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Impact of non-ideal UE hardware on cell-free massive MIMO network with centralized operation

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Science China(Information Sciences) 2024年第4期67卷 255-271页

作者： Ning LI Pingzhi FAN Institute of Mobile communications Southwest Jiaotong university

This paper investigates the impact of non-ideal user equipment(UE) hardware on a cell-free(CF) massive MIMO(mMIMO) network with centralized operation under spatially correlated channels. The minimum mean-squared error(MMSE) estimator can be derived with the help of the generic non-ideal UE hardware model. It is demonstrated that even if the effective signal-to-noise ratio approaches infinity, pilot contamination and imperfect hardware can cause a non-zero estimation error floor. After that, a lower bound is determined for the ergodic uplink capacity of the centralized CF mMIMO network under non-ideal UE hardware. Moreover, the optimal receive combining vector is obtained to maximize the uplink spectral efficiency(SE). The maximum ratio(MR) and regularized zero-forcing(RZF) combining schemes are offered as alternatives in light of the computational complexity of the MMSE receiver. Comparing the RZF to the MMSE scheme under different levels of hardware impairments, our findings indicate that the RZF receiver suffers a negligible loss in total SE. For MR combining, a novel closed-form uplink achievable SE expression is obtained based on the MMSE estimator and the use-and-then-forget bounding technique. This expression gives vital insights into the achievable uplink performance with UE hardware impairments. Besides, for various hardware impairment factors, the impact of pilot sequence length on average sum SE is disclosed for different receive combining schemes. To increase the overall SE of the max-min fairness scheme, a heuristic fractional power control scheme with UE hardware impairments is developed, which can essentially avoid sacrificing the SE of other UEs while maximizing the SE of the unluckiest UE in the whole network. Finally,our theoretical performance analysis and power control algorithm are validated by simulation results, and fundamental design guidelines are provided for selecting hardware satisfying the practical UE requirements.

关键词： cell-free massive MIMO centralized operation spatially correlated channels hardware impairments channel estimation uplink spectral efficiency optimal receive combining pilot length design fractional power control

PERFORMANCE ANALYSIS OF OPTIMAL CHANNEL ESTIMATION AND MULTIUSER DETECTION IN A RANDOMLY-SPREAD CDMA CHANNEL

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Journal of Systems Science & Complexity 2010年第1期23卷 22-34页

作者： Keigo TAKEUCHI Mikko VEHKAPER Toshiyuki TANAKA Ralf R.MLLER Department of Information and Communication Engineering University of Electro-Communications Department of electronics and Telecommunications Norwegian University of Science and Technology Department of Systems Science Graduate School of InformaticsKyoto University

This paper analyzes performance of optimal channel estimation and multiuser detection(MUD) in a block-fading code-division multiple-access (CDMA) channel on the assumptions of randomspreading and large-system limit,by using the replica method developed in statistical mechanics.The authors find that the asymptotic spectral efficiency of the linear minimum mean-squared error(LMMSE) MUD which was proposed and analyzed by Evans and Tse in 2000 is indistinguishable fromthat of the optimal MUD for small system loads.Our results imply that performance of MUD scarcelyimproves even if one spends more computational cost than that of the LMMSE MUD,i.e.,at most thecube of the number of users,on the above-described conditions.

关键词：多用户检测随机大系统 CDMA 信道估计性能分析线性最小均方误差 LMMSE 通道

Energy consumption optimization for edge computing-supported cellular networks based on optimal transport theory

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Science China(Information Sciences) 2024年第2期67卷 201-218页

作者： Xiangyu LV Xiaohu GE Yi ZHONG Qiang LI Yong XIAO School of electronic Information and communications Huazhong University of Science and Technology

With advancements in mobile communication technologies, there have been multiple user device(UD) connections to cellular networks. Because of changes in the spatial distribution of UDs and application requirements, the traditional offloading mechanism based on the nearest distance will result in heavy loads for some base stations(BSs). Because there is a high-order relationship between the energy consumption of the BS processing tasks and the number of computing tasks, the traditional offloading mechanism will result in high energy consumption, and UD’s offloading decision must be dynamically adjusted. The offloading decision of UDs is optimized based on detailed information about various parameters associated with a network from the standpoint of distribution. This information includes details regarding the spatial distribution of UDs,application requirements, and the offloading period of computing tasks. Based on optimal transport theory,an energy consumption optimization algorithm is suggested to lower the total amount of energy consumed by the offloading process of UDs’ computing tasks by reasonably planning the offloading BSs of the UDs in the networks. The simulation results show that the proposed offloading mechanism based on energy consumption optimization reduces the total energy consumption of the offloading process by 28.09% when compared to the traditional offloading mechanism, and the traffic managed by each BS is balanced.

