Zi-Wei Zheng

Tsinghua University, Beijing, Beijing Shi, China

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Publications (18)16.31 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: As an effective technique for combating multipath fading and for high-bit-rate transmission over wireless channels, orthogonal frequency-division multiplexing (OFDM) is extensively used in modern digital television terrestrial broadcasting (DTTB) systems, such as the cyclic prefix OFDM (CP-OFDM) based DVB-T DTTB systems and the time domain synchronous OFDM (TDS-OFDM) based DMB-T DTTB systems, to support high performance bandwidth-efficient multimedia services. OFDM-based DTTB systems are very sensitive to the nonlinear distortion at the transmitter and the imperfect parameters estimation at the receiver. In this paper, the combined effects of nonlinear distortion and imperfect parameters estimation on the performance of the OFDM-based DTTB systems are investigated, a closed form of symbol error probability of the OFDM-based DTTB systems with nonlinear distortion and imperfect parameters estimation is derived. Theoretical results show closely matching with those obtained by simulations for both the CP-OFDM based DVB-T DTTB systems and the TDS-OFDM based DMB-T DTTB systems.
    IEEE Transactions on Broadcasting 07/2005; · 2.09 Impact Factor
  • Zi-Wei Zheng, Zhixing Yang, Yi-Sheng Zhu
    IEICE Transactions. 01/2005; 88-B:3776-3778.
  • Zi-Wei Zheng, Zhixing Yang, Yi-Sheng Zhu
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    ABSTRACT: A robust time and frequency synchronization scheme is proposed for the high rate OFDM-based wireless local area networks (WLANs). The IEEE 802.11a standardized preamble is efficiently utilized and makes the proposed scheme practical. Simulation results under different channel environments are presented to illustrate the effectiveness of the proposed scheme.
    IEICE Transactions. 01/2005; 88-B:3047-3049.
  • Zi-Wei Zheng, Yi-Sheng Zhu
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    ABSTRACT: A new least-squares registration (NLSR) algorithm is developed to accurately estimate and correct the systematic errors of a data fusion system. First, the two-sensor registration problem is expressed by an averaged least-squares (LS) criterion function of the sensor measurements. The criterion function is optimized by a Newton algorithm. Then, the algorithm is extended to multiple-sensor case. The accuracy of the proposed estimation scheme achieves the Cramer-Rao bound (CRB). Theoretical analysis and simulations are employed to assess the performance of the proposed algorithm.
    IEEE Transactions on Aerospace and Electronic Systems 11/2004; · 1.30 Impact Factor
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    ABSTRACT: As an effective technique for combating multipath fading and for high data rate transmission over wireless channels, orthogonal frequency division multiplexing (OFDM) is extensively used in wireless local area network (WLAN) systems to support high performance bandwidth-efficient multimedia services. In this paper, novel synchronization and channel estimation schemes are proposed for the OFDM-based WLAN systems. Analyses and simulation results show that the proposed schemes exhibit good performances and are robust in harsh fading channel environments and low signal-to-noise ratio (SNR) conditions.
    IEEE Transactions on Consumer Electronics 09/2004; · 1.09 Impact Factor
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    ABSTRACT: As an effective technique for combating multipath fading and for high data rate transmission over wireless channels, orthogonal frequency division multiplexing (OFDM) is extensively used in high-rate wireless communication systems, such as, the wireless local area network (WLAN) and the digital television terrestrial broadcasting (DTTB) to support high performance bandwidth-efficient multimedia services. OFDM-based multi-carrier systems are much more sensitive to the nonlinear distortion at the transmitter and the imperfect parameters estimation at the receiver than the single carrier systems. In this paper, the compositive performance effects induced on the OFDM signal by the nonlinear distortion and the imperfect parameters estimation are investigated, a closed form of symbol error probability of the OFDM-based system with nonlinear distortion and imperfect parameters estimation is derived. Theoretical results show closely matching with those obtained by simulations for the OFDM-based system with QPSK, 16QAM, 64QAM modulations.
