The Experts below are selected from a list of 390 Experts worldwide ranked by ideXlab platform
Andreas F. Molisch - One of the best experts on this subject based on the ideXlab platform.
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Joint Optimization of Hybrid Beamforming for Multi-User Massive MIMO Downlink
IEEE Transactions on Wireless Communications, 2018Co-Authors: Zheda Li, Shengqian Han, Seun Sangodoyin, Rui Wang, Andreas F. MolischAbstract:IEEE Considering the design of two-stage beamformers for the downlink of multi-user massive multiple-input-multiple-output (MIMO) system in frequency division duplexing (FDD) mode, this paper investigates the case where both link ends are equipped with hybrid digital/analog (HDA) beamforming structures. A virtual sectorization is realized by channel-statistics-based user grouping and analog beamforming, where the user equipment (UE) only needs to feed back its intra-group effective channel, and the overall cost of channel state information (CSI) acquisition is significantly reduced. Under the Kronecker channel model assumption, we first show that the strongest eigenbeams of the Receive Correlation matrix form the optimal analog combiner to maximize the intra-group signal to inter-group interference plus noise ratio. Then, with the partial knowledge of instantaneous CSI, we jointly optimize the digital precoder and combiner by maximizing a lower bound of the conditional average net sum-rate. Simulations over the propagation channels obtained from geometric-based stochastic models, ray tracing results, and measured outdoor channels, demonstrate that our proposed beamforming strategy outperforms state-of-the-art methods.
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ICC - Hybrid beamforming design for millimeter-wave multi-user massive MIMO downlink
2016 IEEE International Conference on Communications (ICC), 2016Co-Authors: Zheda Li, Andreas F. MolischAbstract:In this paper, we consider the design of two-stage beamformers for the downlink of multi-user frequency-division-duplexing (FDD) massive multiple-input multiple-output (MIMO) systems. We consider the case that both link ends are equipped with hybrid analog/digital (HDA) beamforming structures. With analog beamforming and user grouping based on the second-order channel statistics, the user equipment (UE) only needs to feed back its intra-group effective channel. We first show that the strongest eigenbeams of the Receive Correlation matrix form the optimal analog combiner under the Kronecker channel model assumption. Then, with limited instantaneous channel state information, we jointly optimize the digital precoder and combiner for conditional average net sum-rate maximization by maximizing its lower bound. To initialize our algorithm efficiently, we present a digital precoder design to maximize the conditional average signal-to-leakage-plus-noise ratio (SLNR). Simulation results show significant performance improvements compared to state-of-the-art algorithms.
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Hybrid beamforming design for millimeter-wave multi-user massive MIMO downlink
2016 IEEE International Conference on Communications ICC 2016, 2016Co-Authors: Zheda Li, Shengqian Han, Andreas F. MolischAbstract:In this paper, we consider the design of two- stage beamformers for the downlink of multi-user frequency- division-duplexing (FDD) massive multiple-input multiple-output (MIMO) systems. We consider the case that both link ends are equipped with hybrid analog/digital (HDA) beamforming structures. With analog beamforming and user grouping based on the second-order channel statistics, the user equipment (UE) only needs to feed back its intra-group effective channel.We first show that the strongest eigenbeams of the Receive Correlation matrix form the optimal analog combiner under the Kronecker channel model assumption. Then, with limited instantaneous channel state information, we jointly optimize the digital precoder and combiner for conditional average net sum-rate maximization by maximizing its lower bound. To initialize our algorithm efficiently, we present a digital precoder design to maximize the conditional average signal-to-leakage-plus-noise ratio (SLNR). Simulation results show significant performance improvements compared to state-of-the-art algorithms.
Arogyaswami J. Paulraj - One of the best experts on this subject based on the ideXlab platform.
