (BER) of SC-FDE in severe frequency selective fading channels. However, in frequency non-selective fading channels, the periodic spectrum transmission provides worse BER than the traditional non-periodic transmission. Therefore, the proposed adaptive transmission chooses the appropriate transmission mode by comparing the error vector magnitudes (EVM) of the periodic and non-periodic transmissions. Moreover, since the EVM is measured by the CAZAC-based pilot signals used for channel estimation, additional redundancy is not needed any more. Numerical results show that the proposed adaptive scheme always provides the best performance irrespective of the frequency selectivity in channels while its frequency selectivity gives some BER degradation in the periodic and non-periodic transmissions. © 2010 IEEE.

    DOI

    Scopus

    3
    Citation
    (Scopus)
  • Nonlinear distortion avoidance employing symbol-wise transmit power control for OFDM transmission

    N. Kamiya, F. Maehara

    Proc. 14th International OFDM Workshop 2009 (InOWo'09)   223   223 - 227  2009.09  [Refereed]

    CiNii

  • Performance comparison of bit metric derivation method for OFDM adaptive array

    Y. Wang, F. Maehara

    Proc. ITC-CSCC2009     916 - 919  2009.07  [Refereed]

    CiNii

  • Closed form expression for BER performance of Decode-and-Forward relaying over different time selective fading channel

    S. Uchida, F. Sasamori, F. Maehara

    Proc. ITC-CSCC2009     1354 - 1357  2009.07  [Refereed]

  • Theoretical derivation of bit error rate in MB-OFDM UWB system

    Ryouhei Kaneko, Fumiaki Maehara

    2009 Wireless Telecommunications Symposium, WTS 2009     120 - 124  2009  [Refereed]

     View Summary

    This paper derives the theoretical bit error rate (BER) of the multiband orthogonal frequency division multiplexing (MB-OFDM) system for ultra wideband (UWB) communication. The proposed derivation takes into account the fading correlation caused by time and frequency spreading, which is one of the most significant factors in MB-OFDM UWB system. Moreover, the proposed formula gives consideration to the frequency characteristics of propagation loss that are not negligible in UWB systems. The theoretical results by the proposed approach are compared with the computer simulation results in order to confirm the validity of the proposed derivation.

    DOI

    Scopus

    2
    Citation
    (Scopus)
  • Simple series form formula of BER performance of M-ary QAM/OFDM signals over nonlinear fading channels

    Yuichiro Goto, Akihiro Yamakita, Fumiaki Maehara

    Lecture Notes in Electrical Engineering   41 LNEE   281 - 290  2009  [Refereed]

     View Summary

    This paper proposes a simple series form formula of the bit error rate (BER) for M-ary QAM/OFDM signals under nonlinear fading channels. In the proposed derivation, the effect of the nonlinear distortion due to the soft envelope limiter is approximated by the additive Gaussian noise with the variance equal to the power of the clipped portion of the composite waveform. Since the BER is represented by the simple series form formula, the proposed approach frees us from the time-consuming computer simulations. Moreover, the proposed formula is applicable to arbitrary M-ary quadrature amplitude modulations (QAM). The validity of the proposed approach is confirmed by the agreement with the computer simulation results with parameters of the input back-off (IBO) and average CNR. © 2009 Springer-Verlag.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • Simple series form formula of BER performance for DBPSK/OFDM signals in time selective nonlinear fading channels

    Akihiro Yamakita, Yuichiro Goto, Fumiaki Maehara

    IEEE Pacific RIM Conference on Communications, Computers, and Signal Processing - Proceedings     205 - 210  2009  [Refereed]

     View Summary

    This paper proposes a simple series form formula of the bit error rate (BER) for DBPSK/OFDM signals under time selective nonlinear fading channels. The proposed approach derives the theoretical BER in the presence of nonlinear distortion and time selective fading effects. Since the BER is represented by the simple series form formula, the proposed approach frees us from the time-consuming computer simulations. The validity of the proposed approach is confirmed by the agreement with the computer simulation results under various kinds of system parameters such as the input back-off (IBO) and the normalized maximum Doppler frequency.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • Performance of bit metric derivation method using CCI signals for OFDM adaptive array antenna

    Yunhan Wang, Fumiaki Maehara, Fumio Takahata, Takashi Onodera, Shuuji Urabe

    2009 15th Asia-Pacific Conference on Communications, APCC 2009     174 - 177  2009  [Refereed]

     View Summary

    This paper proposes a bit metric derivation method for OFDM adaptive array in combination with channel coding. In the proposed approach, post-FFT processing is adopted as an OFDM adaptive array architechture and the bit metric required for channel coding is derived considering the effect of the residual CCI signals in the array output of each sub-channel. The transmission performance is evaluated in the presence of severe CCI channels by means of the computer simulations and the effectiveness of the proposed approach is demonstrated compared with the traditional bit metric method. ©2009 IEEE.

    DOI

    Scopus

  • Coverage Area Prediction of In-car Wireless Communications Employing MB-OFDM UWB Systems

    Ryouhei Kaneko, Fumiaki Maehara

    ITST: 2009 9TH INTERNATIONAL CONFERENCE ON INTELLIGENT TRANSPORT SYSTEMS TELECOMMUNICATIONS     667 - 672  2009  [Refereed]

     View Summary

    This paper investigates the coverage area of MB-OFDM UWB system under in-car propagation environments. The coverage area of each transmission speed to satisfy a certain quality of service (QoS) is predicted by combining the transmission performance of MB-OFDM UWB system with actual in-car propagation characteristics. Since the transmission performance of MB-OFDM strongly depends on the delay spread, the coverage area prediction takes into account the delay spread based on the distance between the transmitter and the receiver, as well as the propagation loss. The coverage area in the occupied scenario with four passengers is compared with that in the empty scenario. Computer simulation results show that the coverage area in the occupied scenario turns out to be much smaller than that in the empty scenario due to the large propagation loss and the decrease in the delay spread.

