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IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP)

作者： Xiao, Chengshan Zheng, Yahong Rosa Ding, Zhi Missouri Univ Sci & Technol Dept Elect & Comp Engn Rolla MO 65409 USA Univ Calif Davis Dept Elect & Comp Engn Davis CA 95616 USA

ISBN: (纸本)9781457705397

We study the design optimization of linear precoders that maximize the mutual information in complex-valued vector Gaussian channels under finite alphabet inputs. It is well known that mutual information of a vector channel with discrete constellation source is a highly nonlinear and non-concave function of the linear precoder matrix G, thereby complicating the precoder design optimization. In this paper, we show that the mutual information is a concave function of W = G(h)H(h)HG, where H is the complex-valued channel matrix and superscript "h" represents conjugate transpose. We further propose an iterative algorithm for solving the globally optimal linear precoder G. Illustrative results show that the proposed iterative algorithm is very robust and efficient for global convergence.

关键词： linear precoder mutual information vector Gaussian noise channel global optimization

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DESIGN OPTIMIZATION OF linear precoderS FOR COMPLEX VECTOR GAUSSIAN CHANNELS WITH FINITE ALPHABET INPUTS

DESIGN OPTIMIZATION OF LINEAR PRECODERS FOR COMPLEX VECTOR G...

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IEEE International Conference on Acoustics, Speech and Signal Processing

作者： Chengshan Xiao Yahong Rosa Zheng Zhi Ding Dept. of Electrical & Computer EngineeringMissouri University of Science & TechnologyRolla MO 65409 USA. Dept. of Electrical & Computer Eng.University of CaliforniaDavis CA 95616 USA

ISBN: (纸本)9781457705380

We study the design optimization of linear precoders that maximize the mutual information in complex-valued vector Gaussian channels under finite alphabet inputs. It is well known that mutual information of a vector channel with discrete constellation source is a highly nonlinear and non-concave function of the linear precoder matrix G, thereby complicating the precoder design optimization. In this paper, we show that the mutual information is a concave function of W velence G~(h)H~(h)HG, where H is the complex-valued channel matrix and superscript "h" represents conjugate transpose. We further propose an iterative algorithm for solving the globally optimal linear precoder G. Illustrative results show that the proposed iterative algorithm is very robust and efficient for global convergence.

关键词： linear precoder mutual information vector Gaussian noise channel global optimization

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Robust Designs for Femtocell Networks with Interference from Macrocell Users

Robust Designs for Femtocell Networks with Interference from...

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IEEE GLOBECOM Workshops (GC Wkshps)

作者： Zhou, Qi Ma, Xiaoli Georgia Inst Technol Sch Elect & Comp Engn Atlanta GA 30332 USA

ISBN: (纸本)9781467300407

Femtocell networking is a promising solution to improve the indoor coverage issue and enhance system throughput for next generation wireless networks. However, one of the main concerns to put through femtocells is the interference issue between macrocell and femtocell networks. In this paper, we consider femtocell uplink transmissions with dynamic interference from macrocell users. Without information exchange or subcarrier reallocation between femtocell and macrocell at any base station, we propose a precoded frequency division multiple access (P-FDMA) transmission with novel detectors to mitigate macrocell-to-femtocell uplink co-channel interference (MFU-CCI). It is shown that our design collects multipath diversity without estimating the interference channels and is robust to MFU-CCI. Simulation results validate our findings.

关键词： femtocell macrocell co-channel interference frequency division multiple access uplink interference mitigation multipath diversity linear precoder

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Blind CFO Estimation for linearly Precoded OFDMA Uplink

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2010年第9期58卷 4698-4710页

作者： Movahhedian, Mohammad Ma, Yi Tafazolli, Rahim Univ Surrey Ctr Commun Syst Res Surrey GU2 7XH England

This paper presents a novel method for blind carrier-frequency-offset (CFO) estimation in linearly precoded OFDMA uplink. Our investigation starts from the single-user equivalent (SUE) scenario presented in [ 2] where active users in the network are categorized into a number of reference (synchronized) users (RUs) and a new (asynchronous) user (NU). The major idea is to take advantage of time correlation induced by the linear precoder, which offers a second-order moments-based blind CFO estimation. The precoder design is carefully performed in terms of CFO identifiability, estimation accuracy and overall system performance. In the multiuser scenario, where all users can be misaligned in frequency domain, the proposed CFO estimator is capable of mitigating a considerable portion of interference from neighboring users through exploitation of a novel time-frequency multiuser data-mapping (MU-DM) scheme. To demonstrate the multiuser interference (MUI)-resilience feature of proposed scheme, theoretical analysis is performed through derivation of approximate minimum-mean-square error (MMSE) in both SUE and multiuser scenarios. It is shown that by exploitation of the proposed MU-DM scheme, the approximate multiuser MMSE is very close to that of SUE scenario. Simulation results show that the proposed approach outperforms state-of-the-art approaches in both SUE and multiuser scenarios.

