The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform

Fumiyuki Adachi - One of the best experts on this subject based on the ideXlab platform.

  • VTC Spring - Joint Tomlinson-Harashima Precoding and Transmit Equalization in Time-Domain for Single-Carrier MU-MIMO Block Transmission
    2015 IEEE 81st Vehicular Technology Conference (VTC Spring), 2015
    Co-Authors: Shohei Yoshioka, Shinya Kumagai, Fumiyuki Adachi
    Abstract:

    This paper is concerned with cyclic prefix (CP) inserted broadband single-carrier (SC) multi-user multi-input multi-output (SC-MU-MIMO). The use of Tomlinson-Harashima precoding (THP) is effective to remove the inter-user interference (IUI). To remove the inter-symbol interference (ISI) caused by the Channel Frequency-Selectivity, transmit equalization (TE) can be introduced. In the Degen and Rrühl's SC-MU-MIMO scheme (called as FD-SC-TETHP in this paper), THP and TE are performed separately in the Frequency-domain. The modulo operation in THP suppresses the power increase caused by the IUI removal. TE can remove the ISI and the amplitude variation in the signals of a block received at each user, though it increases the signal power after equalization. This degrades significantly the received signal-to-noise power ratio (SNR). In this paper, we propose a time-domain SC-TETHP (TD-SC-TETHP), in which the ISI subtraction is performed together with IUI subtraction both in the time-domain. The modulo operation suppresses the power increase caused by both IUI and ISI removal. To prevent the amplitude variation, pre-removal of the received signal amplitude variation is inserted between the modulo operation and the precoding matrix multiplication. Uncoded average bit error rate (BER) performance achievable by our proposed TD-SC-TETHP is evaluated by computer simulation to confirm its superiority to the FD-SC-TETHP. Computational complexity is also discussed.

  • analog single carrier transmission with Frequency domain equalization
    Asia-Pacific Conference on Communications, 2013
    Co-Authors: Shinya Kumagai, Tatsunori Obara, Fumiyuki Adachi
    Abstract:

    In this paper, a new analog signal transmission technique called analog single-carrier transmission with Frequency-domain equalization (analog SC-FDE) is proposed. The proposed analog SC-FDE applies discrete Fourier transform (DFT), Frequency-domain spectrum shaping and mapping, inverse DFT (IDFT), and cyclic prefix insertion before transmission. At the receiver, one-tap Frequency-domain equalization (FDE) is applied to take advantage of the Channel Frequency-Selectivity. As an example, in this paper, the analog voice transmission is considered. By computer simulation, we evaluate the normalized mean square error (NMSE) performance to show that analog SC-FDE achieves better NMSE performance than conventional analog signal transmission scheme.

  • Frequency Domain Adaptive Antenna Array for Broadband Single-Carrier Uplink Transmission
    IEICE Transactions on Communications, 2011
    Co-Authors: Wei Peng, Fumiyuki Adachi
    Abstract:

    In this paper, a Frequency domain adaptive antenna array (FDAAA) algorithm is proposed for broadband single-carrier uplink transmissions in a cellular system. By employing AAA weight control in the Frequency domain, the FDAAA receiver is able to suppress the multi-user interference (MUI) and the co-Channel interference (CCI). In addition, the Channel Frequency Selectivity can be exploited to suppress the inter-symbol interference (ISI) and to obtain Frequency diversity (or the multi-path diversity). Another advantage of the FDAAA algorithm is that its performance is not affected by the spread of angles of arrival (AOA) of the received multi-path signal. In this study the structure of FDAAA receiver is discussed and the Frequency domain signal-to-interference-plus-noise-ratio (SINR) after weight control is investigated. The performance of the FDAAA algorithm is confirmed by simulation results. It is shown that, the optimal FDAAA weight to obtain the best BER performance is that which fully cancels the interference when single-cell system is considered; On the other hand, when multi-cell cellular system is considered, the optimal FDAAA weight depends on both the cellular structure and the target signal to noise ratio (SNR) of transmit power control (TPC).

