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On Feasibility Conditions for Linear Interference Alignment over Cognitive Interference Channel: A DoF Analysis with Diversity Tradeoff

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IETE JOURNAL OF RESEARCH 2016年第3期62卷 278-287页

作者： Akbari, Mohammad Falahati, Abolfazl IUST Dept Elect Engn Narmak Tehran Iran

In a multiple-antennas cognitive radio network, the rate of the primary link is maximized by water-filling power allocation along the spatial directions associated with the singular values of primary channel matrix. Due to transmitter power constraint, even when the primary user occupies the entire spectrum, some spatial opportunities remain that can be utilized by secondary users. This scheme is called opportunistic interference alignment (OIA). The feasibility issue of OIA in a general symbol-extended system considering the diversity tradeoff, in particular, is the topic that is considered in this paper. An outer bound on the achievable degrees of freedom and also a necessary condition on the feasibility of a multiuser OIA network are presented analytically. In the remaining parts of the paper, the diversity and rate tradeoff is considered. In order to achieve diversity, it is assumed that the paired nodes utilize a space-time coder before the OIA pre-coder. A closed-form relation is presented that relates the minimum achievable diversity to interference alignment quality and code rate.

关键词： Cognitive radio network degrees of freedom diversity feasibility analysis multiple-input multiple-output system opportunistic interference alignment

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Performance analysis of maximal ratio combining with transmit antenna selection and signal space diversity under exponential antenna correlation

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IET COMMUNICATIONS 2018年第5期12卷 612-619页

作者： Ozyurt, Serdar Kucur, Oguz Ankara Yildirim Beyazit Univ Fac Engn & Nat Sci Ankara Turkey Gebze Tech Univ Dept Elect Engn Kocaeli Turkey

In this work, signal space diversity (SSD) is incorporated into a multiple-input multiple-output system with maximal ratio combining and transmit antenna selection. The performance of the proposed system with phase-shift keying (PSK) modulation is studied under a slow flat Rayleigh fading channel scenario with the correlated receive antennas. By adopting the realistic exponential correlation model, an exact closed-form expression is derived for pairwise error probability. The optimal rotation angles are obtained for binary and quadrature PSK signal constellations. The theoretical analysis is verified by the numerical simulations. It is shown that the error performance of the system can be improved with almost no extra complexity or cost. It is also demonstrated that the proposed scheme with SSD is more resistant against the studied correlation model as compared to the original scheme without SSD.

关键词： diversity reception transmitting antennas quadrature phase shift keying Rayleigh channels receiving antennas error statistics MIMO communication antenna arrays correlation model numerical simulations binary PSK signal constellations quadrature PSK signal constellations optimal rotation angles pairwise error probability exact closed-form expression realistic exponential correlation model correlated receive antennas slow flat Rayleigh fading channel scenario PSK modulation phase-shift keying modulation multiple-input multiple-output system SSD exponential antenna correlation signal space diversity transmit antenna selection maximal ratio combining

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Comparative study of stabilising methods for adaptive speed sensorless full-order observers with stator resistance estimation

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IET CONTROL THEORY AND APPLICATIONS 2010年第6期4卷 993-1004页

作者： Vicente, I. Endemano, A. Garin, X. Brown, M. Univ Manchester Sch Elect & Elect Engn Control Syst Ctr Manchester M60 1QD Lancs England

The full-order Luenberger flux (FOLO) observer combined with adaptive techniques is the most widely used method for sensorless vector-controlled drives in induction machines. These methods suffer inherently from an unstable regenerating region and the unobservable zero stator frequency operating point. Stator resistance estimation is also required in the low speed region leading to a complicated multiple-input multiple-output (MIMO) system, and a novel simplification of the MIMO system into a single-input single-output (SISO) system based on the two-time-scale approach is proposed for a simple stability analysis procedure. Four different stabilisation strategies are suggested for this comparison, based on the main stabilisation methods found in the literature. The 'augmented error signal' and the 'observer gains retuning' methods, based on the Routh-Hurwitz criterion, are used for the stabilisation of the motor speed estimator. The stator resistance stabilisation has been implemented using the 'augmented error signal' method. This has been evaluated using two different gain tuning methods, one based on the Routh-Hurwitz criterion and the other on the averaging analysis technique. The different stabilising strategies are evaluated theoretically according to the simplified SISO system open-loop transfer function zeroes and compared by simulation and extensive experiments. The suggested observer is flexible for any vector controlled drive and results have been validated in a 7.5 kW experimental test bench for rotor flux-oriented vector control (RFOC) and indirect self-control drives. The stability and behaviour of the sensorless scheme are successfully verified for all operating conditions above 0.4 Hz stator frequency.

