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Low-Complexity Sorted QR Decomposition for MIMO Systems Based on Pairwise Column Symmetrization

IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2014年第3期13卷 1388-1396页

作者： Kim, Tae-Hwan Korea Aerosp Univ Sch Elect Telecommun & Comp Engn Goyang Si 412791 Gyung Gi Do South Korea

QR decomposition (QRD) is a preprocessing technique for detecting symbols in multiple-input and multiple-output (MIMO) systems, but the computational complexity is prohibitively high when the systems incorporate a large number of antennas. This paper presents a low-complexity sorted QRD (SQRD) algorithm for MIMO systems. The proposed algorithm performs SQRD through orthogonalizations based on the modified Gram-Schmidt process, rearranging the column vectors of a real-valued MIMO channel matrix in such a way that the symmetry between the vectors is maintained. By using the symmetry, the computations required for orthogonalizing one of the two adjacent vectors can be eliminated effectively, which significantly reduces the computational complexity. Theoretical analyses show that the proposed algorithm reduces the computational complexity required for SQRD by 50% for any MIMO configurations, when compared to the conventional algorithm. In addition, the memory requirement to store resultant matrices is 50% of that in the conventional one.

关键词： multiple-input multiple-output QR decomposition sphere decoding symbol detection preprocessing Gram-Schmidt process

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Few-Mode Fibers Supporting More Than Two LP Modes For Mode-Division-multiplexed Transmission With MIMO DSP

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JOURNAL OF LIGHTWAVE TECHNOLOGY 2014年第14期32卷 2468-2479页

作者： Mori, Takayoshi Sakamoto, Taiji Wada, Masaki Yamamoto, Takashi Yamamoto, Fumihiko NTT Corp Access Network Serv Syst Labs Tsukuba Ibaraki 3050805 Japan

We propose a transmission fiber for mode-division-multiplexed transmission with multiple-input multiple-output (MIMO) digital signal processing supporting four and six linearly polarized (LP) modes over the C + L band. We show numerically that a graded-index core can flexibly tune the differential mode group delay (DMD) and a cladding trench can flexibly control the guiding mode number. We optimized the spacing of the core and trench. Accordingly, we can achieve a few-mode operation of more than two LP modes and low DMD while preventing the high-refractive index difference that leads to manufacturing difficulties and any loss increase. Finally, we successfully fabricated fibers for use in a C + L band WDM-MDM transmission with MIMO DSP, and realized a transmission fiber with a total absolute DMD of less than 40 ps/km for four-LP mode operation and of less than 70 ps/km for six-LP mode operation over the entire C + L band.

关键词： Differential mode delay few-mode fibers multiple-input multiple-output

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Efficient QR-Based Multi-Mode Precoding for Limited Feedback Multi-User MIMO Systems

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WIRELESS PERSONAL COMMUNICATIONS 2014年第2期74卷 969-987页

作者： Pan, Chien-Hung Lee, Ta-Sung Natl Chiao Tung Univ Dept Elect Engn Hsinchu Taiwan

This paper proposes QR-based criteria for efficient selection of multi-mode precoders in multi-user multiple-input multiple-output (MU-MIMO) precoded systems with a limited feedback. In particular, a MU-MIMO QR based precoding scheme is developed which takes advantage of the overall precoder design among users in conjunction with QR detection. A selection criterion is developed to identify the precoder that yields the maximum free distance. Efficient mode selection and tree search strategies are adopted to reduce the complexity associated with the identification of the optimum precoder. To further improve the detection performance in correlated channels, an efficient QR-based MMSE V-BLAST detector is proposed. Computer simulations confirm that the proposed QR-based precoding scheme attains the performance of existing schemes with a significantly lower complexity level.

关键词： QR decomposition Multi-mode precoding multiple-input multiple-output Limited feedback system

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Sum-Rate Maximization in the Multicell MIMO Broadcast Channel With Interference Coordination

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2014年第6期62卷 1501-1513页

作者： Nguyen, Duy H. N. Tho Le-Ngoc McGill Univ Dept Elect & Comp Engn Montreal PQ H3A 0E9 Canada

This paper studies the precoding designs to maximize the weighted sum-rate (WSR) in a multicell multiple-input multiple-output (MIMO) broadcast channel (BC). We consider a multicell network under universal frequency reuse with multiple mobile stations (MS) per cell. With interference coordination (IC) between the multiple cells, the base-station (BS) at each cell only transmits information signals to the MSs within its cell using the dirty paper coding (DPC) technique, while coordinating the intercell interference (ICI) induced to other cells. The main focus of this work is to jointly optimize the encoding covariance matrices across the BSs in order to maximize the network-wideWSR. Since this optimization problem is shown to be nonconvex, obtaining its globally optimal solution is highly complicated. To address this problem, we consider two low-complexity solution approaches with distributed implementation to obtain at least locally optimal solutions. In the first approach, by applying a successive convex approximation technique, the original nonconvex problem is decomposed into a sequence of simpler problems, which can be solved optimally and separately at each BS. In the second approach, the WSR problem is solved via an equivalent problem of weighted sum mean squared error minimization. Both solution approaches will unfold the control signaling among the coordinated BSs to allow their distributed implementation. Simulation results confirm the convergence of the proposed algorithms, as well as their superior performances over schemes with linear precoding or no interference coordination among the BSs.