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Impact of the propagation environment on the performance of space-frequency coded MIMO-OFDM
IEEE Journal on Selected Areas in Communications, 2003Co-Authors: Helmut Bolcskei, Moritz Borgmann, Arogyaswami J. PaulrajAbstract:Previous work on space-frequency coded multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) has been restricted to idealistic propagation conditions. In this paper, using a broadband MIMO channel model taking into account Ricean K-factor, transmit and Receive angle spread, and antenna spacing, we study the impact of the propagation environment on the performance of space-frequency coded MIMO-OFDM. For a given space-frequency code, we quantify the achievable diversity order and coding gain as a function of the propagation parameters. We find that while the presence of spatial Receive Correlation affects all space-frequency codes equally, spatial fading Correlation at the transmit array can result in widely varying performance losses. High-rate space-frequency codes such as spatial multiplexing are typically significantly more affected by transmit Correlation than low-rate codes such as space-frequency block codes. We show that in the MIMO Ricean case the presence of frequency-selectivity typically results in improved performance compared to the frequency-flat case.
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EUSIPCO - Performance of space-frequency coded broadband OFDM under real-world propagation conditions
2002Co-Authors: Helmut Bolcskei, Moritz Borgmann, Arogyaswami J. PaulrajAbstract:In this paper, using a spatial broadband channel model taking into account transmit and Receive antenna Correlation, we study the influence of propagation conditions on the performance of space-frequency coded OFDM. For a given space-frequency code, we quantify the achievable diversity order and coding gain as a function of the transmit and Receive Correlation matrices. We find that the presence of transmit Correlation results in widely varying performance losses. High-rate space-frequency codes such as spatial multiplexing are typically significantly more affected by transmit Correlation than low-rate codes such as space-frequency block codes.
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Performance of space-frequency coded broadband OFDM under real-world propagation conditions
2002 11th European Signal Processing Conference, 2002Co-Authors: Helmut Bolcskei, Moritz Borgmann, Arogyaswami J. PaulrajAbstract:In this paper, using a spatial broadband channel model taking into account transmit and Receive antenna Correlation, we study the influence of propagation conditions on the performance of space-frequency coded OFDM. For a given space-frequency code, we quantify the achievable diversity order and coding gain as a function of the transmit and Receive Correlation matrices. We find that the presence of transmit Correlation results in widely varying performance losses. High-rate space-frequency codes such as spatial multiplexing are typically significantly more affected by transmit Correlation than low-rate codes such as space-frequency block codes.
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Characterizing the statistical properties of mutual information in MIMO channels: insights into diversity-multiplexing tradeoff
Conference Record of the Thirty-Sixth Asilomar Conference on Signals Systems and Computers 2002., 2002Co-Authors: O. Oyman, Helmut Bolcskei, R.u. Nabar, Arogyaswami J. PaulrajAbstract:We consider Gaussian multiple-input multiple-output (MIMO) fading channels assuming that the channel is unknown at the transmitter and perfectly known at the Receiver. Taking into account spatial fading Correlation both at the transmitter and the Receiver, a tight closed-form lower-bounds is provided for ergodic capacity and an accurate closed-form approximations of the variance of mutual information are derived over such channels. Based on these results, we investigate the impact of the number of antennas and transmit and Receive Correlation on ergodic capacity and on the variance of mutual information and draw insights into the tradeoff between diversity gain and spatial multiplexing gain.
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Performance of space-time codes in the presence of spatial fading Correlation
Conference Record of the Thirty-Fourth Asilomar Conference on Signals Systems and Computers (Cat. No.00CH37154), 2000Co-Authors: Helmut Bolcskei, Arogyaswami J. PaulrajAbstract:Previous work on space-time coding has been restricted to the idealistic case of uncorrelated spatial fading. In practice, however insufficient antenna spacing or lack of scattering cause the individual antennas to be correlated. In this paper we study the impact of spatial fading Correlation on the performance of space-time codes. In particular we quantify the loss in diversity gain and coding gain as a function of angle spread and antenna spacing. We furthermore show that if a space-time code achieves full diversity in the uncorrelated case, the diversity order achieved in the correlated case is given by the product of the rank of the transmit Correlation matrix and the rank of the Receive Correlation matrix. Finally, we provide simulation results demonstrating the impact of spatial fading Correlation on the symbol error rate of space-time codes.
David Gesbert - One of the best experts on this subject based on the ideXlab platform.
