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Energy-efficient dual-layer coordinated beamforming scheme in multi-cell massive multiple-input-multiple-output systems

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IET COMMUNICATIONS 2017年第1期11卷 30-38页

作者： Mei, Jie Zhao, Long Zheng, Kan Wang, Xiaoyu Beijing Univ Posts & Telecommun Wireless Signal Proc & Network Lab Minist Educ Beijing 100876 Peoples R China Orange Labs Int Ctr Beijing Orange Int Labs China NPIT Beijing 100013 Peoples R China

To improve the energy efficiency of multi-cell massive multiple-input-multiple-output system while guaranteeing the information transmission quality, this study proposes a dual-layer coordinated beamforming scheme. In the proposed scheme, the beamformer at each evolved node B (eNB) is divided into a cell-layer beamformer and a user-layer beamformer. The cell-layer beamformer is used to mitigate inter-cell interference (ICI) by exchanging long-term channel state information (CSI) among eNBs. The user-layer beamformer serves user according to the local real-time CSI at each eNB. On the basis of the dual-layer structure, the cell-layer beamformers, the user-layer beamformers, and power allocation are jointly optimised in order to minimise the total transmit power across all the eNBs subject to the signal-to-interference-plus-noise ratio requirements and single-antenna power constraints. To make the original problem solvable, the ICI is replaced by its upper bound. Then, the problem is partitioned into two convex sub-problems, and two iterative algorithms are proposed in order to find the sub-optimal solution to the original optimisation problem. Simulation results show that the proposed scheme performs better than two reference schemes including the existing zero-forcing scheme and coordinative multiple point schemes.

关键词： array signal processing MIMO communication cellular radio interference suppression radiofrequency interference energy conservation wireless channels antenna arrays convex programming energy-efficient dual-layer coordinated beamforming scheme multicell massive multiple-input–multiple-output system information transmission quality evolved node B eNB user-layer beamformer cell-layer beamformer intercell interference mitigation ICI mitigation channel state information CSI power allocation signal-to-interference-plus-noise ratio requirement single-antenna power constraint convex subproblem iterative algorithm optimisation problem zero-forcing scheme coordinative multiple point scheme

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Half-ZF beamforming scheme for downlink two-user multiple input single output-based non-orthogonal multiple access systems

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IET COMMUNICATIONS 2017年第10期11卷 1633-1640页

作者： Cai, Wenbo Lv, Guocheng Jin, Ye Peking Univ State Key Lab Adv Opt Commun Syst & Networks Beijing Peoples R China

The authors investigate the beamforming (BF) problem to minimise the power consumption for the downlink 2-user multiple input single output-based non-orthogonal multiple access system. Inspired from the conventional zero-forcing (ZF) scheme, they propose the Half-ZF scheme which only mitigates the interference introduced by the signal of the cell-interior user through the ZF method. Meanwhile, the interference introduced by the signal of the cell-edge user is removed through the SIC technology. We derive the closed-form expression for the BF vectors of the two users under the Half-ZF scheme. The optimal power consumption for the Half-ZF scheme is analysed and the corresponding solution of the BF factors are also obtained. Compared with the conventional ZF scheme, both the Half-ZF scheme and the existing quasi-degradation (QD) scheme can achieve lower power consumption than the ZF scheme. However, the Half-ZF scheme can achieve this advantage under more relaxed conditions. Consequently, the Half-ZF scheme consumes lower power than the QD scheme when combined with the ZF scheme in practical systems.

