Yahong Zheng

Missouri University of Science and Technology, ECE, Faculty Member

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Papers by Yahong Zheng

Low complexity soft-input soft-output block decision feedback equalization

IEEE Journal on Selected Areas in Communications, 2008

A low complexity soft-input soft-output (SISO) block decision feedback equalizer (BDFE) is presen... more A low complexity soft-input soft-output (SISO) block decision feedback equalizer (BDFE) is presented for turbo equalization. The proposed method employs a sub-optimum sequence-based detection, where the soft-output of the equalizer is calculated by evaluating an approximation of the sequence-based a posteriori probability (APP) of the data symbol. The sequence-based APP approximation is enabled by the adoption of both soft a priori information and soft decision feedback, and it leads to better performance and faster convergence compared to symbol-based detection methods as used by most other low complexity equalizers. The performance and convergence property of the proposed algorithm is analyzed by using extrinsic information transfer (EXIT) chart. Both analytical and simulation results show that the new equalizer can achieve a performance similar to that of trellis-based equalization algorithms, with a complexity similar to linear SISO minimum mean square error equalizers.

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Adaptive beamforming using affine projection algorithms

The dynamic adaptive Linear Constrained Mininium Variance (LCMV) beamformer generally uses the No... more The dynamic adaptive Linear Constrained Mininium Variance (LCMV) beamformer generally uses the Normalized LMS (NLMS) algorithm for its robustness a.nd simplicity, but it suffers froin a. low convergence rat,e. This paper proposes a.n alternative beamformer incorporating a siniplifiecl Fast Affine Projection (FAP) a.lgorit,hin, which provides fast, convergence speed and low compnta.tiona1 complexity.

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On constraint design and implementation for broadband adaptive array beamforming

This paper discusses eigenvector constraint design for broadband adaptive array beam forming. The... more This paper discusses eigenvector constraint design for broadband adaptive array beam forming. The constraint equations are constructed using the real and imaginary parts of the steering vectors and the response vectors, thus perm its real arithmetic and guarantees real outputs. A simple and elegant structure is developed for implementing the designed beam former by a Generalized Sidelobe Canceler (GSC). This structure reduces the computational complexity from O (N2) to O (N), where N being the dimension of the weight vector.

Robust near-field adaptive beamforming with distance discrimination

IEEE Transactions on Speech and Audio Processing, 2004

This paper proposes a robust near-field adaptive beamformer for microphone array applications in ... more This paper proposes a robust near-field adaptive beamformer for microphone array applications in small rooms. Robustness against location errors is crucial for near-field adaptive beamforming due to the difficulty in estimating near-field signal locations especially the radial distances. A near-field regionally constrained adaptive beamformer is proposed to design a set of linear constraints by filtering on a low rank subspace of the near-field signal over a spatial region and frequency band such that the beamformer response over the designed spatial-temporal region can be accurately controlled by a small number of linear constraint vectors. The proposed constraint design method is a systematic approach which guarantees real arithmetic implementation and direct time domain algorithms for broadband beamforming. It improves the robustness against large errors in distance and directions of arrival, and achieves good distance discrimination simultaneously. We show with a nine-element uniform linear array that the proposed near-field adaptive beamformer is robust against distance errors as large as 32% of the presumed radial distance and angle errors up to 20 . It can suppress a far field interfering signal with the same angle of incidence as a near-field target by more than 20 dB with no loss of the array gain at the near-field target. The significant distance discrimination of the proposed near-field beamformer also helps to improve the dereverberation gain and reduce the desired signal cancellation in reverberant environments.

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A microphone array system for multimedia applications with near-field signal targets

IEEE Sensors Journal, 2005

A microphone array beamforming system is proposed for multimedia communication applications using... more A microphone array beamforming system is proposed for multimedia communication applications using four sets of small planar arrays mounted on a computer monitor. A new virtual array approach is employed such that the original signals received by the array elements are weighted and delayed to synthesize a large, nonuniformly spaced, harmonically nested virtual array covering the frequency band [50, 7000] Hz of the wideband telephony. Subband multirate processing and near-field beamforming techniques are then used jointly by the nested virtual array to improve the performances in reverberant environments. A new beamforming algorithm is also proposed using a broadband near-field spherically isotropic noise model for array optimization. The near-field noise model assumes a large number of broadband random noises uniformly distributed over a sphere with a finite radius in contrast to the conventional far-field isotropic noise model which has an infinite radius. The radius of the noise model, thus, adds a design parameter in addition to its power for tradeoffs between performance and robustness. It is shown that the near-field beamformers designed by the new algorithm can achieve more than 8-dB reverberation suppression while maintaining sufficient robustness against background noises and signal location errors. Computer simulations and real room experiments also show that the proposed array beamforming system reduces beampattern variations for broadband signals, obtains strong noise and reverberation suppression, and improves the sound quality for near-field targets.