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Precoding of orthogonal space-time block codes in arbitrarily correlated MIMO channels: Iterative and closed-form solutions
IEEE Transactions on Wireless Communications, 2007Co-Authors: Are Hjorungnes, David GesbertAbstract:A memoryless precoder is designed for orthogonal space-time block codes (OSTBCs) for multiple-input multiple-output (MIMO) channels exhibiting joint transmit-Receive Correlation. Unlike most previous similar works which concentrate on transmit Correlation only and pair-wise error probability (PEP) metrics. 1) The precoder is designed to minimize the exact symbol error rate (SER) as function of the channel Correlation coefficients, which are fed back to the transmitter. 2) The Correlation is arbitrary as it may or may not follow the so-called Kronecker structure. 3) The proposed method can handle general propagation settings including those arising from a cooperative macro-diversity (multi-base) scenario. We present two algorithms. The first is suboptimal, but provides a simple closed-form precoder that handles the case of uncorrelated transmitters, correlated Receivers. The second is a fast-converging numerical optimization of the exact SEE which covers the general case. Finally, a number of novel properties of the minimum SER precoder are derived
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Precoding of space-time block coded signals for joint transmit-Receive correlated MIMO channels
IEEE Transactions on Wireless Communications, 2006Co-Authors: Are Hjorungnes, David Gesbert, J. AkhtarAbstract:A memoryless linear precoder is designed for orthogonal space-time block codes (OSTBC) for improved performance over block-fading flat correlated Rayleigh fading multiple-input multiple-output (MIMO) channels. Original features of the proposed technique include 1) the precoder can handle both transmit and Receive Correlation, and 2) the precoder handles any arbitrary joint Correlation structure, including the so-called Kronecker (non-Kronecker) Correlation models. The precoder is designed to minimize a symbol error-based metric as function of the joint slowly-varying channel Correlation coefficients, which are supposed to be known to the transmitter. Several useful properties of the optimal precoder are given, evidencing the impact of Receive Correlation on transmitter optimization in certain situations. An iterative fast-converging numerical optimization algorithm is proposed. Monte Carlo simulations over fading channels are used to validate our claims.
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GLOBECOM - Minimum exact SER precoding of orthogonal space-time block codes for correlated MIMO channels
IEEE Global Telecommunications Conference 2004. GLOBECOM '04., 2004Co-Authors: Are Hjorungnes, David GesbertAbstract:A memoryless precoder is designed for orthogonal space-time block codes for multiple-input multiple-output channels exhibiting joint transmit-Receive Correlation. Unlike most previous similar work which concentrated on transmit Correlation only and pair-wise error probability (PEP) metrics, the precoder is designed to minimize the exact symbol error rate (SER) as a function of the channel Correlation coefficients, which are fed back to the transmitter, and the Correlation may or may not follow the so-called Kronecker structure. The proposed method can handle general propagation settings including those arising from a cooperative macro-diversity (multi-base) scenario. We present two algorithms. The first is suboptimal, but provides a simple closed-form precoder that handles the case of uncorrelated transmitters, correlated Receivers. The second is a fast-converging numerical optimization which covers the general case. The results show the SER based precoder has small gains over the PEP based precoder for moderate signal-to-noise ratios (SNR). Several properties of the minimum SER precoder are given.
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Minimum exact SER precoding of orthogonal space-time block codes for correlated MIMO channels
IEEE Global Telecommunications Conference 2004. GLOBECOM '04., 2004Co-Authors: Are Hjorungnes, David GesbertAbstract:A memoryless precoder is designed for orthogonal space-time block codes for multiple-input multiple-output channels exhibiting joint transmit-Receive Correlation. Unlike most previous similar work which concentrated on transmit Correlation only and pair-wise error probability (PEP) metrics, the precoder is designed to minimize the exact symbol error rate (SER) as a function of the channel Correlation coefficients, which are fed back to the transmitter, and the Correlation may or may not follow the so-called Kronecker structure. The proposed method can handle general propagation settings including those arising from a cooperative macro-diversity (multi-base) scenario. We present two algorithms. The first is suboptimal, but provides a simple closed-form precoder that handles the case of uncorrelated transmitters, correlated Receivers. The second is a fast-converging numerical optimization which covers the general case. The results show the SER based precoder has small gains over the PEP based precoder for moderate signal-to-noise ratios (SNR). Several properties of the minimum SER precoder are given.
