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Achievable degrees of freedom of MIMO two-way X relay channel with delayed CSIT

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Science China(Information Sciences) 2016年第8期59卷 193-203页

作者： Qingyun li Gang WU Hongxiang li shaoqian li National Key Laboratory of Science and Technology on Communications University of Electronic Science and Technology of China Department of Electrical and Computer Engineering University of Louisville

The previous work on interference alignment for multiple-input-multiple-output(MIMO) two-way X relay channel assumes perfect channel state information at the transmitter(CSIT), which is reasonable in slow fading channel. However, in fast fading scenario, this assumption is impractical. In this paper, assuming that each node has delayed CSIT, we study the achievable degrees of freedom(DOF) for MIMO two-way X relay channel in frequency division duplex(FDD) systems. Specifically, in the broadcast(BC) phase, we propose a new multiple-stage transmission(MST) scheme, which utilizes retrospective interference alignment for physical layer network coding(PLNC). We show that MST can achieve significant DOF gain and tremendous power gain over other schemes. When the number of antennas for each user, N, is smaller than the number of the relays, M, the time division multiple access(TDMA) scheme can only achieve an ergodic sum-rate increase by N bps/Hz for every increasing of 3 d B of signal-to-noise power ratio(SNR), while the proposed MST scheme can achieve an ergodic sum-rate increase by M bps/Hz.

关键词： degrees of freedom physical layer network coding interference alignment delayed CSIT multiplestage transmission

Joint optimal sensing time and power allocation for multi-channel cognitive radio networks considering sensing-channel selection

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Science China(Information Sciences) 2014年第4期57卷 134-141页

作者： YU HuoGen TANG WanBin li shaoqian National Key Laboratory of Science and Technology on Communications University of Electronic Science and Technology of China

In this paper,we consider a multi-channel cognitive radio network(CRN)where each secondary user(SU)can only choose to sense a subset of *** formulate a joint optimization problem of sensingchannel selection,sensing time and power allocation under the constraints of average transmit power budget and average interference power budget,which maximizes the CRN’s total *** propose a greedy algorithm to solve the joint optimization problem,which has much less computational ***,it is shown that the search space of the greedy algorithm can be further ***,numerical results demonstrate that the greedy algorithm has comparable performance to the exhaustive search algorithm.

关键词： cognitive radio joint optimization sensing-channel selection sensing time power allocation

Power-time resource allocation for downlink SWIPT-assisted cooperative NOMA systems

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Science China(Information Sciences) 2023年第5期66卷 238-247页

作者： Chengpeng liU lin ZHANG Zhi CHEN shaoqian li National Key Lab of Science and Technology on Communications University of Electronic Science and Technology of China

We study a downlink cooperative non-orthogonal multiple access(NOMA) system in which a base station(BS) serves two paired users on the same frequency band simultaneously, and the near user acts as an energy-constrained relay for the far user since there is no direct link between the BS and the far user due to physical obstacles or heavy shadowing. To replenish energy of the near user for relaying, we enable the near user to harvest energy from BS signals by adopting the simultaneous wireless information and power transfer(SWIPT) technique. Diferent from the linear energy harvesting(EH) model used in most of the existing literature, we adopt a non-linear model for EH. By considering the non-linear features of the practical circuits, we aim to minimize the BS energy consumption while ensuring the minimum required transmission rate of both users. Since the formulated problem contains coupled power and time resource variables, it is challenging to solve it directly. Thus, we propose an optimal power-time resource allocation algorithm by decoupling the variables properly. Simulation results verify the theoretical analysis and show the performance of the considered system.

关键词： NOMA SWIPT relaying non-linear transmit energy

Power allocation for massive MIMO:impact of power amplifier efficiency

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Science China(Information Sciences) 2016年第2期59卷 22-30页

作者： Yingchu GUO Junlin TANG Gang WU shaoqian li National Key Laboratory of Science and Technology on Communications University of Electronic Science and Technology of China

With the rapid development of information technology, massive MIMO is becoming attractive for the fifth generation(5G) communication because of its outstanding performance in both spectral efficiency(SE)and energy efficiency(EE). Recently, many algorithms have been proposed to improve the EE while achieving high SE in massive MIMO systems. In previous work, the power amplifier(PA) efficiency is always considered as a constant. However, the PA efficiency changes with the output power in reality. In the practical situation,the simplification which treats the PA efficiency as a constant will not get the EE optimization based on our analysis. In this paper, we propose a more general EE model of massive MIMO systems considering PA efficiency as a variable, and investigate a power allocation algorithm based on zero-forcing(ZF) precoding so that we can guarantee the SE and EE at the same time. Simulation results show the trade-off between EE and SE, demonstrate the distinction with previous work, and imply that relatively higher transmit power will be more energy efficient.

关键词： 5G massive MIMO energy efficiency green communication power amplifier efficiency

Reliable and Energy-Aware Job Offloading at Terahertz Frequencies for Mobile Edge Computing

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China Communications 2020年第12期17卷 17-36页

作者： Sha Xie Haoran li lingxiang li Zhi Chen shaoqian li National Key Laboratory of Science and Technology on Communications University of Electronic Science and Technology of ChinaChengdu 611731China

In this paper,we co-design the transmission power and the offloading strategy for job offloading to a mobile edge computing(MEC)server at Terahertz(THz)*** goal is to minimize the communication energy consumption while providing ultra-reliable low end-to-end latency(URLLC)*** that end,we first establish a novel reliability framework,where the end-to-end(E2E)delay equals a weighted sum of the local computing delay,the communication delay and the edge computing delay,and the reliability is defined as the probability that the E2E delay remains below a certain pre-defined *** reliability gives a full view of the statistics of the E2E delay,thus constituting advancement over prior works that have considered only average *** on this framework,we establish the communication energy consumption minimization problem under URLLC *** optimization problem is *** handle that issue,we first consider the special single-user case,where we derive the optimal solution by analyzing the structure of the optimization ***,based on the analytical result for the single-user case,we decouple the optimization problem for multi-user scenarios into several sub-optimization problems and propose a sub-optimal algorithm to solve *** results verify the performance of the proposed algorithm.

