• ETRI Journal
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• v.40 no.5
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• pp.570-581
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• 2018

This work analyzes the performance of implementable detectors for the multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) technique under specific and realistic operation system conditions, including antenna correlation and array configuration. A time-domain channel model was used to evaluate the system performance under realistic communication channel and system scenarios, including different channel correlation, modulation order, and antenna array configurations. Several MIMO-OFDM detectors were analyzed for the purpose of achieving high performance combined with high capacity systems and manageable computational complexity. Numerical Monte Carlo simulations demonstrate the channel selectivity effect, while the impact of the number of antennas, adoption of linear against heuristic-based detection schemes, and the spatial correlation effect under linear and planar antenna arrays are analyzed in the MIMO-OFDM context.

• Journal of information and communication convergence engineering
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• v.8 no.4
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• pp.387-392
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• 2010

This study focuses on improving MIMO-OFDM systems by combining a wireless communication architecture known as vertical BLAST(bell laboratories layered space-time) or V-BLAST and STTC(space time trellis coding). In this paper, the combination is done by introducing STTC in each V-BLAST layer. Moreover, this architecture uses multiple antennas that are grouped into small number of antennas which makes it less complex to decode by decoding every group. Whereas, in traditional V-BLAST, all the antennas form one group and they are decoded together at the receiver, therefore, this increases the complexity as the number of antennas is getting high. We compare the bit error rate performance of this system with MIMO-OFDM that uses convolutional coding instead of STTC. Under the same spectral efficiency, the simulation results prove that joining V-BLAST with STTC improves MIMO-OFDM systems performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.10A
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• pp.980-986
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• 2008

Spatial multiuser access is investigated for the reverse link of multiuser multiple-input multiple-output (MIMO) systems. In particular, we consider two alternative a aches to spatial multiuser access that adopt the same detection algorithm at the base station: one is a closed-loop approach based on singular value decomposition (SVD) of the channel matrix, whereas the other is an open-loop approach based in space-time block coding (STBC). We develop multiuser detection algorithms for these two spatial multiuser access schemes based on the minimum mean square error (MMSE) criterion. Then, we compare the bit error rate (BER) performance of the two schemes and a single-user MIMO scheme. Interestingly, it is found that the STBC approach can provide much better BER performance than the SVD approach as well as than a single-user MIMO scheme.

• Journal of information and communication convergence engineering
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• v.9 no.4
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• pp.385-390
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• 2011

In this paper, various ultra-wideband (UWB) spatial multiplxing (SM) multiple input multiple output (MIMO) receivers based on a prerake diversity combining scheme are discussed and their performance is analyzed. Several UWB MIMO detection approaches such as zero forcing (ZF), minimum mean square error (MMSE), ordered successive interference cancellation (OSIC), sorted QR decomposition (SQRD), and maximum likelihood (ML) are considered in order to cope with inter-channel interference. The UWB SM systems based on transmitter-side multipath preprocessing and receiver-side MIMO detection can either boost the transmission data rate or offer significant diversity gain and improved BER performance. The error performance and complexity of linear and nonlinear detection algorithms are comparatively studied on a lognormal multipath fading channel.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6A
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• pp.494-499
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• 2009

In this paper, we provide an efficient method of user selection for achieving the maximum system throughput in downlink multiuser Multiple-Input Multiple-Output (MIMO) systems. A proposed method is for selecting a fine user set only with powers of each user channel and angles between them. This algorithm is simpler than SUS because there is no considering about the optimal value of correlation. The proposed method finds the user set toward maximizing system throughput, so it has high performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.3
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• pp.1156-1173
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• 2021

In this paper, we propose a new joint precoder and postcoder design strategy to support multiple streams per user in multiuser multiple-input multiple-output (MIMO) systems. We propose two step precoding strategies using equal channel gain decomposition and block diagonalization at the transmitter. With the proposed precoder, the multiuser MIMO channel can be decomposed into multiple parallel channels with equal channel gain per user. After applying receive postcoder which is generated and sent by the transmitter, we can use ML based decoder per stream to achieve full receive diversity. Achievable sum rate bound and diversity performance of the proposed algorithm are presented with feedback signaling design and quantitative complexity analysis. Simulation results show that the proposed algorithm asymptotically approaches to the sum rate capacity of the MIMO broadcast channel while maintaining full diversity order.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.6 s.99
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• pp.712-717
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• 2005

This paper presents a system identification method for multi-input, multi-output (MIMO) systems, by which a rational polynomial transfer function model is identified from experimentally determined frequency response function data. Analytically determined information is incorporated in this method to obtain a more reliable model, even in the frequency range where the excitation energy is limited. To verify the suggested method, shaking table test for an actively controlled two-story, bench-scale building employing an active mass damper is conducted. The results show that the proposed method is quite effective and robust for system identification of MIMO systems.

• International journal of advanced smart convergence
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• v.7 no.3
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• pp.37-43
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• 2018

Lattice-reduction (LR) techniques have been developed for signal detection in spatial multiplexing multiple input multiple output (MIMO) systems to obtain the largest diversity gain. Thus, an LR-assisted zero-forcing (ZF) receiver can achieve the maximum diversity gain in spatial multiplexing MIMO systems. In this paper, a simplified analysis of the achievable diversity gain is presented by fitting the channel coefficients lattice-reduced by a complex Lenstra-Lenstra-$Lov{\acute{a}}z$ (LLL) algorithm into approximated Gaussian random variables. It will be shown that the maximum diversity gain corresponding to two times the number of receive antennas can be achieved by the LR-based ZF detector. In addition, the approximated bit error rate (BER) expression is also derived. Finally, the analytical BER performance is comparatively studied with the simulated results.

• Journal of Communications and Networks
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• v.13 no.1
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• pp.63-69
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• 2011

In this paper, we propose a fixed-complexity sphere encoder (FSE) for multi-user multi-input multi-output (MU-MIMO) systems. The proposed FSE accomplishes a scalable tradeoff between performance and complexity. Also, because it has a parallel tree-search structure, the proposed encoder can be easily pipelined, leading to a tremendous reduction in the precoding latency. The complexity of the proposed encoder is also analyzed, and we propose two techniques that reduce it. Simulation and analytical results demonstrate that in a $4{\times}4$ MU-MIMO system, the proposed FSE requires only 11.5% of the computational complexity needed by the conventional QR decomposition with M-algorithm encoder (QRDM-E). Also, the encoding throughput of the proposed encoder is 7.5 times that of the QRDM-E with tolerable degradation in the BER performance, while achieving the optimum diversity order.

• Journal of Communications and Networks
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• v.14 no.2
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• pp.199-205
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• 2012

This work investigates the progressive linear precoder design for packet retransmissions in multi-input multi-output (MIMO) systems with multiple codewords and automatic repeat request (ARQ) bundling feedback. Assuming perfect channel state information, a novel progressive linear ARQ precoder is proposed in the perspective of minimizing the packet error rate. We devise the ARQ precoder by combining power loading and sub channel pairing between current retransmission and previous transmissions. Furthermore, we extend the design to the case that the channel estimation error exists. Numerical results show that the proposed scheme can improve the performance of MIMO ARQ systems significantly regardless of the channel estimation error.