Are Hjorungnes - One of the best experts on this subject based on the ideXlab platform.
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Precoding of orthogonal space-time block codes in arbitrarily correlated MIMO channels: Iterative and closed-form solutions
IEEE Transactions on Wireless Communications, 2007Co-Authors: Are Hjorungnes, David GesbertAbstract:A memoryless precoder is designed for orthogonal space-time block codes (OSTBCs) for multiple-input multiple-output (MIMO) channels exhibiting joint transmit-Receive Correlation. Unlike most previous similar works which concentrate on transmit Correlation only and pair-wise error probability (PEP) metrics. 1) The precoder is designed to minimize the exact symbol error rate (SER) as function of the channel Correlation coefficients, which are fed back to the transmitter. 2) The Correlation is arbitrary as it may or may not follow the so-called Kronecker structure. 3) The proposed method can handle general propagation settings including those arising from a cooperative macro-diversity (multi-base) scenario. We present two algorithms. The first is suboptimal, but provides a simple closed-form precoder that handles the case of uncorrelated transmitters, correlated Receivers. The second is a fast-converging numerical optimization of the exact SEE which covers the general case. Finally, a number of novel properties of the minimum SER precoder are derived
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Precoding of space-time block coded signals for joint transmit-Receive correlated MIMO channels
IEEE Transactions on Wireless Communications, 2006Co-Authors: Are Hjorungnes, David Gesbert, J. AkhtarAbstract:A memoryless linear precoder is designed for orthogonal space-time block codes (OSTBC) for improved performance over block-fading flat correlated Rayleigh fading multiple-input multiple-output (MIMO) channels. Original features of the proposed technique include 1) the precoder can handle both transmit and Receive Correlation, and 2) the precoder handles any arbitrary joint Correlation structure, including the so-called Kronecker (non-Kronecker) Correlation models. The precoder is designed to minimize a symbol error-based metric as function of the joint slowly-varying channel Correlation coefficients, which are supposed to be known to the transmitter. Several useful properties of the optimal precoder are given, evidencing the impact of Receive Correlation on transmitter optimization in certain situations. An iterative fast-converging numerical optimization algorithm is proposed. Monte Carlo simulations over fading channels are used to validate our claims.
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GLOBECOM - Minimum exact SER precoding of orthogonal space-time block codes for correlated MIMO channels
IEEE Global Telecommunications Conference 2004. GLOBECOM '04., 2004Co-Authors: Are Hjorungnes, David GesbertAbstract:A memoryless precoder is designed for orthogonal space-time block codes for multiple-input multiple-output channels exhibiting joint transmit-Receive Correlation. Unlike most previous similar work which concentrated on transmit Correlation only and pair-wise error probability (PEP) metrics, the precoder is designed to minimize the exact symbol error rate (SER) as a function of the channel Correlation coefficients, which are fed back to the transmitter, and the Correlation may or may not follow the so-called Kronecker structure. The proposed method can handle general propagation settings including those arising from a cooperative macro-diversity (multi-base) scenario. We present two algorithms. The first is suboptimal, but provides a simple closed-form precoder that handles the case of uncorrelated transmitters, correlated Receivers. The second is a fast-converging numerical optimization which covers the general case. The results show the SER based precoder has small gains over the PEP based precoder for moderate signal-to-noise ratios (SNR). Several properties of the minimum SER precoder are given.
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Minimum exact SER precoding of orthogonal space-time block codes for correlated MIMO channels
IEEE Global Telecommunications Conference 2004. GLOBECOM '04., 2004Co-Authors: Are Hjorungnes, David GesbertAbstract:A memoryless precoder is designed for orthogonal space-time block codes for multiple-input multiple-output channels exhibiting joint transmit-Receive Correlation. Unlike most previous similar work which concentrated on transmit Correlation only and pair-wise error probability (PEP) metrics, the precoder is designed to minimize the exact symbol error rate (SER) as a function of the channel Correlation coefficients, which are fed back to the transmitter, and the Correlation may or may not follow the so-called Kronecker structure. The proposed method can handle general propagation settings including those arising from a cooperative macro-diversity (multi-base) scenario. We present two algorithms. The first is suboptimal, but provides a simple closed-form precoder that handles the case of uncorrelated transmitters, correlated Receivers. The second is a fast-converging numerical optimization which covers the general case. The results show the SER based precoder has small gains over the PEP based precoder for moderate signal-to-noise ratios (SNR). Several properties of the minimum SER precoder are given.