关键词： Broadcast channel convex optimization coordinated multipoint transmission/reception dirty-paper coding interference coordination MMSE multicell multiple-input multiple-output

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Performances of Transmit Antenna Selection, Receive Antenna Selection, and Maximal-Ratio-Combining-Based Hybrid Techniques in the Presence of Feedback Errors

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2014年第4期63卷 1976-1982页

作者： Yilmaz, Ahmet Kucur, Oguz Turkish Sci & Technol Res Council TUBITAK Informat & Informat Secur Res Ctr BILGEM TR-41470 Gebze Turkey Gebze Inst Technol Dept Elect Engn TR-41400 Gebze Turkey

In this paper, performances of joint transmit and receive antenna selection (JTRAS), transmit antenna selection/maximal ratio combining (TAS/MRC), and transmit antenna selection/receive antenna selection (TAS/RAS) techniques are examined in a unified manner in the presence of feedback errors. Exact and closed-form outage probability, moments, moment-generating function, ergodic capacity, and symbol error probability (SEP) expressions are derived for flat Nakagami-m fading channels. In addition, to obtain diversity order and array gain of the investigated techniques in the presence of feedback errors, asymptotic outage probability and SEP expressions are also derived. Analytical results are validated by Monte Carlo simulations. Results show that the diversity order is significantly reduced in the presence of feedback errors, whereas all the systems provide full diversity order for a perfect feedback channel.

关键词： Diversity order feedback error joint transmit and receive antenna selection (JTRAS) maximal ratio combining (MRC) multiple-input multiple-output Nakagami-m fading receive antenna selection (RAS) transmit antenna selection (TAS)

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An Improved Semi-Orthogonal User Selection Algorithm Based on Condition Number for Multiuser MIMO Systems

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China Communications 2014年第A01期11卷 23-30页

作者： LU Xinlu WU Jun HUANG Xinlin LI Wenfeng LU Jianmin GONG Zhengwei ComputerScienceandTechnologyDepartment TongjiUniversityShanghai201804China HuaweiTechnologiesCo. LtdShanghai201206China

In multiple-input multiple-Out （MIMO） systems, the user selection algorithm plays an important role in the realization of multiplexing gain. In this paper, an improved Semi-orthogonal User Selection algorithm based on condition number is proposed. Besides, a new MIMO pre- coding scheme is designed. The proposed SUS- CN （SUS with condition number） algorithm outperforms the SUS algorithm for the selection of users with better matrix inversion property, thus a higher information rate for selected user pair is achieved. The designed MIMO precoding matrix brings benefits of the power equality at transmitted terminals, the limited dynamic range of the power over time, and a better power efficiency. The simulation results give the key insights into the im- pact of the different condition number value and users on the sum-rate capacity.

关键词： multiple-input multiple-output sumrate capacity condition number semi-orthogonaluser selection

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DESIGN OF A BROADBAND PLANAR MONOPOLE MIMO ANTENNA

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MICROWAVE AND OPTICAL TECHNOLOGY LETTERS 2014年第9期56卷 1994-1997页

作者： Kazim, Jalil Ur Rehman Ahmad, Salman Ali, Usman Owais, Owais COMSATS Inst Informat Technol Abbottabad Dept Elect Engn Abbottabad Pakistan

A broadband multiple-input multiple-output antenna with a size of 60 x 120 x 1.6 mm is presented for the smart phones. Enhanced performance of the antenna is achieved by utilizing dual radiator chopping and ground plane slitting. Supplemental L-shaped meandered ground structure over the top of radiator was added to enhance the performance in the lower frequency band. The proposed antenna covers two frequency bands for return loss <-6 dB, that is, 0.8-0.96 and 1.7-2.7 GHz, respectively, specified for mobile phone operation. The antenna is fabricated and measured results are obtained for return loss, isolation, envelope correlation, and radiation pattern. (C) 2014 Wiley Periodicals, Inc.