关键词： Blind estimation carrier frequency offset (CFO) linear precoder multiuser interference (MUI) orthogonal frequency-division multiple-access (OFDMA) uplink

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Communication over doubly selective channels: Efficient equalization and max-diversity precoding

Communication over doubly selective channels: Efficient equa...

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作者： Hwang, Sung Jun The Ohio State University

学位级别：Ph.D.

We consider the problem of practical communication over a doubly selective (DS) channel, i.e., a time and frequency selective channel. The problem is approached in two different ways: coherent communication and noncoherent communication, and for each communication scheme we propose practical and near-optimal equalizers and maximum-diversity precoders. Toward these ends, we adopt (1) basis expansion (BE) modeling of the channel, which allows for an efficient and unified way of describing a DS channel in both time and frequency domain; and (2) tree-search algorithms (TSAs), which facilitate near-optimal performance with low complexity.@pqdt@break@For practical coherent communication, we focus on the pulse-shaped (PS) multicarrier modulation (MCM), where controlled inter-symbol-interference (ISI) and intercarrier- interference (ICI) can be leveraged for computationally efficient receiver structures. Then, we propose a novel channel adaptive TSA with a novel fast minimum mean-squared error (MMSE) generalized decision-feedback equalizer (GDFE) preprocessing, and a rank-reduced channel estimation by using the BE channel model. Also, a new finding about optimality of MMSE-GDFE preprocessing is presented, which states that under constant modulus constellation the minimum distance property is preserved by the MMSE-GDFE preprocessing.@pqdt@break@Then, two practically realizable noncoherent equalization schemes are proposed: a sequential algorithm and a Bayesian expectation maximization (EM)-based algorithm. The sequential algorithm is derived from the optimal noncoherent metric, and made practical by a fast algorithm and a TSA to evaluate and search over the metric. The Bayesian EM-based noncoherent algorithm is derived from optimal maximum a posteriori (MAP) estimation of the BE parameters, and efficiently implemented via iteration between soft coherent equalizer and soft channel estimator. Efficient operations are accomplished using fast algorithms whose overall complexitie

关键词： Electrical Engineering wireless communication digital communication equalization detection estimation precoding affine precoder linear precoder coherent noncoherent turbo receiver basis expansion noncoherent metric multicarrier ISI ICI diversity order

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Optimal linear precoder design for space-time block coded systems

Optimal linear precoder design for space-time block coded sy...

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2nd IEEE International Conference on Wireless Communications, Networking and Mobile Computing (WiCOM 2006)

作者： Zhao, Zhenshan Xu, Guozhi Shanghai Jiao Tong Univ Dept Elect Engn Shanghai 200030 Peoples R China

ISBN: (纸本)9781424405169

Taking the pairwise error probability (PEP) as the performance criterion and exploiting the channel covariance information at the transmitter, this paper studies the optimal linear precoder design of the correlated multiple-input multiple-output (MIMO) wireless system. The precoder can be used along with an), space-time block codes (STBC), which is an extension of reference [10]. The optimal beamforming direction of the precoder is proved to match the structure of STBC and transmit correlation matrix. The optimal power allocation scheme is related to transmit correlation matrix, receive correlation matrix and STBC The quasi-orthogonal space-time block codes (QSTBC) is taken as an illustration to investigate the performance of the optimal precoder.