  • New bit metric derivation method for adaptive array antenna with channel coding

    F. Maehara, F. Takahata

    Proc. WPMC 2008    2008.09  [Refereed]

    CiNii

  • 同一チャネル干渉下におけるCOFDMシステム用軟判定ゆう度情報生成法

    平明徳, 冠美恵子, 前原文明, 高畑文雄

    電子情報通信学会論文誌B   J91-B ( 5 ) 575 - 584  2008.05  [Refereed]

    J-GLOBAL

  • 適応フィルタによるガードバンドの外挿処理を施したOFDM用周波数領域伝搬路推定法

    池田裕司, 吉田晴人, 平明徳, 前原文明, 高畑文雄

    電子情報通信学会論文誌B   J91-B ( 4 ) 450 - 456  2008.04  [Refereed]

    J-GLOBAL

  • Simple series form formula of BER performance for DQPSK/OFDM signals in comprehensive nonlinear fading channels

    Fumiaki Maehara, Akinori Taira, Fumio Takahata

    2008 IEEE Radio and Wireless Symposium, RWS     37 - 40  2008  [Refereed]

     View Summary

    This paper proposes a simple series form formula of the bit error rate (BER) for DQPSK/OFDM with differential detection under comprehensive nonlinear fading channels. The proposed approach aims to derive the theoretical BER in the presence of both the nonlinear distortion and the inter-symbol interference (ISI) which are the essential factors in evaluating the comprehensive performance of OFDM signals. Since the proposed formula is composed of the simple series form expression, the time-consuming simulations could be avoided. The validity of the proposed approach is confirmed by the agreement with the computer simulation results under various kinds of system parameters such as the input-backoff (IBO) and the multipath delay.

    DOI

    Scopus

    3
    Citation
    (Scopus)
  • A soft bit metric calculation method against co-channel interference in COFDM systems

    A. Taira, M. Kammuri, F. Maehara, F. Takahata

    Proc. WPMC 2007     828 - 832  2007.12  [Refereed]

  • OFDM link adaptation scheme using periodic signals under inter-symbol interference channels

    F. Maehara, A. Taira, F. Takahata

    Proc. 12th International OFDM-Workshop 2007 (InOWo'07)     321 - 325  2007.08  [Refereed]

  • Periodic spectrum transmission for single-carrier transmission frequency-domain equalization

    Fumiaki Maehara, Satoshi Goto, Fumio Takahata

    IEICE Transactions on Communications   E90-B ( 6 ) 1407 - 1414  2007.06  [Refereed]

     View Summary

    This paper proposes a frequency diversity scheme using only even-numbered samples for single-carrier transmission with frequency-domain equalization (SC-FDE). In the proposed scheme, a periodical frequency spectrum generated by using only even-numbered samples in the time domain provides the frequency redundancy, which is utilized for frequency diversity. Moreover, in order to avoid the data rate reduction due to the decrease in the samples within one block, the high-level modulation is applied to each sample and the transmitting power of each sample can be doubled for the equivalent power transmission instead. Computer simulation results show that the proposed scheme provides a steeper BER curve than the typical SC-FDE over frequency selective fading channels, while the typical SC-FDE is more favorable than the proposed scheme over flat fading channels. Moreover, the proposed scheme still retains its characteristic even when channel estimation and channel coding are additionally taken into account.

    DOI

    Scopus

    2
    Citation
    (Scopus)
  • Channel estimation and interference cancellation for MIMO-OFDM systems

    Van Duc Nguyen, Matthias Pätzold, Fumiaki Maehara, Harald Haas, Minh Viet Pham

    IEICE Transactions on Communications   E90-B ( 2 ) 277 - 290  2007.02  [Refereed]

     View Summary

    This paper proposes a new channel estimation method and a new interference cancellation scheme for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems in the presence of intersymbol interference (ISI). The proposed channel estimation method uses special training sequences (TSs) to have a desirable crest-factor of the transmitted training signal, and to prevent the influence of ISI on the channel estimation performance. By using the recommended training sequences, the ill-conditioned problem of the least square (LS) filter integrated in the proposed channel estimator can be avoided. The proposed interference cancellation scheme uses the estimated channel coefficients and the channel state information (CSI) to reproduce the interference components, which are then iteratively cancelled from the received signals. To reduced the error-floor of the demodulated symbols using for the calculations of the interference components, the so-called remodulation technique is also included in the proposed interference cancellation scheme. Simulation results show that the proposed channel estimation method outperforms conventional channel estimation methods, especially in the presence of ISI and if the signal-to-noise ratio (SNR) is larger than 15 dB. The combination of the proposed method with a space-time block code (STBC) to combat the interference influences results in an excellent system performance in terms of symbol error ratio (SER), In comparison with a STBC MIMO-OFDM system with sufficient guard interval (GI), this combination gains 1.52 dB of SNR at the same SER of 1.1 center dot 10(-6) even after performing only one iteration of interference cancellation.

    DOI

    Scopus

    13
    Citation
    (Scopus)
  • Iterative decision feedback channel estimation using metrics comparison for burst mode COFDM transmission

    Haruhito Yoshida, Fumiaki Maehara, Fumio Takahata

    IEICE Transactions on Communications   E89-B ( 12 ) 3475 - 3478  2006.12  [Refereed]

     View Summary

    This letter presents an iterative decision feedback channel estimation scheme for burst mode COFDM transmission. The feature of the proposed scheme is that the channel estimation using metrics comparison is applied to the initial stage of the iterative mechanism, which makes it possible to provide a reliable data stream at the initial stage. Computer simulation results show that the proposed approach provides better BER than the traditional iterative decision feedback channel estimation scheme irrespective of the number of iterations.

    DOI

    Scopus

  • Frequency-domain channel estimation scheme using RLS-Based guard band channel frequency response extrapolation for OFDM systems

    Y. Ikeda, H. Yoshida, F. Maehara, F. Takahata

    Proc. WPMC 2006     302 - 306  2006.09  [Refereed]

  • Adaptive forgetting factor control scheme for decision feedback channel estimation in COFDM transmission

    H. Yoshida, F. Maehara, F. Takahata

    Proc. 11th International OFDM-Workshop 2006 (InOWo'06)     218 - 222  2006.08  [Refereed]

  • Periodic spectrum transmission for single-carrier frequency-domain equalization employing space-time transmit diversity

    Haruhito Yoshida, Tasuku Kuriyama, Fumiaki Maehara, Fumio Takahata

    2006 1st International Symposium on Wireless Pervasive Computing   2006   1 - 5  2006  [Refereed]

     View Summary

    This paper presents the periodic spectrum transmission for single-carrier frequency-domain equalization (SC-FDE) employing space-time transmit diversity (STTD). The proposed scheme utilizes only even-numbered samples within a time-domain data block to create a periodical spectrum which provides frequency redundancy. Frequency redundancy is used for subchannel combining before FDE, which alleviates the loss of orthogonality caused by FDE under frequency selective fading channels. Therefore, the proposed scheme has an advantage of enhancing the overall frequency diversity benefit while keeping the space diversity benefit achieved by STTD. Computer simulation results show that the proposed scheme outperforms the typical SC-FDE using full samples over relatively severe frequency selective fading channels when applying 1-bit/sample transmission.