关键词： multiple-input multiple-output broadband UWB LTE

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Signalling scheme for achieving dynamic degrees of freedom in MIMO Y channel

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INTERNATIONAL JOURNAL OF GRID AND UTILITY COMPUTING 2014年第3期5卷 149-155页

作者： Wang, Yong Guo, Aixiang He, Hong Li, Hui Li, Fengrong Xidian Univ State Key Lab Integrated Serv Networks Xian Shaanxi Peoples R China Chinese Acad Sci Shanghai Inst Microsyst & Informat Technol Key Lab Wireless Sensor Network & Commun Shanghai 200050 Peoples R China

The multiple input and multiple output (MIMO) Y channel is a generalised channel model of the two-way relay channel, which supports point-to-multipoint traffic pattern for unicast. In this paper, a signalling scheme for achieving dynamic Degrees of Freedom (DOF) in the MIMO Y channel is proposed where each user exchanges d pairs of messages with each of the other users simultaneously via an intermediate relay and d is a variable integer. To complete this scheme, two novel signalling techniques are utilised, which are Signal Space Alignment for Network Coding (SSA-NC) and interference nulling beamforming combined with Receiving Antenna Selection (RAS) technique. Dynamic DOF can be obtained by changing d, e.g., more diversity gain can be obtained if d is small, while more DOF can be achieved if d becomes larger.

关键词： MIMO multiple-input multiple-output network coding utility computing degrees of freedom signal space alignment

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Joint Source-Relay Precoding and Power Allocation for Secure Amplify-and-Forward MIMO Relay Networks

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IEEE TRANSACTIONS ON INFORMATION FORENSICS AND SECURITY 2014年第8期9卷 1240-1250页

作者： Wang, Hui-Ming Liu, Feng Xia, Xiang-Gen Xi An Jiao Tong Univ Sch Elect & Informat Engn Minist Educ Key Lab Intelligent Networks & Network Secur Xian 710049 Peoples R China Xidian Univ Inst Elect Xian 710049 Peoples R China Univ Delaware Dept Elect & Comp Engn Newark DE 19716 USA

In this paper, we investigate the security issue of a two-hop amplify-and-forward multiple-input multiple-output wireless relay network in the existence of a multiantenna eavesdropper. The optimal scheme to achieve the secrecy capacity involves a nonconvex optimization and is still an open problem. Aiming to find an efficient way to enhance the secrecy rate with a tractable complexity, we propose a suboptimal joint source and relay linear precoding and power allocation scheme. In the scheme, the source node adopts a generalized singular value decomposition (SVD)-based precoding to transmit the signal in the first phase, and the relay node forwards the received signal based on the SVD precoding in the null-space of the wiretap channel in the second phase. Power allocations in both phases are optimized to maximize the secrecy rate by an alternating iterative optimization algorithm. Each iteration involves two subproblems. One has a water-filling solution and the other has a closed-form solution or a water-filling-like solution as well, both of which are computationally very efficient. The iteration converges fast and we prove that it guarantees to find a stationary optimum. Furthermore, we show that when the eavesdropper has equal or more antennas than the source does, the secrecy rate is a quasi-concave function of the source power so that allocating all the source power is generally not optimal. Numerical evaluation results are provided to show the effectiveness of the iterative algorithm and the proposed secrecy scheme.

关键词： Physical layer security secrecy rate relay multiple-input multiple-output precoding generalized singular value decomposition

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Photonic Precoding for Millimeter-Wave Multicell MIMO in Centralized RoF System

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IEEE PHOTONICS TECHNOLOGY LETTERS 2014年第11期26卷 1116-1119页

作者： Cheng, Lin Zhu, Ming Wang, Jing Xu, Mu Lu, Feng Chang, Gee-Kung Georgia Inst Technol Sch Elect & Comp Engn Atlanta GA 30332 USA

We propose a centralized photonic precoding method for millimeter-wave (MMW) multicell multiple-input multiple-output (MIMO) wireless communications. By applying the multicell MIMO and hence exploiting the spatial multiplexing gain over MMW, the system capacity is enhanced compared with the conventional single-input single-output (SISO) system. Based on radio-over-fiber (RoF) techniques, the multicell function is realized in a centralized location, which simplifies the design of remote access units. Traversing over the optical links enabled by the RoF infrastructure, we implement a novel method of photonic precoding to realize the zero-forcing precoding approach, which simplifies the user equipment complexity. A two-cell MIMO downlink transmission using the proposed method is experimentally demonstrated. Our results show that original signals can be directly recovered at the receivers with a power penalty <1 dB compared with SISO transmission. The effect of varying photonic parameters is also analyzed.

关键词： Centralization multiple-input multiple-output millimeter-wave multi-cell pre-coding radio-over-fiber

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