  • VTC Spring - Multi-User Joint Tx/Iterative Rx MMSE-FDE and Successive MUI Cancellation for Uplink DS-CDMA
    2011 IEEE 73rd Vehicular Technology Conference (VTC Spring), 2011
    Co-Authors: Kazuki Takeda, Fumiyuki Adachi
    Abstract:

    Uplink multi-user direct sequence-code division multi-access (DS-CDMA) suffers from strong multi-user interference (MUI) and self inter-chip interference (ICI) caused by severe Frequency-selective fading. In this paper, we propose a joint Tx/iterative Rx Frequency-domain equalization (FDE) based on minimum mean square error (MMSE) criterion and successive MUI cancellation (MUIC) for DS-CDMA uplink. In the proposed scheme, each user applies one-tap Tx FDE before transmitting signal. At the base station, joint one-tap Rx FDE and successive MUIC is iteratively performed. The FDE weights of users and base station are jointly optimized based on the MMSE criterion in order to reduce MUI and ICI while exploiting Channel Frequency-Selectivity. Computer simulation results show that the proposed scheme provides much improved bit error rate (BER) performance than the conventional iterative Rx MMSE-FDE with successive MUIC.

  • ICICS - Capacity and BER performance considerations on single-carrier Frequency-domain equalization
    2011 8th International Conference on Information Communications & Signal Processing, 2011
    Co-Authors: Fumiyuki Adachi, Tatsunori Obara, Tetsuya Yamamoto
    Abstract:

    Single-carrier (SC) waveform has a lower peak-to-average power ratio than multi-carrier waveform. Furthermore, it can exploit the Channel Frequency-Selectivity through Frequency-domain equalization (FDE) to improve the transmission performance. SC-FDE is a block transmission. The cyclic prefix (CP) is inserted in front of each data block. Instead of CP insertion, the known training sequence (TS) insertion and zero padding (ZP) can be used. In this paper, performance comparison is made among CP-, TS-, and ZP-SC in terms of the Channel capacity and average bit error rate (BER) performance in a Frequency-selective Rayleigh fading Channel.

Jérôme Louveaux - One of the best experts on this subject based on the ideXlab platform.

  • Performance Analysis of Linear Receivers for Uplink Massive MIMO FBMC-OQAM Systems
    IEEE Transactions on Signal Processing, 2018
    Co-Authors: François Rottenberg, Xavier Mestre, François Horlin, Jérôme Louveaux
    Abstract:

    Offset-quadratic-amplitude-modulation-based filterbank multicarrier (FBMC-OQAM) has been shown to be a promising alternative to cyclic prefix-orthogonal Frequency division multiplexing. More recently, the use of FBMC-OQAM has been proposed in combination with massive MIMO communications. In this context, it is interesting to study the overall effect of massive MIMO on the FBMC-OQAM intrinsic interference and its interaction with Channel Frequency Selectivity. In this paper, the performance of an FBMC-OQAM uplink massive MIMO system is theoretically characterized in terms of the output mean squared error (MSE) of the estimated transmitted symbols and for three types of linear receivers, namely, zero forcer, linear minimum mean squared error, and matched filter. Using random matrix theory, the output MSE of these receivers is asymptotically characterized as the number of base station antennas $N$ and the number of users $K$ grow large, while keeping a finite ratio $N/K$ . The obtained expressions allow to draw many conclusions, some of which were already noticed in the literature but not yet theoretically proven. First, the MSE becomes uniform across the Frequency band as a result of the Channel hardening effect. Second, it is shown that a good synchronization of the users is crucial in a massive MIMO scenario. Finally, if the users are well synchronized, the different terms that compose the MSE, such as noise, interuser interference, and the distortion caused by the Channel Frequency Selectivity, become negligible for large values of the ratio $N/K$ . This effect was previously referred to as “self-equalization” in the literature.

