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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

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Energy-efficiency-aware relay selection in distributed full duplex relay network with massive MIMO

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Science China(Information Sciences) 2017年第2期60卷 126-140页

作者： Yongzhi LI Cheng TAO Liu LIU Lingwen ZHANG institute of Broadband Wireless mobile communications Beijing Jiaotong University National mobile communications Research Laboratory Southeast University

This paper considers a distributed full duplex relay network where multiple sources simultaneously transmit their signals to multiple destinations via the cooperation of a set of relay stations(RSs). Each RS is assumed to be equipped with large antenna arrays while all sources and destinations only have a single *** assume the channels are Rician fading and the RSs use linear processing to process the signals with imperfect channel state information(CSI). We derive the closed-form expressions of the end-to-end achievable rates for the maximum-ratio combining/matched-filter(MRC/MF) and the zero-forcing(ZF) processing. These results are then used to pursue a detailed analysis of the power saving of the relay network. Then we study the energy-efficiency-aware relay selection strategy since the energy efficiency affects network lifetime in future wireless network. We propose a sub-optimal strategy with low complexity that only requires the statistical *** show that the energy efficiency of the system can be improved with optimal power allocation and our proposed strategy performs very close to the exhaustive search algorithm which is optimal.

关键词： relay network full duplex massive MIMO relay selection energy efficiency

Investigation of Cross-Correlation Characteristics for Multi-Link Channels in High-Speed Railway Scenarios

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China communications 2018年第8期15卷 108-117页

作者： Tao Zhou Cheng Tao Liu Liu Kai Liu institute of Broadband Wireless mobile communications Beijing Jiaotong University National mobile communications Research Laboratory Southeast University

This paper investigates the cross-correlation characteristics of large-scale parameters(LSPs) and small-scale fading(SSF) for high-speed railway(HSR) multilink propagation scenarios, based on realistic measurements conducted on Beijing to Tianjin HSR line in China. A long-term evolution-based channel sounding system is utilized in the measurements to obtain the channel data. By applying a proposed time-delay based dynamic partition method, multi-link channel impulse responses are extracted from the raw channel data. Then, the statistical results of LSPs, including shadow fading, K-factor, and root-mean-square delay spread are derived and the cross-correlation coefficients of these LPSs are calculated. Moreover, the SSF spatial correlation and cross-correlation of SSF are analyzed. These results can be used to exploit multi-link channel model and to optimize the next-generation HSR communication system.

关键词： high-speed railway communications multi-link channel cross-correlation large-scale parameters small-scale fading.

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A low-floor bit-mapping scheme for LDPC coded BICM for 5G and beyond systems

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Science China(Information Sciences) 2023年第10期66卷 263-277页

作者： Mingyang ZHU Ming JIANG Chunming ZHAO Lijie HU Xiaodong XU National mobile communications Research Laboratory Southeast University Purple Mountain Laboratories China mobile Research institute

This paper proposes a low-floor bit-mapping(LFBM) scheme for bit-interleaved coded modulation(BICM) systems to meet more stringent quality of service requirements of 5G and beyond. For highefficiency transmissions, we consider the 5G low-density parity-check codes with high-order 2m-quadrature amplitude modulations(QAMs). The proposed LFBM scheme overcomes plenty of trapping sets induced by the bit interleaver, which focuses on the waterfall performance too aggressively. When the high-order QAM is used, the row-column interleaver specified by the 5G standard is such a bit interleaver. The LFBM scheme only optimizes the rule of mapping an m-bit tuple output by the row-column interleaver to a modulation symbol, rather than the entire bit interleaver. Therefore, the optimized bit mapper is actually an m-bit permutation module concatenated with the original bit interleaver employed in the current 5G BICM *** simulation results confirm that the LFBM scheme can lower the error floor of the 5G BICM system by approximately two orders of magnitude, while with negligible performance loss in the waterfall region.

关键词： bit-interleaved coded modulation low-density parity-check codes error floors bit mapping high-order modulation

Channel capacity investigation of a linear massive MIMO system using spherical wave model in LOS scenarios

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Science China(Information Sciences) 2016年第2期59卷 45-59页

作者： Liu LIU David W.MATOLAK Cheng TAO Yongzhi LI Bo AI Houjin CHEN institute of Broadband Wireless mobile communications Beijing Jiaotong University Department of Electrical Engineering University of South Carolina National mobile communications Research Laboratory Southeast University

Massive multiple-input multiple-output(MIMO) is a key technology for the 5th generation(5G)of wireless communication systems. The traditional plane wave channel model(PWM) is often not suitable for the large antenna structure, and in certain cases should be replaced by the more accurate spherical wave model(SWM). By using the spherical wave characterization method, this paper investigates the channel capacity performance of a linear massive MIMO system in line-of-sight(LOS) scenarios. Two types of access settings, the point to point(PTP) system and multi-user(MU) system, are considered. In the PTP setting, a geometrical optimization is performed to obtain configurations that are able to generate a full rank channel matrix for a linear massive MIMO system, which yields full spatial diversity even in LOS scenarios. Compared with the approximate and commonly applied rank-1 PWM, this is very useful for fixed wireless access and radio relay systems requiring high throughput. For the MU case, we compare the eigenvalue distributions of the LOS channels using the plane wave and spherical wave characterization method, and sum rate results are obtained by Monte Carlo simulations. The results show that MU systems using the more realistic and accurate SWM can achieve a higher sum rate than results from the PWM. This is beneficial and informative when designing massive MIMO wireless networks.

