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On opportunistic spectrum efficiency in cognitive radio systems

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High Technology Letters 2009年第2期15卷 170-174页

作者：王鹏 Zhong Xiaofeng Xiao Limin Zhou Shidong Wang Jing Bai Yong State Key Laboratory on Microwave and Digital communications Tsinghna National Laboratory for Information Science and Technology Department of Electronic Engineering Tsinghua University Beijing 100084 P.R. China docomo beijing communications laboratories compary limited Beijing 100080 P.R. China

The performance bound of cognitive radio systems is *** use opportunistic spectrum effi-ciency(OSE)as the performance metric,and point out that the maximum achievable OSE can be used toevaluate the maximum value that the introduction of secondary users can add to the conventional *** on assumptions of the PU s traffic model and some reasonable approximations,the ex-pression of OSE is obtained and the maximum achievable OSE is derived by solving an optimization *** results are verified by computer simulation.

关键词： cognitive radio opportunistic spectrum access opportunistic spectrum efficiency

Enhanced uplink non-orthogonal multiple access for 5G and beyond systems

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Frontiers of Information Technology & Electronic Engineering 2018年第3期19卷 340-356页

作者： Wen-jia LIU Xiao-lin HOU Lan CHEN docomo beijing communications laboratories Co. Ltd.

Uplink non-orthogonM multiple access （NOMA） is a promising technique to meet the requirements of the fifth generation （5G） and beyond systems. Various NOMA schemes have been proposed in both academia and industry. However, most existing schemes assume equal average received power, which limits the performance. We propose three enhancements of uplink NOMA to achieve the requirements of massive connectivity and high reliability in 5G, where unequal average received power is exploited as part of the multiple access signature. First, the optimal sequences targeting to generalized Welch-bound equality （GWBE） are obtained for unequal average received power. Then user grouping with multi-level received powers is proposed for better successive interference cancellation （SIC） at the receiver. Finally, sequence grouping based on the cross-correlation properties of sequences is proposed to reduce inter-and intra-group interference. Simulation results show that by incorporating multi-level received powers and sequence grouping into existing NOMA schemes, for an NOMA system with 400% overloading and fixed signature allocation, 3 dB and 10 dB signal-to-noise ratio （SNR） gains at 0.1 block error rate （BLER） target can be achieved compared with existing NOMA schemes and orthogonal multiple access （OMA）, respectively. Besides, 0.01 BLER target can be achieved while an error floor exists in existing NOMA schemes. Under random sequence selection, collision probability is reduced by multi-level powers. In addition, GWBE sequences achieve lower BLER than existing sequences and the gain is large especially for low BLER requirements. This shows that the proposed scheme can support larger connectivity and higher reliability.

关键词： Uplink non-orthogonal multiple access Generalized Welch-bound equality Multi-level received powers Sequence grouping

Deep learning for joint channel estimation and feedback in massive MIMO systems

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Digital communications and Networks 2024年第1期10卷 83-93页

作者： Jiajia Guo Tong Chen Shi Jin Geoffrey Ye Li Xin Wang Xiaolin Hou National Mobile communications Research Laboratory Southeast UniversityNanjing210096China Department of Electrical and Electronic Engineering Imperial College LondonLondonSW72AZUK docomo beijing communications laboratories Co. LtdBeijingChina

The great potentials of massive Multiple-Input Multiple-Output(MIMO)in Frequency Division Duplex(FDD)mode can be fully exploited when the downlink Channel State Information(CSI)is available at base ***,the accurate CsI is difficult to obtain due to the large amount of feedback overhead caused by massive *** this paper,we propose a deep learning based joint channel estimation and feedback framework,which comprehensively realizes the estimation,compression,and reconstruction of downlink channels in FDD massive MIMO *** networks are constructed to perform estimation and feedback explicitly and *** explicit network adopts a multi-Signal-to-Noise-Ratios(SNRs)technique to obtain a single trained channel estimation subnet that works well with different SNRs and employs a deep residual network to reconstruct the channels,while the implicit network directly compresses pilots and sends them back to reduce network *** module is also designed to generate data-bearing *** results show that the two proposed networks exhibit excellent performance of reconstruction and are robust to different environments and quantization errors.

关键词： Channel estimation CSI feedback Deep learning Massive MIMO FDD

Some Observations and Thoughts about Reconfigurable Intelligent Surface Application for 5G Evolution and 6G

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ZTE communications 2022年第1期20卷 14-20页

作者： HOU Xiaolin LI Xiang WANG Xin CHEN Lan SUYAMA Satoshi docomo beijing communications laboratories Co. Ltd.Beijing 100190China NTT docomo INC.Tokyo 239-8536Japan

Reconfigurable intelligent surface(RIS)is one of the hottest research topics for 5G evolution and *** is expected that RIS can improve the system capacity and coverage with low cost and power *** paper first discusses typical applications of RIS for 5G evolution and 6G,including RIS-aided smart channels and RIS-aided mega multiple-input multiple-output(MIMO).Then,several observa-tions from RIS trials and system-level simulations are presented,especially those on the deployment strategy and the potential performance gain of RIS for coverage *** near-field effect and a two-step dynamic RIS beamforming method are also ***,we summarize the challenges and opportunities of the RIS technology for 5G evolution and 6G,including hardware design,system and channel modeling,algorithm design and optimization,and *** also suggest a step-by-step commercialization strategy as a conclusion.