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Experimental evaluation of a nested microphone array with adaptive noise cancellers

IEEE Transactions on Instrumentation and Measurement, 2004

This paper proposes a near-field broadband adaptive beamforming scheme for intelligent computer t... more This paper proposes a near-field broadband adaptive beamforming scheme for intelligent computer telephony and teleconferencing applications, namely the nested microphone array with adaptive noise canceller (NMA-ANC). The NMA-ANC scheme incorporates an harmonically nested array with a nonuniformly subbanded multirate filter bank. Each subband array employs several near-field delay-filter-and-sum beamformers and an adaptive noise canceller (ANC). The proposed NMA-ANC is evaluated via a noise rejection experiment and dereverberation experiment performed in an anechoic chamber and a real conference room, respectively. The experiment data are recorded by a multichannel digital recording system developed using commercial off-the-shelf (COTS) equipments. A perceptual analysis/measurement system (PAMS) test is also carried out using a COTS digital speech level analyzer. The results of the experimental evaluation and PAMS test show that the proposed NMA-ANC scheme is able to improve the sound quality by adaptively rejecting multiple interfering signals and attenuating the reverberant noises and avoiding the desired signal cancellation.

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$Research paper thumbnail of A new variable step-size fractional lower-order moment algorithm for non-Gaussian interference environments$

A new variable step-size fractional lower-order moment algorithm for non-Gaussian interference environments

Page 1. A NEW VARIABLE STEP-SIZE FRACTIONAL LOWER-ORDER MOMENT ALGORITHM FOR NON-GAUSSIAN INTERFE... more

An Affine Projection Sign Algorithm Robust Against Impulsive Interferences

IEEE Signal Processing Letters, 2010

Page 1. IEEE SIGNAL PROCESSING LETTERS, VOL. 17, NO. 4, APRIL 2010 327 An Affine Projection Sign ... more

Improved Frequency-Domain Channel Estimation for Fast Time-Varying MIMO-SCFDE Channels

This paper introduces an improved frequency domain channel estimation method based on interpolati... more This paper introduces an improved frequency domain channel estimation method based on interpolation vectors for single carrier frequency domain equalization (SC-FDE) with the multiple-input multiple-output (MIMO) scheme. The proposed algorithm is derived by employing the least squares (LS) criterion, and a specified application for the wide sense stationary uncorrelated scattering (WSSUS) Rayleigh fading channel is presented. The channel frequency domain responses estimated at two adjacent pilot blocks are used to track the time-variant channel information, which can effectively improve the accuracy of channel estimation without significantly increasing complexity. Maximum mean square error (MMSE) frequency domain equalization based on the estimated channel is employed in the receiver to recover transmitted signals. This paper also investigates a training sequence design method for multiple transmit antennas and a noise variance estimation method. Numerical simulation results show that the proposed methods can perform very well for fading channels with long multipath delay and high Doppler spread.

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A statistical simulation model for mobile radio fading channels

Page 1. A Statistical Simulation Model for Mobile Radio Fading Channels Chengshan Xiao and Yahong... more

Simulation models with correct statistical properties for Rayleigh fading channels

IEEE Transactions on Communications, 2003

In this paper, new sum-of-sinusoids statistical simulation models are proposed for Rayleigh fadin... more In this paper, new sum-of-sinusoids statistical simulation models are proposed for Rayleigh fading channels. These new models employ random path gain, random initial phase, and conditional random Doppler frequency for all individual sinusoids. It is shown that the autocorrelations and cross correlations of the quadrature components, and the autocorrelation of the complex envelope of the new simulators match the desired ones exactly, even if the number of sinusoids is as small as a single-digit integer. Moreover, the probability density functions of the envelope and phase, the level crossing rate, the average fade duration, and the autocorrelation of the squared fading envelope which contains fourthorder statistics of the new simulators, asymptotically approach the correct ones as the number of sinusoids approaches infinity, while good convergence is achieved even when the number of sinusoids is as small as eight. The new simulators can be directly used to generate multiple uncorrelated fading waveforms for frequency selective fading channels, multiple-input multiple-output channels, and diversity combining scenarios. Statistical properties of one of the new simulators are evaluated by numerical results, finding good agreements.