关键词： massive MIMO channel model plane wave model spherical wave model channel capacity

Advances in broadband wireless communications under high-mobility scenarios

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Chinese Science Bulletin 2014年第35期59卷 4974-4975页

作者： Pingzhi Fan institute of mobile communications Southwest Jiaotong University

未来活动通讯系统瞄准提供很高的数据传播率，甚至在象高速度的车轮轨道火车，磁悬浮火车火车，高速公路车辆，飞机，指导导弹或太空船那样的高活动性的情形。一个特别地重要的商业应用程序是对高速度的宽带的强壮、增加的世界范围的要... 详细信息

未来活动通讯系统瞄准提供很高的数据传播率，甚至在象高速度的车轮轨道火车，磁悬浮火车火车，高速公路车辆，飞机，指导导弹或太空船那样的高活动性的情形。一个特别地重要的商业应用程序是对高速度的宽带的强壮、增加的世界范围的要求无线通讯(多达 574.8 ? km/h 测试速度或 380 ? km/h 广告速度)为象为旅客的机载的娱乐服务那样的应用程序在铁路，提供的数据，声音和录像满足，火车控制，训练派遣，火车传感器地位处理和监视。在如此的高活动性的情形，有很多通讯挑战，包括快移交，更新的地点，当模特儿的高速度的隧道，评价和均等， anti-Doppler 传播技术，快力量控制，和奉献网络建筑学。因为在很高速度的情形的信号传播将不可避免地经历 s ……

关键词：宽带无线通信高流动性高速轮轨列车场景数据传输速率移动通信系统商业应用移动通讯技术

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Slicing capacity-centered mode selection and resource optimization for network-assisted full-duplex cell-free distributed massive MIMO systems

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Science China(Information Sciences) 2024年第1期67卷 203-220页

作者： Jie WANG Jiamin LI Pengcheng ZHU Dongming WANG Hongbiao ZHANG Yue HAO Bin SHENG National mobile communications Research Laboratory Southeast University 2. Purple Mountain Laboratories China mobile Research institute

Network-assisted full-duplex(NAFD) cell-free distributed massive multiple-input multipleoutput(MIMO) systems enable uplink(UL) and downlink(DL) communications within the same timefrequency resources,which potentially reduce latency by avoiding the overhead of switching UL/DL ***,how to choose UL/DL modes remains an important factor affecting system *** the dramatic increase in the number of users and access points(APs),massive access brings significant overhead in the mode ***,the different quality of service(QoS) among users also makes the effective utilization of resources *** one of the most promising technologies in sixth-generation(6G),network slicing enables the adaptive configuration of limited UL/DL resources through the resource isolation assisted NAFD ***,we propose a slicing capacity-centered *** this scheme,APs are motivated by slicing requirements and associated slices to form different *** mode selection and resource allocation are performed within each subsystem to reduce overhead and improve resource *** implement this scheme efficiently,a double-layer deep reinforcement learning(DRL)mechanism is used to realize the joint optimization of mode selection and resource *** results show that the slicing capacity-centered scheme can effectively improve resource utilization and reduce overhead.

关键词： network-assisted full-duplex network slicing mode selection resource optimization deep reinforcement learning

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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 ***,radars and communication systems are often seen to be “competing” for the same *** this scenario,an integrated platform for radar and communication systems seems to be an optimal solution to address the *** 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) *** preamble waveforms can be simultaneously used for channel estimation and radar sensing in RadCom *** ambiguity function of the proposed waveforms displays low/zero sidelobes within a time-delay correlation ***,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 (Rad-Com) systems MIMO radar zero correlation zone (ZCZ) sequence set zero odd-correlation zone (ZOCZ) sequence set

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A Modified Doppler Frequency Trajectory Undergoing Varying Velocities in HSR communications

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China communications 2016年第1期13卷 17-21页

作者： LIU Liu TAO Cheng SUN Rongchen CHEN Houjin institute of Broadband Wireless mobile communications School of Electronics and Information EngineeringBeijing Jiaotong University National mobile communications Research Laboratory Southeast University

The varying trajectory of Doppler frequency under changing speed motion conditionsare investigated in Highspeed Railway(HSR) *** on the geometrical physical parameters,instantaneous Doppler trajectories and expression forms of the change rate arededuced,including acceleration and deceleration *** modified models provide more accurate and realisticapproximations in modeling rapidly fading channels.

关键词： Doppler shift varying veloci-ty high speed railway.

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