  • Parallel Equalization Structure for MIMO FBMC-OQAM Systems Under Strong Time and Frequency Selectivity
    IEEE Transactions on Signal Processing, 2017
    Co-Authors: François Rottenberg, Xavier Mestre, François Horlin, Dmitry Petrov, Jérôme Louveaux
    Abstract:

    Offset-QAM-based filterbank multicarrier (FBMC-OQAM) has been shown to be a promising alternative to cyclic prefix-orthogonal Frequency division multiplexing for the future generation of wireless communication systems. Unfortunately, as the Channel gets more selective in time and Frequency, the FBMC-OQAM orthogonality is progressively destroyed and distortion appears after the demodulation process at the receiver. While Channel Frequency Selectivity has been very widely studied in the FBMC literature, the impact of time Selectivity of the Channel has not received that much attention. In this paper, the effect of the two types of Selectivity on a multiple-input multiple-output (MIMO) FBMC system is characterized and a parallel equalization structure that can compensate for the doubly dispersive nature of the Channel is proposed. This design uses multiple analysis filterbanks and extends previous approaches that were dealing only with Channel Frequency Selectivity. A theoretical approximation of the remaining distortion after equalization is given. The study is performed for a general MIMO system but can also be particularized to single-input single-output systems. Simulation results demonstrate the high efficiency of the proposed receiver structure and the accuracy of the theoretical approximations is verified.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

  • MIMO-FBMC Receivers
    Orthogonal Waveforms and Filter Banks for Future Communication Systems, 2017
    Co-Authors: Eleftherios Kofidis, David Gregoratti, Jérôme Louveaux, Xavier Mestre, Markku Renfors, Didier Le Ruyet, Rozalina Zakaria
    Abstract:

    This chapter overviews existing work in MIMO-FBMC/OQAM Channel estimation and equalization, with emphasis on the more recent developments addressing strong Channel Frequency Selectivity. Both preamble-based and scattered pilots-based schemes for Channel estimation are considered. The equalization approaches covered include maximum likelihood sequence estimation, successive interference cancellation, and equalizers based on Frequency sampling and on parallel multistage receiver structures. Adaptive (linear and nonlinear) methods for doubly dispersive Channels are given special attention.

  • Single-Tap Precoders and Decoders for Multiuser MIMO FBMC-OQAM Under Strong Channel Frequency Selectivity
    IEEE Transactions on Signal Processing, 2017
    Co-Authors: François Rottenberg, Xavier Mestre, François Horlin, Jérôme Louveaux
    Abstract:

    The design of linear precoders or decoders for multiuser multiple-input multiple-output filterbank multicarrier (FBMC) modulations in the case of a strong Channel Frequency Selectivity is presented. The users and the base station (BS) communicate using space division multiple access. The low complexity proposed solution is based on a single tap per-subcarrier precoding/decoding matrix at the BS in the downlink/uplink. As opposed to classical approaches that assume flat Channel Frequency Selectivity at the subcarrier level, the BS does not make this assumption and takes into account the distortion caused by Channel Frequency Selectivity. The expression of the FBMC asymptotic mean squared error (MSE) in the case of strong Channel Selectivity derived in earlier works is developed and extended. The linear precoders and decoders are found by optimizing the MSE formula under two design criteria, namely zero forcing or minimum MSE. Finally, simulation results demonstrate the performance of the optimized design. As long as the number of BS antennas is larger than the number of users, it is shown that those extra degrees of freedom can be used to compensate for the Channel Frequency Selectivity.