    IEEE Transactions on Consumer Electronics 09/2004; · 1.09 Impact Factor
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    ABSTRACT: Wireless communications for mobile telephone and data transmission is currently undergoing very rapid development. Code division multiple-access (CDMA) implemented with direct sequence spread spectrum signaling is among the most promising multiplexing technologies for cellular telecommunications services. In this paper, jointly period inserted pilot symbols assisted recursive (PIPSAR) channel estimation and interference suppression techniques are proposed for uplink CDMA mobile communication systems. The uplink CDMA mobile communication system model is described in the form of space-time domain through antenna array and multipath expression. Interference suppression is achieved by using adaptive minimum mean squared error (MMSE) digital filters that span several successive received chip oversampling vectors of a symbol interval. PIPSAR techniques are used to estimate channel parameters. The correlation between the successive periods is considered to further improve the performance of the proposed scheme. Analysis and simulations are used to evaluate the performance of the proposed scheme. Copyright © 2004 John Wiley & Sons, Ltd.
    Wireless Communications and Mobile Computing 07/2004; 4(5):483 - 489. · 0.86 Impact Factor
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    ABSTRACT: As an effective technique for combating multipath fading and for high-bit-rate transmission over wireless channels, orthogonal frequency-division multiplexing (OFDM) is extensively used in modern digital television terrestrial broadcasting (DTTB) systems to support high performance bandwidth-efficient multimedia services. In this paper, novel synchronization schemes, including timing, frequency offset estimation, and phase error tracking, are proposed for the time domain synchronous OFDM (TDS-OFDM) based DTTB systems. Simulations under different channel situations verify the efficiency of the proposed schemes.
    IEEE Transactions on Broadcasting 07/2004; · 2.09 Impact Factor
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    ABSTRACT: In many wireless broadband physical channels, such as mobile urban radio channels, Doppler-spread is decidedly occurring and the channel characteristics are of both time-selectivity and frequency-selectivity (double-selectivity), which produces performance degradation for those systems only utilizing the frequency-selectivity channel characteristics. A double time domain spread unitary space-time modulated orthogonal frequency division multiplexing (OFDM) scheme is proposed for high data rate multiuser downlink broadband mobile communication. The proposed scheme makes the system not only capable of efficiently exploiting the double-selective characteristics of the wireless mobile fading channels to attain large diversity gain but also with both high data rate and high system capacity.
    Vehicular Technology Conference, 2004. VTC 2004-Spring. 2004 IEEE 59th; 06/2004
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    ABSTRACT: As an effective technique for combating multipath fading and for high-bit-rate transmission over wireless channels, orthogonal frequency-division multiplexing (OFDM) is extensively used in modern digital television terrestrial broadcasting (DTTB) systems to support high performance bandwidth-efficient multimedia services. In this paper, a robust phase noise suppression scheme is proposed for the time domain synchronous OFDM (TDS-OFDM) based DTTB systems. Simulation results under different channel environments are presented to illustrate the effectiveness of the proposed scheme.
    IEEE Transactions on Consumer Electronics 06/2004; · 1.09 Impact Factor
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    ABSTRACT: As an effective technique for combating multipath fading and for high-bit-rate transmission over wireless channels, orthogonal frequency-division multiplexing (OFDM) is extensively used in modern terrestrial digital television broadcasting systems to support high performance bandwidth-efficient multimedia services. Cutoff rate and outage probability are two important criteria to evaluate the performance of a practical communication system in radio engineering. In this paper, the cutoff rate and outage probability performance are compared between two important terrestrial digital television broadcasting systems, the cyclic prefix OFDM based DVB-T system and the time domain synchronous OFDM based DMB-T system, under different mobile multipath channel conditions. The DVB-T system and the DMB-T system are summarily introduced. The cutoff rate and outage probability expressions are developed, and simulation results are given for both the DVB-T system and the DMB-T system.
    IEEE Transactions on Broadcasting 01/2004; · 2.09 Impact Factor
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    ABSTRACT: Correct time and frequency synchronization is important for the performance of orthogonal frequency division multiplexing (OFDM) systems. Correct and timely channel situation information enables coherent modulation. A joint time domain synchronization and channel estimation scheme is explored for the TDS-OFDM (time-domain synchronous orthogonal frequency division multiplexing) DTTB (digital television terrestrial broadcasting) systems. DTTB includes DVB-T and terrestrial digital multimedia/television broadcasting (DMB-T). The proposed scheme not only saves bandwidth but also improves the system performance under different channel situations.