关键词： linear precoder space-time block codes pairwise error probability

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precoder design for space-time coded MIMO systems with imperfect channel state information

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2008年第6期7卷 1977-1981页

作者： Huang, Jane W. An, Edward K. S. Lau, Vincent K. N. Univ British Columbia Dept Elect & Comp Engn Vancouver BC V5Z 1M9 Canada Hong Kong Univ Sci & Technol Dept Elect & Comp Engn Hong Kong Hong Kong Peoples R China

We address the problem of designing a linear precoder for space-time coded multiple-input multiple-output (MIMO) system with imperfect knowledge of channel state information at the transmitter (CSIT), subject to a total transmit power constraint. Assuming an uncorrelated flat-fading channel and using a maximum likelihood decoder at the receiver, we analytically reveal that the derived precoder is a function of the noise variance, the eigenvalues of the estimated channel matrix and the eigenvalues of the codeword distance matrix. Furthermore, the power allocation on the eigenvalues of the precoder is shown to follow the water-pouring policy and hence the proposed precoder allocates more power to the stronger channels.

关键词： channel state information linear precoder MIMO space-time code

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linear precoding for MIMO channels with outdated channel state information in multiuser space-time block coded systems with multi-packet reception

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2008年第6期7卷 2300-2306页

作者： Au, Edward K. S. Huang, Jane W. Lau, Vincent K. N. Hong Kong Univ Sci & Technol Dept Elect & Comp Engn Hong Kong Hong Kong Peoples R China Univ British Columbia Dept Elect & Comp Engn Vancouver BC V5Z 1M9 Canada

We propose a joint set of linear precoder designs for single cell uplink multiuser space-time block coded multiple-input multiple-output systems with multi-packet reception by exploiting outdated channel state information. By deriving the pairwise error probability with respect to both minimum and average codeword distance design metrics, we formulate the design as an optimization problem subject to transmit power constraint for each user. Due to the non-convex nature of the optimization problem, we devise an iterative algorithm to solve for linear precoding structure for general space-time block code. For orthogonal space-time block code, we also propose a simplified distributed algorithm to solve for a closed-form solution. Asymptotic analysis on the effect of quality of the outdated channel state information (CSI) on the precoder structure is also presented. Simulation results are provided to demonstrate the effectiveness of the proposed designs for different space-time block codes at various CSI qualities.

关键词： channel state information linear precoder MIMO multiuser

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Multiuser diversity for MIMO broadcast and multiple access channel with linear precoder and receiver

Multiuser diversity for MIMO broadcast and multiple access c...

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15th IEEE International Symposium on Personal, Indoor, Mobile, Radio Communications (PIMRC 2004)

作者： Shao, X Yuan, JH Rapajic, P Univ New S Wales Sch Elect Engn & Telecom Sydney NSW 2052 Australia

ISBN: (纸本)0780385233

In this paper, we study the multiuser diversity in both multiple-input multiple output (MIMO) multiple-access channel (MAC) and MIMO broadcast channel (BC). We consider multi-user scheduling with linear receivers for uplink and linear precoders for downlink. In each time slot, a group of users are selected in either transmission or reception. Based on the performance analysis, a criterion of selecting a number of active users to optimize error performance is presented. We show that the linear processing for downlink and uplink achieves the same SNR. This makes it convenient to use a single scheduling algorithm in both downlink and uplink. Furthermore, we present an analysis of the performance of the proposed scheduling algorithm. It is shown that the analysis agrees with the simulation.

关键词： multiuser diversity MIMO BC MIMO MAC linear precoder linear receiver

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MIMO precoding structures for frequency-flat and frequency-selective fading channels

MIMO precoding structures for frequency-flat and frequency-s...

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1st International Conference on Communications and Electronics (ICCE 2006)

作者： Bahrami, Hamid Reza Le-Ngoc, Tho McGill Univ Dept ECE 3480 Univ Montreal PQ H3A 2A7 Canada

ISBN: (纸本)9781424405688

This paper presents optimum MIMO precoder designs based on transmit and receive correlation matrices to maximize the ergodic channel capacily for both frequency-flat and frequency-selective fading channels. It is shown that the optimum MIMO precoder in a frequency-flat fading channel is an eigen beamformer with beams referred to the eigen-modes of the transmit correlation matrix. By using the multi-path representation of a frequency-selective fading channel, the corresponding optimum precoding structure is derived. For a frequency-selective fading channel that can be represented by L uncorrelated effective paths, the optimum precoding structure consists of P+L parallel eigen-beamformers. Simulation results show that the proposed precoders can improve the ergodic capacity of both frequency-flat and frequency-selective fading channels, especially for channels with high spatial correlation.

关键词： MIMO channel linear precoder partial channel knowledge spatial correlation

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