  • ICASSP - Single-tap equalizer for MIMO FBMC systems under doubly selective Channels
    2017 IEEE International Conference on Acoustics Speech and Signal Processing (ICASSP), 2017
    Co-Authors: François Rottenberg, Xavier Mestre, François Horlin, Jérôme Louveaux
    Abstract:

    Offset-QAM-based filterbank multicarrier (FBMC-OQAM) modulations are known to progressively loose their orthogonality as the Channel gets more selective in time and Frequency. The effect of Channel Frequency Selectivity on FBMC-OQAM systems has been extensively studied in the literature. Many compensations methods have been proposed to combat it. However, most of them have a significant implementation complexity and do not take into account the time selective nature of the Channel. In this paper, we propose a MIMO equalizing structure for doubly selective Channel based on a simple single-tap per-subcarrier decoding matrix. The decoding matrices are designed to minimize the mean squared error of the symbol estimate. This decoder exploits the degrees of freedom offered by the extra antennas at the receiver to compensate for the distortion induced by time and Frequency Selectivity. Simulation results demonstrate the performance gain of the proposed design with respect to classical designs.SCOPUS: cp.pinfo:eu-repo/semantics/publishe

Xavier Mestre - One of the best experts on this subject based on the ideXlab platform.

  • Performance Analysis of Linear Receivers for Uplink Massive MIMO FBMC-OQAM Systems
    IEEE Transactions on Signal Processing, 2018
    Co-Authors: François Rottenberg, Xavier Mestre, François Horlin, Jérôme Louveaux
    Abstract:

    Offset-quadratic-amplitude-modulation-based filterbank multicarrier (FBMC-OQAM) has been shown to be a promising alternative to cyclic prefix-orthogonal Frequency division multiplexing. More recently, the use of FBMC-OQAM has been proposed in combination with massive MIMO communications. In this context, it is interesting to study the overall effect of massive MIMO on the FBMC-OQAM intrinsic interference and its interaction with Channel Frequency Selectivity. In this paper, the performance of an FBMC-OQAM uplink massive MIMO system is theoretically characterized in terms of the output mean squared error (MSE) of the estimated transmitted symbols and for three types of linear receivers, namely, zero forcer, linear minimum mean squared error, and matched filter. Using random matrix theory, the output MSE of these receivers is asymptotically characterized as the number of base station antennas $N$ and the number of users $K$ grow large, while keeping a finite ratio $N/K$ . The obtained expressions allow to draw many conclusions, some of which were already noticed in the literature but not yet theoretically proven. First, the MSE becomes uniform across the Frequency band as a result of the Channel hardening effect. Second, it is shown that a good synchronization of the users is crucial in a massive MIMO scenario. Finally, if the users are well synchronized, the different terms that compose the MSE, such as noise, interuser interference, and the distortion caused by the Channel Frequency Selectivity, become negligible for large values of the ratio $N/K$ . This effect was previously referred to as “self-equalization” in the literature.

  • Parallel Equalization Structure for MIMO FBMC-OQAM Systems Under Strong Time and Frequency Selectivity
    IEEE Transactions on Signal Processing, 2017
    Co-Authors: François Rottenberg, Xavier Mestre, François Horlin, Dmitry Petrov, Jérôme Louveaux
    Abstract:

    Offset-QAM-based filterbank multicarrier (FBMC-OQAM) has been shown to be a promising alternative to cyclic prefix-orthogonal Frequency division multiplexing for the future generation of wireless communication systems. Unfortunately, as the Channel gets more selective in time and Frequency, the FBMC-OQAM orthogonality is progressively destroyed and distortion appears after the demodulation process at the receiver. While Channel Frequency Selectivity has been very widely studied in the FBMC literature, the impact of time Selectivity of the Channel has not received that much attention. In this paper, the effect of the two types of Selectivity on a multiple-input multiple-output (MIMO) FBMC system is characterized and a parallel equalization structure that can compensate for the doubly dispersive nature of the Channel is proposed. This design uses multiple analysis filterbanks and extends previous approaches that were dealing only with Channel Frequency Selectivity. A theoretical approximation of the remaining distortion after equalization is given. The study is performed for a general MIMO system but can also be particularized to single-input single-output systems. Simulation results demonstrate the high efficiency of the proposed receiver structure and the accuracy of the theoretical approximations is verified.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