  • Inter-symbol interference suppression scheme using periodic signal waveform for fixed-rate COFDM systems

    Fumiaki Maehara, Satoshi Goto, Fumio Takahata

    IEEE Vehicular Technology Conference   5   2339 - 2343  2006  [Refereed]

     View Summary

    This paper proposes an inter-symbol interference (ISI) suppression scheme using the periodic signal waveform for fixed-rate coded OFDM systems. In this scheme, the periodic signal waveform composed of the even-numbered sub-carrier group is used for extending the guard interval, and the odd-numbered sub-carrier group is also enable to be available by means of frequency conversion in order to realize the sub-carrier group selection. This paper mainly focuses on the combining effect of the sub-carrier group selection and the channel coding scheme in the inter-symbol interference (ISI) condition. Computer simulation result show that the proposed scheme has the great potential to create the combined frequency diversity effect without the error floor even in the severe ISI condition.

  • Performance of periodic spectrum transmission for single-carrier with frequency-domain equalization using channel coding

    Tasuku Kuriyama, Haruhito Yoshida, Akinori Taira, Fumiaki Maehara, Fumio Takahata

    HUT-ICCE 2006 First International Conference on Communications and Electronics, Proceedings   PART 1   96 - 101  2006  [Refereed]

     View Summary

    This paper presents the performance of periodic spectrum transmission for single-carrier with frequency-domain equalization (SC-FDE) using channel coding. So far, we have proposed periodic spectrum transmission and showed the effectiveness of enhancing a frequency diversity benefit compared with the typical case when adopting a low rate transmission such as 1-bit/sample. In this paper, the impact of channel coding on the proposed scheme is intensively discussed compared with coded OFDM (COFDM) as well as the typical SC-FDE. This is because OFDM is sure to be the promising approach when taking channel coding into account. Computer simulation results show that the proposed scheme 1-bit/sample transmission outperforms COFDM irrespective of coding rate.

    DOI

    Scopus

  • Fading Compensation Scheme Using Metrics Comparison for Burst Mode COFDM Transmission Using Double-Ended Pilot Symbols

    吉田晴人, 前原文明, 高畑文雄

    電子情報通信学会論文誌 B   J88-B ( 10 ) 2119 - 2122  2005.10  [Refereed]

     View Summary

    This paper proposes a fading compensation scheme for burst mode COFDM transmission based on the pilot symbols inserted at both ends. The feature of the proposed scheme is that the decision variables are determined by the metrics based on the two-way decision feedback channel estimation and compensation. Numerical results given by computer simulation showed the effectiveness of the proposed scheme.

    CiNii J-GLOBAL

  • Closed form expression of average bit error rate for TDD transmit diversity employing maximal ratio combining

    Fumiaki Maehara

    IEICE Transactions on Communications   E88-B ( 5 ) 2136 - 2141  2005.05  [Refereed]

     View Summary

    This paper presents a closed form expression of an exact average bit error rate (BER) for a time-division duplex (TDD) transmit diversity scheme employing maximal ratio combining (MRC) over time selective flat Rayleigh fading channels. In the proposed analysis, the feed back delay which degrades the BER performance is taken into account. The results are generally applicable to an arbitrary modulation scheme, as well as an arbitrary number of transmitting branches. To confirm the validity of the proposed analysis, the theoretical results are compared with the simulated ones.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • A dual-mode decision feedback channel estimation over fast fading channels for COFDM transmission

    H. Yoshida, F. Maehara, F. Takahata

    Proc. IASTED International Conference on Networks and Communication Systems (NCS 2005)     457 - 461  2005.04  [Refereed]

  • Series expression of BER performance for DQPSK/OFDM signals employing selection combining diversity reception over nonlinear fading channels

    Fumiaki Maehara

    IEEE Vehicular Technology Conference   61 ( 2 ) 1007 - 1011  2005  [Refereed]

     View Summary

    This paper presents an analytical expression of the bit error rate (BER) performance for DQPSK/OFDM signals using selection combining diversity reception under nonlinear fading channels. In the proposed approach, the soft envelope limiter is assumed to be a peak limited devices and the effects of nonlinear distortion are treated as the additive Gaussian noise with zero mean and suitable variance. This approach has an advantage of reducing the computational cost dramatically compared with the computer simulation because the proposed formula for predicting the BER performance consists of a simple series form. The theoretical results show perfect agreement with those obtained by the computer simulation. © 2005 IEEE.

  • Inter-symbol interference suppression employing sub-carrier group selection for OFDM-TDD transmit diversity

    Fumiaki Maehara, Takeshi Ikenaga, Fumio Takahata, Satoshi Goto

    2nd International Symposium on Wireless Communications Systems 2005, ISWCS 2005 - Conference Proceedings   2005   515 - 519  2005  [Refereed]

     View Summary

    This paper proposes an inter-symbol interference (ISI) suppression scheme using the sub-carrier group selection for orthogonal frequency division multiplexing (ORM) time division duplex (TDD) transmit diversity. Although transmit diversity is quite effective in improving the transmission performance, the ISI due to the long multipath delays causes the error floor and leads to a loss of the space diversity benefit. To cope with this degradation, the periodic time domain waveform obtained by the even-numbered sub-carrier group is used for the extension of the guard interval. Moreover, the odd-numbered sub-carrier group is also applied to exploit the frequency diversity benefit, which is realized by carrying out the simple frequency conversion at the receiver. To keep the constant transmission rate even in the sub-carrier group transmission, the high-level modulation scheme with power enhancement is applied. The computer simulation results show that the proposed scheme not only prevents the error floor due to the ISI but also achieves the space and frequency diversity benefit without the extension of the guard interval.

    DOI

    Scopus

  • Performance comparison of carrier interferometry OFDM and OFDM using space diversity reception and channel coding

    Fumiaki Maehara, Hans Peter Kuchenbecker

    IEICE Transactions on Communications   E87-B ( 12 ) 3801 - 3808  2004.12  [Refereed]

     View Summary

    This paper presents a performance comparison between carrier interferometry coded OFDM (CI/COFDM) and typical coded OFDM (COMM) using multiple receive antennas. The feature of CI/COFDM with diversity reception is to combine the time diversity benefit introduced by channel coding with the frequency and space diversity benefits created by frequency-domain equalization (FDE). Simulation results for QPSK showed that, at the perfect channel estimation, CI/COFDM outperforms COMM under frequency and time selective fading channels because of the powerful time diversity benefit introduced by channel coding with time interleaving. However, at the imperfect channel estimation, this advantage of CI/COFDM over COFDM becomes very limited.

