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Fractional full duplex cellular network: a stochastic geometry approach

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Science China(Information Sciences) 2018年第2期61卷 50-64页

作者： Wenping BI Limin XIAO Xin SU Shidong ZHOU State Key Laboratory on Microwave and Digital Communications Tsinghua National laboratory for Information Science and Technology Department of Electronic Engineering Tsinghua University

In-band full-duplex(FD) communication has been considered as a promising technology to enhance the spectral efficiency(SE) for the next generation of wireless system. However, the severe interference in FD cellular network may largely degrade the system performance, especially for cell edge users. In this paper, multi-cell cellular network consisting of BSs with FD capability and legacy half duplex(HD) users is studied. In order to relieve the received interference and enhance the system SE, a new resource allocation strategy named fractional FD(FFD) is proposed and its main idea and procedure are described as follows.Firstly, the frequency and time resources are partitioned into FD resource blocks(RBs) and HD RBs based on the network topology. Then all the users are classified into two groups named cell center users(CCUs)and cell edge users(CEUs) based on their channel conditions. At last, in each cell, each FD RB is allocated to a pair of CCUs with one in uplink and the other in downlink transmission direction, while only one CEU in the uplink(or downlink) transmission direction is scheduled over each HD RB. Tractable results of both the coverage probabilities and the ergodic rates of FFD, FD and HD systems are derived using stochastic geometry method. Numerical results show that, FFD can significantly improve the coverage probability of all users especially for CEUs compared with FD cellular system, and higher system SE is obtained compared with FD and HD cellular network. With proper design of the classification criterion and under the simulation settings of this paper, the SE of FFD system outperforms FD and HD system by 1.25 and 1.38 times,respectively.

关键词： full duplex half duplex stochastic geometry radio resources allocation small cell

Queue-aware energy-efficient scheduling and power allocation with feedback reduction in small-cell networks

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Science China(Information Sciences) 2018年第4期61卷 246-252页

作者： Hongxin WEI Yunzhou LI Limin XIAO Shidong ZHOU State Key Laboratory on Microwave and Digital Communications Tsinghua National Laboratory Information Science and Technology Department of Electronic Engineering Tsinghua University

In small cell networks(SCNs),the path loss becomes smaller,and energy efficiency could be improved.If plenty of small base stations(BSs)are deployed,the energy consumption of each BSs can be small enough to make the t... 详细信息

关键词： CSI Queue-aware energy-efficient scheduling and power allocation with feedback reduction in small-cell networks

Achievable Secrecy Rate Region of Two-Way Communication with Secret key Feedback

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Tsinghua Science and Technology 2018年第2期23卷 126-134页

作者： Tao Li Shidong Zhou Department of Electronic Engineering State Key Laboratory on Microwave and Digital Communications and National Laboratory for Information Science and Technology Tsinghua University Beijing100084 China. Department of Electronic Engineering and state key laboratory oil microwave and digital communications Tsinghua University Beijing 100084 China.

This paper investigates the achievable secrecy rate region of the Gaussian two-way wiretap channel,which describes the simultaneous secure two-way transmission of a confidential message. Through adjusting the time-sharing factor and the rate at which the random secret key is fed back, the allocation and optimization for the secrecy rates of two-way communication are achieved. Under peak and average power constraints, the achievable secrecy rate regions of the two-way communication are derived respectively.

关键词： physical layer security two-way communication feed back one-time-pad random secret key secrecy rate region

Energy-efficient Butler-matrix-based hybrid beamforming for multiuser mm Wave MIMO system

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Science China(Information Sciences) 2017年第8期60卷 48-57页

作者： Jiahui LI Limin XIAO Xibin XU Xin SU Shidong ZHOU State Key Laboratory on Microwave and Digital Communications Tsinghua National Laboratory for Information Science and TechnologyDepartment of Electronic Engineering Tsinghua University

In order to reduce the cost and power consumption of radio frequency(RF) chains in a millimeterwave(mm Wave) multiple-input multiple-output(MIMO) system, hybrid analog/digital beamforming(HBF)can be utilized to reduce the number of RF chains. The HBF consists of an analog beamforming(ABF) stage and a digital beamforming(DBF) stage. The ABF is always realized by using phase shifters and the DBF is done in a low-dimensional digital domain. However, phase shifters have several drawbacks, such as high power consumption and inconsistency of insertion loss. In this paper, we propose an energy-efficient HBF structure to handle these problems, which utilizes the Butler phase shifting matrix in the ABF stage. With the Butlermatrix-based ABF, several fixed beam directions can be obtained, and the best beam directions of different Butler matrices can be chosen by using exhaustive search. To reduce the high complexity of exhaustive search,we further provide a low complexity HBF algorithm. Simulations under the conditions of perfect channel state information(CSI) and estimated CSI verify the effectiveness of our proposed Butler-matrix-based HBF structure and related algorithms.