  • MIMO-FBMC Receivers
    Orthogonal Waveforms and Filter Banks for Future Communication Systems, 2017
    Co-Authors: Eleftherios Kofidis, David Gregoratti, Jérôme Louveaux, Xavier Mestre, Markku Renfors, Didier Le Ruyet, Rozalina Zakaria
    Abstract:

    This chapter overviews existing work in MIMO-FBMC/OQAM Channel estimation and equalization, with emphasis on the more recent developments addressing strong Channel Frequency Selectivity. Both preamble-based and scattered pilots-based schemes for Channel estimation are considered. The equalization approaches covered include maximum likelihood sequence estimation, successive interference cancellation, and equalizers based on Frequency sampling and on parallel multistage receiver structures. Adaptive (linear and nonlinear) methods for doubly dispersive Channels are given special attention.

  • MIMO-FBMC Transceivers
    Orthogonal Waveforms and Filter Banks for Future Communication Systems, 2017
    Co-Authors: Màrius Caus, David Gregoratti, Xavier Mestre, Ana I. Perez-neira, Martin Haardt, Yao Cheng, Leonardo Gomes Baltar
    Abstract:

    The chapter shows that the FBMC/OQAM extension to MIMO architectures is not trivial since different multiantenna links are subject to independent fading conditions. As a consequence, the superposition of signals at the receiver does not preserve the characteristics of the modulation so that the intrinsic interference is not in quadrature with the desired data. Hence, the perfect reconstruction property cannot be exploited unless the Channel is compensated. To get rid of the interference, it is desirable to have an equivalent response, which encompasses the precoder, the Channel and the equalizer, with a diagonal structure. If the Channel Frequency response is sufficiently smooth in the pass band region of one subcarrier, OFDM-based solutions can be successfully applied. However, when the Channel Frequency Selectivity is severe, new MIMO techniques have to be devised. With the aim of providing a concise overview and a valuable insight into the signal processing developments that allow the combination of FBMC/OQAM with MIMO, this chapter describes and assesses the state-of-the-art MIMO precoding and decoding designs for FBMC/OQAM systems in mild- and strong-Frequency Selectivity scenarios.

  • Single-Tap Precoders and Decoders for Multiuser MIMO FBMC-OQAM Under Strong Channel Frequency Selectivity
    IEEE Transactions on Signal Processing, 2017
    Co-Authors: François Rottenberg, Xavier Mestre, François Horlin, Jérôme Louveaux
    Abstract:

    The design of linear precoders or decoders for multiuser multiple-input multiple-output filterbank multicarrier (FBMC) modulations in the case of a strong Channel Frequency Selectivity is presented. The users and the base station (BS) communicate using space division multiple access. The low complexity proposed solution is based on a single tap per-subcarrier precoding/decoding matrix at the BS in the downlink/uplink. As opposed to classical approaches that assume flat Channel Frequency Selectivity at the subcarrier level, the BS does not make this assumption and takes into account the distortion caused by Channel Frequency Selectivity. The expression of the FBMC asymptotic mean squared error (MSE) in the case of strong Channel Selectivity derived in earlier works is developed and extended. The linear precoders and decoders are found by optimizing the MSE formula under two design criteria, namely zero forcing or minimum MSE. Finally, simulation results demonstrate the performance of the optimized design. As long as the number of BS antennas is larger than the number of users, it is shown that those extra degrees of freedom can be used to compensate for the Channel Frequency Selectivity.

François Rottenberg - One of the best experts on this subject based on the ideXlab platform.