关键词： 5G evolution 6G beamforming coverage RIS

Over-sampling basis expansion model aided channel estimation for OFDM systems with ICI

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The Journal of China Universities of Posts and Telecommunications 2008年第4期15卷 7-13页

作者： LIU Si-yang LIU Yuan-an WANG Fei-fei XIE Gang ZHANG Ran-ran Key Laboratory of Universal Wireless communications (beijing University of Posts and Telecommunications) Ministry of Education Beijing 100876 China

The rapid variation of channel can induce the intercarrier interference in orthogonal frequency-division multiplexing （OFDM） systems. Intercarrier interference will significantly increase the difficulty of OFDM channel estimation because too many channel coefficients need be estimated. In this article, a novel channel estimator is proposed to resolve the above problem. This estimator consists of two parts： the channel parameter estimation unit （CPEU）, which is used to estimate the number of channel taps and the multipath time delays, and the channel coefficient estimation unit （CCEU）, which is used to estimate the channel coefficients by using the estimated channel parameters provided by CPEU. In CCEU, the over-sampling basis expansion model is resorted to solve the problem that a large number of channel coefficients need to be estimated. Finally, simulation results are given to scale the performance of the proposed scheme.

关键词： OFDM ICI over-sampling basis expansion model (OBEM)

An improved dynamic user equipment power saving mechanism for LTE system and performance analysis

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Science China(Information Sciences) 2010年第10期53卷 2075-2086页

作者： XU HaiBo, TIAN Hui , HUANG Bo & ZHANG Ping Key Laboratory of Universal Wireless communications, Ministry of Education beijing University of Posts and Telecommunications, beijing 100876, China Key Laboratory of Universal Wireless communications Ministry of Education Beijing University of Posts and Telecommunications Beijing China

In order to minimize the power consumption of user equipments (UEs), and further to support various services and transmissions of large amount of data, the power saving mechanisms have been investigated for most remarkable wireless systems. In this paper, an improved dynamic discontinuous reception (D-DRX) scheme is presented for LTE system, which is able to adaptively adjust the inactivity timer and the sleep period of UEs’ receivers. Moreover, theoretical analysis based on the Markov chain is provided for the D-DRX scheme. Several numerical examples quantitatively show that the D-DRX scheme can capture various packet arrival patterns and scheduling behaviors of system to make a better tradeoff between power saving and packet delay by considering the length of packet queue.

关键词： power saving DRX Markov chain LTE-advanced

An optimized non-unitary linear precoding design for OSTBCs

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Science China(Information Sciences) 2010年第2期53卷 335-343页

作者： HUANG HaiYang , WU Gang, LU Lu & LI ShaoQian National Key Laboratory of communications, University of Electronic Science and Technology of China, Chengdu 610054, China National Key Laboratory of communications University of Electronic Science and Technology of China Chengdu China

This paper tackles the optimization of non-unitary linear precoding design for orthogonal spacetime block codes (OSTBCs). We dig out the transmission potentials by the analysis from eigen-space point of view according to the unique structure of OSTBCs. The proposed precoding form is proven to be theoretically optimized. Compared with the classical unitary Grassmannian codebook design, the non-unitary codebook further improves the overall performance of practical systems. The constraint on codebook size to guarantee full diversity order is given and proven. Based on this, we investigate the codebook construction method combined with a water-filling (WF) technique to reduce the impact of antenna correlation. The advantages of the novel design are verified via numerical simulations.

关键词： multi-antenna linear precoding OSTBCs non-unitary design antenna correlation

Dynamic spectrum allocation for cell range extension in tiered Macro-Pico heterogeneous networks

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The Journal of China Universities of Posts and Telecommunications 2013年第1期20卷 66-72页

作者： TIAN Peng TIAN Hui GAO Li-qi ZHANG Jun WANG Meng School of Information and Communication Engineering Beijing University of Posts and Telecommunications

Heterogeneous networks are employed in the next generation communication systems to enhance the area spectral efficiency （ASE）, where cell range extension （CRE） is a promising technique to improve the cell edge performance and utilize the low power node （LPN） resources more effectively. In this paper we propose a dynamic spectrum aUocation scheme for Macro-Pico scenario to mitigate both the co-tier and cross-tier interferences. The available system spectrum is divided into different parts by four steps, i.e. user set partition, service request collection, cross-tier occupation and CRE occupation decision, while the service request of each user is taken into consideration. During the process implementation, the reference signal receiving power （RSRP） threshold is derived by mathematical means to judge cell edge macro users when a predefined ratio is given. Simulation results show that the proposed scheme reaches almost the same cell edge performance with the best existing option, meanwhile provides higher overall system throughput and better spectral efficiency. Therefore, much better balance is achieved.

关键词： spectrum allocation heterogeneous network elCIC range extension pico cells