关键词： optimal transport theory edge computing energy consumption reduction dynamic voltage frequency scaling

Doppler-resilient waveform design in integrated MIMO radar-communication systems

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Science China(Information Sciences) 2024年第1期67卷 187-202页

作者： Zhengchun ZHOU Bing LIU Bingsheng SHEN Avik Ranjan ADHIKARY Pingzhi FAN Institute of Mobile communications Southwest Jiaotong University Department of Mathematics Southwest Jiaotong University

In recent years,the increased high-rate wireless services(5G and 6G) and reliable sensing capabilities(automotive radar,air traffic control,geophysical monitoring),have led to more serious spectrum congestion.Conventionally,radars and communication systems are often seen to be “competing” for the same resources.In this scenario,an integrated platform for radar and communication systems seems to be an optimal solution to address the problem.In this paper,we propose a preamble waveform design based on zero-correlation zone(ZCZ) and zero odd-correlation zone(ZOCZ) sequence sets,which are Doppler resilient in multiple-input,multiple-output(MIMO) radar.The preamble waveforms can be simultaneously used for channel estimation and radar sensing in RadCom systems.The ambiguity function of the proposed waveforms displays low/zero sidelobes within a time-delay correlation zone.Finally,we give some numerical results to show the efficiency of the proposed waveforms in radar sensing and channel estimation.

关键词： ambiguity function correlation channel estimation integrated radar and communication (RadCom) systems MIMO radar zero correlation zone (ZCZ) sequence set zero odd-correlation zone (ZOCZ) sequence set

Generation of 160 nm vacuum ultraviolet light at 82 MHz in a KBBF crystal by the fifth-harmonic of a Ti:sapphire laser

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Chinese Optics Letters 2024年第5期22卷 95-99页

作者：张赟汪丽蓉 Department of Engineering Science The University of Electro-CommunicationsTokyo 182-8585Japan State Key Laboratory of Quantum Optics and Quantum Optics Devices Institute of Laser SpectroscopyShanxi UniversityTaiyuan 030006China Collaborative Innovation Center of Extreme Optics Shanxi UniversityTaiyuan 030006China

We report the generation of quasi-cw vacuum ultraviolet(VUV)light at 160 nm with a repetition rate of 82 MHz by two second-harmonic generations and one sum frequency mixing.The VUV laser light is produced as a fifth-harmonic generation of a mode-locked ps Ti:sapphire laser system by successive stages with nonlinear crystals of LBO and KBBF.A stable generation of laser light at 200 nm for more than 6 h is the most important step for obtaining the generation of light at a wavelength of 160 nm.

关键词： vacuum ultraviolet light second harmonic generation sum frequency mixing

Spectrally resolved Franson interference

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Science China(Physics,Mechanics & Astronomy) 2024年第5期67卷 11-17页

作者： Rui-Bo Jin Zi-Qi Zeng Dan Xu Chen-Zhi Yuan Bai-Hong Li You Wang Ryosuke Shimizu Masahiro Takeoka Mikio Fujiwara Masahide Sasaki Pei-Xiang Lu Hubei Key Laboratory of Optical Information and Pattern Recognition Wuhan Institute of TechnologyWuhan 430205China School of Physics and Information Science Shaanxi University of Science and TechnologyXi'an 710021China Southwest Institute of Technical Physics Chengdu 610041China Graduate School of Informatics and Engineering University of Electro-CommunicationsTokyo 182-8585Japan Department of electronics and Electrical Engineering Keio UniversityKanagawa 223-8522Japan National Institute of Information and communications Technology Tokyo 184-8795Japan

Franson interference can be used to test the nonlocal features of energy-time entanglement and has become a standard in quantum physics.However,most of the previous Franson interference experiments were demonstrated in the time domain,and the spectral properties of Franson interference have not been fully explored.Here,we theoretically and experimentally demonstrate spectrally resolved Franson interference using biphotons with different correlations,including positive correlation,negative correlation,and non-correlation.It is found that the joint spectral intensities of the biphotons can be modulated along both the signal and idler directions,which has potential applications in generating high-dimensional frequency entanglement and time-frequency grid states.This work may provide a new perspective for understanding the spectral-temporal properties of the Franson interferometer.