关键词： Butler matrix energy-efficient hybrid beamforming MIMO mm Wave multiuser

Sectorization based pilot reuse for improving net spectral efficiency in the multicell massive MIMO system

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Science China(Information Sciences) 2016年第2期59卷 97-111页

作者： Jiahui LI Limin XIAO Xibin XU Shidong ZHOU State Key Laboratory on Microwave and Digital Communications Tsinghua National laboratory for Information Science and Technology Department of Electronic Engineering Tsinghua University

A sectorization method using the uniform circular array(UCA) is proposed to improve the net spectral efficiency(SE) of the multicell massive MIMO system, which is an important index for evaluating the performance of a communication system. We derive the ergodic achievable uplink net SE per cell of a general sectorized system and obtain its deterministic approximation based on the large random matrix theory.Different weight matrices are considered for the sectorized system and the one with the best performance is utilized for further analysis. The consistency of the deterministic approximation with the result of Monte-Carlo simulation is proved at the same time. At last, numerical results indicate that the net SE per cell can be greatly improved compared to the conventional multicell massive MIMO system, which validates the effectiveness of the sectorization method. Moreover, comparisons with other pilot reuse methods are also made in this paper.

关键词： massive MIMO multicell net SE pilot reuse sectorization UCA

Bi-Spectrum Scattering Model for Dielectric Randomly Rough Surface

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Tsinghua Science and Technology 2003年第5期8卷 617-623页

作者：刘宁李宗谦 State Key Laboratory on Microwave and Digital Communications

The bistatic scattering model is offen used for remote microwave sensing. The bi-spectrum model (BSM) for conducting surfaces was used to develop a scattering model for dielectric randomly rough surfaces to estimate their bistatic scattering coefficients. The model for dielectric rough surfaces differs from the BSM for a conducting surface by including Fresnell reflection and transmission from dielectric rough surfaces. The bistatic scattering coefficients were defined to satisfy the reciprocal theorem. Values calculated using the BSM for dielectric randomly rough surfaces compare well with those of the integral equation model (IEM) and with experimental data, showing that the BSM accuracy is acceptable and its range of validity is similar to that of IEM while the BSM expression is simpler than that of IEM.

关键词： dielectric randomly rough surface spectral domain bi-spectrum method bistatic scattering coefficients bi-spectrum scattering model microwave remote sensing

LDPC Coded TDS-OFDM for PLC Systems

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Tsinghua Science and Technology 2010年第3期15卷 312-318页

作者：戴凌龙符剑王军 State Key Laboratory on Microwave and Digital Communications Department of Electronic EngineeringTsinghua University

Powerline communications （PLC） have drawn great interest in recent years. However, most PLC standards such as HomePlug AV use the cyclic-prefix OFDM （CP-OFDM） technology. This paper presents a broadband PLC system using low density parity check （LDPC） coded time domain synchronous OFDM （TDS-OFDM）, whose spectrum efficiency is about 10% higher than that of CP-OFDM. With the same bandwidth and the ability to combat the time delay spread as HomePlug AV, this system can provide a maximum throughput of 199.7 Mbps physical layer data rate. Simulations over the measured practical powerline channel in Beijing, China, show that LDPC in the TDS-OFDM system dramatically improves the bit error rate performance, and verify the feasibility and performance of the TDS-OFDM technology for PLC systems.

关键词： powerline communications （PLC） time domain synchronous OFDM （TDS-OFDM） low density parity check （LDPC） HomePlug AV channel measurement

A New TDD Scheme and Interference-Aware Precoding for Device-to-Device Underlay Massive MIMO

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China communications 2016年第S2期13卷 100-108页

作者： Xinxin Liu Xueru Li Yunzhou Li Ming Zhao Jing Wang State Key Laboratory on Microwave and Digital Communications Tsinghua National Laboratory for Information Science and Technology Tsinghua University Department of Electronic Engineering Tsinghua University

In device-to-device(D2D)underlay cellular networks with downlink spectrum sharing,massive MIMO seems promising as the large number of antennas at the base station(BS) can be utilized to suppress interference.However,the channel state information(CSI) from the BS to D2D receivers is required to obtain this advantage.In this paper,we first propose a novel time division duplex(TDD) scheme for D2D users to acquire this CSI,without additional pilot overhead.Moreover,we propose an interference-aware MMSE precoder utilizing the acquired CSI from the BS to not only cellular users but also D2D users to suppress the cellular-to-D2D interference.Simulation results show that our proposed TDD scheme and precoder can significantly improve the achievable sum spectral efficiency(SE) and D2D SE,compared to the classical MMSE precoder.Compared with the interferenceaware ZF precoder,whose performance severely degrades for large user numbers,our proposed interference-aware MMSE precoder can always guarantees a high and stable performance in terms of achievable SE.

关键词： device-to-device massive MIMO TDD scheme precoding

GOP-Level Bit Allocation Using Reverse Dynamic Programming

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Tsinghua Science and Technology 2009年第2期14卷 183-188页

作者：路羊谢军李航崔慧娟 State Key Laboratory on Microwave and Digital Communications Department of Electronic EngineeringTsinghua University

An efficient adaptive group of pictures （GOP）-Ievel bit allocation algorithm was developed based on reverse dynamic programming （RDP）. The algorithm gives the initial delay and sequence distortion curve with just one iteration of the algorithm. A simple GOP-level rate and distortion model was then developed for two-level constant quality rate control. The initial delay values and the corresponding optimal GOP-level bit allocation scheme can be obtained for video streaming along with the proper initial delay for various distortion tolerance levels. Simulations show that the algorithm provides an efficient solution for delay and buffer constrained GOP-level rate control for video streaming.

关键词： initial delay distortion adaptive group of pictures （GOP） bit allocation consistent quality