  • Performance Analysis of Linear Receivers for Uplink Massive MIMO FBMC-OQAM Systems
    IEEE Transactions on Signal Processing, 2018
    Co-Authors: François Rottenberg, Xavier Mestre, François Horlin, Jérôme Louveaux
    Abstract:

    Offset-quadratic-amplitude-modulation-based filterbank multicarrier (FBMC-OQAM) has been shown to be a promising alternative to cyclic prefix-orthogonal Frequency division multiplexing. More recently, the use of FBMC-OQAM has been proposed in combination with massive MIMO communications. In this context, it is interesting to study the overall effect of massive MIMO on the FBMC-OQAM intrinsic interference and its interaction with Channel Frequency Selectivity. In this paper, the performance of an FBMC-OQAM uplink massive MIMO system is theoretically characterized in terms of the output mean squared error (MSE) of the estimated transmitted symbols and for three types of linear receivers, namely, zero forcer, linear minimum mean squared error, and matched filter. Using random matrix theory, the output MSE of these receivers is asymptotically characterized as the number of base station antennas $N$ and the number of users $K$ grow large, while keeping a finite ratio $N/K$ . The obtained expressions allow to draw many conclusions, some of which were already noticed in the literature but not yet theoretically proven. First, the MSE becomes uniform across the Frequency band as a result of the Channel hardening effect. Second, it is shown that a good synchronization of the users is crucial in a massive MIMO scenario. Finally, if the users are well synchronized, the different terms that compose the MSE, such as noise, interuser interference, and the distortion caused by the Channel Frequency Selectivity, become negligible for large values of the ratio $N/K$ . This effect was previously referred to as “self-equalization” in the literature.

  • Parallel Equalization Structure for MIMO FBMC-OQAM Systems Under Strong Time and Frequency Selectivity
    IEEE Transactions on Signal Processing, 2017
    Co-Authors: François Rottenberg, Xavier Mestre, François Horlin, Dmitry Petrov, Jérôme Louveaux
    Abstract:

    Offset-QAM-based filterbank multicarrier (FBMC-OQAM) has been shown to be a promising alternative to cyclic prefix-orthogonal Frequency division multiplexing for the future generation of wireless communication systems. Unfortunately, as the Channel gets more selective in time and Frequency, the FBMC-OQAM orthogonality is progressively destroyed and distortion appears after the demodulation process at the receiver. While Channel Frequency Selectivity has been very widely studied in the FBMC literature, the impact of time Selectivity of the Channel has not received that much attention. In this paper, the effect of the two types of Selectivity on a multiple-input multiple-output (MIMO) FBMC system is characterized and a parallel equalization structure that can compensate for the doubly dispersive nature of the Channel is proposed. This design uses multiple analysis filterbanks and extends previous approaches that were dealing only with Channel Frequency Selectivity. A theoretical approximation of the remaining distortion after equalization is given. The study is performed for a general MIMO system but can also be particularized to single-input single-output systems. Simulation results demonstrate the high efficiency of the proposed receiver structure and the accuracy of the theoretical approximations is verified.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

  • Single-Tap Precoders and Decoders for Multiuser MIMO FBMC-OQAM Under Strong Channel Frequency Selectivity
    IEEE Transactions on Signal Processing, 2017
    Co-Authors: François Rottenberg, Xavier Mestre, François Horlin, Jérôme Louveaux
    Abstract:

    The design of linear precoders or decoders for multiuser multiple-input multiple-output filterbank multicarrier (FBMC) modulations in the case of a strong Channel Frequency Selectivity is presented. The users and the base station (BS) communicate using space division multiple access. The low complexity proposed solution is based on a single tap per-subcarrier precoding/decoding matrix at the BS in the downlink/uplink. As opposed to classical approaches that assume flat Channel Frequency Selectivity at the subcarrier level, the BS does not make this assumption and takes into account the distortion caused by Channel Frequency Selectivity. The expression of the FBMC asymptotic mean squared error (MSE) in the case of strong Channel Selectivity derived in earlier works is developed and extended. The linear precoders and decoders are found by optimizing the MSE formula under two design criteria, namely zero forcing or minimum MSE. Finally, simulation results demonstrate the performance of the optimized design. As long as the number of BS antennas is larger than the number of users, it is shown that those extra degrees of freedom can be used to compensate for the Channel Frequency Selectivity.