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Frequency-domain equalization for single carrier MIMO underwater acoustic communications

Page 1. Frequency-Domain Equalization for Single Carrier MIMO Underwater Acoustic Communications ... more

Channel Equalization and Symbol Detection for Single Carrier Broadband MIMO Systems with Multiple Carrier Frequency Offsets

Page 1. Channel Equalization and Symbol Detection for Single Carrier Broadband MIMO Systems with ... more

Channel Estimation and Phase-Correction for Robust Underwater Acoustic Communications

This paper presents a new channel estimation, equalization, and phase correction scheme to combat... more This paper presents a new channel estimation, equalization, and phase correction scheme to combat the convergence and stability problem encountered by time-domain adaptive equalizers in underwater acoustic communication systems. Large Doppler spread and symbol scaling in underwater channels have been challenging problems causing significant phase drift and performance degradation. Our new method targets this problem by first allowing phase errors in the estimation of the fading channel coefficients and then perform group-wise (rather than symbol-wise) phase estimation and correction after equalization and multiple channel combining. Single transmitter and multiple receiver data obtained through ocean experiments have been processed using the proposed method and the results show that the new methods can achieve Bit Error Rate (BER) on the order of 10 −4 with very high stability.

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A discrete-time model for spatio-temporally correlated MIMO WSSUS multipath channels

In this paper, a statistical discrete-time model is proposed for simulating wideband MIMO channel... more In this paper, a statistical discrete-time model is proposed for simulating wideband MIMO channels which experience spatially and temporally correlated, widesense stationary uncorrelated scattering (WSSUS) multipath Rayleigh fading. A new method is also presented to efficiently generate the correlated MIMO channel coefficients, which can be used for accurate simulation of physical continuous-time MIMO channels. The statistic accuracy of the discrete-time MIMO channel model is rigorously verified through theoretical analysis and extensive simulations in different criteria.

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Frequency-domain channel estimation and equalization for shallow-water acoustic communications

Physical Communication, 2010

A new frequency-domain channel estimation and equalization (FDE) scheme is proposed for single ca... more A new frequency-domain channel estimation and equalization (FDE) scheme is proposed for single carrier (SC) underwater acoustic communications. The proposed SC-FDE employs a small training signal block for initial channel estimation in the frequency domain and converts the estimated transfer function to a desired DFT (discrete Fourier transform) size for channel equalization of the data blocks. The frequency domain equalizer is designed using the linear minimum mean square error criterion. A new phase coherent detection scheme is also proposed and deployed to combat the phase drift due to the instantaneous Doppler in the underwater channels. The channel transfer functions and group-averaged phase drift are re-estimated adaptively in a decision-directed manner for each data block in a packet, which contains M blocks of QPSK data. The proposed SC-FDE method is applied to single input multiple output (SIMO) systems using the experimental data measured off the coast of Panama City, Florida, USA, June 2007. The uncoded bit error rate of the SIMO systems varies between 1.3% to 6.8 × 10 −5 when 4 ∼ 8 receive hydrophones are utilized, and the source-receiver range is 5.06 km.

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Novel Sum-of-Sinusoids Simulation Models for Rayleigh and Rician Fading Channels

IEEE Transactions on Wireless Communications, 2006

Page 1. IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, VOL. 5, NO. 12, DECEMBER 2006 3667 Novel Su... more

Second-order statistical properties of the WSS Jakes' fading channel simulator

IEEE Transactions on Communications, 2002

Page 1. 888 IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. 50, NO. 6, JUNE 2002 Second-Order Statistic... more

Time-domain receiver design for MIMO underwater acoustic communications

In this paper, we propose a time-domain receiver design scheme for high data rate single carrier ... more In this paper, we propose a time-domain receiver design scheme for high data rate single carrier multiple-input, multiple-output (MIMO) underwater acoustic communications. In this scheme, each received packet is artificially partitioned into blocks for processing. The MIMO channel is initially estimated using training blocks at the front of transmitted packets from all transducers. With the estimated MIMO channel, one data block following the training blocks is equalized. The phase rotation in the equalized data block is compensated by a group-wise phase correction operation, before symbol detection. The newly detected data block along with K - 1 previous data (or pilot) blocks are utilized to re-estimate the channel, which is employed to equalize the next new data block. The block-wise processing procedure is repeated until all blocks in the received packet are processed and demodulated. The proposed receiver scheme is tested with MakaiEx05 experimental data measured at Kauai, Hawaii, in September 2005. Processing results show that it works effectively with 2 times 8 BPSK, QPSK and 8PSK transmissions at the symbol period of 0.1 milliseconds. The average uncoded bit error rate (BER) is on the order of 8 times 10-4 for BPSK, 3 times 10-2 for QPSK, and 8 times 10-2 for 8PSK transmission.

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Channel Estimation for Frequency-Domain Equalization of Single-Carrier Broadband Wireless Communications

IEEE Transactions on Vehicular Technology, 2009

the Wireless Communications and Networking Conference (WCNC), over the past several years. Chengs... more

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