关键词： multi-access systems array signal processing vectors cellular radio interference suppression power consumption half-ZF beamforming scheme downlink two-user multiple input single output-based NOMA power consumption minimisation interference mitigation zero-forcing scheme cell-interior user cell-edge user SIC technology closed-form expression BF vectors quasi-degradation scheme QD scheme nonorthogonal multiple access systems successive interference cancellation technology

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Performance analysis of V-OFDM for acoustic communication along drill strings

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IET COMMUNICATIONS 2017年第4期11卷 576-583页

作者： Ma, Dong Shi, Yibing Zhang, Wei Liu, Guozhen Univ Elect Sci & Technol China Sch Automat Engn 2006 Xiyuan Ave Chengdu Peoples R China Univ Elect Sci & Technol China Informat Geosci Res Ctr 2006 Xiyuan Ave Chengdu Peoples R China

To achieve real-time and high-speed communication between the surface and the bottom hole, acoustic communication along drill strings has become the most promising method for the efficient utilisation of oil fields. Vector orthogonal frequency division multiplexing (V-OFDM) is a general transmission scheme that has two special forms, orthogonal frequency division multiplexing and single carrier frequency domain equalisation. Owing to its flexibility regarding the size of the vector block, it can be adapted to meet different requirements. In this study, the authors first employ V-OFDM modulation in uplink and downlink acoustic communication. Aiming for mass-data transmission and a simple transmitter in the uplink, small-data transmission and a simple receiver in the downlink, and strong noise interference, they investigate the transmission performance with different synchronisation timing errors and detection schemes, zero-forcing and the minimum mean square error. Simulation and circuit test results are presented to demonstrate the effectiveness of the proposed different transmission schemes and the corresponding performance analysis.

关键词： acoustic communication (telecommunication) OFDM modulation data communication least mean squares methods timing synchronisation oil drilling performance analysis drill strings real-time communication high-speed communication oil fields vector orthogonal frequency division multiplexing single carrier frequency domain equalisation V-OFDM modulation uplink acoustic communication downlink acoustic communication mass-data transmission small-data transmission noise interference transmission performance synchronisation timing errors minimum mean square error scheme zero-forcing scheme

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Hybrid Time/Frequency Domain Compensator for RF Impairments in OFDM Systems

Hybrid Time/Frequency Domain Compensator for RF Impairments ...

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22nd IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC)

作者： Kiayani, Adnan Anttila, Lauri Zou, Yaning Valkama, Mikko Tampere Univ Technol Dept Commun Engn FI-33101 Tampere Finland

ISBN: (纸本)9781457713484

I/Q signal processing based communication systems suffer from analog front-end (FE) imperfections such as in-phase and quadrature-phase (I/Q) imbalance and carrier frequency offset (CFO). These impairments are commonly encountered in all practical implementations, and severely degrade the obtainable link performance. Moreover, orthogonal frequency division multiplexing (OFDM)-based systems are particularly sensitive to radio frequency (RF) impairments. In this paper, we analyze the impact of transmitter and receiver I/Q imbalance together with channel distortion and CFO error on an ideal transmit signal, and propose low-complexity DSP algorithms and compensation structure for coping with such imperfections. Based on our proposed estimation/compensation structure, we are able to decouple the impairments and process them individually with rather low-complexity. More specifically, we first apply a blind algorithm for receiver I/Q imbalance compensation, followed by an efficient time domain CFO estimator and compensator. The transmitter I/Q imbalance and channel are then equalized jointly, in the frequency domain, with maximum-likelihood (ML) or zero-forcing (ZF) schemes, respectively. The applied algorithms are either blind working without aid of any training symbol or use only one OFDM symbol for impairments estimation, providing an efficient alternative solution with reduced complexity. The computer simulation results indicate a close to ideal performance of ZF scheme, and sugget that additional performance improvement due to frequency diversity can be obtained when ML estimation technique is employed.

关键词： CFO error Channel estimation Estimation I/Q signal processing based communication system Joints ML estimation OFDM OFDM modulation OFDM symbol OFDM system OFDM-based system RF impairment Radio transmitters Receivers ZF scheme analog front-end imperfection blind algorithm carrier frequency offset channel distortion communication complexity diversity reception estimation-compensation structure frequency diversity frequency domain compensator in-phase imbalance link performance low-complexity DSP algorithm maximum likelihood estimation maximum-likelihood scheme orthogonal frequency division multiplexing quadrature-phase imbalance radio frequency impairment radio receivers radio transmitters receiver I/Q imbalance time domain CFO estimator time domain compensator transmitter I/Q imbalance wireless channels zero-forcing scheme

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