关键词： machine vector control adaptive speed indirect self-control drives asynchronous machines multiple-input multiple-output system Control of electric power systems observer gain retuning method Multivariable control systems open-loop transfer function zeroes zero stator frequency operating point adaptive speed sensorless full-order observers Stability in control theory full-order Luenberger flux observer stability analysis stabilising methods MIMO systems sensorless machine control induction machines augmented error signal Asynchronous machines stators Routh-Hurwitz criterion Routh methods single-input single-output system rotor flux-oriented vector control observers sensorless vector-controlled drives Simulation, modelling and identification rotors stator resistance estimation

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Comparative performance assessment between FFT-based and FRFT-based MIMO-OFDM systems in underwater acoustic communications

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IET COMMUNICATIONS 2018年第6期12卷 719-726页

作者： Nassiri, Mahdi Baghersalimi, Gholamreza Univ Guilan Dept Elect Engn Rasht Iran

In this study, the performance of multiple-input multiple-output (MIMO) systems based on the fractional Fourier transform (FRFT) and the fast Fourier transform (FFT) in underwater acoustic (UWA) communication channels is evaluated and compared for various conditions including the number of subcarriers, modulation schemes, the number of paths between the transmitter and the receiver, Doppler frequencies, and MIMO modes including diversity and multiplexing. The study demonstrates while the computational complexity of the FRFT is in the order of the FFT, the performance of the FRFT-based UWA system is superior to that of the FFT-based system for all multipath scenarios, and for the flat fading channel, they achieve the same performance.

关键词： OFDM modulation fast Fourier transforms MIMO communication underwater acoustic communication acoustic receivers radio transmitters radio receivers multiplexing communication complexity fading channels comparative performance assessment FFT-based MIMO-OFDM system FRFT-based MIMO-OFDM system underwater acoustic communication channel multiple-input multiple-output system fractional Fourier transform fast Fourier transform UWA communication channel modulation scheme transmitter receiver Doppler frequency multiplexing computational complexity flat fading channel multipath channel

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Dual-monopole array backed by a reflector for antenna diversity/MIMO systems

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IET MICROWAVES ANTENNAS & PROPAGATION 2008年第4期2卷 383-388页

作者： Hui, H. T. Tiong, T. C. Natl Univ Singapore Dept Elect & Comp Engn Singapore 117576 Singapore Univ Queensland Sch Informat Technol & Elect Engn St Lucia Qld 4072 Australia

A dual-monopole array backed by a plane reflector is designed and rigorously analysed to provide information on the installations and applications of monopole arrays mounted on a wall or ceiling for antenna diversity/multiple-input and multiple-output (MIMO) operations. The optimum design of the array is determined through computer simulation. On the basis of the experimental measurements and theoretical investigations in a typical rich multipath environment, the authors found that both the diversity gain and the average MIMO capacity of the array are almost unaffected by the distance of the array from the reflector if the distance is greater than similar to 0.16 gimel. On the other hand, both the diversity gain and the average MIMO capacity are significantly reduced once the separation between the monopoles is less than similar to 0.2 gimel. The findings have reference values for the design of monopole arrays in diversity/MIMO systems

关键词： monopole antenna arrays plane reflector antenna radiation patterns Radio links and equipment MIMO antenna diversity diversity reception multiple-input multiple-output system Antenna arrays dual-monopole array MIMO communication reflector antennas

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Lattice reduction-based iterative receivers: using partial bit-wise MMSE filter with randomised sampling and MAP-aided integer perturbation

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IET COMMUNICATIONS 2016年第11期10卷 1394-1400页

作者： Bai, Lin Li, Tian Zhao, Lewen Choi, Jinho Beihang Univ Sch Elect & Informat Engn Beijing Peoples R China Supelec Gif Sur Yvette France Gwangju Inst Sci & Technol Sch Informat & Commun Gwangju South Korea

For iterative detection and decoding (IDD) in multiple-input multiple-output systems, the maximum a posteriori probability (MAP) detector would be ideal in terms of the performance. However, due to its high computational complexity, various suboptimal low-complexity approximate MAP detectors have been studied. In this study, a lattice reduction (LR)-based detector is considered for a near-optimal performance for IDD. The authors improve further the performance by employing a partial bit-wise minimum mean square error (MMSE) approach with randomised sampling, which has a lower complexity than that of the full bit-wise MMSE method. Moreover, the list of candidate vectors obtained by randomised sampling is extended using a MAP-aided integer perturbation algorithm for a better performance with low additional complexity. Through simulation results, it is shown that a near-optimal performance can be obtained which is better than that of the LR-based randomised successive interference cancellation and the full bit-wise MMSE methods.