  • Inter-symbol interference suppression scheme employing sub-carrier group selection for fixed-rate OFDM systems

    F. Maehara, H.-P. Kuchenbecker

    Proc. 9th International OFDM-Workshop 2004 (InOWo'04)    2004.09  [Refereed]

    CiNii

  • Frequency diversity application to single-carrier transmission with frequency-domain equalization

    F. Maehara, H.-P. Kuchenbecker

    Proc. WPMC 2004   Vol.1   324 - 328  2004.08  [Refereed]

    CiNii

  • Inter-symbol interference suppression scheme using even-numbered sub-carriers for fixed-rate OFDM systems

    Fumiaki Maehara, Fumihito Sasamori, Fumio Takahata

    IEICE Transactions on Communications   E87-B ( 4 ) 866 - 872  2004.04  [Refereed]

     View Summary

    This paper proposes an inter-symbol interference (ISI) suppression scheme using only the even-numbered sub-carriers for the fixed-rate OFDM systems with the 2-dimensional modulation. The proposed scheme is based on the principle that the first half of the waveform in the time domain is the same as the second half when an OFDM symbol is composed of only the even-numbered sub-carriers. The feature of the proposed scheme is that, in the case of the maximum multipath delay beyond the duration of the guard interval, the OFDM symbol with only the even-numbered sub-carriers is transmitted in order to generate the extended virtual guard interval and that the high-level modulation with the sub-carrier power enhancement is applied to achieve the constant data rate. In addition, at the receiver, only the second half of the OFDM symbol is used for the FFT processing to avoid the ISI. Moreover, the condition of the maximum multipath delay is notified to the transmitter by using the feedback channel. Numerical results given by computer simulation showed that the proposed scheme provides far better bit error rate (BER) performance than the traditional OFDM transmission using all sub-carriers under the multipath delay beyond the duration of the guard interval.

  • A novel design of transmit diversity using space-time block Ccoding for coded carrier interferometry OFDM

    F. Maehara, H.-P. Kuchenbecker

    Proc. First IEEE VTS Asia Pacific Wireless Communications Symposium (APWCS)     98 - 102  2004.01  [Refereed]

  • Performance of space diversity reception for coded carrier interferometry OFDM

    Fumiaki Maehara, Hans Peter Kuchenbecker

    IEEE Vehicular Technology Conference   59 ( 1 ) 520 - 524  2004  [Refereed]

     View Summary

    Carrier interferometry orthogonal frequency division multiplexing (CI/OFDM) creates a full frequency diversity benefit without bandwidth expansion. In this paper, we present the bit error rate (BER) performance of carrier interferometry coded OFDM (CI/COFDM) employing multiple receive antennas over the frequency and time selective fading channels. The main feature of this architecture is to combine the time diversity benefit achieved by channel coding with the space and frequency diversity benefits exploited by CI/OFDM using space diversity reception. We also compare the BER performance of this architecture with that of typical coded OFDM (COFDM) employing subchannel space combining diversity reception. Numerical results obtained by the computer simulation showed that CI/OFDM outperforms OFDM when applying both space diversity reception and channel coding.

  • Approximate expression of BER performance in DS-CDMA systems over multi-path fading channels

    Fumihito Sasamori, Shiro Handa, Fumiaki Maehara, Fumio Takahata, Shinjiro Oshita

    IEICE Transactions on Communications   E86-B ( 8 ) 2523 - 2528  2003.08  [Refereed]

     View Summary

    The transmission quality in mobile wireless communication systems is affected by not only AWGN but also multi-path fading. Particularly, the Doppler frequency, the delay spread and the Rician factor have a great influence upon the quality over fading channels. This letter proposes the approximate equation for easily calculating the BER in DS-CDMA systems over multi-path fading channels. The validity of the approximate equation is confirmed from the fact that the BER calculated by the equation coincides with that by the computer simulation.

  • Inter-symbol interference suppression scheme using even-numbered sub-carriers for OFDM systems

    F. Maehara, F. Sasamori, F. Takahata

    Proc. IST Mobile & Wireless Communications Summit 2003   Vol. 1   83 - 87  2003.06  [Refereed]

    CiNii

  • Approximate equation of average bit-error rate in DS-CDMA systems over fading channels

    Fumihito Sasamori, Fumiaki Maehara, Shiro Handa, Shinjiro Oshita, Fumio Takahata

    IEEE Transactions on Communications   51 ( 3 ) 409 - 415  2003.03  [Refereed]

     View Summary

    The transmission quality in mobile wireless communications is affected not only by additive white Gaussian noise, but also by multipath fading, which drastically changes the amplitudes and phases of wireless signals. It is one of the key themes in direct-sequence code-division multiple-access systems to evaluate average bit error rate (BER) performances as parameters of the Doppler frequency, the delay profile, the number of simultaneous access users, and so on. This paper proposes the approximate equation for easily calculating the average BER over fading channels (multiray fading models). The performance evaluations are carried out in the two-ray model, the IMT2000 model, and the COST207 model. It is confirmed from the coincidence of approximate results with computer simulation results that the proposed approach is applicable to a variety of parameters.

    DOI

    Scopus

    3
    Citation
    (Scopus)
  • Linear predictive maximal ratio combining transmitter diversity for OFDM-TDMA/TDD systems

    F Maehara, F Sasamori, F Takahata

    IEICE TRANSACTIONS ON COMMUNICATIONS   E86B ( 1 ) 221 - 229  2003.01  [Refereed]

     View Summary

    This paper proposes a 2-dimensional linear propagation prediction (LPP) in maximal ratio combining (MRC) transmitter diversity for orthogonal frequency division multiplexing (OFDM) time division multiple access-time division duplex (TDMA/TDD) systems in order to overcome the degradation of the transmission performance due to the fast fading or the TDD duration. In the proposed scheme, the downlink channel condition of each sub-channel is predicted by interpolating the uplink fading fluctuation with both the amplitude and phase, and the predicted downlink channel condition is used for the weighting factor to employ MRC transmitter diversity. Numerical results obtained by the computer simulation show that the proposed 2-dimensional LPP with the second-order Lagrangeis interpolation predicts the downlink channel condition accurately under the fast fading or the long TDD duration. Moreover, in such a condition, the proposed LPP provides far better performance than the conventional I-dimensional LPP.

