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...
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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.
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 ...
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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.
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 r...
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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.
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) tec...
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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.
In multiple-inputmultiple-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 ...
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In multiple-inputmultiple-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.
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 pla...
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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.
The multipleinput and multipleoutput (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 f...
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The multipleinput and multipleoutput (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.
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 th...
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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.
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 mul...
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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.
In this paper, we consider optimization of a two-way multiple-input multiple-output (MIMO) amplify-and-forward relay network which consists of a pair of transceivers and several relay nodes. multiple antennas are equi...
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In this paper, we consider optimization of a two-way multiple-input multiple-output (MIMO) amplify-and-forward relay network which consists of a pair of transceivers and several relay nodes. multiple antennas are equipped on the transceivers and relays. multiple access broadcast scheme which finishes communication in two time slots is considered. In the first time slot, signals received by the relays are scaled by several beamforming matrices. In the second time slot, the relays transmit the scaled signals to the two transceivers. Upon receiving these signals, a MIMO equalizer is implemented at each transceiver to recover the desired signal. In this paper, zero forcing equalizers are used. Joint optimization of the beamforming matrices and the equalizers are realized using the following criteria: 1) the total relay transmission power is minimized subject to the minimal output signal-to-noise ratio (SNR) constraint at each transceiver, 2) the minimal output SNR of the two transceivers is maximized subject to total relay transmission power constraint, and 3) the minimal output SNR of the two transceivers is maximized subject to individual relay transmission power constraint. It is shown that the proposed optimization problems can be formulated as the second-order cone programming problems which can be solved efficiently. The validity of the proposed algorithm is verified by computer simulations.
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