关键词： resolved correlation spectral

Learning background restoration and local sparse dictionary for infrared small target detection

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Optoelectronics Letters 2024年第7期20卷 437-448页

作者： HE Yue ZHANG Rui XI Chunmei ZHU Hu School of communications and Information Engineering Nanjing University of Posts and Telecommunications

This paper proposes a method for learning background restoration for infrared small target detection, employing a local sparse dictionary alongside an equalized structural texture representation. The method is specifically designed for the detection of small infrared targets, accommodating various levels of brightness, spatial size, and intensity. Our proposed model intelligently combines global low-rankness and local sparsity to estimate the rank of the background tensor, leveraging spatial and structural information to overcome the limitations posed by insufficient detailed texture knowledge. Subsequently, a structural texture representation, combining local gradient maps and local intensity maps, is applied to emphasize small objects. By comparing our method with nine advanced and representative approaches and quantifying the comparison using various metrics, the experimental results indicate that our proposed method has achieved favorable outcomes in both quantitative assessments and visual results.

关键词： A

Remote Control for Robotic Systems Using CORBA as Communication Architecture

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仪器仪表学报 2002年第S2期23卷 968-974+979页

作者： Songmin Jia Yoshiro Hada Gang Ye Kunikatsu Takase (Graduate School of Information Systems ,university of electro-communications ,Chofu-City, Tokyo 182-8585, Japan) Graduate School of Information Systems University of Electro-communications Cho fu-City Tokyo 182-8585 Japan

This paper proposes a novel method to implement network connections among a client and remote robotic systems using CORBA for developing telecare system to aid the aged or disabled. The proposed method makes system have low cost and wide availability, high scaling and inter-operating ability to allow the clients and server objects, written in different languages, run in different operating system, and connected in different network to inter-operate. It also makes system easy to be extended and integrated with the other technologies and applications distributed over the Internet. Using CORBA as a communication architecture, we developed hardware base, task-level robot arm control server, live image feedback server and mobile robot control server, which can provide some basic care services to aid the aged and disabled.

关键词： Control Robotic system Internet architecture iGPS CORBA

Blockchain-Based MCS Detection Framework of Abnormal Spectrum Usage for Satellite Spectrum Sharing Scenario

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China communications 2024年第2期21卷 32-48页

作者： Ning Yang Heng Wang Jingming Hu Bangning Zhang Daoxing Guo Yuan Liu College of communications Engineering Army Engineering UniversityNanjing 210007China

In this paper, the problem of abnormal spectrum usage between satellite spectrum sharing systems is investigated to support multi-satellite spectrum coexistence. Given the cost of monitoring, the mobility of low-orbit satellites, and the directional nature of their signals, traditional monitoring methods are no longer suitable, especially in the case of multiple power level. Mobile crowdsensing(MCS), as a new technology, can make full use of idle resources to complete a variety of perceptual tasks. However, traditional MCS heavily relies on a centralized server and is vulnerable to single point of failure attacks. Therefore, we replace the original centralized server with a blockchain-based distributed service provider to enable its security. Therefore, in this work, we propose a blockchain-based MCS framework, in which we explain in detail how this framework can achieve abnormal frequency behavior monitoring in an inter-satellite spectrum sharing system. Then, under certain false alarm probability, we propose an abnormal spectrum detection algorithm based on mixed hypothesis test to maximize detection probability in single power level and multiple power level scenarios, respectively. Finally, a Bad out of Good(BooG) detector is proposed to ease the computational pressure on the blockchain nodes. Simulation results show the effectiveness of the proposed framework.

关键词： blockchain hypothesis test mobile crowdsensing satellite communication spectrum sharing