  • ICASSP - Single-tap equalizer for MIMO FBMC systems under doubly selective Channels
    2017 IEEE International Conference on Acoustics Speech and Signal Processing (ICASSP), 2017
    Co-Authors: François Rottenberg, Xavier Mestre, François Horlin, Jérôme Louveaux
    Abstract:

    Offset-QAM-based filterbank multicarrier (FBMC-OQAM) modulations are known to progressively loose their orthogonality as the Channel gets more selective in time and Frequency. The effect of Channel Frequency Selectivity on FBMC-OQAM systems has been extensively studied in the literature. Many compensations methods have been proposed to combat it. However, most of them have a significant implementation complexity and do not take into account the time selective nature of the Channel. In this paper, we propose a MIMO equalizing structure for doubly selective Channel based on a simple single-tap per-subcarrier decoding matrix. The decoding matrices are designed to minimize the mean squared error of the symbol estimate. This decoder exploits the degrees of freedom offered by the extra antennas at the receiver to compensate for the distortion induced by time and Frequency Selectivity. Simulation results demonstrate the performance gain of the proposed design with respect to classical designs.SCOPUS: cp.pinfo:eu-repo/semantics/publishe

  • linear receivers for massive mimo fbmc oqam under strong Channel Frequency Selectivity
    IEEE Signal Processing Workshop on Statistical Signal Processing, 2016
    Co-Authors: Xavier Mestre, François Rottenberg, Monica Navarro
    Abstract:

    Filterbank Multicarrier (FBMC) modulations based on OQAM (FBMC/OQAM) have become a promising alternative to conventional OFDM because of their higher spectral efficiency and their improved Selectivity in the Frequency domain. Unfortunately, the orthogonality of these modulations is lost when the Channel presents strong Frequency Selectivity, meaning that the Channel response cannot be approximated as Frequency flat within each subcarrier bandwidth. In this paper, this effect is analyzed in the massive MIMO setting, whereby the number of transmit and receive antennas is asymptotically large (but not as large as the number of subcarriers). It is formally shown that, under these asymptotic conditions, the output mean squared error (MSE) at each subcarrier converges to a constant independent of the subcarrier index. This was previously referred to as “self-equalization” principle in the FBMC/OQAM literature. It is demonstrated here that this phenomenon is a direct consequence of Channel hardening effect in large scale MIMO configurations.

Kazuki Takeda - One of the best experts on this subject based on the ideXlab platform.

  • VTC Spring - Multi-User Joint Tx/Iterative Rx MMSE-FDE and Successive MUI Cancellation for Uplink DS-CDMA
    2011 IEEE 73rd Vehicular Technology Conference (VTC Spring), 2011
    Co-Authors: Kazuki Takeda, Fumiyuki Adachi
    Abstract:

    Uplink multi-user direct sequence-code division multi-access (DS-CDMA) suffers from strong multi-user interference (MUI) and self inter-chip interference (ICI) caused by severe Frequency-selective fading. In this paper, we propose a joint Tx/iterative Rx Frequency-domain equalization (FDE) based on minimum mean square error (MMSE) criterion and successive MUI cancellation (MUIC) for DS-CDMA uplink. In the proposed scheme, each user applies one-tap Tx FDE before transmitting signal. At the base station, joint one-tap Rx FDE and successive MUIC is iteratively performed. The FDE weights of users and base station are jointly optimized based on the MMSE criterion in order to reduce MUI and ICI while exploiting Channel Frequency-Selectivity. Computer simulation results show that the proposed scheme provides much improved bit error rate (BER) performance than the conventional iterative Rx MMSE-FDE with successive MUIC.

