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On the use of H-inf criterion in channel estimation and precoding in massive MIMO systems

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Science China(Information Sciences) 2017年第2期60卷 151-164页

作者： Peng XU dongming wang Feng QI School of Computer Science and Engineering Northeastern University National Mobile Communications Research Laboratory Southeast University Key Laboratory of Opto-Electronic Information Processing Institute of AutomationChinese Academy of Science

In this paper, a channel estimation(CE) and precoding scheme by using H-infinity(H-inf) criterion for mitigation of pilot contamination(PC) in massive multiple input multiple output(MIMO) orthogonal frequency division multiplexing(OFDM) systems is investigated. Firstly, different thresholds in H-inf CE and precoding are considered. Secondly, asymptotic analysis is presented to simplify the H-inf precoding, which shows that the complexity of an order of magnitude is reduced. Thirdly, approximate downlink achievable data rates per user are studied for different CE and precoding schemes, such as H-inf and minimum mean square error(MMSE) CE, MMSE, zero-forcing(ZF) and H-inf precoding. The analysis shows that the proposed scheme can provide dual mitigation to the PC. That is, the H-inf CE mitigates the PC by adjusting its thresholds, and the H-inf precoding is utilized to suppress the PC by considering inter-cell interference. The numerical results show that joint use of H-inf CE and H-inf precoding outperforms existing schemes in terms of mitigation to the PC.

关键词： massive MIMO pilot contamination precoding channel estimation H-inf

Impact of RF mismatches on the performance of massive MIMO systems with ZF precoding

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Science China(Information Sciences) 2016年第2期59卷 31-44页

作者： Hao WEI dongming wang Jiangzhou wang Xiaohu YOU National Mobile Communications Research Laboratory Southeast University School of Engineering and Digital Arts University of Kent

Thanks to the channel reciprocity, the time division duplex(TDD) operation is more preferred in massive multiple-input multiple-output(MIMO) systems. Avoiding the heavy feedback of downlink channel state information(CSI) from the user equipment(UE) to the base station(BS), the uplink CSI can be exploited for the downlink precoding. However, due to the mismatches of the radio frequency(RF) circuits at both sides of the link, the whole communication channels are usually not symmetric in practical systems. This paper is focused on the RF mismatches at the UEs and the BS for the multi-user massive MIMO systems with zero forcing(ZF) precoding. The closed-form expressions of the ergodic sum-rates are derived for evaluating the impact of RF mismatches on the system performance. Theoretical analysis and simulation results show that the RF mismatches at the UEs only lead to a negligible performance loss. However, it is imperative to perform reciprocity calibration at the BS, because the RF mismatches at the BS contribute to the inter-user interference(IUI) and result in a severe system performance degradation.

关键词： massive MIMO RF mismatch TDD operation channel reciprocity antenna calibration

TDD reciprocity calibration for multi-user massive MIMO systems with iterative coordinate descent

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Science China(Information Sciences) 2016年第10期59卷 93-102页

作者： Hao WEI dongming wang Jiangzhou wang Xiaohu YOU National Mobile Communications Research Laboratory Southeast University School of Engineering and Digital Arts University of Kent

For massive multiple-input multiple-output(MIMO) antenna systems, time division duplexing(TDD) is preferred since the downlink precoding matrix can be obtained through the uplink channel estimation,thanks to the channel reciprocity. However, the mismatches of the transceiver radio frequency(RF) circuits at both sides of the link make the whole communication channel non-symmetric. This paper extends the total least square(TLS) method to the case of self-calibration, where only the antennas of the access points(APs) are involved to exchange the calibration signals with each other and the feedback from the user equipments(UEs)is not required. Then, the proof of the equivalence between the TLS method and the least square(LS) method is presented. Furthermore, to avoid the eigenvalue decomposition required by these two methods to obtain the calibration coefficients, a novel algorithm named as iterative coordinate descent(ICD) method is *** analysis and simulation results show that the ICD method significantly reduces the complexity and achieves almost the same performance of the LS method.