  • Approximate equation of bit error rate in OFDM systems over specular multipath fading channels

    Fumihito Sasamori, Atsuhiro Yamano, Shiro Handa, Fumiaki Maehara, Fumio Takahata, Shinjiro Oshita

    IEEE Wireless Communications and Networking Conference, WCNC   3   2096 - 2101  2003  [Refereed]

     View Summary

    Orthogonal frequency division multiplexing (OFDM) systems can avoid the effect of multipath fading by absorbing delayed waves into guard interval. But as the effect of delayed waves over guard interval becomes stronger, it causes the bit error rate (BER) performance in OFDM systems to be more degraded. This paper proposes the approximate derivation method of the BER in DQPSK/OFDM systems over frequency selective fading channels. In this study, we will derive the approximate equation of the BER with differential coding/differential detection in the time domain. We confirm that the BER derived from the proposed approximate equation coincides with that by computer simulation even when such parameters as the Doppler frequency shift, the delay spread, the Rician factor and so on are varied.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • OFDM伝送におけるSIR重み付け受信ダイバーシチ

    前原文明, 栗田明, 笹森文仁, 高畑文雄

    電子情報通信学会論文誌(B)   Vol. J85-B ( No. 12 ) 2399 - 2403  2002.12  [Refereed]

    CiNii

  • 高速フェージング環境下におけるOFDM伝送を対象としたフェージング補償方式

    吉田晴人, 前原文明, 笹森文仁, 高畑文雄

    電子情報通信学会論文誌(B)   Vol. J85-B ( No. 11 ) 1874 - 1883  2002.11  [Refereed]

    CiNii

  • Analytical Approximate Derivation of BPSK-BER Characteristics in Adjacent Two Channels’ Interference.

    山田智紀, 斎藤朋彰, 前原文明, 高畑文雄

    電子情報通信学会論文誌 B   J85-B ( 3 ) 417 - 423  2002.03  [Refereed]

    J-GLOBAL

  • Theoretical derivation method of bit error rate in TDMA/TDD transmitter diversity under cochannel interference

    Fumiaki Maehara, Fumihito Sasamori, Fumio Takahata

    IEICE Transactions on Communications   E85-B ( 3 ) 663 - 666  2002.03  [Refereed]

     View Summary

    Transmitter diversity is a powerful technique to improve the transmission quality of downlink in microcellular mobile communications systems. Under cochannel interference (CCI) at the base station (BS), the transmitter diversity is not necessarily effective, because the desired-plus-interference signal power used as a criterion of downlink branch selection is not always relative to the downlink propagation condition. This paper proposes the theoretical derivation of bit error rate (BER) performance in the transmitter diversity under CCI occurring at BS, as parameters of average SIR at BS, normalized Doppler frequency, and so on. It is confirmed from the correspondence of theoretical results with simulation results that the proposed theoretical approach is applicable to the CCI environments at BS.

  • Approximate equation of bit error rate in DQPSK/OFDM systems over fading channels

    F. Sasamori, H. Umeda, S. Handa, F. Maehara, F. Takahata, S. Ohshita

    Proc. European Wireless 2002   Vol. 1   602 - 607  2002.02  [Refereed]

  • A Compensating Method based on Recursive Processing of Nonlinear Distortion for OFDM.

    細野博之, 細川泰輔, 前田毅, 前原文明, 高畑文雄

    電子情報通信学会論文誌 B   J85-B ( 1 ) 9 - 19  2002.01  [Refereed]

    J-GLOBAL

  • Theoretical derivation method of bit error rate in maximal ratio combining TDD transmitter diversity

    F. Maehara, F. Sasamori, F. Takahata

    2002 4th International Workshop on Mobile and Wireless Communications Network, MWCN 2002     61 - 65  2002  [Refereed]

     View Summary

    This paper proposes a theoretical derivation method of the BER performance in maximal ratio combining (MRC) time division duplex (TDD) transmitter diversity, as parameters of Doppler frequency and so on. The proposed theoretical approach can be applied not only to single-carrier transmission under flat fading but also to orthogonal frequency division multiplexing (OFDM) under frequency selective fading. In this paper, we choose OFDM transmission, in addition to single-carrier transmission, as an example of the system model to obtain the numerical results, and the comparison between the theoretical results and the simulated ones is demonstrated to confirm the validity of the proposed theoretical approach.

    DOI

    Scopus

  • Effect of Maximal Ratio Combining based on Desired Signal Level to TDMA/TDD Transmitter Diversity.

    前原文明, 高畑文雄

    電子情報通信学会論文誌 B   J84-B ( 11 ) 2062 - 2066  2001.11  [Refereed]

    J-GLOBAL

  • Linear predictive maximal ratio combining transmitter diversity for broadband wireless communications systems

    F. Maehara, F. Takahata

    Proc. WPMC 2001   2   1065 - 1070  2001.09  [Refereed]

    CiNii

  • New derivation method of BPSK bit error rate performance in cochannel interference

    F. Maehara, T. Saito, F. Takahata

    IEICE Transactions on Communications   E84-B ( 9 ) 2701 - 2704  2001.09  [Refereed]

     View Summary

    New method for deriving the bit error rate (BER) of the BPSK signal in the cochannel interference is proposed, which utilizes the eye pattern of the interference signal, and is different from the conventional method based on the conversion of the interference components to thermal noise. The validity of the proposed derivation method is quantitatively evaluated in terms of the BER performance and is confirmed by comparing with the results obtained by the computer simulation.

  • A transmitter diversity with desired signal power selection using matched filter

    Fumiaki Maehara, Fumihito Sasamori, Fumio Takahata

    IEICE Transactions on Communications   E84-B ( 2 ) 255 - 262  2001.02  [Refereed]

     View Summary

    The paper proposes a transmitter diversity scheme with a desired signal selection for the mobile communication systems in which the severe cochannel interference (CCI) is assumed to occur at the base station. The feature of the proposed scheme is that the criterion of the downlink branch selection is based on the desired signal power estimated by the correlation between the received signal and the unique word at the matched filter. Moreover, the unique word length control method according to the instantaneous SIR is applied to the proposed scheme, taking account of the uplink transmission efficiency. Computer simulation results show that the proposed scheme provides the better performance than the conventional transmitter diversity in the seven CCI environments, and that the unique word length control method applied to the proposed scheme decreases the unique word length without the degradation of the transmission quality, comparing with the fixed unique word length method.

  • SIR weighting combining diversity using matched filter for personal communication systems

    Fumiaki Maehara, Osamu Nakamura, Hitoshi Takanashi

    Wireless Personal Communications   15 ( 3 ) 181 - 197  2000.12  [Refereed]

     View Summary

    We propose a novel SLR weighting postdetection combining diversity scheme with a new accurate SIR estimation method. The SIR is estimated and used as the weighting factor to compensate severe cochannel interference, one of the most important issues for PCS in terms of frequency utilization. The improvement offered by the proposal depends on SIR estimation accuracy. The SIR is, in this paper, estimated by a matched filter where the auto-correlation between received signal and unique word is calculated. Computer simulations confirm that the SIR of each diversity branch can be estimated easily and accurately by the proposed SIR estimation method. The proposed diversity scheme achieves a performance very close to that of ideal SINR weighting diversity under Rayleigh fading with severe cochannel interference. When average SIR = 10 dB and the number of branches (L) = 4, the proposed diversity scheme lowers the required E-b/N-0 by 5 dB at BER = 1 x 10(-3) compared to conventional maximal ratio combining diversity. This paper also presents the unique word length required to realize adequate performance, i.e., robustness against high-pitch Rayleigh fading.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • Derivation Method of BER Performance in Adjacent Channel Interference and Cochannel Interference of PSK signals

    T. Yamada, D. Ikuta, F. Maehara, F. Takahata

    Proc. APCC 2000   Vol. 2   1102 - 1106  2000.11  [Refereed]

    CiNii

  • SIR Weighting Combining Diversity for Digital Mobile Communications.