关键词： MIMO communication radio receivers iterative decoding least mean squares methods filtering theory maximum likelihood decoding probability computational complexity vectors interference suppression radiofrequency interference lattice reduction-based iterative receiver partial bit-wise MMSE filter randomised sampling MAP-aided integer perturbation algorithm iterative detection and decoding IDD multiple-input multiple-output system maximum a posteriori probability detector MAP detector suboptimal low-computational complexity LR minimum mean square error approach vector randomised successive interference cancellation full bit-wise MMSE method

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Space alignment for cognitive transmission with multiple primary users

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ELECTRONICS LETTERS 2013年第25期49卷 1619-1620页

作者： Bai, Xiaojuan Xidian Univ ISN Lab State Key Lab Integrated Serv Networks Xian 710071 Peoples R China Northwest Normal Univ Coll Phys & Elect Engn Lanzhou Peoples R China

A space-alignment (SA) scheme with K primary users in different cells working in the same frequency band based on K-symbol extension for cognitive transmission in a multiple-input multiple-output system is proposed. The main idea is that the secondary transmitter sends a supersymbol over the K timeslot;meanwhile, the secondary transmitter aligns its transmit directions by precoding to the kth primary channel eigenmodes unused at the kth timeslot, and at the same time adapts its transmit power to satisfy the interference-power constraints at the other K -1 primary receivers. The simulation results show that the proposed scheme achieves a higher performance compared with both the SA scheme with the single primary user and the scheme of the direct singular value decomposition of the secondary channel with interference-power constraint.

关键词： cognitive radio eigenvalues and eigenfunctions MIMO communication radio transmitters radiofrequency interference singular value decomposition direct singular value decomposition SA scheme interference-power constraints kth timeslot kth primary channel eigenmodes supersymbol secondary transmitter multiple-input multiple-output system K-symbol extension frequency-band multiple primary users cognitive transmission space-alignment scheme

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A New Reduced KSD-SIC Algorithm Based on the Noise Variance

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SENSOR LETTERS 2012年第8期10卷 1774-1778页

作者： Mao, Xinyu Ren, Shubo Xiang, Haige Peking Univ Sch Elect Engn & Comp Sci Beijing 100871 Peoples R China

A new reduced algorithm based on the K-best sphere decoding and the successive interference cancellation algorithm is proposed for detection of multiple-input multiple-output systems. This algorithm divides the detection into two parts: the previous part detects by K-best SD algorithm, the later part detects by the SIC algorithm. Then a threshold based on the noise variance is proposed to further reduce the complexity of the algorithm. Any nodes those have metric larger than it will be cut during detecting. Simulation results show that the propose algorithm reduce the calculation complexity efficiently while at the same time the performance drop is almost neglectable.

关键词： multiple-input multiple-output system Sphere Decoding K-Best Sphere Decoding Successive Interference Cancellation

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Equivalent circuit model of MIMO based on coupling matrix

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ELECTRONICS LETTERS 2015年第9期51卷 665-666页

作者： Wu, Rui-Zhi Wang, Peng Li, Rui-Peng Zheng, Qiang Univ Elect Sci & Technol China Res Inst Elect Sci & Technol Chengdu 611731 Peoples R China

An equivalent circuit model of coupled antennas for the multiple-input multiple-output (MIMO) system based on coupling matrix theory is presented. It is demonstrated that a four-port network including two resonators can be a good description of MIMO antennas such as asymmetric coplanar strip fed antennas. The equivalent circuit is established by coupling matrix extraction which is a widely used method in the coupling matrix analysis of filters. This equivalent circuit model for the MIMO system should be helpful in MIMO or decoupling network designs.

关键词： MIMO communication antenna arrays equivalent circuits matrix algebra MIMO antennas asymmetric coplanar strip-fed antennas coupling matrix analysis coupling matrix extraction coupling matrix theory decoupling network designs equivalent circuit model filters four-port network multiple-input multiple-output system resonators

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QR decomposition aided belief propagation detector for MIMO systems

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ELECTRONICS LETTERS 2015年第11期51卷 873-874页

作者： Park, Sangjoon Choi, Sooyong Yonsei Univ Sch Elect & Elect Engn Seoul 120749 South Korea

A QR decomposition aided belief propagation (QR-BP) detector for multiple-input multiple-output (MIMO) systems is proposed. Before the iterative message passing process, linear transformation is performed by using the unitary matrix obtained from the QR decomposition of the original MIMO channel matrix. Then, the original MIMO channel matrix is replaced by an upper triangular channel matrix after the linear transformation and the proposed QR-BP detector operates over the new bipartite graph from the upper triangular channel matrix. Therefore, the number of cycles in the new bipartite graph is significantly decreased when compared with the fully connected bipartite graph from the original MIMO channel matrix. In addition, since the unitary matrix is utilised for the linear transformation, there is no information loss on the likelihoods estimated from noisy observations. Simulation results verify that the proposed QR-BP detector outperforms existing BP detectors and achieves near-optimum performance close to the maximum-likelihood detector in terms of bit error ratio.

关键词： MIMO communication graph theory matrix algebra maximum likelihood detection message passing MIMO channel matrix MIMO systems QR decomposition aided belief propagation detector QR-BP detector bipartite graph bit error ratio iterative message passing process linear transformation maximum-likelihood detector multiple-input multiple-output system unitary matrix upper triangular channel matrix

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