关键词： TDD reciprocity calibration total least squares coordinate descent large-scale MIMO

The second discriminant of a univariate polynomial

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Science China Mathematics 2021年第6期64卷 1157-1180页

作者： dongming wang Jing Yang BDBC LMIB and School of Mathematics and Systems ScienceBeihang UniversityBeijing 100191China SMS HCICGuangxi University for NationalitiesNanning 530006China Centre National de la Recherche Scientifique Paris 75794France

We define the second discriminant D_(2)of a univariate polynomial f of degree greater than 2 as the product of the linear forms 2r_(k)-r_(i)-r_(j)for all triples of roots r_(i),r_(k),r_(j)of f with i 详细信息

We define the second discriminant D_(2)of a univariate polynomial f of degree greater than 2 as the product of the linear forms 2r_(k)-r_(i)-r_(j)for all triples of roots r_(i),r_(k),r_(j)of f with i

关键词： determinant discriminant polynomial ideal resultant root configuration

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A framework for improving uniformity of parameterizations of curves

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Science China(Information Sciences) 2013年第10期56卷 190-211页

作者： HONG Hoon wang dongming YANG Jing Department of Mathematics North Carolina State University LIP6 CNRS—Universit′e Pierre et Marie Curie 4 place Jussieu—BP 16975252 Paris cedex 05 France LMIB—School of Mathematics and Systems Science Beihang University

We defne quasi-speed as a generalization of linear speed and angular speed for parameterizations of curves and use the uniformity of quasi-speed to measure the quality of the *** such conceptual setting,a general framework is developed for studying uniformity behaviors under reparameterization via proper parameter transformation and for computing reparameterizations with improved uniformity of quasispeed by means of optimal single-piece,C0piecewise,and C1piecewise M¨obius *** are described for uniformity-improved reparameterization using diferent Mo¨bius transformations with diferent optimization *** are presented to illustrate the concepts,the framework,and the *** results are provided to validate the framework and to show the efciency of the algorithms.

关键词： parametric curve framework quasi-speed uniform parameterization uniformity-improved reparameterization optimal Mo¨bius transformation

Impacts of practical channel impairments on the downlink spectral efficiency of large-scale distributed antenna systems

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Science China(Information Sciences) 2019年第2期62卷 146-159页

作者： Jiamin LI dongming wang Pengcheng ZHU Xiaohu YOU National Mobile Communications Research Laboratory Southeast University

Channel impairments are major limiting factors in the performance of large-scale antenna systems. In this paper, we analyze the impacts of practical channel impairments caused by pilot contamination,Doppler shift, and phase noise on the downlink spectral efficiency of large-scale distributed antenna systems(L-DASs) with maximum ratio transmission(MRT) and zero-forcing(ZF) beamforming, in which per user power normalization is considered. Using a joint channel model that allows study of the simultaneous impacts of these channel impairments, we derive accurate and tractable closed-form approximations for the ergodic achievable downlink rate, thereby enabling spectral efficiency analysis of L-DASs and an efficient evaluation of the impacts of the channel impairments. It is shown that channel impairments reduce the downlink spectral efficiency and have a significant impact on ZF beamforming. The asymptotic user rate limit is also determined, from which we analyze the asymptotic performance of L-DASs with channel impairments. The analytical results show that MRT and ZF beamforming achieve the same asymptotic performance limit even with channel impairments. It is also found that the use of a large-scale antenna array at the base station sides can weaken the impacts of channel impairments.