    前原文明, 笹森文仁, 高畑文雄

    電子情報通信学会論文誌 B   J83-B ( 10 ) 1374 - 1380  2000.10  [Refereed]

    J-GLOBAL

  • Theoretical Performance of Bit Error Rate in TDMA/TDD Transmitter Diversity under Cochannel Interference

    F. Maehara, F. Sasamori, F. Takahata

    Proc. ISAP 2000   Vol. 4   1489 - 1492  2000.08  [Refereed]

    CiNii

  • Approximate Derivation of Average Bit Error Rate in DS-CDMA Systems under Frequency Selective Rayleigh Fading Environment.

    笹森文仁, 前原文明, 高畑文雄

    電子情報通信学会論文誌 B   J83-B ( 7 ) 960 - 969  2000.07  [Refereed]

    J-GLOBAL

  • New derivation methods of BER performance in channel interference of PSK signals

    Fumiaki Maehara, Tomoaki Saito, Fumio Takahata

    IEEE International Conference on Personal Wireless Communications     123 - 127  2000  [Refereed]

     View Summary

    New methods for deriving the bit error rate (BER) in the cochannel interference and the adjacent channel interference am proposed, which utilize the eye pattern of the interference signal and the probability density function of components in interference signals, respectively, and are different from the conventional method based on the conversion of the interference components to thermal noise. These methods are quantitatively evaluated and confirmed as the effective approach in terms of BER performance by the comparison between the results calculated by these methods and the results obtained by the experiment and computer simulation.

  • 16値QAM変調方式を適用した広帯域陸上移動通信用復調器

    境田博, 前原文明, 高畑文雄

    電子情報通信学会論文誌(B-II)   Vol.J79-B-II ( No. 8 ) 431 - 440  1996.08  [Refereed]

    CiNii

▼display all

Books and Other Publications

  • ディジタル無線通信入門

    高畑文雄, 前原文明, 笹森文仁

    培風館  2002.06

Presentations

  • 無線通信シミュレーションのための基礎理論

    前原文明

    電子情報通信学会大会講演論文集(CD-ROM) 

    Presentation date: 2016

    Event date:
    2016
     
     
  • BS-2-6 Study on Packet Transmission Technique for Non-linear MU-MIMO Transmission

    TOMEBA Hiromichi, YOSHIMURA Tomoki, ONODERA Takashi, MAEHARA Fumiaki, TAKAHATA Fumio

    Proceedings of the Society Conference of IEICE 

    Presentation date: 2015.08

    Event date:
    2015.08
     
     
  • AS-1-4 Coverage Area Performance of In-car MB-OFDM UWB Communication

    YAMAKITA Akihiro, WATANABE Yuki, KANEKO Ryouhei, MAEHARA Fumiaki

    Proceedings of the Society Conference of IEICE 

    Presentation date: 2010.08

    Event date:
    2010.08
     
     
  • Applicability of MB-OFDM UWB System to In-car Wireless Communication

    MAEHARA Fumiaki, KANEKO Ryouhei, YAMAKITA Akihiro

    IEICE technical report  The Institute of Electronics, Information and Communication Engineers

    Presentation date: 2010.02

    Event date:
    2010.02
     
     

     View Summary

    Recent years, increasing weight and deployment cost of complicated wire harness is revealing especially in a luxury car. Therefore, it is expected that in-car network is built by wireless communication having an excellent environment-compatibility, as well as wired network. In this report, we investigate the applicability of MB-OFDM UWB to in-car wireless communication from the viewpoint of the coverage area and then describe the practical problems to be solved for in-car UWB wireless communication.

Research Projects

  • 複数UCAを用いたOAM多重伝送におけるモード間干渉抑圧と容量拡大に関する研究

    日本学術振興会  科学研究費助成事業

    Project Year :

    2022.04
    -
    2025.03
     

    前原 文明, 齋藤 周平

  • 直交多元接続との連携による非直交多元接続方式の特性改善に関する研究

    Project Year :

    2019.04
    -
    2022.03
     

     View Summary

    本研究課題では,2020年に我が国が世界に先駆けて導入を目指す第5世代移動通信システム(5G)の中核技術である非直交多元接続(NOMA)を取り上げ,ユーザ間のチャネル利得差が小さい場合にその適用効果が減少する問題をNOMAと直交多元接続(OMA)の帯域内同時利用により克服するとともに,今後の無線サービスの多様化を見据え,ユーザの伝搬路情報だけでなく,多様な要求スループットも考慮したリソース割当てを行う方式を提案する.本提案方式により,NOMAのシステム容量の向上が図れるだけでなく,多様なモバイルトラヒックを効率的に収容できることから,5G以降のモバイルネットワークのさらなる高度化が期待できる.本研究課題は,第5世代移動通信システム(5G)の高速・大容量化の鍵を握る非直交多元接続(NOMA)を採り上げ,NOMAだけでなく直交多元接続(OMA)の組み合わせにより,システム容量の向上を図る方式を提案するとともに,その有効性を明らかにするものである.本年度は,NOMAが有する,ユーザ間のチャネル利得が小さい場合にOMAと比較してシステム容量が低下するといった問題を克服すべく,NOMA単独だけでなく,OMA単独やNOMAとOMAを同時利用する複数のリソースパターンを各ユーザのチャネル状態に応じて適切に選択する方式を提案するとともに,その有効性を計算機シミュレーションにより評価した.具体的には,まず,無線伝搬路として周波数非選択性を想定し,ユーザ間のチャネル利得差が小さい場合におけるNOMAの問題点を定量的に明らかにした.さらに,無線伝搬路として,周波数非選択性に加え,周波数選択性を想定し,各セル内にユーザが一様に分布したときの提案方式のシステム容量特性をNOMA単独あるいはOMA単独の場合を比較対象にとって計算機シミュレーションにより取得・評価した.特性評価の結果,提案方式は,伝搬路の周波数選択性の有無やセル内で一様のユーザ分布といった基本的なモバイルネットワークのシナリオにおいて,NOMA単独,OMA単独,NOMAとOMAの同時利用といった複数のリソースパターンを適切に選択し,システム容量を向上できることがわかった.本研究課題は,研究実績報告に記載した通り,現在まで研究計画書に記載した通りに進捗しており,概ね順調に進展しているものと判断できる.特に,本年度,本研究課題を進めていく上で最も基盤となる,無線伝搬路を想定し,複数ユーザが同時に送受信を行うことを想定したNOMAの信号処理シミュレータを構築するとともに,NOMAの問題点の把握と基本的な特性評価が完了できたことが最大の成果であり,これは今後の技術提案を含めた検討を加速させる上で大きな意義を有するものと考えられる.本年度,検討を行ったNOMAにおけるユーザ間のチャネル利得差が小さい場合の伝送特性劣化の検証とNOMA及びOMA の同時利用の適用効果に関する基礎的な知見をベースに,多様なユーザ要求スループットを考慮したリソース割当てに関する技術提案を行い,その有効性を計算機シミュレーションにより評価する.具体的には,以下の項目について研究を進める.<BR>(1) 多様なユーザ要求スループットを考慮したリソース割当ての有効性評価5G以降のモバイルネットワークでは,多種多様な無線アプリケーションの実現が見込まれる点に鑑み,各ユーザのチャネル状況だけでなく,多様な要求スループットを考慮したときのリソースパターンの選択法を検討するとともに,その有効性をNOMA単独及びOMA単独を比較対象にとって,計算機ミュレーションにより評価する.(2) 提案方式へのユーザスケジューリングの導入・評価実際のシステムでは,多元接続方式の上位にユーザスケジューリングが適用される点に鑑み,公平性を担保するProportional Fairness(PF)を取り上げ,それを考慮したときの提案方式のシステム容量特性を評価する.このようなユーザスケジューリングを考慮した本特性評価により,提案方式とユーザスケジューリングが総合特性に与える影響を明らかにすることができるものと考えられる