    Vehicular Technology Conference, 2003. VTC 2003-Fall. 2003 IEEE 58th; 11/2003
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    ABSTRACT: Orthogonal frequency-division multiplexing (OFDM) is extensively used in modern terrestrial digital television broadcasting systems to support high performance bandwidth-efficient multimedia services. Cutoff rate and outage probability are two important criterions to evaluate the performances of a practical communication system in radio engineering. In this paper, the cutoff rate and outage probability performances are compared between two important terrestrial digital television broadcasting systems, the cyclic prefix OFDM based DVB-T system and the time domain synchronous OFDM based DMB-T system, under different multipath channel conditions.
    Personal, Indoor and Mobile Radio Communications, 2003. PIMRC 2003. 14th IEEE Proceedings on; 10/2003
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    ABSTRACT: In many physical channels, such as urban and indoor radio channels, the ambient noise is known through experimental measurements to be decidedly non-Gaussian, which makes the system performance degradation under non-Gaussian channels for those only utilizing the conventional Gaussian interference suppression scheme. In this paper, a robust multi-stage nonlinear interference suppression scheme is developed for synchronous DS-CDMA system under either Gaussian or non-Gaussian noise channels. For the DS-CDMA systems, simulation results show that the proposed scheme not only has nearly the same performance with the classical Gaussian interference suppression scheme under Gaussian noise channels, but also offers significant performance gain over the classical Gaussian interference suppression scheme under non-Gaussian noise channels.
    Personal, Indoor and Mobile Radio Communications, 2003. PIMRC 2003. 14th IEEE Proceedings on; 10/2003
  • ZI-Wei Zheng, Zhi-Xing Yang, Yi-Sheng Zhu
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    ABSTRACT: Techniques are proposed for interference suppression for the uplink of multiuser CDMA systems. The multiuser CDMA uplink communication system model is described in space-time domain form through an antenna array and a multipath expression. A linear prediction technique is used to perform channel estimation. Based on the estimated channel state information, constrained minimum power digital filters are used to suppress interference. The prefiltered multipath signals from all antennas are combined to get the final decision statistic. The correlation between the successive periods is considered to improve further the performance of the proposed scheme. Simulations demonstrate the effectiveness of the proposed scheme.
    Acoustics, Speech, and Signal Processing, 2003. Proceedings. (ICASSP '03). 2003 IEEE International Conference on; 05/2003
  • Zi-Wei Zheng, Yi-Sheng Zhu
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    ABSTRACT: In this paper, a space-time soft receiver is developed for convolutionally coded DS-CDMA systems with time-selective fading in both Gaussian and nonGaussian channels. The whole interference, including intersymbol interference (ISI), multiple access interference (MAI), and narrowband interference (NBI), is considered. Low-complexity continuously iterative nonlinear space-time soft interference cancellation and decoding techniques are proposed. The estimation of the parameters of the probability density function (PDF) of the whole interference and noise per propagation path per antenna element is directly computed by using the outputs of a chip-matched filter. The optimal combining weight is used to combine all the soft receiving signals to make the final statistic decision. Simulation results demonstrate that the proposed receiver structure offers significant performance gain over some existing approaches in both Gaussian and nonGaussian time-selective fading channels.
    Wireless Personal Multimedia Communications, 2002. The 5th International Symposium on; 11/2002
  • Zi-Wei Zheng, Yi-Sheng Zhu
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    ABSTRACT: In this paper, channel estimation and interference cancellation techniques are presented jointly for multipath DS-CDMA systems employing long spreading codes. The linear prediction (LP) approach is applied to estimate the channel response of the desired user, which is based on interference cancellation. The minimum-mean-square-error (MMSE) criterion is used to make the final statistical decision based on the estimated parameters. It is shown that the proposed receiver performs well in the presence of frequency-selective multipath fading.
    Circuits and Systems, 2002. APCCAS '02. 2002 Asia-Pacific Conference on; 02/2002
  • Zi-Wei Zheng, Yi-Sheng Zhu
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    ABSTRACT: In this paper, the problem of blind space-time constrained multiuser detection for asynchronous DS-CDMA systems operating in multipath channels is considered. Multiple linear prediction is applied to estimate the column vector subspace of the channel matrix using only the spreading code of the desired user, which is used to construct the interference suppression constraint. At each antenna, intersymbol interference (ISI) and multiple access interference (MAI) are simultaneously suppressed by novel space-time constrained multiuser detection. Outputs from each antenna are combined to get the final receiver decision statistic. Optimal combining weight is derived. Simulations demonstrate the effectiveness of the proposed scheme.
    Communications, Circuits and Systems and West Sino Expositions, IEEE 2002 International Conference on; 01/2002