关键词： Doppler shift phase noise large-scale distributed antenna systems spectral efficiency pilot contamination

Foreword to the Special Issue

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Journal of Systems Science & Complexity 2019年第1期32卷 1-2页

作者： GAO Xiao-Shan LI Hongbo wang dongming Key Laboratory of Mathematics Mechanization Academy of Mathematics and Systems Science University of Chinese Academy of Sciences Chinese Academy of Sciences LMIB–SKLSDE–School of Mathematics and Systems Science/Beijing Advanced Innovation Center for Big Data and Brain Computing Beihang University Centre National de la Recherche Scientifique

On May 12,2019 we shall celebrate the centenary birthday of the late Professor Wu Wen-Tsun (1919-2017),one of the most famous and influential mathematicians in *** made foundational contributions to the field of topology and established Mathematics Mechanization as a *** devoted himself to an academic career of more than six decades with leadership and extensive activities of research and education across mathematics to computer science and artificial *** scope of his research spans from algebraic topology, differential topology,and algebraic geometry to automated reasoning,symbolic computation, and game theory,and to the history of *** early work in topology was a major breakthrough,leading to well-known and now classical results including the characteristic class and formulas named after *** the late 1970s,he pioneered the research of Mathematics Mechanization through his invention of the "Wu method",which revolutionized the field of automated reasoning.

关键词： shall celebrate centenary birthday established Mathematics

维普期刊数据库

Joint optimization of spectral efficiency and energy efficiency with low-precision ADCs in cell-free massive MIMO systems

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Science China(Information Sciences) 2022年第5期65卷 169-183页

作者： Han wang Chang SUN Jiamin LI Pengcheng ZHU dongming wang Xiaohu YOU National Mobile Communications Research Laboratory Southeast University Purple Mountain Laboratories

In cell-free massive multiple-input multiple-output(MIMO) systems, it is beneficial to apply low-precision analog-to-digital converters(ADCs) to reduce power consumption, hardware cost, and the load on backhaul link. However, low-precision ADCs will result in serious degradation in spectral efficiency(SE). It is important to achieve a good tradeoff between SE and energy efficiency(EE) for cell-free massive MIMO systems with low-precision ADCs. In this paper, we first derive the closed-form expressions of uplink achievable rates with maximal ratio combining(MRC) receiver and zero-forcing(ZF) receiver in cell-free massive MIMO systems. Then we analyze the EE model of cell-free massive MIMO systems. Based on the above analysis, the tradeoff between SE and EE is studied. Moreover, we propose two quantization bit allocation algorithms to optimize the SE and EE jointly from the perspective of multi-objective *** algorithm is based on the deep Q-network(DQN) and the other one is based on the non-dominated sorting genetic algorithm Ⅱ(NSGA-Ⅱ). The proposed algorithms provide more feasible solutions and achieve better system performance than equal quantization bit allocation algorithm. Numerical results verify the accuracy of the derived closed-form expressions and the effectiveness of the proposed optimization algorithms.

关键词： cell-free massive MIMO low-precision ADC spectral efficiency energy efficiency multi-objective optimization

Hybrid beamforming design for mm Wave OFDM distributed antenna systems

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Science China(Information Sciences) 2020年第9期63卷 231-242+201-203页

作者： Yu ZHANG dongming wang Yiming HUO Xiaodai DONG Xiaohu YOU National Mobile Communications Research Laboratory Southeast University Purple Mountain Laboratory Southeast University Department of Electrical and Computer Engineering University of Victoria

This paper presents a hybrid beamforming design for millimeter-wave(mm Wave) orthogonal frequency division multiplexing(OFDM) distributed antenna systems(DASs). First, we derive a downlink signal transmission model that considers the delay spread differences(DSDs) caused by the distributed nature of the network. We then propose a cooperative wideband hybrid beamforming method under the transmitting power constraints of each remote access unit. In a simulation study, the proposed method performed comparably to fully-digital beamforming, even when operated with practical finite-resolution phase shifters. We further confirm that the DSDs are the dominant cause of performance degradation in mm Wave OFDM DASs.

关键词： hybrid beamforming distributed antenna systems millimeter wave OFDM delay spread differences synchronization