关键词： Terahertz(THz)communications mobile edge computing(MEC) ultra-reliable low end-to-end latency(URLLC)services green communications

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Interference cancellation aided channel estimation for OFDM/OQAM system

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Science China(Information Sciences) 2013年第12期56卷 163-170页

作者： CHENG GuoBing XIAO Yue HU Su li shaoqian National Key Laboratory of Science and Technology on Communications University of Electronic Scienceand Technology of China Telecommunication Engineering Institute of Air-force Engineering University National Mobile Communications Research Laboratory Southeast University

Orthogonal frequency division multiplexing ofset-QAM(OFDM/OQAM)is a promising multicarrier transmission technique for its merits such as operating without cyclic prefx(CP)and flexibility of introducing well time-frequency localized pulse ***,under dispersive channel condition,the intrinsic inter-symbol and inter-carrier interference arises in OFDM/OQAM ***,the surrounding data symbols will cause interferences to the pilot symbols,leading to channel estimation error and degradation of system *** this paper,an efcient pilot structure and a channel estimation method are proposed for OFDM/OQAM *** basic principal is to rebuild the transmitted symbols around the considered pilot position through pre-decision,then calculate and cancel the interference from the received *** and simulation results show that the proposed scheme outperforms conventional ones with respect to both channel estimation accuracy and bit error rate(BER)performance while with less pilot consumption.

关键词： OFDM/OQAM channel estimation interference cancellation

Performance Analysis of Hybrid FSO/RF Transmission Assisted Airborne Free-Space Optical Communication System

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Journal of Communications and Information Networks 2022年第3期7卷 252-258页

作者： Shiqi Wu shaoqian li Yixiang lin Haijun Zhou University of Electronic Science and Technology of China Chengdu 610054China China Electronics Technology Group Corporation 10th Research Institute Chengdu 610036China

This paper investigates the reliability problem of airborne free-space optical(FSO)communications,and a hybrid FSO/radio frequency(RF)communication system with parallel transmission is proposed,where the data stream is transmitted over both FSO and RF links ***,to combat channel fading,maximal ratio combining is utilized at the receiver for combining received signals from both *** performances of the proposed system are analytically derived in terms of the outage probability and the average bite-error rate(BER).Numerical results show that the proposed hybrid FSO/RF system with parallel transmission outperforms a single airborne FSO or a single RF link,which provides technical guidance for designing reliable high-speed airborne communication systems.

关键词： FSO hybrid FSO/RF pointing error outage probability bit-error rate

Local Observations-Based Energy-Efficient Multi-Cell Beamforming via Multi-Agent Reinforcement Learning

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Journal of Communications and Information Networks 2022年第2期7卷 170-180页

作者： Kaiwen Yu Gang Wu shaoqian li Geoffrey Ye li The National Key Laboratory of Science and Technology on Communications University of Electronic Science and Technology of ChinaChengdu 611731China Imperial College London.London SW72AZ U.K.

With affordable overhead on information exchange,energy-efficient beamforming has potential to achieve both low power consumption and high spectral *** paper formulates the problem of joint beamforming and power allocation for a multiple-input single-output(MISO)multi-cell network with local observations by taking the energy efficiency into *** reduce the complexity of joint processing of received signals in presence of a large number of base station(BS),a new distributed framework is proposed for beamforming with multi-cell cooperation or *** optimization problem is modeled as a partially observable Markov decision process(POMDP)and is solved by a distributed multi-agent self-decision beamforming(DMAB)algorithm based on the distributed deep recurrent Q-network(D2RQN).Furthermore,limited-information exchange scheme is designed for the inter-cell cooperation to boost the global *** proposed learning architecture,with considerably less information exchange,is effective and scalable for a high-dimensional problem with increasing ***,the proposed DMAB algorithms outperform distributed deep Q-network(DQN)based methods and non-learning based methods with significant performance improvement.

关键词： distributed beamforming energy efficiency deep reinforcement learning interference-cooperation POMDP

Golay Sequence Based Time-Domain Compensation of Frequency-Dependent I/Q Imbalance

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China Communications 2014年第6期11卷 1-11页

作者： CHEN Lei LUO Zhigang CHENG Xiantao li shaoqian National Key Laboratory of Science and Technology on Communications University of Electronic Science and Technology of China

A time-domain frequencydependent I/Q imbalance compensation scheme based on Golay complementary sequence for receiver is presented. By utilizing property of Golay sequence, the signal and its conjugate interference(image interference)in preamble are separated by correlation and used to estimate I/Q imbalance *** that, a Least Square(LS) estimation of compensation filter is obtained and adopted in the compensation structure. Two applications of the presented algorithm are discussed: we could either estimate the channel along with I/Q imbalance or estimate the imbalance parameter only to maintain a lower cost. Both applications are testified by simulation. The results show that the image interference is significantly suppressed even in poor SNR condition, and the computation cost of the algorithms is low.

关键词： wireless communication, I/Qimbalance time-domain compensation golaysequence

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