  • INVITED PAPER Special Section on Signal Design and its Application in Communications Recent Advances in Single-Carrier Frequency-Domain Equalization and Distributed Antenna Network
    2010
    Co-Authors: Fumiyuki Adachi, Tatsunori Obara, Tetsuya Yamamoto, Kazuki Takeda, Hiroki Matsuda
    Abstract:

    SUMMARY Broadband wireless technology that enables a variety of gigabit-per-second class data services is a requirement in future wireless communication systems. Broadband wireless Channels become extremely Frequency-selective and cause severe inter-symbol interference (ISI). Furthermore, the average received signal power changes in a random manner because of the shadowing and distance-dependant path losses resulted from the movement of a mobile terminal (MT). Accordingly, the transmission performance severely degrades. To overcome the performance degradation, two most promising approaches are the Frequency-domain equalization (FDE) and distributed antenna network (DAN). The former takes advantage of Channel Frequency-Selectivity to obtain the Frequency-diversity gain. In DAN, a group of distributed antennas serve each user to mitigate the negative impact of shadowing and path losses. This article will introduce the recent advances in FDE and DAN for the broadband single-carrier (SC) transmissions.

  • PIMRC - Multicode DS-CDMA with joint transmit/receive Frequency-domain equalization
    2009 IEEE 20th International Symposium on Personal Indoor and Mobile Radio Communications, 2009
    Co-Authors: Kazuki Takeda, Hiromichi Tomeba, Fumiyuki Adachi
    Abstract:

    Bit error rate (BER) performance of multicode direct-sequence code division multiple access (DS-CDMA) in a Frequency-selective Channel severely degrades due to strong inter-chip interference (ICI). Frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can take advantage of the Channel Frequency-Selectivity and significantly improve the BER performance. However, the performance improvement is limited by the residual ICI which is present after MMSE-FDE. In this paper, we apply a joint transmit/receive MMSE-FDE (called double MMSE-FDE in this paper) for multicode DS-CDMA signal transmissions to further improve the BER performance. We derive the conditional BER for the given Channel realization and evaluate the achievable average BER performance by Monte-Carlo numerical computation method. The BER performance is confirmed by the computer simulation.

  • Recent advances in single-carrier Frequency-domain equalization and distributed antenna network
    2009 7th International Conference on Information Communications and Signal Processing (ICICS), 2009
    Co-Authors: Fumiyuki Adachi, Tatsunori Obara, Tetsuya Yamamoto, Kazuki Takeda, Hiroki Matsuda
    Abstract:

    In the future wireless communication systems, the broadband wireless technology which enables Giga-bps class data services is demanded. Broadband wireless Channels become extremely Frequency-selective and cause severe inter-symbol interference (ISI). Furthermore, the average received signal power changes in a random manner because of the shadowing and path losses according to the movement of a mobile terminal (MT). Accordingly, the transmission performance severely degrades. Development of some advanced equalization and networking is necessary to overcome the performance degradation. Among them, promising are the Frequency-domain equalization (FDE) and distributed antenna network (DAN). The former takes advantage of Channel Frequency-Selectivity to obtain the Frequency-diversity gain. In DAN, a group of distributed antennas serve each user to mitigate the negative impact of shadowing and path losses. This article will introduce the recent advances in FDE and DAN for the broadband single-carrier (SC) transmissions.

  • Broadband CDMA techniques
    IEEE Wireless Communications, 2005
    Co-Authors: Fumiyuki Adachi, Shinsuke Takaoka, Deepshikha Garg, Kazuki Takeda
    Abstract:

    A very high-speed wireless access of 100 Mb/s to 1 Gb/s is required for fourth-generation mobile communications systems. However, for such high-speed data transmissions, the Channel is severely Frequency-selective due to the presence of many interfering paths with different time delays. A promising wireless access technique that can overcome the Channel Frequency-Selectivity and even take advantage of this Selectivity to improve the transmission performance is CDMA. There may be two approaches in CDMA technique: direct sequence CDMA and multicarrier CDMA. A lot of attention is paid to MC-CDMA. However, recently it has been revealed that DS-CDMA can achieve good performance comparable to MC-CDMA if proper Frequency domain equalization is adopted. This article discusses their similarities and performances. A major transmission mode in 4G systems is packet-based. Automatic repeat request combined with Channel coding is a very important technique. Recent research activity on this technique is also introduced.