  • Application of Laguerre-Gaussian beams to optical wireless communications

    Project Year :

    2017.04
    -
    2020.03
     

  • Research on system capacity enhancement using network MIMO-OFDM for mobile communications

    Project Year :

    2016.04
    -
    2019.03
     

     View Summary

    This research proposes a new transmission scheme to cope with problems in applying OFDM to network MIMO. Considering that network MIMO-OFDM suffers from degradation in the transmission efficiency in the presence of the difference in the multipath delay among multiple mobile terminals, the guard interval (GI) control scheme allowing some amount of inter-symbol interference (ISI) is proposed, which leads to achieving maximum system capacity. Thanks to the proposed approach, system capacity of wireless broadband networks can be further enhanced

  • Research on robust SC-FDE transmission over time selective fading channels

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2013.04
    -
    2016.03
     

    MAEHARA Fumiaki

     View Summary

    This research proposes a single carrier transmission with frequency domain equalization (SC-FDE) employing decision feedback channel estimation to cope with both frequency selective fading and time selective fading which are two main problems in realizing high speed mobile communications systems. The feature of the proposed approach is to theoretically derive the effect of time selective fading by using the terminal speed and to provide the appropriate forgetting factor according to the actual channel condition composed of thermal noise and time selective fading. The numerical results obtained by computer simulations showed that the proposed scheme determines the appropriate forgetting factor and provides good performance regardless of terminal mobility, which further improves spectral efficiency of uplink mobile communications with various degrees of terminal mobility

  • Theoretical Derivation Method of Bit Error Rate for OFDM Signals over Nonlinear Channels

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2006.04
    -
    2009.03
     

    MAEHARA Fumiaki

  • 陸上移動無線通信における電波伝搬モデルと情報伝送の高速化技術に関する研究

    日本学術振興会  科学研究費助成事業

    Project Year :

    2002
    -
    2004
     

    前原 文明

     View Summary

    (1)周波数ダイバーシチを適用したシンボル間干渉抑圧法
    昨年度検討を行った偶数番号のサブキャリヤと多値変調を用いたシンボル間干渉抑圧法に対して,奇数番号のサブキャリヤを適用した周波数ダイバーシチを提案し,さらなる特性改善を行った.具体的には,受信側で周波数変換を施すことによって,奇数番号のサブキャリヤ受信が可能となることに着目し,各シンボルのビット誤り率が最小となるように送信側で,偶数と奇数のサブキャリヤの配置を制御するものである.計算機シミュレーションの結果,遅延スプレッドが大きくなるにしたがって,提案方式の特性が,従来の干渉抑圧法よりも良好となることが明らかとなった.
    (2)CI/OFDM方式における周波数ダイバーシチの構成法
    CI/OFDM方式の特性改善を目的として,周波数ダイバーシチを用いた一構成を提案した.具体的には,1シンボル内のサンプリング周期を2倍に拡大することによって,スペクトラムの周期性を実現し,周波数軸上での周波数ダイバーシチ効果を実現するものである.計算機シミュレーションの結果,遅延スプレッドが大きくなるにしたがって,提案方式の特性が通常のCI/OFDM方式よりも良好となることが明らかとなった.なお,本提案方式は,付加的なハードウェアを必要とせず,ソフトウェア信号処理のみで構成できる利点がある.

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Misc

  • Foreword.

    Fumiaki Maehara

    IEICE Trans. Fundam. Electron. Commun. Comput. Sci.   102-A ( 1 ) 155 - 155  2019

    DOI

  • Foreword: Special section on wideband systems

    Fumiaki Maehara

    IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences   E101A ( 1 ) 160  2018.01

    DOI

  • Significance of Theoretical Analysis in Wireless Systems and its Fascination

    MAEHARA Fumiaki

    IEICE ESS Fundamentals Review   7 ( 1 ) 60 - 71  2013

     View Summary

    The transmission performance of wireless systems depends on the radio propagation as well as the modulation scheme and signal-to-noise ratio. Therefore, it is essential to evaluate the transmission performance under the radio propagation specified by the target wireless system. Considering the performance evaluation, the theoretical approach is expected to be more attractive than computer simulation because the theoretical approach gives an overview of the transmission performance thanks to being formulated using essential system parameters. We explain the theoretical derivation method of the transmission performance using a simple radio propagation model and then introduce some examples of the theoretical derivation for MIMO and OFDM, which have been widely adopted for recent wireless systems.