Zheda Li - One of the best experts on this subject based on the ideXlab platform.
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Joint Optimization of Hybrid Beamforming for Multi-User Massive MIMO Downlink
IEEE Transactions on Wireless Communications, 2018Co-Authors: Zheda Li, Shengqian Han, Seun Sangodoyin, Rui Wang, Andreas F. MolischAbstract:IEEE Considering the design of two-stage beamformers for the downlink of multi-user massive multiple-input-multiple-output (MIMO) system in frequency division duplexing (FDD) mode, this paper investigates the case where both link ends are equipped with hybrid digital/analog (HDA) beamforming structures. A virtual sectorization is realized by channel-statistics-based user grouping and analog beamforming, where the user equipment (UE) only needs to feed back its intra-group effective channel, and the overall cost of channel state information (CSI) acquisition is significantly reduced. Under the Kronecker channel model assumption, we first show that the strongest eigenbeams of the Receive Correlation matrix form the optimal analog combiner to maximize the intra-group signal to inter-group interference plus noise ratio. Then, with the partial knowledge of instantaneous CSI, we jointly optimize the digital precoder and combiner by maximizing a lower bound of the conditional average net sum-rate. Simulations over the propagation channels obtained from geometric-based stochastic models, ray tracing results, and measured outdoor channels, demonstrate that our proposed beamforming strategy outperforms state-of-the-art methods.
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ICC - Hybrid beamforming design for millimeter-wave multi-user massive MIMO downlink
2016 IEEE International Conference on Communications (ICC), 2016Co-Authors: Zheda Li, Andreas F. MolischAbstract:In this paper, we consider the design of two-stage beamformers for the downlink of multi-user frequency-division-duplexing (FDD) massive multiple-input multiple-output (MIMO) systems. We consider the case that both link ends are equipped with hybrid analog/digital (HDA) beamforming structures. With analog beamforming and user grouping based on the second-order channel statistics, the user equipment (UE) only needs to feed back its intra-group effective channel. We first show that the strongest eigenbeams of the Receive Correlation matrix form the optimal analog combiner under the Kronecker channel model assumption. Then, with limited instantaneous channel state information, we jointly optimize the digital precoder and combiner for conditional average net sum-rate maximization by maximizing its lower bound. To initialize our algorithm efficiently, we present a digital precoder design to maximize the conditional average signal-to-leakage-plus-noise ratio (SLNR). Simulation results show significant performance improvements compared to state-of-the-art algorithms.
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Hybrid beamforming design for millimeter-wave multi-user massive MIMO downlink
2016 IEEE International Conference on Communications ICC 2016, 2016Co-Authors: Zheda Li, Shengqian Han, Andreas F. MolischAbstract:In this paper, we consider the design of two- stage beamformers for the downlink of multi-user frequency- division-duplexing (FDD) massive multiple-input multiple-output (MIMO) systems. We consider the case that both link ends are equipped with hybrid analog/digital (HDA) beamforming structures. With analog beamforming and user grouping based on the second-order channel statistics, the user equipment (UE) only needs to feed back its intra-group effective channel.We first show that the strongest eigenbeams of the Receive Correlation matrix form the optimal analog combiner under the Kronecker channel model assumption. Then, with limited instantaneous channel state information, we jointly optimize the digital precoder and combiner for conditional average net sum-rate maximization by maximizing its lower bound. To initialize our algorithm efficiently, we present a digital precoder design to maximize the conditional average signal-to-leakage-plus-noise ratio (SLNR). Simulation results show significant performance improvements compared to state-of-the-art algorithms.