    DOI DOI2 CiNii

  • 鉄橋を渡る列車と畳込みの関係

    前原文明

    電子情報通信学会通信ソサイエティマガジン   2008 ( No. 4 ) 21 - 4_21  2008.03

    DOI CiNii

Industrial Property Rights

  • 無線通信システム、基地局および制御方法

    前原 文明

    Patent

  • 無線通信システム及び無線通信方法

    前原 文明

    Patent

  • 無線通信システム、無線通信方法及び送信装置

    前原 文明

    Patent

  • 無線通信システム、集中制御局および可動基地局配置方法

    6752462

    前原 文明

    Patent

  • 無線通信方法および無線通信装置

    6319768

    前原 文明

    Patent

  • 無線通信装置及び無線通信方法

    6108554

    前原 文明

    Patent

  • 無線通信システム、無線通信装置及び無線通信方法

    6098980

    前原 文明

    Patent

  • 送信装置、受信装置および通信システム

    6280508

    前原 文明, 髙畑 文雄

    Patent

  • 送信装置、受信装置および通信システム

    前原 文明, 髙畑 文雄

    Patent

  • 通信装置及び通信システム

    髙畑 文雄, 前原 文明

    Patent

  • 受信装置、通信システムおよび受信方法

    髙畑 文雄, 前原 文明

    Patent

  • 通信システムおよび通信方法

    5053200

    髙畑 文雄, 前原 文明

    Patent

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Syllabus

▼display all

 

Sub-affiliation

  • Faculty of Science and Engineering   Graduate School of Fundamental Science and Engineering

Research Institute

  • 2022
    -
    2024

    Waseda Research Institute for Science and Engineering   Concurrent Researcher

Internal Special Research Projects

  • OAM多重伝送への偏波多重の適用とその効果に関する研究

    2023  

     View Summary

    Thisresearch investigates the feasibility of employing polarization multiplexing inOAM (Orbital Angular Momentum) transmission, which is anticipated to be aprospective technology for the sixth-generation mobile communication systems(6G) expected to realize by 2030. Specifically, focusing on the advantageousproperty that OAM signals can utilize polarization multiplexing alongside modemultiplexing, we conduct an analytical assessment of the system capacity forMIMO-OAM incorporating mode and polarization multiplexing. The numerical results indicate that the effectiveness ofpolarization remains consistent regardless of the number of MIMO streams inscenarios without mode limitations. However, it was observed that in caseswhere mode limitations exist, the effectiveness of polarization diminishes dueto the decrease in stream power attributed to polarization at relatively longerlink distances. Furthermore, increasing the number of MIMO streams was found toenhance spatial diversity effects, thereby boosting system capacityirrespective of mode limitations.

  • OAM多重伝送への偏波多重の適用とその効果に関する研究

    2022  

     View Summary

    This research work investigates the applicability of polarization multiplexing to OAM (Orbital Angular Momentum) transmission which is expected to be a new candidate technology for the sixth-generation mobile communication systems (6G) aiming for realizing in 2030. Specifically, focusing on a useful property that OAM signals can apply polarization multiplexing in addition to mode multiplexing, we analytically evaluate the system capacity of UCA-OAM transmission with mode and polarization multiplexing in the presence of ground reflection. In our evaluation, we consider the influence of polarization on the reflected wave, which clarifies the necessity of equalizer at the receiver. The numerical results demonstrated that, in the case of vertical polarization, the adoption of high directional antenna instead of equalizer can improve the throughput compared with that of isotropic antenna because the impact of the reflected wave is smaller than that in the case of horizontal polarization. In contrast, assuming horizontal polarization, the inter-mode interference and inter-symbol interference become severe owing to a large impact of reflected wave, which indicates that the adoption of equalizer is required in addition to the directional antenna.

  • 非直交多元接続と直交多元接続の帯域内同時利用に関する研究

    2021  

     View Summary

    Non-orthogonalmultiple access (NOMA) can be seen as a promising approach to meet a dramaticincrease in demand for the system capacity. So far, we have proposed a hybrid multiple access scheme considering the desired user trafficvolume as well as channel conditions. In the proposed approach, by using NOMAand orthogonal multiple access (OMA) in the same bandwidth, a resource patterncombined with different user requirements is introduced to effectively meet thedemands of diversified wireless services in 5G and beyond. In this work,considering that recent base stations (BSs) are equipped with multiple antennas,maximum ratio transmission (MRT) is applied to the proposed approach. Thus, thespatial diversity gain is reflected on calculating the actual throughput usedfor choosing the best resource pattern. The effectiveness of the proposedscheme is demonstrated through computer simulations by considering the antennaconfiguration under diversified user traffic for enhanced mobile broadband(eMBB) and ultra-reliable and low-latency communications (URLLC).

  • 直交多元接続との連携による非直交多元接続方式の特性改善に関する研究

    2020  

     View Summary

    Sparse code multiple access (SCMA) is apromising approach for massive machine type communication (mMTC) which is oneof the usage scenarios for the fifth-generation mobile communications systems(5G). SCMA improves the system capacity at relatively high CNR, but in low CNR,its non-orthogonality between users makes system capacity smaller thanorthogonal frequency division multiple access (OFDMA). So far, we have proposeda hybrid approach using simultaneously SCMA and OFDMA to cope with thisproblem, and its effectiveness has been validated. In this work, we propose asystem selection method employing deep learning based on user positioninformation. In the proposed method, the multiple access scheme that maximizesthe system throughput is selected from SCMA-only, OFDMA-only, and their hybridapproach. The effectiveness of the proposed scheme is demonstrated in terms ofsystem throughput under different user distributions via computer simulations.

  • 直交多元接続との連携による非直交多元接続方式の特性改善に関する研究

    2019  

     View Summary

    Sparse code multiple access (SCMA) isa promising approach for massive machine type communication (mMTC) which is oneof the usage scenarios for the fifth-generation mobile communications systems(5G). Although SCMA improves the system capacity in relatively high CNR, the SCMAperformance is poorer than orthogonal frequency division multiple access(OFDMA) in low CNR due to non-orthogonal multiple access. In this work, we proposea user clustering method for uplink SCMA/OFDMA to further enhance the systemcapacity especially in low CNR. In our proposed scheme, users are clusteredinto two groups according to channel gain, and SCMA and OFDMA are applied tothe groups with large channel gain and small channel gain, respectively. Theeffectiveness of the proposed scheme is demonstrated by comparing it with SCMAand OFDMA under different user distributions.

  • 移動通信のためのネットワーク MIMO-OFDMによる通信容量拡大に関する研究

    2017  

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    In this work, we proposed the inter-symbolinterference suppression method employing compressed sensing for OFDM systemswhich can be seen as a promising transmission technique in 5th generation (5G)mobile networks. The feature of the proposed approach is to demodulate thelatter part of the time domain OFDM symbol by using compressed sensing underthe assumption of sparse subcarrier allocation. Numerical results by means ofcomputer simulation showed that the superiority of the proposed method over thetradition method using FFT demodulation can be found in the mid-range delayspread.

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